TSUNAMI ... EARTHQUAKES .. SEISMOTECTONICS .. HURRICANES ..TORNADOES VOLCANIC ERUPTIONS .. NATURAL DISASTERS .. DISASTER ARCHAEOLOGY . .. .. CLIMATE CHANGE....OCEAN GOVERNANCE........................... Announcements .. Completed Events .. Special Bulletins: Recent Disasters .. Books & Book Reviews .. Tsunami Society Dr. George PC:. Bio Summary Publications .. Recent Publications . Recent Books. Miscellaneous Writings . Consulting Services

Website Navigation Guide

	Enter your search terms Submit search form
	Web www.drgeorgepc.com

CALIFORNIA EARTHQUAKE - THE BIG ONE

THE NEXT GREAT CALIFORNIA EARTHQUAKE

George Pararas-Carayannis, Ph.D.

THE BIG ONE - The Next Great California Earthquake/ Why, Where & When It Will Happen. A comprehensive reference of past California disasters and what can be expected when the next "BIG ONE" strikes.)

------------------------------------------

Learn How To Assess Potential California Earthquake And Tsunami Risks!
A factual, well researched book of earthquake and tsunami disasters in California, with an in-depth analysis of fault behaviors and explanation of where and when the next great earthquake can be expected.

Do you live in California and Are YOU prepared for "THE BIG ONE"?

DO YOU know .... what earthquakes are? Why they happen? What destructive earthquakes have done in California? Whether they can be predicted - and if so, how?

DO YOU know .... if you live near an active California fault? How faults behave? What California's tsunami risk is?

If you have answered "NO" to any of these questions, or if you are a student interested in the earth sciences, a public official concerned about public safety, a scientist interested in a quick factual reference, or simply a California resident interested in the safety of your family and a realistic overview of earthquake risk areas in California, .........

THEN THIS BOOK, "THE BIG ONE", IS FOR YOU!
Learn How To Assess Potential California Earthquake And Tsunami Risks!

REVIEW ENTIRE TABLE OF CONTENTS

ABOUT THE AUTHOR ..................................................................... QUESTIONS? email for a copy of the book.

MORE ABOUT THE BOOK

Millions of California residents live near one of the most seismic regions in the world, the San Andreas fault. In 1989, the Loma Prieta earthquake was devastating. In 1994 the Northridge earthquake was terribly disastrous. However, neither of these earthquakes will compare to the next catastrophic earthquake due to strike California in a matter of a few years, OR SOONER.

"The Big One" is a fully illustrated, comprehensive reference book in an easy-to-understand, question and answer format. It reviews the current knowledge and provides information that improves understanding and puts California's earthquake danger in proper perspective.

"The Big One" contains valuable information designed to: increase public awareness, influence public policy and contribute to the protection of life and property.

"The Big One" can help you define if there a tsunami threat in your area or what areas may constitute a potential tsunami hazard.

"The Big One" takes you on a historical journey of past earthquake disasters and explores contemporary knowledge regarding California earthquakes: what they are, why they happen, where they occur, what they have done, and how they can be predicted.

"The Big One" discusses earthquake and tsunami hazard potential in California, reviews current evidence collected on the faults of California of their present behavior, and gives a breakdown of specific geographical regions that have the highest risk.

"The Big One" provides an overview of earthquake prediction, describes what can be expected in the future and answers basic questions as to where and when "The Big One" will strike so that measures for public safety can be taken.

Additionally, "The Big One" contains a comprehensive glossary, a section regarding public safety, and a comprehensive list of cities, towns and localities that are in close proximity to major faults which will be affected by earthquakes in the future.

TABLE OF CONTENTS

CHAPTERS 1- 17

1. The Big One

What happened in Northern California at 5:04 P.M., on 17 October 1989?
What is a possible scenario for the Big One in California?
How California's Civil Defense Responds and Mobilizes?
Disaster Reports from: Kern County
Los Angeles County
Orange County
Riverside County
San Bernardino County
Santa Barbara County
Ventura County
Is this only a Partial Scenario of the Big One? / What Could Really Happen?

ORDER BOOK

2. Causes of Earthquakes - Fundamental Principles

What are the causes of earthquakes in California and around the world?
The Earth and Its Interior
How Big is our earth? / How do we know what the earth's interior is like?
What is the earth's core made of? / What processes contribute to the high temperatures in the interior of the earth? / What is the earth's mantle?
What are the mantle's convection cells and currents?
How fast do convection currents move within the earth's mantle?
What is the "Mohorovicic Discontinuity"?
The Earth's Crust and Forces Acting Upon It
How is the earth's crust created? / How thick is the earth's crust?
How do convection currents in the earth's interior affect the earth's crust?
How do the forces within the earth's interior cause earthquakes on its surface?
Where is the earth's crust most unstable?
Sea Floor Spreading, Plate Tectonics and Continental Drift
How magnetic field studies of the earth contributed to theories that help in our understanding of earthquakes? / How are the rates of crustal movements measured?
What is the theory of Plate Tectonics? / How do tectonic plates move? How fast do tectonic plates move?
What is the theory of Sea Floor Spreading? / How do we know that the ocean floor spreads? / How are mid-ocean ridges and ocean volcanoes formed? / How are the great ocean floor fractures created? Which are some of the best known great ocean floor fractures?
What is the theory of Continental Drift? / How do continents float? / How do we know that the earth's continents drift? / How fast are the continents drifting? / How are volcanoes, mountains and other major geological features formed?
Is part of California moving or drifting?
Destruction of the Earth's Crust
How subduction destroys the Earth's crust ? / What is the Benioff zone?
How are the deep ocean trenches formed?
Earthquakes
What are earthquakes? / What would happen if there were no earthquakes on earth?
How do tectonic plate movements cause earthquakes?
Where do earthquakes occur? / Where do the great earthquakes occur?
Are large earthquakes limited only to areas of subduction?
Which are the earth's major seismic belts? / Where is the Transhimalaian seismic belt?
Where is the Circum-Pacific seismic belt? / Why is the Circum-Pacific Seismic Belt called the "Pacific ring of fire"? / What are the causes of earthquakes along the Pacific Ring of Fire ? / Why does Japan experience so many destructive earthquakes?
What are the causes of large earthquakes in the Aleutian islands and in Alaska?
Plate Tectonics and Earthquake Prediction earth science
How do the great tectonic plates interact to the north of California?
Can Plate Tectonics be used to predict earthquakes?
What studies of tectonic plate interactions could help in predicting earthquakes? earth science
Destructive Earthquakes
Which was the most devastating earthquake in history in terms of lives lost?
Which were the strongest earthquakes in the 20th century?
What was the great Tangshan Earthquake in China?
What are the Causes of Earthquakes in California?
What tectonic processes are responsible for earthquakes in California?
Why do earthquakes occur so frequently in California?
What is California's Transform Fault System?
How was the San Andreas Fault System created?
Do large earthquakes occur along the entire length of the San Andreas Fault?
How do the great ocean floor fractures relate to earthquake activity in California?
ORDER BOOK RETURN TO TOP

3. Understanding California's Earthquakes - Fundamental Principles

What is seismology?
Historical Perspective
Is seismology an old science? / Who was the father of modern seismology? / When did earthquake science begin in the U.S.? / Who were some of the early American seismologists?
What was the significance of the 1906 San Francisco earthquake?
How comprehensive is seismic research in California?
What are some of the significant advances and challenges for the future?
Faults and Faulting
What is a fault? / What are the different types of faulting? / What kind of earthquake faulting occurs in California? / How can hard rocks deform elastically along a fault?
What is the "theory of elastic rebound"? / What is fault creep? / How can fault creep be used to predict the magnitudes of future earthquakes?
Understanding California Earthquakes
How frequently do earthquakes occur around the world? / What Triggers Earthquakes?
What is the relationship of strain on a fault to earthquakes?
How is strain used to estimate the recurrence of earthquakes in California?
How much strain was released by the October 17, 1989, Loma Prieta earthquake in California? / How reliable are strain measurements in determining how soon earthquakes will strike again California?
How does earthquake energy travel? / What are seismic waves? / How are seismic waves generated? / What are "primary", "compressional" or P-waves? / What are "secondary", "shear" or S-waves? / What are "surface" waves? / What is seismic wave refraction? / How do studies of seismic waves help determine earthquake motions and fault slip?
How are earthquakes recorded? / How are earthquakes located?
What other methods exist for locating earthquakes?
Earthquake Magnitude and Intensity
What is earthquake magnitude? / What is the difference between earthquake magnitude and intensity? / What is the Richter scale? / How does earthquake's energy release relate to magnitude? / What other methods are used to measure earthquake energy release and size? / What is the Seismic Moment of an earthquake? / How does the seismic moment of an earthquake relate to its Richter magnitude?
How is earthquake depth determined?
What is earthquake intensity? / Is the intensity of an earthquake the same everywhere?
How was earthquake intensity initially measured? / What was the original Mercalli scale? What is the Modified Mercalli Intensity scale? / What is an earthquake intensity map? What is an isoseismal? What is seismology?

ORDER BOOK RETURN TO TOP

4. Experiencing the Big One

What will the ground movements be like and how long will they last?
Will the shaking cause ground liquefaction?
What will happen to buildings?
Why and how buildings may fail?
What kind of noises may be expected?
Will light and other electrical phenomena appear before or after the Big One strikes?
What kind of odors may be produced?

