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Case HistoriesPhoenix Kobe
A lesson in Disaster Recovery: comments on community In this section we discuss the magnitudes and effects of major historical earthquakes. Some of these earthquakes were catastrophic, with widespread destruction resulting in loss of hundreds of thousands of lives. Others, however, although being high magnitude events, were not as destructive, and had much smaller death tolls. By comparing the examples discussed, the contrasting effects for events with similar magnitudes can be explained, e.g. different foundation conditions, different building practices, differences in earthquake associated hazards (tsunamis, landslides, fires). 
(geological controls) Magnitude: Ms 8.75 Loss of life: 60,000 Damage: Destroyed half of city of Lisbon The 1755 Lisbon earthquake is possibly the largest historical earthquake known and was felt widely over south-western Europe and north-eastern Africa. Lisbon is built on soft sediments and rock; the part of the city founded on the sediments was almost completely destroyed by the violent shaking and vertical displacement characteristic of this earthquake. The earthquake also triggered tsunami which submerged the lower town beneath 15 m of water, were recorded on both sides of the Atlantic and caused seiching in ponds and lakes throughout western Europe.
(costly insurance losses) Magnitude: Ms 8.3 Loss of life: 700 Damage: $350 million - $1 billion US The 1906 San Francisco earthquake occurred on a section of the famous San Andreas fault. The fault of the San Andreas fault totals 500 km in the past 100 million years, with a rate of strain of 5 mm yr-1. The 1906 earthquake caused rupturing along 300 km of this fault, with a maximum horizontal offset of 6.4 m. The effects of the 1906 San Francisco earthquake were exacerbated by the fact that the earthquake toppled gas lanterns in wooden buildings, causing fires throughout the city. The earthquake also triggered landslides which broke gas mains and water mains which, respectively, (1) fed the fire, and (2) prevented ready dousing of the flames. The waterfront area was underlain by mud and artificial fill, and surface rupture was greatest in these areas. The earthquake and fire destroyed 30 schools, 80 churches and 250,000 homes.
(fire storm) Magnitude: Ms 8.3 Loss of life: 127,000 Damage: 470,000 homes destroyed, 80,000 people injured The 1923 Tokyo earthquake was centred in Sagami Bay, south west of two main population centres, Tokyo and Yokohama. This earthquakes compares with the San Francisco event in the fact that many fires were started and these were responsible for most of the deaths by burning or asphyxiation. The earthquake also caused vertical displacement of the seafloor in Sagami Bay. Parts of the bay deepened by 100 - 200 m, with a maximum displacement of about 400 m. This displacement triggered a 10 m tsunami which also caused much destruction along the shore. The earthquake was preceded by days of a tropical cyclone, and it has been suggested that this may have caused the earthquake, with low pressure releasing the burden on the earth's crust. The cyclonic winds also acted to fan the flames of the fires, which raged out of control, destroying nearly ½ million homes.
(widespread landsliding and tsunamis) Magnitude: Ms 8.4 - 8.75 Duration: 4-7 minutes, 1200 aftershocks Loss of life: 130 Damage: $300 - 750 million US The 1964 Alaska earthquake occurred on the Danali fault, parallel to the Alaskan coast and subjected an area of about 250,000 km2 to vertical displacement, with maximum uplift of 12 m. Ground rupture was observed along 800 km of the fault's length. Damage caused by the 1964 Anchorage earthquake was greatest in Anchorage, 130 km west of the epicentre and underlain by Pleistocene-aged clays (the Bootlegger Cove Clay). These glacial clays have low shear strength, high water content and are very sensitive to vibration and shaking. The earthquake caused these clays to liquefy, triggering large scale landslides, which destroyed over 75 homes and caused the docks and warehouses in Valdez to sink into the sea. Most of the damage caused by this earthquake was through ground failure. The earthquake also triggered 7-10 m-high tsunamis, which overwhelmed Alaskan coastal towns over the nine hours following the earthquake. The tsunamis also swept down the western coast of the USA, damaging coastal towns and cities as far south as San Diego.
Magnitude: Ms 7.8 Focal depth: 25 km Intensity: VIII Loss of life: 66,000 The 1970 Peru earthquake is one of the most destructive in Latin American history. The high death toll was in part a consequence of the weak adobe building construction used, and in part due to a catastrophic landslide triggered by the earthquake which buried 20,000 people.
(costly earthquake to a western society infrastructure) Magnitude: Richter 6.6 Focal depth: 13 km Duration: 60 seconds Loss of life: 64 Damage: $1 billion San
Fernando is a suburb of Los Angeles. The San Fernando earthquake
did not occur on the San Andreas fault, but was a result of thrusting
of a smaller fault 30 km to the south
(costliest earthquake in US history) Magnitude: Ms 7.1 Focal depth: 17.6 km Duration: 15 seconds Loss of life: 62 Damage: $6 US billion, 3,700 injured, 10,000 homeless The 1989 Loma Prieta earthquake occurred on a segment of the San Andreas fault that was recognised as occupying a seismic gap and thus having a high probability for rupture in the future. The earthquake was felt in Los Angeles (558 SE of San Francisco) and Reno (300 km NE). The earthquake destroyed or damaged older buildings which were built before earthquake building codes were enforced. However, even structures which had been reinforced after the experience of the San Fernando earthquake collapsed. The earthquake also triggered liquefaction of loose, saturated sand and artificial fill, and caused numerous landslides and slumps. Most of the urban development after the 1906 earthquake was on unconsolidated landfill, and in one district many houses completely collapsed.
(an unexpected earthquake in a seismically quiet continent, where buildings were not earthquake-proof) Magnitude: Richter 5.6 Focal depth: 11.5 km Duration: 30 seconds Loss of life: 12 Damage: $ millions AUS The
continent of Australia lies well away from recognised seismic zones
surrounding the Pacific Ocean, and the town of Newcastle is included
in a zone of negligible seismic risk on published design standard
maps (although having experienced two earthquakes in 1868 and 1925).
The 1989 earthquake was unexpected, and devastating. The relatively
shallow earthquake caused violent ground shaking which badly damaged
the old buildings in the town, some of which collapsed and crushed
people and cars. Essential services were also cut. The cause of
the earthquake is unclear. Seismic activity in Australia may be
a result of compression of the Australian continent by tectonic
activity at the margins of the Australian Plate, or the 7 cm yr-1
northward migration of the continent. It may also be caused by volcanism
as the continent drifts across a mantle hotspot compressing the
continent and causing earthquakes.
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west.
Displacements ranged from 2-3 m, and ground acceleration > 1
g (horizontal) was recorded. The earthquake triggered thousands
of landslides and fracturing and slumping of the ground surface.
Buildings were badly damaged or collapsed, roads and railways were
blocked and bridges and freeway overpasses collapsed. Liquefaction
of dam cores destabilised two hydro electric dams which almost failed.
Important lessons were learned from this earthquake - many of the
damaged buildings were built to earthquake specifications, yet did
not withstand the shaking. Building codes subsequently were tightened.
The hundreds of dams in the region have been reinforced.