Tsunami, Earthquakes, Hurricanes, Volcanic Eruptions and other Natural and Man-Made Hazards and Disasters - by Dr. George Pararas Carayannis


Tsunami, Earthquakes, Hurricanes, Volcanic Eruptions, Climate Change and other Natural and Man-Made Hazards and Disasters - Disaster Archaeology.



George Pararas-Carayannis

(Excerpts from a post-Tsunami Survey conducted on 30 November - 3 December, 1975, and from subsequent reports)



On Wednesday, 29 November 1975, the largest local earthquake to strike the Hawaiian Islands since 1868 - subsequently named the Kalapana Earthquake of 1975 - generated the most destructive local tsunami of the 20th Century. The earthquake was particularly damaging in Hilo. The tsunami was particularly destructive on the southern, eastern and western coasts of the Island of Hawaii. There was extensive damage at Keahou Landing, Punalu'u, Honuapo, Kaalualu Bay and at Keahou. The tsunami's far field effects were negligible. There was minor damage to boats and harbor facilities on Catalina Island in California.


The Kalapana Earthquakes of 1975

Two earthquakes occurred on 29 November 1975. The first was a foreshock at 13:35 GMT (3:35 a. m local time) with 5.7 magnitude and epicenter near Lae'apuki on Kilauea volcano's southern flank. The second and larger earthquake occurred a little over an hour later, at 14:48 GMT (4:48 a.m. local time). Its Richter magnitude was 7.2 and its epicenter was at 19.3 N, 155.0 W - near Kamoamoa - just a few miles east (immediately off the southeast coast) but closer to the shore than the earlier foreshock. Its focal depth was only 8 km below the surface, near the magmatic chambers of Kilauea volcano's Puna Rift Zone.




















Damages and Death Toll

Although the major Kalapana earthquake had a rather large surface-wave magnitude of 7.2, there was relatively minor damage to about a dozen homes within 10 miles of the epicenter. However, at Hilo, about 45 miles from the epicenter, the damage was heavy to the Hilo Hospital and several other substantial buildings.

The death toll was remarkably low but that was because the earthquake (and the tsunami) occurred in a region of the Island of Hawaii with low population density at the time. Only two people lost their lives and twenty-eight (28) were injured. The deaths, injuries, and about a third of the property damage, were caused by the tsunami.

Total property damage losses in the Hawaiian Islands from both the earthquake and tsunami were estimated at about $4.1 million (1975 dollars). Of the property losses, about $2.1 million was to private property and about $2 million to public property.

Crustal Displacements

The major earthquake of 29 November 1975 occurred east of the area that had been affected by the earthquake of 3 April 1868. The crustal movements involved uplift, subsidence and slope failure along the Hilina Slump of the Kilauea volcano, on the southern coast of the Island of Hawaii. A large crustal block slid horizontally towards the ocean and partly subsided, while the offshore area uplifted.

Maximum horizontal displacement of approximately 7.9 meters (26 feet) and vertical subsidence of approximately 3.5 meters (11.5 feet) occurred near Keahou Landing. The displacements decreased to the east and west. In fact, subsidence decreased rapidly to the west. At Punalu'u, the shoreline actually uplifted by about 10 centimeters (4 inches) (Pararas-Carayannis 1975).

Subsequent surveys determined subsidence of about 3 meters (9.8 feet) at Halape Park to the east. The large coconut grove area adjacent to the Beach Park subsided by as much as 3.0 and 3.5 meters (10-11.5 feet). Further to the east, the subsidence decreased to 1.1 meters (3.6 feet) at Kamoamoa, 0.8 meters (2.6 feet) at Kaimu, 0.4 meters (1.3 feet) at Pohoiki, and 0.25 meters (0.8 feet) at Kapoho.