5. Can California's earthquakes and the Big One be predicted?

How does predicting earthquakes differ from earthquake forecasting?
What are short, intermediate and long term earthquake predictions?
Who conducts earthquake prediction research in California?
What is the status of earthquake prediction research in California?
What are some of the methods used in earthquake prediction?
How reliable are studies of plate tectonics in earthquake prediction?
How reliable are studies of elastic deformation in predicting major earthquakes and the Big One? / How reliable are the historical/statistical probability methods of earthquake prediction in California? / How reliable are overall earthquake predictions in California?
Have the Chinese been more successful in predicting big earthquakes?
What are some of the dangers of predicting the Big One in California?
Will earthquake prediction ever become a reality?

ORDER BOOK RETURN TO TOP

6. What methods are used to predict earthquakes in California?

What are some of the additional methods and instruments used for earthquake prediction in California?
How are statistical methods used to predict California earthquakes?
How is the recurrence frequency of California earthquakes estimated?
How does earthquake clustering interfere with estimating the recurrence frequency of California earthquakes?
How is the Seismic Gap Theory used in the statistical prediction of California earthquakes?
What physical/geochemical measurements and observations are used to forecast or predict California earthquakes?
Why are crustal deformation studies important in earthquake prediction?
Which are some of the earthquakes precursor events that can be measured to predict earthquakes? / What are the causes of earthquake precursor phenomena?
How reliable are earthquake precursor events in predicting earthquakes?
How will precursory phenomena help predict earthquakes in the future?
What is "Dilatancy" and why the crust of the earth near a fault deforms before an earthquake?
How are changes in the tilt of the ground used to predict earthquakes?
Why are strain measurements made along active faults?
How are changes in the strain and slip along faults used in earthquake prediction?
How reliable are strain measurements in earthquake prediction?
Why are slip rate measurements made along active faults?
Why are fault creep measurements made? How is fault creep measured?
How are past earthquakes dated with use of slip rates?
Why are measurements of fault creep along active faults significant in predicting earthquakes in California?
How are trees used to date earthquakes and measure past ground movements along faults?
How is the water level of wells affected before and after an earthquake?
How can wells act as seismometers to measure earthquake waves?
Why is hydrogen being monitored in the prediction of earthquakes?
How is radon gas used in earthquake prediction?
Can clouds be used in earthquake prediction?
What is the Load/Unload Response Ratio (LURR) method of earthquake prediction?
Can animal behavior be monitored to predict earthquakes?
How animal behavior has helped in the prediction of some earthquakes in China?
How is animal behavior research in China expected to help in the prediction
of future earthquakes?
How can research in animal behavior help design sensitive seismic sensors
that could be used in short term earthquake prediction?
How can animals be used in an operational earthquake warning system?

ORDER BOOK RETURN TO TOP

7. How is California's earthquake risk determined and evaluated?

What are the earthquake risk zoning categories? / How is earthquake risk determined?
How does the earthquake risk vary by location?
How are statistical techniques used in earthquake risk analysis?
How is earthquake risk mapped and zoned? / What is microzonation of the earthquake hazard? / Why is it important to determine and evaluate the earthquake risk in California?
Why is mapping of faults and studies of past earthquakes important in evaluating the earthquake risk in California?
Which is the law that requires earthquake-resistant design and construction for all public schools in California?
What are the Alquist-Priolo Act's criteria for developing seismic zonation of the earthquake hazard in California?
How did the Loma Prieta earthquake help evaluation of seismic risk?
How did the 1994 Northridge earthquake affect changes of the Uniform Building Code?
Why is detailed mapping and zoning (microzonation) of the earthquake risk critical for certain areas in California?
How do computer models help evaluate the earthquake risk?

8. The faults of California - Do you live near a dangerous fault?

How was California's Fault Zone formed?
How were California's faults created?
What types of faults exist in California?
What is the San Andreas Fault System?
Major faults of Northern California
Northern San Andreas Fault
Eureka and Cape Mendocino to Bodega
Bodega to Los Gatos (San Francisco and Bay segment); Los Gatos to Cholame
What is the seismicity of the northern segment of the San Andreas Fault System?
Major faults of Northern California
Hayward Fault
Calaveras and Paicines Faults
Pleasanton Fault
Sargent Fault
Green Valley, Rodgers Creek, Maacama, Healdsburg, Rinconada, Greenville,
Cordelia, West Valley, Concord, Antioch, and Alexander Valley Faults
Green Valley Fault
Concord Fault
Antioch Fault
Alexander Valley Fault
Fresh Water Fault
Rogers Creek and Healdsburg Faults
Pilarcitos, Seal Cove, San Gregorio and Hosgri Faults
Owens Valley Fault
Major faults of Southern California
San Andreas Fault - Cholame to Cajon Pass
San Andreas Fault - Cajon Pass to the Mexican Border
White Wolf Fault
Cucamonga Fault
San Jacinto Fault System (Glen Helen, Claremont, Casa Loma, Clark, Buck Ridge,
Coyote Creek, San Felipe Hills, Imperial, Superstition Hills and Superstition
Mountain faults)
Nacimiento Fault
Santa Ynez Fault Zone (Santa Ynez, Mission Ridge, Mesa and Lavigia faults)
Faults in the Los Angeles Area
Newport-Inglewood Fault Zone
Norwalk Fault
Whittier Fault
San Fernando Valley Fault
Sierra Madre Fault Zone
San Fernando Fault (Sylmar and Tujunga segments)
Raymond Hill Fault
Northridge Hills Fault
Elsinore Fault
Imperial Fault
Submarine Faults

9. The largest historical earthquakes of California

Larger Earthquakes in California from 1769 to 2000
Earthquake of 28 July 1769
Earthquake of 8 December 1812
Earthquake of 21 December, 1812
Earthquake of 10 June 1836
Earthquake of June 1838
Earthquake of 19 January 1857 (The Great Fort Tejon Earthquake)
Earthquake of 3 July 1861
Earthquake of 1 October 1865
Earthquake of 8 October 1865
Earthquake of 21 October 1868
Earthquake of 26 March 1872 (The Great Owens Valley Earthquake)
Earthquake of 11 April 1885
Earthquake of May 1889
Earthquake of 24 February 1892
Earthquake of 19 April 1892
Earthquake of 30 March 1898
Earthquake of 22 July 1899
Earthquake of 25 December 1899
Earthquake of July 1902
Earthquake of 18 April 1906: (The Great San Francisco Earthquake)
Earthquake of 19 September 1907
Earthquake of 1 July 1911
Earthquake of 22 June 1915
Earthquake of 7 October 1915
Earthquake of 21 April 1918
Earthquake of 31 January 1922
Earthquake of 29 June 1925
Earthquake of 20 August 1927
Earthquake of 4 November 1927
Earthquake of 6 June 1932
Earthquake of 10 March 1933 (The Long Beach earthquake)
Earthquake of 16 May 1933
Earthquake of 2 October, 1934
Earthquake of 18 May 1940
Earthquake of 30 June 1941
Earthquake of 14 November 1941
Earthquake of 4 December 1948
Earthquake of 21 July 1952 (The Kern County Earthquake)
Earthquake of 23 October 1955
Earthquake of 8 April 1968
Earthquake of 9 February 1971
Earthquake of 1 August 1975
Earthquake of 15 October 1979
Earthquake of 2 May 1983
Earthquake of 24 April 1984
Earthquake of 1 October 1987
Earthquake of 10 June 1988
Earthquake of 27 June 1988
Earthquake of 17 October 1989 (The Loma Prieta Earthquake)
Earthquake of 28 June 1991
Earthquake of 17 August 1991
Earthquake of 25 April 1992
Earthquake of 28 June 1992
Earthquake of 17 January 1994 (The Northridge Earthquake)
Earthquake of 1 September 1994
Earthquake of 19 February 1995
What were the magnitudes, intensities and locations of the large destructive earthquakes in California?

10. The Fort Tejon Earthquake of 1857 - what is its significance?

The January 9, 1857 Fort Tejon Earthquake
What were the earthquake's foreshocks and aftershocks?
What were the intensities of the ground motions?
What were the earthquake's rupture, displacements and other surface effects?
What were the death toll and damages?
What was the significance of the 1857 earthquake for future destructive earthquakes in the area?

11. The Great San Francisco Earthquake of 18 April 1906 - What is its significance?

The Great San Francisco Earthquake of 18 April 1906
What were the earthquake's rupture and ground displacements?
How strong were the ground motions and earthquake intensities?
How much destruction did the Great Fire Do?
How Quick and Effective were the Recovery Efforts in San Francisco?
What were the casualties and damages?
What is the significance of the Great San Francisco Earthquake of 1906?
How did geologic conditions affect earthquake intensities?
Did the 1906 earthquake leave sufficient strain in the rocks which may cause another destructive earthquake in the Bay area?
What caused the seismic quietness after the 1906 earthquake?
What were the effects of the 1906 earthquake on the subsequent seismicity of the Bay Region and of Central California?

