THE
EARTHQUAKE OF 8 OCTOBER 2005 IN NORTHERN PAKISTAN
George
Pararas-Carayannis
Introduction
A massive earthquake
struck Pakistan and parts of India and Afghanistan on Saturday
morning October 8, 2005. This was the strongest earthquake in
the area during the last hundred years.
This earthquake was
by far the most destructive disaster in the region. Current reports
indicate that close to 80,000 people were killed and at least
50,000 more were injured in the northern areas of Pakistan, in
the Pakistani-controlled Kashmir, in the Indian-controlled Kashmir
(known as Jammu-Kashmir), and in Northern India. Thousands of
houses were destroyed.
Pakistani Kashmir's
main city, Muzaffarabad, was severely affected with almost half
of its homes destroyed. Indian Kashmir was also severely damaged
with hundreds of dead and injured, mostly in the town of Uri.
There were numerous
deaths also in major Pakistani cities of Islamabad and Rawalpindi.
A 10-story residential building (known as the Margalla Tower)
collapsed completely in Islamabad killing most of the occupants.
The death toll is expected to rise significantly as reports from
remote areas filter in.
Collapsed
building in Islabadam
Earthquake
Origin Time, Epicenter, Magnitude, Focal Depth and Aftershocks
The
earthquake occurred on Saturday, October 8, 2005 at 03:50:38
(UTC). Its epicenter was at 34.402 degrees North, 73.560 degrees
east, about 90 km north-northeast of Pakistan's capital, Islamabad.
It was felt in major cities, including Islamabad and Lahore,
and India's capital of New Delhi. The earthquake was relatively
shallow and thus had greater intensity and destructiveness. According
to the U.S. Geological Survey the focal depth was very shallow
at about 10 km. The shallowness of the earthquake contributed
significantly to destruction in the region.
The moment magnitude
was measured to be 7.6 (U.S. Geological Survey), 7.5 (Pakistani
Meteorological Service) and 7.8 (Japan Meteorological Agency).
A final estimate of the moment magnitude of the earthquake is
7.7. More than 20 aftershocks ranging from 4.5 to 6.3 in magnitude
struck the area in 18 hours following the main shock. The aftershocks
are expected to continue. for days, weeks and months.
Physical
Map of the Northern Pakistan and Kashmir Region affected by the
Earthquake
Landslides
The high relief of
unstable mountains makes Northern Pakistan very vulnerable to
extensive landslides when an earthquake strikes the region. Heavy
monsoon rains - particularly if they occur before or after an
earthquake, can be the catalyst to further devastating landslides.
The earthquake of 8 October 2005 was responsible for many
landslides. Strong earthquake aftershocks may also trigger additional
landslides of unstable mountain slopes and endanger villages
in the region. As it can be seen from the two images below taken
by the Advanced Spaceborne Thermal Emission and Reflection Radiometer
(ASTER) before and after the earthquake, there were extensive
landslides in and around the city of Muzaffarabad. The landslides
blocked the roads, thus further isolating the stricken region.
In the ASTER images below, vegetation is shown in red, water
is shown in blue and the city of Muzaffarabad is shown in grey.
The image taken on October 27, 2005 (almost three weeks after
the earthquake) shows the land exposed by landslides to be white
and tan in color.
NASA
images of landslides in Pakistancreated by Jesse Allen, Earth
Observatory, using data obtained from the University of Maryland's
Global Land Cover Facility.
Tectonic
Setting - Geological Instability - Regional Seismic Activity
The earthquake occurred
along a tectonic boundary which is characterized by high seismic
activity. Major tectonic elements along this particular zone
of deformation were formed during the Cenozoic and Mesozoic eras.
The zone extends from the Makran region in southwest Pakistan,
to the Hazara-Kashmir syntaxial bend in the north. This seismic
boundary has been formed by the interaction of the Indian, Arabian
and Eurasian Plates. The Indian tectonic plate is moving in a
northward direction at a rate of about 40 mm/yr (1.6 inches/year).
It collides and is forced beneath the Eurasian tectonic plate.
This process has continued for millions of years. Major active
fault systems traverse Northern India and Western and Northern
Pakistan.Compression along these boundaries results in thrust
or reverse type of faulting with the net result being an upward
displacement of crustal material. This process of orogenesis
has formed the Himalayan Mountain Range as well as the Pamir,
Karakoram, and the Hindu Kush ranges and the Tibetan Plateau.
In the northern part of Pakistan, the Hindu Kush mountains converge
with the Karakoram Range, a part of the Himalayan mountain system.
Northward
movement of the Indian Tectonic Plate has resulted in major fault
systems in Pakistan, Kashmir and Northern India. Epicenter of
the 8 October 2005 earthquake (Modified base map after Jadoon
and Khurshid, 1996). Seismicity of the region (USGS graphic).