The coastline was not the only altered area. According to the Volcano Observatory of the U.S. Geological Survey, even the summit of Kilauea subsided by about 1.2 meters (3.9 feet) and moved towards the ocean by about the same amount. A small, short-lived eruption took place inside Kilauea's caldera, apparently triggered by the earthquake.

A better understanding of the pattern of displacements in the offshore region was deduced from inspection of the local tide gauge records of the tsunami. The records show an upward initial tsunami wave motion (see tide gauge records below). This indicates that the offshore portion of the displaced crustal block actually uplifted, as the onshore section subsided and moved outward. Also, this pattern of crustal movement indicates that the flank failure of Kilauea was not entirely due to gravitational effects of instability, but may have been partially caused by compressional lateral magma migration from shallow magmatic chambers of the volcano, or by lateral magmastatic forces along an arcuate failure surface, or along a secondary zone of crustal weakness on the upper slope of the Hilina Slump. In fact, recent paleomagnetic studies (Riley et al., 1999) show that differential rates of movement and rotation occur between sections of the Hilina Slump. This would support that Kilauea's flank failures can be triggered by several mechanisms.

Aerial view of permanent subsidence ranging from 3.0 to 3.5 meters at the Halape Beach Park coconut grove on Hawaii Island. (Photo: National Park Service)



Historical Earthquakes on the southern Island of Hawaii have been caused by a variety of flank failures triggered by volcanic, tectonic, isostatic, gravitational and earth tide mechanisms (modified web graphic).


The tsunami of 29 November 1975 was the first major tsunami of local origin to strike the Hawaiian Islands since 1868. The waves were particularly destructive along the southern coast of the Island Hawaii, but less destructive along the eastern and western parts of the island. The tsunami killed two and injured 19 more people at Halape beach, on the southern coast of the Island. Tide gauges in the Hawaiian Islands and on the West Coast, Alaska, Japan, and Pacific islands recorded the tsunami. (Cox and Morgan, 1977, p. 57-72; Pararas-Carayannis and Calebaugh, 1977, Soloviev et al., 1986, Loomis, 1975).

Tsunami Warning

The travel time of the first of the tsunami waves along the southern coast of the Island of Hawaii ranged from less than a minute to as long as 15 to 25 minutes. A local Tsunami Warning was issued by Hawaii 's Civil Defense Agency. However, because of the short interval between the earthquake and the arrival of the tsunami, the warning was issued after the first wave had already struck the southern part of the Island of Hawaii. The first of the waves struck Punalu'u only 84 seconds after the earthquake.

Near Field Tsunami Effects

A comprehensive post-tsunami survey of the immediate tsunami generating area and of the eastern and western coast of Hawaii was undertaken by the author and Lt. Dennis Sigrist which documented the tsunami's near field effects (Pararas-Carayannis, 1975). Reports appeared in the ITIC Tsunami Newsletter (Vol. VIII, No. 4, December, 1975) and in the ITIC Director's ITSU bi-annual report. The following is a summary report of the effects of the tsunami in the Hawaiian Islands.

Halape ­ The Halape area was part of the crustal block of the tsunami generating area that subsided. As the photos show, the ground where there was a large coconut grove area adjacent to the Beach Park at Halape subsided by as much as 3.0 and 3.5 meters (10-11.5 feet). The grove itself was left submerged in 1.2 m of water.

There were thirty-two campers at Halape when the earthquakes occurred and later when the second earthquake generated a major tsunami. There are several eyewitness accounts in the literature concerning the events at the park that night, so they will not repeated here. According to the campers, the first tsunami wave observed at Halape was only 1.5 meters (almost 5 feet). However, the second wave was 7.9 meters (about 26 feet). Two people were killed and nineteen more were injured. Four horses were drowned. The highest was the second wave, which reached 14.6 m above the post submergence level of the sea. Subsequent waves were much smaller

Another photograph of the coconut grove at Halape Beach Park (Photo credit: P.W. Lipman taken on December 3, 1975)

Keahou Landing - A maximum tsunami runup of 14.3 meters (almost 47 feet) was measured at the Keauhou Landing, where the waves completely destroyed the pier and overturned large fuel tanks.

