新疆天山近7级地震前震群活动的时空分布演化特征

通过普查与系统研究发现, 新疆天山近7级强震之前, 震群活动携带了丰富震兆信息。 主要结果如下: ① 震前1年半至3年多, 包括未来强震震中在内的整个地震带或某一区段震群活动明显增强; ② 在未来强震震中附近, 震群的数量最多且空间分布最为集中, 这些大量密集的震群构成的震群环包围了未来主震震中, 即形成震群空区或空段。 震群空区或空段的几何形状大多为椭圆, 其最大尺度约200 km; ③ 强震之前, 震群数量的多少, 随未来强震震级的增加而增加; ④ 个别强震前几个月, 震群增加的速率有加快的趋势, 同时震群空区内出现填空, 可作为近7级强震进入短期异常阶段的参考标志。 最后, 对所得结果的物理机制以及在地震预报中的应用等问题进行了讨论。

Evolving Characteristics of Swarm Distrbution before M7 Earthquakes in the Tianshan Area, China

Through investigation and systematic study, it has been found that swarm activity carries rich precursory information. Main results are as follows: ① One and a half to three years before strong earthquakes, swarm activity obviously increases in the whole seismic zone or some segment including future strong earthquake epicenter; ② Around the future epicenter, the number of swarm is the greatest and the swarm most concentrated, the swarm ring surrounds the future main shock, forming swarm gap of eliptical configuration with maximum scale about 200 km; ③ The number of swarms increases with the future earthquake magnitude; ④ Several months before some strongearthquakes, the swarm increasing rate tends to accelerate with gap filling, this can be referred as index of short-term stage for M7 earthquakes; ⑤ Based upon the above results, sucessful short-term prediction has been made for the Oct.5, 2008 Wuqia M6.8 earthquake, Xinjiang Uygur Autonomous Region.