关键词: 隐伏活断层, 地表破裂带, 宽度

Abstract: Okada's(1992)elastic half-space theory is applied to calculate the surface displacement and the amount of differential displacement produced by buried active faults. The theory has been verified to some extent by the 1992 Landers earthquake, United State, the 1994 Northridge earthquake, United State, the 1995 Kobe earthquake, Japan and the 1999 Izmit earthquake, Turkey. According to the criteria given in 《The Regulations of Seismic Design of Building》(GB50011-2001),the threshold value of differential displacement of buried seismogenic fault for producing surface rupture is estimated to be 0.1m for two adjacent points of 5m distance. This means that if the surface displacement produced by any buried fault is larger than 0.1m, then surface rupture zone will occur. If it is smaller than 0.1m, then the hazard that the buried fault may cause can be neglected. How the width and displacement of surface rupture zones vary with the buried depth, dip angle, motion mode and offset of the active fault is analyzed and discussed by applying the same theory and regulations. The results show that: 1)for buried normal fault, with increasing of the buried depth of the fault the width of surface rupture zones increases gradually to a peak value, and then decreases again. The point of peak value migrates toward the footwall of the fault(downfaulted block); 2)when the dip angle of the fault(normal fault)becomes small and the other parameters remain unchanged, the surface rupture zone will distribute mainly on the downfaulted block and the width becomes narrower; 3)as compared to the case of buried normal fault, the differential displacement produced by buried strike-slip fault attenuates more quickly when the buried depth of the fault becomes greater. It may imply that the normal fault is more risky; 4)the width and displacement of the surface rupture zone increase significantly with increasing displacement on the buried active fault. These primary results provide scientific basis for city planning and the seismic design of lifeline engineering and constructions across buried active faults. However, how to decide the threshold value of surface rupture and how to build up a more reasonable model for the middle and shallow crust need far more detailed study.

Key words: buried active fault, surface rupture zone, width