Punalu'u - The first wave was relatively small and arrived only 84 seconds after the earthquake. The largest wave arrived about 10 minutes later and was particularly destructive. Maximum tsunami run-up was 7.6 meters (about 25 feet) and penetrated about 137 m (450 ft) inland. The second wave destroyed seven houses, a large restaurant, a gift shop, and two cars. Four concrete, steel-reinforced beams in front of the beach pavilion were either toppled or bent severely due to the waves Coconut trees were severed by the destructive force of the waves. Total damage amounted to about $1 million (1975 dollars).

Tsunami destruction at Punalu'u (Photo: G. Pararas-Carayannis taken 29 Nov 1975)

Honuapo - The tsunami damaged a fishing pier, the beach park facilities and a warehouse.

Kaalualu Bay - The waves damaged vehicles campsites and destroyed canoes. At Napoopoo a shed was moved off its foundations.

Keahou ­ There was damage to dock facilities and boats. One boat was carried by the waves and deposited in the parking lot. Another boat sank, and other boats and the dock facilities were damaged.

Hilo - A timely tsunami watch by Hawaii's Civil Defense Agency resulted in evacuation of low-lying areas. The water begun to recede at 5:10 A.M. - draining the harbor. The Coast Guard Cutter U.S.S. Cape Small settled into the harbor bottom and listed. The waves sunk four boats and damaged three others. A car was swept off the pier into the bay. The maximum observed tsunami wave height at the mouth of Wailoa River was about 12 feet.

Lahaina - Maui - There were reports of sailboats hitting bottom at the harbor

Hana ­ Maui - No report of damage. A fisherman reported unusual recession of the water at 5:30 A.M.

The Tsunami of 29 November 1975 as Recorded by Tide Stations in the Hawaiian Islands

A relatively small tsunami was recorded by tide gauges in the harbors of Hilo, Kahului, Honolulu and Nawiliwili (Pararas-Carayannis, 1975). Copies of the tide gauge recordings were provided in the ITIC Tsunami Newsletter (Vol. VIII, No. 4, December, 1975).

The following maximum heights were recorded: Hilo, Hawaii 5.7 feet; Kahului, Maui 3.0 feet; Honolulu, Oahu: 0.1 feet; Nawiliwili, Kauai 0.9 feet. The actual tsunami runup on open water coast locations was considerably higher than what was recorded by tide gauges which were located in more sheltered areas. For example maximum observed tsunami wave height at the mouth of Wailoa River was 12 feet while the maximum recorded by the Hilo gauge was 5.7 feet.

The Tsunami of 29 November 1975, as Recorded by the Hilo Tide Gauge on the Island of Hawaii

The Tsunami of 29 November 1975, as Recorded by the Kahului Tide Gauge on the Island of Maui.

The Tsunami of 29 November 1975, as Recorded by the Honolulu Tide Gauge on the Island of Oahu

The Tsunami of 29 November 1975, as Recorded by the Nawiliwili Tide Gauge in the Island of Kauai.

Far Field Tsunami Effects

In addition to the tide stations in the Hawaiian Islands, many other tide stations on the U.S. West Coast, Alaska and Japan recorded a minor tsunami. Also, minor tsunami waves were recorded in American Samoa and in Western Samoa and several other Pacific islands. (Cox and Morgan, 1977, p. 57-72; Pararas-Carayannis and Calebaugh, 1977; Pararas-Carayannis and Dong, 1980; Soloviev et al., 1986, Loomis, 1975).

Alaska - The Yakutat tide gauge recorded a wave of 2 inches in amplitude. The Sitka gauge recorded a wave of 4 inches in amplitude.

American Samoa - The Pago Pago tide gauge recorded a wave with amplitude of 0.11 m.