12. The 1989 Loma Prieta Earthquake - Was it the Big One?

Why is the 1989 Loma Prieta earthquake significant?
How strong was the Loma Prieta earthquake?
What were the Loma Prieta earthquake's major aftershocks?
What were the intensities and ground motions?
What was unusual about the Loma Prieta's rupture, displacements and other surface effects?
Did the Loma Prieta earthquake generate a tsunami?
How extensive was ground liquefaction in the Bay area?
What were the death toll and overall damages?
What was Loma Prieta earthquake's extent of destruction in the Bay area?
How extensive was the earthquake's damage in San Francisco?
What happened at the Candlestick Park?
What happened at the Nimitz Freeway?
What happened at the San Francisco-Oakland Bay Bridge?
What was the extent of damage in the region south of San Francisco?
What relief and recovery efforts were undertaken?
Was the Loma Prieta earthquake the long awaited Big One?
What is the significance of the Loma Prieta Earthquake for future destructive earthquakes in the Bay Area?
How did the Loma Prieta event relate to past earthquakes?
What is Loma Prieta's significance for future destructive earthquakes in the Bay area?

13. The Northridge Earthquake of 1994 - What was learned from it?

The Earthquake of 17 January 1994 (Northridge Earthquake)
Why is the 1994 Northridge earthquake significant?
What were the death toll and damages?
Which are the dangerous faults of San Fernando Valley?
What was the rupture of the fault that caused the 1994 Northridge Earthquake?
What was unusual about the 1994 Northridge earthquake's intensities and ground motions?
Why valleys, like San Fernando, are more susceptible to the earthquake hazard?
What was learned from the 1994 Northridge earthquake's ground motions, surface effects and damages?
How does the 1994 Northridge earthquake compare to the 1971 San Fernando Earthquake?
What retrofit programs and building code changes were established as a result of the Northridge earthquake?
What are the implications of the Northridge earthquake for future destructive events in the Los Angeles Metropolitan area?

14. Can California Earthquakes be Controlled or Prevented?

What type of man-made earthquakes have been observed?
What do field and laboratory experiments indicate?
What research has been proposed for control of earthquakes in California?
What are some of the social and economic implications of earthquake control measures?
Will control of California earthquakes be feasible in the future?

15. California's Tsunami Threat - Will the Big One generate a destructive tsunami?

What destructive tsunamis have been in United States and worldwide?
Tsunami - Some Basic Concepts
What is a tsunami?
What is the origin and meaning of the word "tsunami"?
Is a tsunami the same thing as a "tidal wave"?
Is a tsunami the same thing as a "seismic sea wave"?
What are the causes of tsunamis?
Where are tsunamis more frequently generated?
How do earthquakes generate tsunamis?
How big are the earthquakes that generate tsunamis?
How volcanic explosions generate tsunamis?
How landslides generate tsunamis?
Can asteroids and meteorites cause tsunamis?
What is the height of a tsunami in the deep ocean?
How does tsunami energy travel across the ocean and how far can tsunami waves travel?
How fast do tsunamis travel in the deep ocean?
Why cant' tsunamis be seen at sea or from the air?
What happens when a tsunami reaches the shore?
How high can tsunamis reach?
What is the tsunami runup?
What kind of earthquakes generate large tsunamis?
What determines how destructive a tsunami will be locally and at distant shore?
The Tsunami Threat of California
How quickly will a tsunami generated in Alaska or the Aleutian islands reach California?
What is the history of tsunamis in California?
How frequent are tsunamis in California?
What is the tsunami threat from local California earthquakes?
What kind of tsunami did the Cape Mendocino earthquake of April 25, 1992 generate?
Did the 1989 Loma Prieta earthquake in California generate a small tsunami?
What kind of tsunami did the Santa Barbara earthquake of November 4, 1927 generate?
What kind of tsunamis did the Santa Barbara earthquakes of 1812 generate?
What are some of the conflicting reports about the 1812 Santa Barbara tsunami?
What is the tsunami threat in California from distant earthquake sources?
What were the effects of the 1964 Alaska tsunami in California?
How was Crescent City affected by the tsunami waves of the 1964 great Alaska earthquake?
What is California's tsunami threat from an earthquake on the Cascadia Subduction Zone?
How will California be affected by a tsunami originating from an earthquake on the Cascadia Subduction Zone?
What is California's overall tsunami threat?
Will the Big One generate a destructive tsunami in California?
What is the International Tsunami Warning System?
How does the Tsunami Warning System work?
What are the capabilities and the limitations of the Tsunami Warning System?
How are tsunami warnings disseminated in California?
How effective is the Tsunami Warning System in California?

16. Where in California Will The Big One Strike?

Why and how do scientists study the faults where past big earthquake have occurred?
What kind of research is going on presently?
What does the geographical distribution of the larger earthquakes on the San Andreas fault system indicate?
What do past earthquake clustering patterns and movements near and away from the San Andreas fault suggest?
What does the absence of small earthquakes from the San Andreas segments of the 1857 and 1906 events indicate?
Where are the present seismic gaps on the San Andreas fault system?
Where are seismic gaps in the Bay Area where additional earthquakes will occur?
What has been learned from measurements of ground movements?
What do past earthquake ground movements reveal?
What do measurements of aseismic creep imply?
What does the fault break of the 1857 earthquake suggest?
Where are the present locked segments of the San Andreas Fault?
What does the seismic quietness of the San Andreas segments of the Carrizo Plain and the Mojave signify?
What does the higher level of seismicity in the Big Bend area of the San Andreas reflect?
What is happening presently at the southern end of the 1857 earthquake rupture of the San Andreas fault?
What do the differences in earthquake depths convey?
What was learned from the studies of the Palmdale uplift?
Where are the sites of future large earthquakes in Northern California?
Was the 1989 Loma Prieta earthquake the one expected, or is there another one coming?
Where are the sites of future large earthquakes in Southern California?
Where in California will the Big One most likely strike?

17. When will the Big One strike?

How often do earthquakes occur worldwide?
What is the global frequency of earthquakes of any given magnitude?
What is the global frequency of larger earthquakes?
Can Plate Tectonics help estimate when earthquakes will occur in California?
Why and how past seismic activity is studied to determine when large earthquakes will strike again California?
Why are past earthquakes studied?
How are past earthquakes studied?
What do clues from past earthquakes reveal?
How are measurements of strain used to estimate when large earthquakes will occur in the future?
Did the Parkfield Experiment help in the prediction of the Big One?
How often and where earthquakes can be expected in Northern California?
What does the pattern of renewed earthquake activity in Northern California indicate?
When will moderate earthquakes occur again in the Bay Area?
Is a major earthquake highly likely to occur in Northern California?
What does the pattern of past earthquake activity in Southern California indicate?
How often and where major earthquakes can be expected in Southern California?
Is a major earthquake highly likely to occur soon in Southern California?
Will the Big One Strike California Unannounced?
Will small or moderate earthquakes proceed the Big One?
Will precursory events and phenomena herald the Big One's arrival?
When will the Big One strike?
How often and where major earthquakes can be expected to strike along the San Andreas Fault?
What is the significance of the recent increase in earthquake activity in the Bay Area?
Do studies of strain in Northern California indicate when the Big One will strike?
What is the Probability of Occurrence of Major Earthquakes in California?
When will the Big One strike Northern California and the Bay Area?
When will the Big One strike Southern California?

ABOUT THE AUTHOR ..................................................................... QUESTIONS? email for a copy of the book.

© 2002 George Pararas-Carayannis - All Rights Reserved

The Big One - The Next Great California Earthquake

Now available from Amazon, Barnes and Noble and other major bookstores.

                                      ABSTRACT


The Bohai Sea borders northeastern China's most populous and highest economic value coastal areas where several megacities are located. Critical infrastructure facilities exist or are under construction, including a nuclear power plant and super port facilities. Large reserves of oil have been discovered and a number of offshore oil platforms have been built. The extent of development along coastal areas requires a better assessment of potential tsunami risks. Although tsunamis do not pose as much of a threat as earthquakes in this region, locally destructive tsunamis have been generated in the past and future events could have significant impacts on coastal populations and China's economy, particularly because most of the development has taken place in low-lying regions, including river deltas. The present study examines the geotectonics of the Bohai basin region, the impact of past historical events, and the potential for local tsunami generation from a variety of direct and collateral source mechanisms triggered by intra plate earthquakes. More specifically, the present study examines: a)major active faults bounding the Bohai Basin; b) the resulting crustal deformation patterns of tectonic structures that have resulted in catastrophic earthquakes in recent years; c) the basin-wide extension - with local inversion - extending into the Bohai Sea that generated tsunamigenic earthquakes in 1888 and 1969; and d) deformational future seismic events with the potential to generate local tsunamis directly or by collateral mechanisms of folding, en-echelon bookshelf failures, or from destabilization/dissociation of structural accumulations of gas hydrate deposits within the basin's thick sedimentary stratigraphic layers.

1. INTRODUCTION


The Bohai Sea (also referred to as the Bohai Gulf or Bay, or just the Bo Hai) is a semienclosed coastal, shallow sea on the northeastern coast of China. The gulf is formed by the Liaodong Peninsula to the northeast and the Shandong Peninsula to the south (Fig. 1). It has a mean depth of about 20 m and a maximum depth of about 70 m near the northern coast of the Bohai Strait where it connects with the Yellow Sea (Fig. 2). Bo Hai consists of three bays: Laizhou Bay to the south, Liaodong Bay to the north, and Bohai Bay to the west. Major rivers, the Huang He, the Liao He, and the Hai He empty into Bo Hai. The Bohai Sea borders northeastern China's most populous and highest economic value coastal areas where several megacities are located in developed regions of Shandong, Hebei, Liaoning and Tianjin Province. Dalian, on the the eastern shore of Liaodong Peninsula of Liaoning Province, is an example of such a developing coastal megacity.