Seismicity
of the Region (USGS graphic)
Earthquake Activity
In Pakistan
Northern, Western
as well as Southern Pakistan, Kashmir and Northern India and
Afghanistan are along zones of high seismic activity. Most of
the earthquakes in Pakistan occur in the north and western regions,
along the boundary of the Indian tectonic plate with the Iranian
and Afghan micro-plates. As mentioned, the more intense seismic
activity occurs near regions of thrust faulting which is developing
at the Himalayan foothills in both Northern Pakistan and Northern
India. In
the last hundred years eight earthquakes with magnitude of more
than 6 have been recorded in the Uttar Pradesh region of India.
These quakes resulted by the gradual shifting of the India tectonic
plate beneath the Tibetan plate in the geologically young Himalayan
Mountain range and along the Himalayan arc.
The Chaman Thrust
Fault system is a continuation on land of an extensive transform
fault system in the Arabian Sea known as the Owen Fault Zone.
The Chaman Fault System is a major fracture which begins in the
Balochistan Province. The great Quetta earthquake (M7.7) of 31
May 1935 occurred along the Chaman Fault. The powerful earthquake
devastated the town of Quetta and the adjoining region.
The Chaman Thrust
Fault system extends along Pakistan's frontier with Afghanistan.
It begins near Kalat, in the northern Makran range, passes near
Quetta and continues in a north-northeastern direction to Kabul,
Afghanistan - after branching off to form the Main
Karakoram Thrust (MKT) System.
The Main Mantle Thrust
(MMT) System parallels the Chatham Fault System on the east side
of the Pishin Basin. Both the MKT and the MMT turn eastward in
the Hazara-Kashmir syntaxial bend near the the Main Boundary
Thrust (MBT), the region of major tectonic plate collision. The
October 8, 2005 earthquake occurred near this active seismic
zone in Northern Pakistan, in the Himalayan foothills. Its focal
mechanism and slip and strike components are consistent with
the compressive type of thrust faulting which is characteristic
for the region and has resulted in folding and the formation
of extensive anticlinal ridges in the vicinity of Muzaffarabad
- Pakistani Kashmir's main city. Also, other major thrust zones
exist along the Kirthar, Sulaiman and Salt mountain ranges of
Pakistan.
The earthquake
occurred in the Hazara-Kashmir syntaxial bend near the Main Mantle
Thrust (MMT) the Main Karakoram Thrust (MKT) and the Main Boundary
Thrust (MBT) (Modified base map of Pakistan Geological Survey-
after Bakht, 2000)
Most earthquakes in
Pakistan occur in the north and western sections of the country
along the boundary of the Indian tectonic plate with the Iranian
and Afghan micro-plates. As indicated, numerous earthquakes occur
along the Chaman Fault System.
Four major faults
exist in and around Karachi and other parts of deltaic Indus,
and the southern coast of Makran. The first of these is the Allah
Bund Fault. It traverses Shahbundar, Jah, Pakistan Steel Mills,
and continues to the eastern parts of Karachi - ending near Cape
Monz. Earthquakes along this particular fault have been responsible
for considerable destruction in the past. A major earthquake
in the 13th century destroyed Bhanbhor. Another major earthquake
in 1896, was responsible for extensive damage in Shahbundar.
The second major fault
near Karachi is an extension of the one that begins near Rann
of the Kutch region. The third is the Pubb fault which ends into
Arabian sea near the Makran coast. Finally, the fourth major
fault near Karachi is located in the lower Dadu district, near
Surajani. Many earthquakes have occurred on these faults.
Another major fault
along the offshore Makran coast (Balochistan and Sindh Provinces),
is the result of active subduction zone where major earthquakes
have occurred in the past. This zone forms the boundary of the
Arabian plate subducting under the Iranian micro-plate. However,
the seismicity of the Makran region is relatively low compared
to the neighboring regions, which have been devastated regularly
by large earthquakes (Jacob and Quittmeyer, 1979). Although infrequent,
large earthquakes do occur from time to time along the Makran
coast. The great earthquake of 28 November 1945 is an example
of the size earthquakes this fault can produce. It generated
a destructive tsunami in the Northern Arabian Sea.
Recent Earthquakes
in the Region
On
29 March 1999, a destructive earthquake with magnitude of 6.8
struck the Kumaon hills of Uttar Pradesh, 185 miles (295 kilometers)
northeast of New Delhi near India's border with China. Another
destructive earthquake in 1991, measuring 6.1, killed more than
1,000 people near the town of Uttarkashi in the same region.
Epicenter
of the 29 March 1999 Earthquake in the Uttar Pradesh Region
Most recently, in
February 2004, a pair of earthquakes of 5.5 and 5.4 magnitude
in Northern Pakistan killed at least 21 people and injured dozens
more. Hundreds of homes built of mud, stone and timber were destroyed
in a rugged, mountainous area about 90 miles northwest of Islamabad.
In January 2001, some
20,000 people died in a magnitude 7.7 quake that was centered
in India but also caused damage and deaths in Pakistan.
Recent earthquakes
in neighboring Iran took a heavy toll on human life. The 2003
earthquake (M6.7) killed 32,000. Another earthquake in 1999 killed
40,000 people in that country.
Although not as frequent
as in Uttar Pradesh, earthquakes in India's western region of
Gujarat - as that of 25 January 2001 - have been more powerful
and extremely destructive. The Gujarat earthquake killed 11,500
in India.