Western Samoa - The Apia station recorded a 0.17 m oscillation.

California - In California, there was minor damage to harbor facilities on Catalina Island. Tsunami waves of up to nine feet at the Isthmus Harbor destroyed a small floating dock and broke loose another floating dock. According to newspaper accounts, the water receded and several boats were stranded on the bottom of the harbor but refloated by subsequent waves (San Pedro Pilot, December 1, 1975). A small surge occurred at Marina del Rey near Santa Monica (Santa Monica Evening Outlook, December 1, 1975; Spaeth, 1977; Soloviev et al., 1992).

Tsunami Generating Area

As with the 1868 event, Hilo was greatly affected by the shock waves of the 1975 earthquake but not as much by the tsunamis generated by these events. This is suggestive of the directionality of slumping and of the limited dimensions of distinct slope failure events along the southern flanks of the Kilauea and Mauna Loa volcanoes.

Hawaii's southern coast showing coastal faults parallel to the east rift zone of the Kilauea volcano, and the Generation Area of the 1975 Tsunami in relation to the Hilina Slump where flank failures have occurred in the past (Base map modified after Morgan et al. 2001).

Slope failures and subsidence along Kilauea southern flank have been frequent in the past and have generated local destructive tsunamis. However, flank failures associated with the more recent earthquakes, appear to have occurred in phases, over a period of time, and not necessarily as single, large-scale events involving great volumes of crustal material. However, large prehistoric flank failures appear to have occurred, particularly along the western flank of the Mauna Loa volcano. Such failures must have generated large local tsunamis in the past.

As described previously, a large crustal block of the flank of the Kilauea volcano slid horizontally towards the ocean and subsided, while the offshore region uplifted (Pararas-Carayannis 1975). Although there was considerable subsidence along the coast, the entire offshore region of tsunami generation is estimated to have risen by an average of about 1.2 meters (3.9 feet). Since the initial wave motion of the tsunami at all recording tide gauge stations in the Hawaiian Islands was upwards, it strongly supports that the offshore area uplifted.

The offshore crustal displacements correspond to the tsunami generating area, which is estimated to be about 70 km long and 30 km wide with the long axis of the displaced crustal block being parallel to the coast. Although these represent estimates, the volume of displaced water, as well as the total energy that went into tsunami generation can be calculated. The total volume of displaced material that contributed to tsunami generation was roughly estimated to be 2.52 cubic km (Pararas-Carayannis 1976 a, b).

Generating Mechanism of the 1975 Tsunami in Hawaii

A sudden flank collapse process generated the 1975 tsunami, which was closely associated with Kilauea's ongoing volcanic activity and the instability of the volcano's southern flank. Such instability along fractures controlled by regional faults along the Puna Rift Zone results in both aseismic and seismic slippage. The offshore geomorphological features on the Hilina Slump - and the tide gauge recordings of the tsunami - indicate that the 1975 flank failure and earthquake were triggered by compressional forces of moving lava within Kilauea's magmatic chambers below and within ascending lava dikes - having a hydraulic piston effect on a weakened flank crustal block. Gravitational settling followed the crustal movement. This appears to be the mechanism by which most flank failure events occur on Kilauea and the Mauna Loa volcanoes.

In conclusion, therefore, the tsunami was generated by the combination of the net sudden subsidence and uplift of the ocean floor, as well as from the lateral crustal compression of a crustal block in a seaward direction. The compression and the lateral crustal movement on the Hilina Slump probably formed a horst in the offshore region. This horst would demarcate the outer edge of the tsunami generation area and the origin of the faster first tsunami wave. This would explain the initial upward wave motion recorded by the tide gauges around the islands. The faster traveling wave originated along the deeper offshore perimeter of the tsunami generating area. The tsunami travel times also support this conclusion.

