WENCHUAN EARTHQUAKE (MW 7.9, 12 MAY 2008) SICHUAN, CHINA.GEOTECTONIC REGIME AND DAMAGE MACRO-DISTRIBUTION

摘要

The Mw 7.9 R earthquake on the 12th May 2008 that hit Sichuan prefecture caused tenths of thousands of casualties and had enormous consequences. The earthquake was triggered by a reverse fault of NE-SW trend dipping towards the NW, having a length of 100 km and focal depth of 19 km. According to the damage records,an estimation of the intensities was carried out based on the EMS 1998 and a correlation of their distribution with the geotectonic, seismo-tectonic, morphological etc, data was carried out. From this investigation three macro-distribution intensity zones were identified: (i) Zone A in the mountainous region, west of the reverse fault with estimated intensities approaching XΙEMS-1998 and locally ΧΙΙEMS-1998 due to the prevailing morphological and geotechnical conditions as well as to the fact that the region represents the hanging wall, (ii) Zone B in between the mountainous region and a morphologically flat region, representing the trace of the seismic fault with intensities approaching VIIIEMS-1998 and locally IXEMS-1998, and (iii) Zone C, the low land region with estimated intensities ranging from VIEMS-1998 to VIIEMS-1998 due to the geotechnical conditions and to the fact that this region represents the footwall.