EVIDENCE AND METHODS FOR DETERMINING THE SAFETY DISTANCE FROM THE POTENTIAL EARTHQUAKE SURFACE RUPTURE ON ACTIVE FAULT
XU Xi-wei YU Gui-hua MA Wen-tao RAN Yong-kang CHEN Gui-hua HAN Zhu-jun Zhang Lan-feng (Institute of Geology, China Seismological Bureau, Beijing 100029, China) YOU Hui-chuan (Institute of Geophysics, China Seismological Bureau, Beijing 100081, China)
A large number of observed data about the widths of earthquake surface ruptures produced on diverse types of active faults, as well as the widths of intense deformation zones in trench logs across active faults are presented in this paper. Combining these data with the close relation between the damage zone of surface construction and the spatial position of active fault, the authors propose that a minimum distance (safety distance) of 30m away from active fault is essentially required for constructions to prevent the effect of faulting. The more accurate safety distance required for various types of active faults can be tested and modified through the analysis of the deformation features of strata in trench logs across the fault. The required safety distance in some specific sites, such as the step-overs of active faults, as well as the area defined by sub-parallel secondary faults on both sides, should be the sum of the width of the area and 15m from area boundaries. It is suggested that this "safety distance" should be taken as a legal regulation for constructions and buildings. In addition, further attention should be paid to the identification of active fault and precise determination of the geometric structures of the surface fault strand, so that earthquake hazards can be positively and effectively reduced.