921 Earthquake

Technical data
The earthquake struck at 01:47:12 am (Taiwan Time) on Tuesday, 21 September 1999 (i.e., 1999-09-21, hence "921"). The epicentre was at 23.77° N latitude, 120.98° E longitude, 9.2 km (5.7 mi) southwest of Sun Moon Lake, near the town of Jiji, Nantou. The tremor measured 7.6 on the Moment magnitude scale, 7.3 on the Richter scale, and the focal depth was 8.0 km (5.0 mi). The Central Weather Bureau recorded a total of 12,911 aftershocks in the month following the main tremor. The earthquake was in an unusual location for Taiwan, which experiences the majority of its earthquakes off the eastern coast, such quakes normally causing little damage. One of the aftershocks, on September 26, was a strong earthquake in its own right, measuring 6.8 on the Richter scale and causing some already weakened buildings to collapse, killing another three people.

Due to an extensive network of sensors and monitoring stations, the quake was the best recorded and analysed large quake in history. At one station, a peak ground motion of 300 cm/s (3 m/s; 10 ft/s) was recorded, the highest ever measurement taken in an earthquake anywhere. Soil liquefaction was observed at Yuanlin and caused settlement of building foundations and filling in of water wells fromsand boils. The earthquake occurred along the Chelongpu Fault (traditional Chinese: 車籠埔斷層; pinyin: Chēlóngpǔ duàncéng) in the western part of the island of Taiwan. The fault stretches along the foothills of the Central Mountains in Nantou County and Taichung County (now part of Taichung City). Some sections of land near the fault were raised as much as 7 m (23 ft). Near Dongshih, near the northern end of the fault, a 7 m (23 ft) high waterfall was created by the earthquake.

Damage

Damage caused by the earthquake included 2,415 deaths, 29 missing, 11,305 severely wounded, with 51,711 buildings completely destroyed, 53,768 buildings severely damaged, and a total of NT$300 billion (US$10 billion) worth of damage. Power was cut to a large proportion of the island, due to damage to power stations, transmission stations, and the automatic shutdown of Taiwan's three nuclear power plants, which were restarted two days later. National electricity provider Taipower stated that a day after the quake power had been restored to 69% of the country. 102 major bridges were badly damaged, with many having to be torn down. The Central Cross-Island Highway, at the time the only major complete route across the mountains in central Taiwan, was badly damaged. Subsequent storm damage and the high cost of restoration means that the highway remains closed as of 2009 and is not expected to be reopened. There were a total of 132 landslides during the main quake and the aftershocks, some causing loss of life as rockfalls crushed houses. 870 schools suffered damage, with 125 severely damaged, closing many down for months or even permanently in a few cases.

More information can be found at: http://en.wikipedia.org/wiki/921_earthquake


CREDITS: WIKIPEDIA