Figure 1. Bohai Sea, NE China.


Critical infastructure facilities exist or are under construction throughout the region. Currently, China has nine nuclear generators in commercial operation along its eastern coasts. The first nuclear power plant in the northeast - the Hongyanhe Nuclear Power Plant - is being constructed at the Donggang Town of Wafangdian City, in Liaoning. Furthermore, large reserves of oil have been discovered and a number of offshore oil platforms have been built or are under construction. The extent of development along the coastal areas of the Bohai Sea requires a better assessment of potential tsunami risks. Although tsunamis do not pose as much of a threat as earthquakes in this region, locally destructive tsunamis could be generated in the future that could have significant impacts on the coastal populations and the economy of China, particularly because most of the development has taken place in low-lying regions, including river deltas. The present study examines the geotectonics of the Bohai Basin region, the impact of past historical events and evaluates the potential for local tsunami generation from a variety of direct and collateral source mechanisms triggered by earthquake, landslides or other collateral occurrences.

Fig. 2. Bathymetry of the Bohai Sea

2. SEISMOTECTONIC SETTING OF THE BOHAI BASIN AND SEA.

 The collision of India with the Asian mainland during the earliest Eocene (~50 Ma) has resulted in the growth of the world's largest orogenic belt - the Himalayas and the associated Tibetan plateau. The seismicity of the entire region is the result of extension caused in part by crustal extrusion of Southeastern Asia (Tapponnier and Molnar, 1977; Peltzer and Tapponnier, 1988; Pararas-Carayannis, 2008d). China's seimotectonic evolution is characterized by the merger of several microcontinents throughout the entire Phanerozoic (Zhang et al., 1984; Hendrix and Davis, 2001; Yin and Nie, 1996). The collision and associated convergence and extension have created 64 major tectonic zones in China, which can be subdivided into a smaller number of tectonic "regions" (Davies et al. 2001; Zhang et al., 1984).

The seismotectonic setting of eastern China is complex. Most of the large earthquakes in the region are associated with a mechanism of eastward extension that results in shallow crustal mass transfer. The extension process was initiated by early Tethyan Torsion and subsequent Sinian Torsion which continued during the Cenozoic (Fig. 3).

Fig. 3. Tethyan Structure of Eastern China and Adjacent Seas

The Bohai Basin was formed during the Late Quaternary to the east of the Cenozoic rift basin of North China and underwent compound and complex tectonic events during its formation and development (Ye, et al., 1985; Hellinger et al, 1985). The Basin is an apparent collage of island arcs and possible microcontinental blocks on the Mongolian accretionary fold belt and has a complex seismotectonic setting (Davis et al., 2001). It covers an area of about 200,000 km2. Two different deformational mechanisms have been proposed for its Cenozoic formation (Castellanos & Mann, 2005).

The first mechanism postulates a two-stage extension consisting of Paleogene rifting in a WNW-ESE direction followed by Neogene thermal subsidence. The two-stage rifting mechanism is attributed to the combined rollback of the subducted Pacific plate beneath the Asian continent, lithospheric extension of the overriding continental plate, and to thermally-driven, regional subsidence (Ye et al., 1985). The second postulated mechanism pertains to a more localized Cenozoic pull-apart basin - formed at a right-step in a right-lateral shear system parallel to the Asian continental margin (Allen et al., 1997).

Either of the postulated evolutionary mechanisms of pull-apart rifting or subduction/rollback could account for the extensive deformation that has taken place in the Bohai Basin and has created the recent predominent strike-slip faulting and the right-stepping pull-apart control on a younger sag section. Either mechanism can account for the significant and evolving structural changes and the formation of dense seismic zones in the Bohai Basin, that can generate tsunamis.

Most of the numerous strike-slip and normal faults on land in the Liaoning, Beijing, Tianjin, Hebei and Shandong Provinces are active structures responsible for a number of major destructive earthquakes in the past. The earthquakes have occurred along numerous active faults that bound the Basin. The Bohai Sea is part of this inner-land sea basin.

Fig. 4. Bohai Sea Faults - Recent (red circles) and Historical (green circles) Earthquakes (Section of Modified Missouri University Graphic)

Similarly, the geotectonics of the Bohai Sea are complex. Regional compressive stresses have formed a series of active tectonic zones and a group of conjugated shear fracturing systems on land which extend into the sea. Since the Oligocene period, there has been active subsidence in the middle part of the Bohai Sea, forming an extensive depression known as "Bozhong" (Yu et al., 1995). This is the area that is rich in oil. The extensive subsidence has been caused by the superimposition of local tensional stresses produced by the left-lateral strike-slip on the Beijing-Penglai seismogenic zone, the right lateral strike-slip on the Yingkou-Weifang fault zone and the activity of the pull-apart structural system in the eastern basin, as well as by the uplift of the deep mantle (Xu et al, 2004). The major part of this depression in the northwest quadrant is bounded by the north-west trending Beijing-Penglai fault zone and the north-north-east trending Tan-Lu fault zone (Xu et al, 2004) (Fig. 4, Fig.5).

3.  SEISMICITY OF THE BOHAI BASIN AND SEA

The long-term crustal deformation patterns in the Bohai Basin and Sea - as determined from GPS measurements (Chen et al., 2007) - exhibit a relatively complete left-lateral strike-slip movement along the active fault zone, although there is also some evidence of reverse type of faulting movement that could be significant for tsunami generation. Most of the recent small and large earthquakes in the Bohai Basin had ruptures with prominent NE orientation, although, further north, there is also a seismic dense zone that has a NW direction (Fig. 5). However, studies of crustal deformation by stages (Chen et al., 2007) also indicate that a series of NE-trending large-scale, anomalous gradient zones have appeared along the Zhangjiakou-Bohai Sea fault zone. The seismicity of the basin is stronger south of the 39th parallel - and this is the area where most of the larger earthquakes have occurred in the past. Almost all of the dense seismic zones that can produce strong earthquakes are concentrated in this southern part of the Bohai Sea (Wang, 2007). As the historic record indicates such shallow seismic activity near densely populated areas as Haicheng or Tangshan can be extremely damaging. Also, such earthquakes can generate local tsunamis.

Fig. 5. Major seismotectonic and seismogenic fault zones in the Bohai Basin and Sea. Earthquake epicenters and focal mechanisms of recent earthquakes. Bathymetry based on GEBCO digital data base (modified graphic, after Yang & Xu, 2004 and Xu et al,. 2004).

According to historical records there have been 6 great earthquakes of Ms 8 and 16 major earthquakes of Ms 7 in the area, in the past 2000 years (Gu, 1983; Ma, 1988, Pararas-Carayannis. 2007). Generally, these large earthquakes have occurred along the major active faults that bound the Bohai Basin. Numerous strike-slip and normal faults on land in the Liaoning and Hebei Provinces are the predominant active structures where very destructive earthquakes occurred more recently.

As previously indicated, the fault-plane solutions of earthquakes in the area usually show right-lateral strike-slips with prominent NE orientation, although some had NW orientation with a normal dip-slip component.

Reccurrence frequencies also vary. Although earthquake recurrence intervals along any individual fault in the Bohai Basin is relatively long (usually in the range of several thousand years), the composite recurrence interval for the whole region is in the order of a few decades (Ma et al., 1989). Five earthquakes with Ms > 7 have occurred in this region between 1966 and 1976. These earthquakes resulted in hundreds of thousands of casualties and in significant economic damage. Worse of all was the July 28, 1976 Tangshan earthquake in the Hebei Province.

The complex intraplate earthquakes in North China are presently being studied by US institutions funded by the National Science Foundation’s PIRE (Partnerships for International Research and Education) in close collaboration with numerous Chinese institutions. The studies include integration of seismic imaging of earth structure, geodetic measurement of crustal deformation, paleoseismic reconstruction of earthquake histories, and geodynamic computer simulations. Such studies are expected to provide a better understanding as to the causes of large earthquakes in Northeast China, such as the 1976 Tangshan event that leveled the city and caused the greatest death toll in recent history.

3A. Historical Bohai Basin Earthquakes and Tsunamis.


A review of recent and historic earthquakes is relevant in assessing the potential for tsunami generation in the Bohai Sea. As stated, six earthquakes of Ms 8 and sixteen earthquakes of Ms 7 occurred in the past 2,000 years - some of which were tsunamigenic (Wang J., 2007; Pararas-Carayannis, 2007). The records are not clear, particularly for the older events.

 According to these records, tsunamigenic earthquakes occurred in 1548 and in 1888 (Fig. 6). Other possible tsunamis may have been generated by earthquakes in 173 and in 1597, although the latter is doubted as being a strong event (Wang, 2007) - thus the reported tsunami may have been generated by a collateral mechanism. Many more tsunami must have occurred but have remained undocumented.

Fig. 6. Historical earthquakes in the Bohai Sea and in Northeast China.

