Spatial variation of seismic moment release before strong and intermediatestrength earthquakes in the fifth seismicactivity period of northeastern China region
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摘要: 为考察中国东北地区中强震前是否存在与地震孕育过程物理相关的地震矩加速释放现象，利用ldquo;地震矩释放程度rdquo; m值对该地区第五活跃期内的5例中强震进行了时空扫描研究．通过考察删除余震的影响，提取了MS5.0 以上地震与地震矩加速释放相关的特征时、空尺度，并作为时——空扫描的模型参数．采用震前5个月逐月扫描的方式，得到了震前m值随时间变化的图像．结果显示，其中4例在未来的震中附近出现稳定和集中分布的地震矩释放加速区．这表明东北地区中强震前的地震矩加速释放现象具有一定的普遍性，矩释放加速扫描方法对判断未来可能的中强震破裂成核点有一定的指导意义．采用相同的计算参数设置，还考察了震前破裂成核点的Benioff应变释放情况．结果显示，有3例在破裂成核点的地震矩加速释放现象明显．这表明，对于东北地区的中强地震，利用矩释放程度时空扫描寻找未来中强震的破裂成核点，尚需其它方法作为辅助．Abstract: To investigate whether the accelerating moment release (AMR) appeared before strong and intermediate-strength earthquakes, related to earthquake preparation process, or not, this study carried out a spatio-temporal scanning over them value, denoting AMR level, derived from the seismic activity in the fifth active period of northeast China region. By referring other studies the spatiotemporal windows of mvalue scanning for searching AMR before MSge;5 earthquakes were determined. For the earthquake data during the 5 months before each MSge;5 earthquake a monthly spatial scanning was performed, and the temporalmvariations before theMSge;5 earthquakes were obtained. The result indicates that AMR appeared before the 4 earthquakes out of the 5 studied cases. The same scanning were performed to search for precursory variation of Benioff strain release around the rupture nucleation point before the strong and intermediatestrength earthquakes. The result shows that accelerating Benioff strain release emerged before 3, out of 5, MSge;5 earthquakes studied.
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