Such flank failure processes are characteristic of the mechanisms of earthquakes that occur with frequency along the southern coast of the Island of Hawaii. Tsunamigenic earthquakes occur when aseismic slippage stops due to locking along the coastal faults and critical stresses build up along potential decollment surfaces. The magmastatic pressures or moving lava in the volcano's chambers or along flank dikes, or even gravitational forces or tidal forces (including earth tides) can trigger the release of the stored stress. Larger earthquakes occur with the more significant flank failures. Most of the time, Kilauea's southern flank along the Hilina Slump region, slips aseismically without tsunami generation. However, larger failures occur although separated by decades in time.

Tsunami Travel Times and Runup

Subsequently to this author's initial 1975 field survey, there were numerous other reports pertaining to the time of arrival of the first tsunami wave at different locations around the Hawaiian Islands, the heights of subsequent waves, and the maximum observed runup. Cox and Morgan (1977) summarized these reports and prepared the tsunami refraction diagrams shown here. Also, for the purpose of hazard zonation, Cox (1979) estimated the runup heights of the 1975 tsunami for places where there had been no actual physical measurements or observations. For the immediate tsunami generating area where there had been substantial subsidence, the given runup height estimates were based on the pre-subsidence mean sea level datum. Although Cox somewhat underestimated the dimensions of the tsunami generating area, the tsunami travel times are fairly accurate for the initial wave which originated in deeper water off the Kalapana coast. As pointed earlier, the actual tsunami runup on open water coast locations around the Hawaiian Islands were considerably higher than what was recorded by tide gauges in sheltered harbors.


Past and Future Tsunamis ­ Vulnerability of the Hawaiian Islands to Local Tsunamis

Failure of the southern flank of Kilauea (and Mauna Loa) is an ongoing process that has been responsible for numerous earthquakes and local tsunamis throughout Hawaii's geological history.

The numerous faults (palis) along the Puna Rift Zone with their tilting walls indicate a seaward progression of edifice failure. Also, the numerous "horsts" and "grabens" in the offshore region of the Hilina Slump ­ as well as toes of debris avalanches on the ocean floor - indicate that past flank failures and associated earthquakes resulted from gravitational and volcanically-induced compressional forces.

Composite Satellite Photo of the Island of Hawaii (8 photos)

The offshore geomorphological features are characteristic of large crustal block movements from past earthquakes and parallel those of the 1975 Kalapana event. The failures appear to have occurred as discreet events along the submarine portion of the Hilina Slump over a long period of time. Such discreet failures have generated destructive tsunamis in the past. The destructive local tsunamis of 1823(?) and 1868 were generated by such flank failures of Kilauea and Mauna Loa volcanoes. In 1989, the southern region of Hawaii experienced smaller, damaging earthquakes, but no tsunami was generated.

In view of the instability of the southern flanks of Kilauea (and of Mauna Loa), the area is vulnerable to local tsunamis. In older times this was not as critical since the population density was low. However, since 1975 the population density on the southern coast of the Island of Hawaii has increased dramatically. Thus, a repeat of an earthquake and tsunami as in 1975, can be expected to result in many more casualties and extensive property losses.

Tsunami preparedness for the Hawaiian Islands ­ and particularly the Island of Hawaii ­ must take into consideration the increased level of risk associated with the recent development of the coastal areas. Appropriate measures must be taken to factor the added risk to any community development and the construction of supporting infrastructure.






Cox and Morgan, 1977

Loomis, 1975

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Pararas-Carayannis, G., 2004. Factors Contributing to Explosivity, Structural Flank Instabilities, Mass Edifice Failures and Debris Avanlanches of Volcanoes - Potential for Tsunami Generation

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San Pedro Pilot, December 1, 1975 / Santa Monica Evening Outlook, December 1, 1975

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Soloviev et al., 1986

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Factors Contributing to Explosivity, Structural Flank Instabilities, Mass Edifice Failures and Debris Avanlanches of Volcanoes - Potential for Tsunami Generation

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