【摘要】 目前地震断层相互作用问题已引起地震学家的广泛关注。许多研究表明一条断层的破裂可以影响附近其他断层趋于破裂的进程 ,两条断层间的确切作用取决于它们的相对位置、破裂机制、错动量和介质力学性质。本研究给出了华北地区 70 0年来由于长期构造加载及地震断层错动导致的累积库仑破裂应力变化 (ΔCCFS)的演化过程。长期构造加载场由GPS观测得到的地壳平均应变率场给出。关于历史地震断层破裂参数的估算 ,根据的是华北地区有现代仪器记录的大震资料归算地震烈度与断层破裂长度、震级和地震矩的统计关系 ;根据地质调查得到的地震断层走向、倾角以及本地区的构造应力场方向估计滑动角。考虑粘弹性成层介质地壳模型 ,计算长期构造加载和地震形变 (同震及震后介质粘弹性驰豫变形 )造成的累积应力场变化。将累积应力场变化投影到后续地震断层面和滑动方向上得到ΔCCFS ,并研究其对后续地震发生的触发作用。对 130 3年以来华北地区发生的 4 9个M≥ 6 5地震研究结果表明 :ΔCCFS对 4 8个后续地震中的 38个有触发作用 ,触发率达到 79 2 %。应用当今累积应力场变化于华北地区 130 3年～ 2 0 0 3年发生的M≥ 5地震 ,我们发现触发率达到 75 5 % ,于 1976年以来发生的M≥ 5地震触发率达 82 1%。未被触发的地震中更多还原

【Abstract】 Fault interaction and earthquake occurrence have attracted much attention in seismological community during recent years. Many studies showed that rupture of one fault could encourage or discourage earthquake nucleation on a neighboring fault, depending on the relative geometry of the two faults and the earthquake rupture mechanisms. In this paper, we simulate the evolution process of cumulative Coulomb failure stress change (ΔCCFS) in North China since 1303, manifested by secular tectonic stress loading and occurrence of large earthquakes. Secular tectonic stress loading is averaged from crustal strain rates derived from GPS. Fault rupture parameters of historical earthquakes are estimated as follows: the earthquake rupture length and the amount of slip are derived based on their statistical relationships with the earthquake intensity distribution and magnitude, calibrated using parameters of instrumental measured contemporary earthquakes. The earthquake rake angle is derived based on geologically determined fault setting parameters and seismically estimated orientation of regional tectonic stresses. Assuming a layered visco-elastic medium, we calculate stress evolution resulted from secular tectonic loading and coseismic and postseismic deformation. On the eve of each large earthquake, the accumulated stress field is project to the fault surface of that earthquake and the ΔCCFS is evaluated to assess the triggering effect of ΔCCFS 49 earthquakes with M≥6.5 occurred in North China since 1303. Statistics shows that 39 out of the 48 subsequent events were triggered by positive ΔCCFS, yielding a triggering rate of 81.3%. If we use the accumulative stress field to evaluate the ΔCCFS for the M≥5 earthquakes occurred in North China since 1303,we find that 75.5% of those events were triggered. The triggering rate for the M≥5 earthquakes after the 1976 Ninghe earthquake is up to 82.1%. The triggering rates can be higher if corrections are made for some aftershocks which were wrongly identified as occurred in stress shadow zones because of errors in parameter estimates of historical earthquakes. Our study shows very high correlation between positive ΔCCFS and earthquake occurrences. Relatively high ΔCCFS in North China at present time is concentrated around the Bohai Sea, the west segment of the Northern Qinling fault, western end of the Zhangjiakou-Bohai Sea seismic zone, and the Taiyuan basin, Shanxi graben, suggesting relatively higher earthquake potential in these areas.更多还原