Analysis Of Regional Crustal Stability And Seismic Risk Probability In GuiZhou Province

Guizhou tectonic unit is divided into Yangzhi platform, Jiangnan and Youjiang orogenic belts. Under the effect of plate activation,there appeared the displacements and earthquakes near structural belts. Compared with the national earth crustal activity, generally, Guizhou is a comparatively stability Region.Against the whole nation, in GuiZhou intensity and frequency of earthquakes is moderate, which is relevant to its special terrane environments, that is at the south edge of South-North Earthquake Zone in China). But, the intensity and frequency of earthquakes is more different throughout GuiZhou.The earthquake of GuiZhou is controlled strictly by geological structure and closely related to the activity of structural belts. In space, majority of earthquakes are focus in the west, distribute along the deep faults. The middle to strong earthquakes are located on intersection by north-west and north-east active faults, in which Neocathaysian structural system plays important role, whereas the others overlap with it. According to the forming history and spatial characteristics of active structure zones, they can be divided into 5 types.Geophysics field and variation of deep structure shows that the stability of earth crust is relatively better, no more earthquakes appeared.Neoid active faults are closely related to earthquake, but its scale is small and length is short, so it isn't able to trigger the large scale of earthquakes. Stress field by mathematical simulation indicates the neoid active faults closely concerned with earthquake are distributed in middle and west region, where the earthquakes may be appeared due to the stress concentration derived from the plat movement, nevertheless the possibility of earthquakes more than 5 grades is small.The earthquake of GuiZhou has undergone 4 active periods in recent century as same as the whole nation's, nowadays it is coming into the 5th active period, approximately after 1988.Based on the principle and index system applying the approach of fuzzy mathematics to the stability zonation, the stability in Guizhou is described into 3 big types and 9 small types.