Epicenter
of the 25 January 2001 Earthquake in Gujarat
The most destructive
recent earthquake in the same general area occurred on 20 November
2002 in Northwestern Kashmir. This earthquake had a magnitude
6.4 and its epicenter was 245 km NNE of Islamabad. According
to official reports at least 19 people were killed, 40 were injured,
and hundreds of buildings were extensively damaged in the Dashkin-Doian-Mushkin
area.
Last Time the Region Experienced Destructive
Earthquakes of Similar Strength
No earthquake of similar
strength as that of October 7, 2005 has occurred in Northern
Pakistan or Kashmir in recent years. As reported earlier, the
more recent event in the same general area was a 6.4 magnitude
earthquake in Northwestern Kashmir on 20 November 2002. It affected
the same region and was widely felt in Islamabad a to the Southwest.
However, the death toll in northern Pakistan was by far lower.
Only 17 people died and 65 more were injured.
However, the historic
record shows that the largest earthquake to strike Pakistan in
the 20th Century occurred on 31 May 1935, near Quetta (Balochistan)
- a very active seismic region of Pakistan. Up to the 8 October
2005 event this had been the deadliest earthquake in the region.
It killed about 35,000 people, although some estimates of up
to 50,000 have been provided. The Quetta earthquake, as it was
named, had a Moment Magnitude (Mw) of 8.1. Its epicenter was
at 27.4 N and 88.75 E.
Pakistan's
Seimic Risk Map (Pakistan Geological Survey)
The city of Quetta
which was completely devastated the earthquake (M7.7) of 31 May
1935. About 30,000 people were killed and thousands more were
injured. Also, there was extensive destruction and thousands
of deaths in Mastung and in all the villages between Quetta and
Kalat.
A great earthquake
(Moment Magnitude Mw 8.0) on 28 November 1945, off Pakistan's
Coast of Makran (Balochistan) in the Northern Arabian Sea generated
a destructive tsunami in the Northern Arabian Sea. More than
4000 people were killed on the Makran Coast of Pakistan by the
earthquake and the tsunami. Also, the tsunami was responsible
for great loss of life and destruction along the coasts of Iran,
Oman and Western India.
Major earthquakes
in neighboring Northern India have also caused destruction and
deaths in Pakistan. The 1905 Kangra earthquake in India caused
extensive destruction in Lahore, Pakistan.
A complete listing
of other historical earthquakes in Pakistan will be provided
in subsequent updates of this report.
Future Earthquakes
in the Region
Aftershocks some of them major - should be expected
in the following weeks and even months in the immediate region.
Already many aftershocks, one of them as large as 6.2 in magnitude,
have struck the area. Another large earthquake is also possible
in the same general region as the stress release on a fault may
energize other sections of the fault or other faults in Northern
Pakistan.
Other significant earthquakes in the general South East Asian
area may occur in the Uttar Pradesh region of India or elsewhere
in Pakistan, Kashmir, or even Afghanistan, as the slippage from
the recent shock may have stressed other major thrust faults
in the entire region.
Lessons
Learned
Preparedness and strict
Seismic Building Codes could have mitigated the extent of the
damage and could have reduced significantly the death toll -
perhaps by as much as 80%. The photographs of collapsed buildings
indicate lack of proper building codes. Governments in the region
must develop better programs of public preparedness and designate
appropriate antiseismic building codes and construction standards
to provide safety from the most severe of the earthquakes that
historically have affected the region and which will occur again
in the future.
REFERENCES
Ambraseys, N. and
Bilham, R., 2003, "Earthquakes
and Associated Deformation in North Baluchistan 1892-2001", Bulletin of the Seismological
Society of America, Vol .93 ,No. 4, p. 1573 - 1605.
Bakht M. S., 2000.
An Overview of Geothermal
Resources of Pakistan.
Report of the Geological Survey of Pakistan. Proceedings World
Geothermal Congress, Kyushu - Tohoku, Japan, May 28 - June 10,
2000
Jacob, K. H. and Quittmeyer,
R. L., 1979. The
Makran region of Pakistan and Iran: Trench-arc system with active
plate subduction.
In: Farah, A. and de Jong, K. A. (Editors), Geodynamics of Pakistan:
305-317.
Jadoon, I.A.K., 1992,
"Ocean/continental
transitional crust underneath the Sulaiman Thrust Lobe and an
evoluationary tectonic model for the Indian/Afghan Collision
Zone", Pakistan
Journal of Hydrocarbon Research, v.4, no.2, p.33-45.
Pararas-Carayannis,
G., 2001,
"The Earthquake of 25 January 2001 in India" http://www.geocities.com/CapeCanaveral/Station/8361/Quake2001India.html
Pararas-Carayannis,
G., 2001, "The Earthquake
and Tsunami of 28 November 1945 in Southern Pakistan" http://www.drgeorgepc.com/Tsunami1945Pakistan.html
Ramanathan, K., and
Mukherji, S., 1938, "A
seismological study of the Baluchistan, Quetta, earthquake of
May 31, 1935",
Records of the Geological Survey of India, Vol. 73, p. 483 -
513.
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