12-05-2008

12-05-2008 The devastating earthquake that struck Sichuan province five years ago marked one of a series in the earthquake-prone region. The earthquake occurred in an area that is deforming as two tectonic plates - the Indian plate and the Eurasian plate - collide. Deadliest earthquakes in China 1927 1920 1303 Shanxi Haiyuan, Ningxia Gulang, Jiangsu 40.900 234,117 deaths deaths 200,000 deaths 1290 Chihli, Inner Mongolia 100,000 deaths 6.8 1976 Tangshan, Hubei Deadliest earthquake in China in 20th century 7.5 2008 Wenchuan, Sichuan China's deadliest earthquake in the last 36 years 87,449 deaths 242,419 deaths 7.7 7.8 1668 Tancheng. Shandong 50,000 deaths 8.6 magnitude 2013 Yaan, Sichuan Last earthquake in Sichuan 7.9 1556 Shaanxi World's deadliest earthquake of all time 800,000 deaths 261 deaths 1786 Kangding-Luding. Sichuan 1925 Dali, Yunnan 5,000 deaths 100,000 deaths 1970 Tonghai, Yunnan 15,621 deaths Seismic hazard map of the world and main plates Seismic hazard map of China This map shows the different levels of expected earthquake ground motions in China and their likely effect on existing natural conditions and man-made structures for public safety considerations. I Risk zone Divergent plate Transformation plate aa Convergent plate Risk Low Moderate High Very high Atlantic Ocean EUROASIA PLATE NORTH AMERICA PLATE PACIFIC PLATE Beijingo -Caribbean ARABIC Plate PLATE INDIA PHILIPPINES PLATE PACIFIC AFRICAN PLATE PLATE PLATE Tibetan Plate Epicenter • Shanghai Yangtze Plate NAZCA PLATE Movement plates direction AUSTRALIAN PLATE FIJI PLATE SOUTH India Plate Hong Kong AMERICAN ANTARCTIC PLATE Hong Kong is located in an area of low to moderate seismicity. The current codes of practice for building design do not require any seismic considerations ANTARCTIC PLATE Movement of the earth crust The 7.9 magnitude earthquake ruptured the Longmen Shan fault which marks the eastern edge of Tibet where the steep Longmen Shan mountain range meets the plains of the Sichuan basin Longmen Shan fault The rupture started at the epicentre and over the next 50 seconds travelled a few TIBETAN PLATEAU hundred kilometres toward the north The slip, displacement of the two land masses with respect to each other along the fault line, in some places is as large as 12 metres Longmen Mountains Dujiangyan Pengzhou Fault SICHUAN BASIN Xindu 65km Chengdu 19km deep Shuangliu Inflation through influx of weak lower crust Very close to the earth's surface Xinjin Qionglai 65km Strong lower crust Acts as a barrier to lower crustal flow Mesozoic sediments layer Sichuan's earthquake seismogram Aftershocks occurred mainly along and in the vicinity of the fault line ruptured by the original May 12 quake People dead Buildings H damaged 21million Economic loss (HK$) 667billion Children People injured 374,643 People affected 45.5million People evacuated 15million Left homeless 5million Buildings collapsed 5.36million Roads damaged 53,000km dead 87,449 19,065 Extent of tremors Northern Pakistan Time from which vibrations were felt India Bangladesh Bangkok Sichuan Hong Kong Hanoi Taiwan 10 minutes 4 Sources: USGS, Sina.com. Encyclopedia of Geology (Elsevier) SCMP Graphic: Adolfo Arranz