The September 22, 1548 earthquake had an estimated magnitude M 7.0 and epicenter at about 121.0 E. Its latitude is not known but it is believed that it occurred at sea. The earthquake of October 6, 1597 had an estimated magnitude of M 7.0 and epicenter at about 38.5 N. 120.0 E. The most significant tsunamigenic earthquakes occurred in 1888 and in 1969. The tsunamigenic earthquake of June 13, 1888 had an estimated magnitude M 7.5 and epicenter at about 38.5 N, 119.0 E. (Wu and Zang, 1989).

The most recent tsunamigenic earthquakes in the Bohai Sea occurred on July 18, 1969.

On February 4, 1975, and on July 28, 1976, there were major earthquakes in the Bohai Basin. The 1975 Haicheng and the 1976 Tangshan earthquakes were extremely destructive. The two 1976 Tangshan earthquakes in Hebei Province resulted in the greatest death toll in recent history. Their impact on land around Tangshan has been described adequately in the literature but there has been no information on whether a tsunami was generated. However, the seismic intensities, the aftershock distribution and the observed crustal movements of the Tangshan quake,s indicate that the coastal region of Bohai Bay was impacted, and therefore a local tsunami must have been generated but not reported. Apparently, the degree of earthquake destruction on land shrouded the damaging effects and impact from a tsunami.

The Earthquake and Tsunami of July 18, 1969


The shallow tsunamigenic earthquake of July 18, 1969 in the Bohai Sea had an estimated Richter magnitude of M 7.4 and epicenter at 38.2 N, 119.4 E. Its strike was f=195°, its dip angle was d=85 degrees and its slip angle l=65 degrees. The seismic moment was M o=0.9x1019, its rupture length was L=59.9km and the rupture propagation speed was estimated at Vr=3.5km/s; The angle from the strike to the propagation direction were n wL R =160 (Wu & Zang, 1989, 1992) (Fig. 7). The quake generated a small tsunami with a height ranging from 1~2 m. above normal tide level. The tsunami was responsible for losses in the coastal region near Tangshan in the Hebei Province, but no details are available. Also, no details are available as to the height of the tide at the time of the earthquake and whether the 1 to 2 meter reported tsunami occurred at high or low tide (Pararas-Carayannis, 2008a).



Fig. 7. Epicenter and major aftershoks of the Earthquake of July 18, 1969 in the Bohai Sea.

The Haicheng Earthquake of February 4, 1975 in the Liaoning Province


The Haicheng earthquake of February 4, 1975 had magnitude M=7.3 and epicenter at 40.6 N, 122.8 E (Chen Y. et al. 1976, Zhu and Wu, 1982; Wang et al., 2006; Pararas-Carayannis, 2008b). The region where it occurred is characterized by an active structural system which extends, not only in the Haicheng-Yingkou region but, also along the entire South Liaoning Province. The seismic activity on this structural system is mostly concentrated along a belt bounded by the Liao River depression and the Liaodong Peninsula uplift (Earthquake Administration of Liaoning Province). The activity of the tectonic structure is oriented in NW direction and has formed a series of active faults as well as new folds. Active faults in the region with a NE orientation include the Niuju-Youyangou, the Jinshanling, the Shuangtaizihe-Zhaojiabaozi fault and the Jinzhou. Other faults in the area include the Dayanghe, the Ximuhe, the Zhuanghe and the Yalujiang (Earthquake Administration of Liaoning Province).

Fig. 8. Epicenter, major aftershocks of the Earthquake of February 4, 1975 near Haicheng, Liaoning Province.

The epicenter of the Haicheng earthquake was located in the region where faults with the NE and NW directions converge, but do not intersect. Stress along the Dayanghe fault - which has a NW orientation - was apparently released by this earthquake (Figure 8 ). Although far from the sea and thus did not generate a tsunami, the same seismic zone extends into the Bohai Sea, so there is the potential for future tsunami generation if an earthquake occurs closer to the coast of Liaodong Bay or on the Yellow Sea coast of Liaoning Province.


As indicated, the coseismal intensity lines, the aftershock distribution as shown in Figure 8 and subsequent surveys of crustal displacement
patterns indicate that the main rupture plane of this event involved a left-lateral strike slip with a NWW orientation (strike = 288°, dip = 78° N, rake = 342°). Subsequent studies of the seismic waves estimated the seismic moment to be 3 x 1026 dyne-cm and the source duration 7 sec. Since the fault length of this earthquake was about 22 km, the observed P waves supported a rupture velocity estimate of about 3.2 km/sec. The average dislocation was computed to be 2.8 m and the stress drop about 53 bars (Cipar, 1979).


The July 28, 1976 Tangshan Earthquakes in Hebei Province


Two earthquakes on July 28, 1976 in the Hebei Province of northeastern China struck and totally destroyed the city of Tangshan (Pararas-Carayannis, 2008c). The main quake had magnitude of M 7.8 (later revised to Mw 7.6) and epicenter at 39.4 N. 118.0 E. (Fig. 9).

Fig. 9. Epicenter, major aftershocks of the Earthquake of July 28, 1976  near Tangshan, Hebei Province

Many sources listed it as 8.2 on the Richter scale, but Chinese government's official sources revised it to 7.8. It was followed by a major 7.1 magnitude destructive aftershock, some 15 hours
later, that had a magnitude of M 7.1 and epicenter at 39.7 N., 118.5 E. (Mei, 1982; Pararas-Carayannis,  2008c).

Both events were shallow (15 km) and occurred near the coast of Bohai Bay. Many strong aftershocks followed the main earthquake, two of which had magnitudes of 6.0 or more. In the following days, there were many more aftershocks ranging in magnitude from 5 to 5.5. Several months later, on Nov 15, 1976, a magnitude 6.0 earthquake struck again the same region (Pararas-Carayannis, 2008c). The intensities of the 1976 earthquake’s ground motions were extensively surveyed and reported (Figure 10). In the epicentral area the intensity was estimated at XI (State Seismological Bureau). The region with intensity X was reported as being elliptical in shape and covering a total area of about 370 km2.

The region of intensity of IX was reported as being rhombic in shape, also trending in a northeast direction and covering an area of about 1,800 km2. The region of intensity VIII extended in a southeastward direction and covered an area of about 7,300 km2. The region of intensity VII was reported to cover an area of about 33,000 km2.

Fig. 10. Intensities of Ground Motions of the Tangshan Earthquake (after Wang Fang 1976, State Seismological Bureau of China). Postulated Tsunami Generating Area.

The zone of maximum destruction was estimated to be about 47 square kilometers. It included the city of Tangshan and the southern suburb along the Beijing-Shanhaiguan railway. Over a four-by-five mile area the devastation of the city was nearly total. About ninety-three percent of residential buildings and seventy-eight percent of commercial and industrial buildings in Tangshan were destroyed. The actual death toll from this earthquake may never been known with certainty. According to official government accounts the earthquake killed 242,769 people and severely injured another 169,851. However, based on the density of the population and the extent of destruction, these figures have been disputed. At the time Tangshan had 1.6 million inhabitants. Since the earthquake destroyed ninety three percent of all residential buildings, the death toll was estimated to be three times greater than what was reported - ranging from 655,000 to 779,000 people. The extremely high death toll makes the 1976 Tangshan event the second worse earthquake disaster in recorded history. The most destructive earthquake ever, occurred four centuries earlier in 1556 in Shaanxi, China. It is estimated that the 1556 earthquake killed 830,000 people. Another earthquake in the Gansu region in 1920 had killed about 200,000.


The 1976 earthquake ruptured a five-mile (8 km) section of a 25-mile strike-slip fault with a north-northeast orientation that passes through the city Tangshan. The fault is part of an extensive strike-slip fault system, known as Tancheng-Ljiang, or Tan-Lu. This system extends in a north-northeast direction for more than 3,200 miles from the north bank of the Yangtze River in eastern China to the west across the Russian border.

Specifically, the earthquake occurred at the junction of the YanShan fold-fault zone and the Cangdong fault zone. The YanShan fold-fault zone runs in an east-west direction and lies north of the Tangshan region. To the south, there are several sub parallel northeast-trending fault zones known as the Shanxi fault depression structural belt, the Taihang piedmont fault zone, the Cangdong fault zone, and the Tangcheng-Lijiang fault zone. According to the scientific literature, each of these zones has produced several earthquakes. Several episodes of uplift and other anomalous variations along different segments of the fault zones that comprise the Yan Shan Seismic Belt have been reported.

There were substantial ground movements along the segment of the fault that ruptured. Along the west side the ground moved laterally for about five feet in a north/northeast direction, sub parallel to the major axis of the meizoseismic zone. However, in some areas, horizontal ground displacements of up to 7 meters were subsequently measured. On the eastern side of the rupture, the ground block tipped upward near the south end and downward at the northern end. The quake's intensities, the aftershock distribution, the crustal displacements and the downward tilting at the southern end must have included a good portion of Bohai Bay, thus a local tsunami must have been generated.

4. POTENTIAL FOR FUTURE TSUNAMI GENERATION IN THE BOHAI SEA


Tsunamigenic earthquakes have been generated in the past along active tectonic structures that crisscross the Bohai Sea. In spite of predominantly lateral strike-slip components that characterize most earthquakes in this region, destructive local tsunamis may be generated by a combination of direct and collateral mechanisms that could involve upward and downward crustal block movements, folding of thick sedimentary layers, landslides, destabilization of gas hydrates deposits and mass sediment flows.

