本文分析了京津唐张地区1985～2003年详实的重复重力测量资料，重力变化的图像显示该地区的重力变化具有明显的区域性特征；最为显著的变化是测网南部地区出现的较大范围重力增加，增加幅值在(100～300)×10^(-8)m·s^(-2)之间...本文分析了京津唐张地区1985～2003年详实的重复重力测量资料，重力变化的图像显示该地区的重力变化具有明显的区域性特征；最为显著的变化是测网南部地区出现的较大范围重力增加，增加幅值在(100～300)×10^(-8)m·s^(-2)之间，从可搜集到的高程及地下水资料分析，造成这一变化的主要原因是该地区大量开采地下流体而引起的大面积地面沉降；测网北部山区重力趋势性减小，19年减小幅值约30×10^(-87)m·s^(-2)，与香山绝对重力点的变化量相当，高程及地下水对此种趋势的影响不大，大面积山区继承性、同步性的构造运动可能是造成地表重力趋势性变化的主要原因；而东部地区重力变化的明显特征是1990年6月至1994年6月间有一重力的快速下降然后上升过程，这可能是与1995年10月滦县 M 5.9地震有关的重力变化．相比之下地下水位的变化对重力趋势的影响较微弱．展开更多
Gravity variation data observed in the process of seismogenesis and occurrences of earthquakes show that the location with the greatest gravity changes does not necessarily coincide with the epicenter. To explain this...Gravity variation data observed in the process of seismogenesis and occurrences of earthquakes show that the location with the greatest gravity changes does not necessarily coincide with the epicenter. To explain this we defined the center of effective mass of stress volume as hypocentroid, and the vertical projection of which on the earths surface as epicentroid. Here we adopt three rotating models, including spheroid, ellipsoid and cylinder, to represent the region of an impending earthquake. Based on the models of gravity variations induced by uniform dilatancy, epicentroids associated with sixteen earthquakes with M>4.0 occurred in 1981~2000 in the Beijing-Tianjin-Tangshan-Zhangjiakou region are determined by means of a proposed least squares iterative inversion method. The results indicate that cylinder model is preferable to the other two, and epicentroids obtained by the cylinder model separate from the epicenters by a range of 0~40 km. Epicentroids are inevitably located within intact tectonic blocks, and usually cluster in groups; while the epicenters are generally located at the terminations of faults or at the intersections of faults. It seems that there exist earthquake-hatching areas in the block among faults. Earthquakes hatch in these areas, but occur around these areas, meanwhile the existence of faults may play an important role in controlling the processes.展开更多
文摘本文分析了京津唐张地区1985～2003年详实的重复重力测量资料，重力变化的图像显示该地区的重力变化具有明显的区域性特征；最为显著的变化是测网南部地区出现的较大范围重力增加，增加幅值在(100～300)×10^(-8)m·s^(-2)之间，从可搜集到的高程及地下水资料分析，造成这一变化的主要原因是该地区大量开采地下流体而引起的大面积地面沉降；测网北部山区重力趋势性减小，19年减小幅值约30×10^(-87)m·s^(-2)，与香山绝对重力点的变化量相当，高程及地下水对此种趋势的影响不大，大面积山区继承性、同步性的构造运动可能是造成地表重力趋势性变化的主要原因；而东部地区重力变化的明显特征是1990年6月至1994年6月间有一重力的快速下降然后上升过程，这可能是与1995年10月滦县 M 5.9地震有关的重力变化．相比之下地下水位的变化对重力趋势的影响较微弱．
基金State Natural Science Foundation of China (49774224)Joint Seismological Science Foundation of China (102019).
文摘Gravity variation data observed in the process of seismogenesis and occurrences of earthquakes show that the location with the greatest gravity changes does not necessarily coincide with the epicenter. To explain this we defined the center of effective mass of stress volume as hypocentroid, and the vertical projection of which on the earths surface as epicentroid. Here we adopt three rotating models, including spheroid, ellipsoid and cylinder, to represent the region of an impending earthquake. Based on the models of gravity variations induced by uniform dilatancy, epicentroids associated with sixteen earthquakes with M>4.0 occurred in 1981~2000 in the Beijing-Tianjin-Tangshan-Zhangjiakou region are determined by means of a proposed least squares iterative inversion method. The results indicate that cylinder model is preferable to the other two, and epicentroids obtained by the cylinder model separate from the epicenters by a range of 0~40 km. Epicentroids are inevitably located within intact tectonic blocks, and usually cluster in groups; while the epicenters are generally located at the terminations of faults or at the intersections of faults. It seems that there exist earthquake-hatching areas in the block among faults. Earthquakes hatch in these areas, but occur around these areas, meanwhile the existence of faults may play an important role in controlling the processes.