4A. Potential for Tsunami Generation from Geotectonic Mechanisms


Analysis of relations between structures and stratigraphic units along cross sections in the Bohai Basin using broadband instrumentation (Zhao & Zheng, 2005), infers the occurrence of past, multiple, deformational seismic events and confirms the basin-wide extension with local inversion which extends extensively into the Bohai Sea. Furthermore, from studies of recent earthquakes in China (Pararas-Carayannis, 2007, 2008) and additional review of the literature on the evolution of Bohai Basin, it has become apparent that the principal regional compressive stresses from crustal extension in this region have a NEE-SWW orientation in the central part of the Bohai, in line with the Beijing-Penglai seismogenic zone but a NE orientation further offshore, in line with the Tan-Lu Fault (Fig. 4, Fig. 5). Counter clockwise drag is responsible for the apparent dextral torsion in this eastern region. Stresses from the crustal extension have formed a series of active tectonic zones and conjugated shear fracturing systems on land, as well as in the Sea.

According to recent literature (Chen et al., 2007), the Zhangjiakou-Bohai Sea seismotectonic zone controls the present-day strong earthquake activities in the region. Other major active tectonic zones include the northern section of the northeast trending Yingkou-Weifang and the Miaoxibei-Huanghekou-Linyi fault zones, and the northwest striking Beijing-Penglai fault zone, which intersect at the center of the Bohai Sea basin - as partly illustrated in Figures 4 and 5. These tectonic zones subdivide the Bohai Sea area into four secondary neotectonic areas, which are subject to a dominant horizontal, or nearly horizontal, compressive stress field in the direction NE60–90 degrees, while the tensional stress is in a NW30 degree direction (Chen et al., 2007). The long-term crustal deformation patterns in this region exhibit a relatively complete left-lateral strike-slip movement, but there is also some evidence of reverse type of faulting movement (Wang, T., 1988). Although poorly mapped, reverse faults, normal faults and strike-slip faults reach far into the Bohai Sea. Sea floor movements from earthquakes occurring along reverse and normal faults have the potential to generate tsunamis.


Fortunately, most of the earthquakes in this eastern region of the basin have relatively short ruptures, thus sea foor displacements would tend to be limited and tsunamis would be localized. For example, the 1976 Tangshan earthquake ruptured only a five miles (8 kms) along a 25-mile section of a strike-slip fault. Obviously, the multi-directional orientations of the highly fractured faults in this region create asperities which limit rupture length. However, the ground motions of the Tangshan earthquake, the distribution of intensities extending into the Bohai Bay and the observed upward movement of the ground block near the south end of the rupture, as well as the downward movemeny of the crustal block at the northern end, infer that anomalous disturbances of the sea floor can occur along coastal areas of Bohai Bay near Tangshan, as well as in areas further offshore. There were apparent gravity anomalies before and after the earthquake (Chen Y. et al. 1976). Similar ground movement anomalies have been associated also with other historical tsunamigenic earthquakes along faults bordering coastal areas of the Yellow and South China Seas.


Similarly, the 1974 Haicheng earthquake had a short rupture with a NW orientation along the Dayanghe fault. Its epicenter was located in the region where faults with the NE and NW directions converge, but do not intersect. Although far from the sea and could not have generated a tsunami, the quake was along a fault in the same seismic zone which extends into the Bohai Sea.

Thus, there is potential for future tsunami generation if an earthquake occurs closer to the coast of Liaodong Bay.
In brief, local destructive tsunamis can be generated by earthquakes along shear fractures in the Bohai Sea, but particularly along the NE-trending and more active tectonic zones south of the 39th parallel.

4B. Potential for Tsunami Generation from Collateral Mechanisms - Sedimentary folding and En-echelon structural failures.


As indicated, most of the earthquakes in the Bohai Sea involve primarily crustal movements with lateral, strike-slips which usually do not generate large tsunamis. However, the Bohai is loaded with sediments carried by major rivers such as Huang He, Luan He, Liao and Alu Jiang (Fig. 11, 12). The excessive sedimentation may be a significant factor for tsunami generation.

Fig. 11. Satellite photo showing the heavy load of sediments from major rivers flowing into the Bohai Sea.

Deformational seismic events - which apparently occur frequently - have the potential to generate local tsunamis directly or by collateral mechanisms of stratigraphic folding and/or by en-echelon bookshelf failures of the thick sedimentary layers, or by the triggering of submarine landslides. To assess such potential tsunami mechanisms, the structural and tectonic evolution of the Bohai Basin must be re-examined and evaluated.

Major rivers deposit large loads of sediments in the the Bohai and Yellow Seas and have created unstable slopes on the shelf that could become potential sources of landlside-generated tsunamis.



Fig. 12  Major rivers deposit large loads of sediments in the the Bohai and Yellow Seas and have created unstable slopes on the shelf that could become potential sources of landlside-generated tsunamis.

Apparently, geological structure played an important role in the development of palaeochannels in the North China Plain and in the offshore areas. Mountain uplift, subsidence of the plain, and tectonic movement of the basement since the Cenozoic, have interacted with the flashy fluvial regime involving high sediment loads and frequent channel changes (Xu et al, 1996). Over eons of time, the numerous rivers traversing the Bohai Basin have deposited great quantitities of sediments which have filled out full grabens or half grabens - bounded by conjugated shear fracturing systems - which extend into the sea. Thus, the tectonics of the region have influenced changes of the ancient river systems and channels - although now these channels are buried by sediments. Processes of channel development from present tectonic activity continue. Although the Bohai Sea is not a region near a zone of subduction, the predominent lateral compressive forces of earthquakes along faults that bound the buried grabens, can result in folding and/or in oblique-to-the-rupture bookshelf-types of failures within the thick layers of the loose surficial and the compacted, deeper sediments.

The deeper sedimentary layers are probably well consolidated but still prone to folding or en-echelon failure from the tectonic compressive forces, which could generate tsunamis in the manner illustrated by Figure 13. Subjected to similar forces, the surficial sedimentary layers would be more susceptible to slumping and landslides. Slumping or folding could generate local tsunamis. However, the potential for tsunami generation from submarine landslides would tend to be limited and localized, since the Bohai is a relatively shallow sea and the slopes are relatively gentle.


Fig. 13. Tsunami Generation by Compressive Folding of Deeper Sedimentary Layers in the Ductile Zone and En-Echelon and Bookshelf Faulting of Surficial Layers.

In brief, future tectonic movements associated with larger earthquakes in this region - and the compressive forces they generate - could interact with the now submerged fluvial regimes that contain high sediment loads and thus could generate massive sediment movements - even on relatively gentle bathymetric slopes. Such movements could contribute to local tsunami generation. Folding and en-echelon bookshelf type of failures of the deeper consolidated sediment layers could become collateral mechanisms for greater tsunami generation. Such collateral mechanisms can contribute significantly to the generation of destructive local tsunamis anywhere in the Bohai Sea, but particularly south of the 39th parallel, where the denser seismic zones are concentrated, the seismicity is stronger, and greater sedimentation from the Huang He river (Yellow River) has occurred.

4C. En-Echelon Structural Failure Within  Consolidated Sedimentary Layers - Mechanism of Tsunami Generation.


As indicated, stress and tectonic displacements caused by an earthquake along a fault - whether strike-slip, normal, or inverse - in a multi-layered sedimentary environment such as that of the Bohai Sea, can induce structural failures that may be oblique to the overall fault orientation and thus result in collateral displacements, en-echelon structural failures, and bookshelf faulting of the seafloor that could enhance tsunami generation. Shear cracks along a fault may be vertical and planar but may result in splits into two or more interacting sections at a stratigraphic interface with different density and stress drop - depending on rigidity contrasts between the adjoining media.

The deeper sediments along such faults in the Bohai Sea may be characterized by different elastic parameters, depending on the degree of hydration, particle size distribution and compaction densities. Structural inhomogeneities within these deeper, better-consolidated layers may result in a series of bookshelf type of structural failures, which will be oblique in orientation to the overall faulting trend. Oblique, en-echelon type of failures could result in multiple ruptures that could also affect the sediments of the upper layers - thus changing the spatial geometry and characteristics of the source area and the mechanism of tsunami generation. Slower rupture rates with different azimuthal orientation can be expected within these layers. Furthermore, net sea floor displacements can be expected to vary and the tsunami's directivity to be different from what may be inferred from fault orientation or focal plane solutions.

Fig. 14.  Stress concentration induced by strike-slip faulting across layer interfaces. (Modified Graphic http://hraun.vedur.is/ja/prenlab2final/img114.gif)

For example, the simplified mechanical/geometrical effects left by a model earthquake within a transform fault plane at the sedimentary discontinuity interphase have been extensively investigated by employing the "displacement discontinuity method" (Bonafede & Neri, 2000). Figure 14 illustrates a simple case of such stress-induced displacement discontinuity and the potential changes in the geometry and characteristics of the tsunami source. Additional investigations have dealt with the two-dimensional dynamics of shallow reverse type of faulting upon discontinuity interphases (Madariaga, ?).

However, in an actual multi-layered sedimentary environment such as that which exists in the Bohai Sea, the geometrical complexities and stress drop values can be expected to vary along planar strike-slip or reverse faults. Faulting in such an environment cannot remain planar. Strike-slip faulting at depth may be accompanied by en-echelon surface breaks in a shallow sedimentary layer - where the stress drop may be lower at the discontinuity interphase, while ductile deformation at depth may be accommodated by antithetic faulting in the upper brittle layer - enhanced with lower rigidity but higher stress - thus resulting in bookshelf faulting that can augment tsunami generation and alter tsunami directivity (Fig. 14). Such bookshelf failure of sedimentary layers are believed to have resulted in the augmentation and apparent directivity from the north (rather than from the west) when the tsunami of December 26, 2004 struck Aceh, in Sumatra. It is believed that similar bookshelf and en-echelon failures within subducted sediments were associated with the September 2, 1992 earthquake off the coast of Nicaragua and enhanced the tsunami runup (Pararas-Carayannis, 1992).

Indeed, studies of aftershock distribution of earthquakes around the world indicate extensive concentration of their focal depths along sedimentary bedding planes - which would also support that such failure mechanisms contribute to tsunami enhancement and differences in azimuthal tsunami source parameters (Figures 13, 14).

Similarly, en-echelon failures with elevated and depressed portions of ramp could alter the sea floor and contribute to tsunami generation (Fig. 15).

Fig. 15. Tsunami Generation by En Echelon Step Fault Displacement and by Sea Floor Changes with Elevated and Depressed Ramp Structure.

Therefore, we may conclude that such distribution of aftershocks - localized along sedimentary discontinuity layers - not only would indicate the asymmetric interactions between the original fault plane of an earthquake and the shalower sedimentary layers, but would also indicate that significant residual, compressive or tensile stresses can remain over the shallower portion of the fault surface, after the major shock and fault rupture. Thus, strong aftershocks of major or great earthquakes in such sedimentary environments could be significant in tsunami generation and could trigger, at a later time, collateral submarine landslides or other sea floor collapses and structural failures.


In brief, the potential for tsunami generationt in the Bohai Sea is exacerbated by the thick accumulation of sediments (in different states of consolidation) and the multi-layered stratigraphic distribution of sediments with different shear strengths, densities and rigiditites.  Folowing an earthquake, en-echelon, bookshelf type of failures with oblique directivity to the general strike orientation could impart greater tsunami energy and alter tsunami directivity. Thus, any mathematical modeling study must consider such complexities of source inputs for such environments of extreme sedimentation.

4D. Potential for tsunami generation from destabilization of Gas Hydrate deposits and mass sediment flows.

As indicated, the Bohai Sea is a region rich in oil and natural gas. Great offshore oil fields, such as the Shengli, the Dagang the Jidong, the Suizhong and the Chengbei, were discovered in recent years and are now being exploited. Numerous oil platforms, scattered in the Bohai, pump huge quantities of natural gas and oil which supply China's increasing energy needs. Apparently, there are also huge structural accumulations of natural gas hydrates (primarily methane hydrate) near known fault systems (Watson et al.,1987). Such gas hydrates must exist in different configurations below the sea floor and include massive thick solid zones, continuous layers, nodules, and widely disseminated interstitial material in the different sedimentary layers. Each of these types of hydrate accumulations may affect differently the seafloor stability. Such natural gas hydrate deposits may be transitionally unstable in shallow (first meters below seafloor) sediments in areas where seafloor temperature or pressure changes over time. Repetitive gas hydrate formation and decomposition are known to cause sediment deformation, slumps, gas blowout craters, and increase the rate of gas and oil venting to the water column (Milkov, 2002). Since collapse of hydrate-bearing sediments is accompanied by the generation of excess pore pressureand the release of amounts of methane gases, it is likely to cause a breakdown of offshore structures and slope failures. Furthermore, gas hydrate accumulations, if destabilized and dissociated by an earthquake's ground motions and the associated changes in pressure, could cause mass sediment flows - and thus generate local tsunamis (Max, 2002). Dissociation of gas hydrate in surficial sediments, as illustrated by Figures 16 and 17, could reduce substantially the shear strength of distinct layers and result in the formation of a thixotropic mass which could act as a slip surface for subsequent structural failure and downslope mass sediment flows.


Fig. 16. Tsunami generation by the destabilization and collapse of gas hydrate deposits in sedimenatry environments ( modified graphic of Center for Gas Hydrate Research http://geosystems.kaist.ac.kr/ERG-1.html

In brief, hydrate-bearing sediments in the Bohai Sea may destabilize spontaneously by an earthquake’s ground motions or slowly on their own without a triggering mechaniss. Often the mere pumping of oil or natural gas could result in destabilization. Often, gas production methods include depressurization, inhibitor injection, thermal stimulation, and their combinations, or intentional gas extraction from the hydrate itself.  The dissociation of the gas hydrate deposits by  earthquake ground motions, particularly near offshore oil platforms, could result in large scale slip and sediment mass flows and be a collateral mechanism for tsunami wave generation or enhancemnt. Combined with extensive surface ice during the winter months, local tsunami waves could possibly cause damage to oil rigs operating in the Bohai Sea, as well as to nearby coastal facilities, by the transport and impact of large pieces of floating ice. Given this scenario extensive damage could occur, even with tsunami waves of moderate height amplitude.


Fig. 17. Structural slope failure and potential tsunami generation from the  dissociation of gas hydrates (Modified graphic of the National Energy Technology Laboratory, U.S. Department of Energy (DOE)).

4E. Effects of Astronomical Tides and Ice on Potential Tsunami Destructiveness in the Bohai Sea.


The tides in the Bohai Sea are relatively high (Fig. 18). The tides are primarily dominated by semidiurnal (M2 and S2) and diurnal (K1 and O1) motions (Xu et al 1996). The range of tide heights varies significantly from a minimum of about 2 meters along the shores of Laizhou Bay, to 4.6 meters along the eastern coasts of the Liaoning Province on the Korea Bay, as much as 7 meters along the western coast of North Korea, and even as much as 9 meters further south along the coast bordering the Yellow Sea.

The large extent of the astronomical tide variation could have a signifincant effect if a tsunamigenic earthquake occurs at high or near high tide. For example, if a tsunami was generated at high tide, the eastern shore of Liaodong Peninsula of the Liaoning Province could experience waves that could be 4.6 meters higher than those generated at low tide. Thus, events occurring at high tide could be significantly more destructive. For example, the site where the cooling system of the Hongyanhe Nuclear Power Plant is located could be impacted by tsunami waves that could be 2.7 meters higher than waves generated at low tide.

Fig. 18.  Extent of astronomical tide height variation along coastal areas of the Bohai and Yellow Seas (Modified after Xu et al. 1996).

Similarly, the numerous offshore oil platforms that are scattered throughout the Bohai Sea may be susceptible to potential damage if a tsunami is generated in the region. As indicated, given the relatively shallow water depths and the abundant ice-infested waters of the region during the winter months, large pieces of ice carried by the tsunami waves could have a destructive impact. Although ice-induced forces on oil platfom structures and vibrations have been studied in the past (Zhang and Wang, 2008), the dynamic forces from ice carried by tsunami wave action have not been evaluated. The severity of the potential impact would depend on the design of the platform structures. Being more rigid, caisson-built oil platform structures would be expected to fare better than the more common, jacket-built type of oil platform structures which are lighter and weaker.

5. CONCLUSIONS

The Bohai Sea surrounds one of China's most populous and highest economic value regions. Recent earthquakes on land have had great impact. Tunamis do not pose as much of a threat, but locally destructive tsunamis could be generated in the future which can be expected to have more significant impact since most of the recent development has taken place along low-lying coastal areas where several megacities are located and infrastructure facilities exist or are under construction. In spite of predominantly lateral strike-slip components that characterize most earthquakes in this region, there is also evidence of reverse type of faulting movements. Although poorly mapped, reverse faults, normal faults and strike-slip faults reach into the Bohai Sea and earthquakes occurring along such faults can generate tsunamis.

Destructive local tsunamis may be generated by earthquakes along shear fractures in the Bohai Sea, but particularly along the NE-trending and more active tectonic zones south of the 39th parallel. Local tsunamis may be also generated by a combination of collateral mechanisms that could involve folding of thick sedimentary layers, landslides, destabilization/dissociation of gas hydrates deposits and mass sediment flows.

Future tectonic movements associated with larger earthquakes in this region could interact with the now submerged fluvial regimes that contain high sediment loads and thus could generate massive sediment movements. Folding and en-echelon bookshelf type of failures of the deeper consolidated sediment layers could become collateral mechanisms for greater tsunami generation, particularly in areas where denser seismic zones are concentrated, the seismicity is stronger, and greater sedimentation has occurred. Thus the potential for tsunami generation in the Bohai Sea is exacerbated by the thick accumulation of sediments and the multi-layered stereographic distribution of sediments with different shear strengths, densities and rigidities.  Following an earthquake, en-echelon, bookshelf type of failures with oblique directivity to the general strike orientation could impart greater tsunami energy and alter expected tsunami directivity.

Finally, dissociation of the abundant gas hydrate deposits by an earthquake ground motions, particularly near offshore oil platforms, could result in large scale slip and sediment mass flows. Combined with extensive surface ice during the winter months, local tsunami waves could possibly cause damage to oil rigs operating in the Bohai Sea, as well as to nearby coastal facilities, by the transport and impact of large pieces of floating ice.

6. REFERENCES

Bonafede, M.; Neri, A., 2000. Effects induced by an earthquake on its fault plane:a boundary element study. Geophysical Journal International, Volume 141, Issue 1, pp. 43-56, 2000.

Castellanos, Hugo and Paul Mann, 2005. Pull-Apart vs. Subduction Rollback Mechanisms For The Cenozoic Formation Of Bohai Basin, Eastern China
AGU Fall Meeting, San Francisco, CA. 2005.

Chen, Yun-Tai; Gu, Hao-Ding; Lu, Zao-Xun, 1976. "Variations of gravity before and after the Haicheng earthquake, 1975 and the Tangshan earthquake, 1976", Physics of the Earth and Planetary Interiors, Volume 18, Issue 4, p. 330-338.

Chen Guo-guang, Xu Jie, Ma Zong-jin1, Deng Qi-dong, Zhang Jin and Zhao Jun-meng, 2007. Recent tectonic stress field and major earthquakes of the Bohai sea basin, Acta Seismologica Sinica, Volume 17, Number 4 / July, 2004, pp.438-446, Published by Springer in Earth and Environmental Science, 2007.

Cipar John 1979, "Source processes of the Haicheng, China earthquake from observations of P and S waves", Bulletin of the Seismological Society of America; December 1979; v. 69; no. 6; p. 1903-1916.

Davis, G. A., Zheng, Y., Wang, C., Darby, B. J., Zhang, C., and Gehrels, G., 2001, Mesozoic tectonic evolution of the Yanshan fold and thrust belt, with emphasis on Hebei and Lianoning provinces, northern China: Memoir - Geological Society of America, v. 194, p. 171-197.

Earthquake Administration of Liaoning Province, Quan Yingdao, "An Earthquake of MS7.3 in Haicheng, Liaoning Province on February 4, 1975", World Data Center for Seismology, Beijing.

Hellinger, S.J., Shedlock, K.M., Sclater, J.G. and H. Ye, 1985. The Cenozoic evolution of the north China basin, Tectonics 4 (1985) 343–358.

Hendrix, M.S., and Davis, G.A., 2001, Paleozoic and Mesozoic tectonic evolution of central Asia: from continental assembly to intracontinental deformation: Boulder, Colo., Geological Society of America, vi, 447 p.

Science of Tsunami Hazards, Vol. 28, No. 1, page 63   (2009)
Keilis-Borok, V. I. and Soloviev, A., (Edis.), 2003. Nonlinear Dynamics of the Lithosphere and Earthquake Prediction. Springer-Verlag, Berlin-Heidelberg.

Ma, L. and Gao, X., 1996. The state of intensive monitoring and prediction at the Metropolitan Area before Asian Game in 1990. He, Y. N. (Ed.), The Selected Papers of Earthquake Prediction in China, Dedicated to the 30 th International Geological Congress, Seismological Press, Beijing, 255-259.

Madariaga, Raul, 2008?. Dynamics of shallow reverse faulting in 2D

Max, Michael D. 2002, Mass Flow in Marine Sediment: Physical Causes and Possible Examples from the Geological Record, Tsunami Society Symposium, Honolulu, Hawaii 2002.

Mei, S. R. (Ed.), 1982. Tangshan Earthquake in 1976. Seismological Press, Beijing (in Chinese, reviewed abstract in English).

Milkov, Alexei V. 2002, Global Distribution and Significance of Natural Gas Hydrate. Tsunami Society Symposium, Honolulu, Hawaii 2002.

Pararas-Carayannis, G., 1992. The Earthquake and Tsunami of 2 September 1992 in Nicaragua. Wepage Article: http://www.drgeorgepc.com/Tsunami1992Nicaragua.html

Pararas-Carayannis, G., 2007. Historical Earthquakes in China. Webpage Article: http://www.drgeorgepc.com/EarthquakesChina.html

Pararas-Carayannis, G., 2008a, The Earthquake and Tsunami of July 18, 1969 in the Bohai Sea, China. Webpage Article: http://drgeorgepc.com/Earthquake1969ChinaBohai.html

Pararas-Carayannis, G., 2008b. The Earthquake of February 4, 1975 in Haicheng, China. Webpage Article:http://drgeorgepc.com/Earthquake1975ChinaHaicheng.html

Pararas-Carayannis, G., 2008c. The Tangshan Earthquake of July 28,1976 in China. Webpage Article: http://drgeorgepc.com/Earthquake1976ChinaTangshan.html

Pararas-Carayannis, G. 2008d. The Earthquake of May 12, 2008 in the Sichuan Province of China. Website: http://www.drgeorgepc.com/Earthquake2008ChinaSichuan.html

Shou, Zhonghao 1999. "The Haicheng Earthquake and Its Prediction", Science and Utopya 65, page 34, November 1999" (in Turkish; Reviewed English abstract)

Ye, H., Shedlock, K.M., Hellinger, S.J. and J.G. Sclater, 1985. The north china basin: an example of a Cenozoic rifted intraplate basin, Tectonics 4 (1985) 153– 169.

Yin, X. C., Wang, Y. C., Peng, K. Y. and Bai, Y. L., 2000. Development of a new approach to earthquake prediction: Load/Unload Response Ratio (LURR) theory. Pure Appl. Geophys. 157, 2365-2383.

Yin, A., and Nie, S., 1996, A Phanerozoic palinspastic reconstruction of China and its neighboring regions, in Yin, A., and Harrison, T. M., eds., The Tectonic evolution of Asia: Cambridge [England] ; New York, Cambridge University Press, p. 442-485.

Yu Jianguo, Li Sanzhong, Wang Jinduo, Timothy M. Kusky ; Wang Xinhong ; Lu Shengqiang, 1995. Relationship between salt diapirism and faulting in the central structural belt of the Dongying sag, Bohai Gulf basin, ChinaQuaternary International Volume 25, 1995, Pages 13-17.

Wu Zhongliang and Shaoxian Zang, 1989. Source parameters of bohai earthquake, July 18, 1969 and yongshan earthquake, May 11, 1974 determined by synthetic seismograms of teleseismic P waves. Acta Seismologica Sinica. Seismological Society of China. Volume 5, Number 1 / February, 1992, pp. 1993-1344 (Online Issue)

Zhang, Z.M., Liou, J.G., and Coleman, R.G., 1984, An outline of the plate tectonics of China: Geological Society of America Bulletin, v. 95, p. 295-312.

Zhang, G. M. and Ma, L. (Eds.), 1993. Study on the Datong-Yonggao Earthquake. Seismological Press, Beijing (in Chinese; reviwed English Abstract).

Zhang, Y. X., Liu, G. P., Chen, Q. F., Ma, L. and Yang, W. Z., 1998. The feature of anomaly evolution before Shunyi M S 4.0 earthquake and estimation for the tendency of the quake by LURR. Earthquake 18(1), 49-56 (in Chinese).

Zhang, Y. X. and Liu, G. P., 2000. Study on characteristics of anomalies near by epicenter of Zhangbei M S 6.2 earthquake and their spatial and temporal evolution. Earthquake 20(1), 53-58.

Zhu, F. M. and Wu, G., 1982. The Haicheng Earthquake in 1975. Seismological Press, Beijing (in Chinese - English abstract).

Wang, K., Chen,Q.-F., Sun, S. and A. Wang, 2006, Predicting the 1975 Haicheng Earthquake, Bulletin of the Seismological Society of America, June 1, 2006; 96(3): 757 - 795.

Wang Jian, 2007. Historical earthquakes and a tsunami in Bohai Sea. Journal Acta Seismologica Sinica. Publisher Seismological Society of China ISSN 1000-9116 (Print) 1993-1344 (Online), Volume 20, Number 5 / September, 2007.

Wang, T.H., 1988. Genetic types of thrust faults in Eastern China petroliferous regions, Earth Sci. 13 (1988) 627– 634.

Watson, M.P., Hayward, A.B., Parkinson, D.N. and Z. Zhang, 1987. Plate tectonic evolution, basin development and petroleum source rock deposition onshore China, Mar. Pet. Geol. 4 (1987) 205– 225.

Xu Qinghai, Wu Chen, Yang Xiaolan and Zhang Ningjia, 1996. Palaeochannels on the North China Plain: relationships between their development and tectonics. Studies of the Palaeochannels on the North China Plain, Geomorphology, Volume 18, Issue 1, December 1996, Pages 27-35.

Zhang D., and S. Wang, 2008, Failure modes analyses of ice-resist jacket platforms in Bohai Sea. Dalian University of Technology, Dalian 116024, China ( Abstract seen)

Zhao Liang and Tianyu Zheng, 2005, Seismic structure of the Bohai Bay Basin, northern China: Implications for basin evolution. Earth and Planetary Science Letters 231, Issues 1-2 (Feb. 2005) Pages 9– 22.

Zhongliang Wu and Shaoxian Zang, 1992, Seismological Society of China (Acta Seismological Sinica Publisher), ISSN 1000-9116 (Print) 1993-1344 (Online) Issue Volume 5, Number 1 / February, 1992.

	Enter your search terms Submit search form
	Web www.drgeorgepc.com

Tsunami ... Earthquakes .. Seismotectonics .. Hurricanes ... Volcanic Eruptions..Tornadoes..Natural Disasters. Disaster Archaeology. Climate Change . Ocean Governance

Announcements .. Completed Events .. Special Bulletins: Recent Disasters .. Books & Book Reviews .. Tsunami Society

Dr. George Pararas-Carayannis:. Bio Summary .. Publications .. Recent Publications .. Recent Books .. Miscellaneous Writings .. Consulting Services