用非均匀速度模型对汶川8.0级地震余震重新定位

Nonuniform velocity model used in the relocation of Wenchuan Ms 8.0 earthquake and aftershocks

为了进一步探讨龙门山断裂带深部结构,根据四川省地震局提供的地震原始资料,采用Hypo 2000对汶川大地震以及震后M≥2.0级余震进行重新定位。从2008年5月12日汶川发生8.0级大地震后,截止到2011年4月15日,获得了26 278个地震记录。重新定位后对结果的总结为:(1)主震发生在龙门山推覆构造带中央断裂中段的北川-映秀断裂上,余震主要沿龙门山断裂带方向延伸,呈南北分段分布。重新定位后的到时残差为±0.35s,水平误差为±1.32km,深度误差为±5km。(2)在主震附近的映秀、理县和黑水有一条北西向的余震带与龙门山断裂带的捩断层一致。(3)在青川附近(龙门山断裂带的北端),此段成为余震密集地区,这与历史上此地很少有地震发生不吻合。

To further explore the depth structure of the Longmenshan fault zone, according to the original seismic data from the Sichuan Seismological Bureau, the authors relocated the Wenchuan Ms 8.0 earthquake and M≥2.0 aftershocks using the position methods of Hypo 2000. By the end of April 15, 2011, 26278 earthquakes were recorded. After relocation, the results were summarized as follows： （1） The main shock occurred on the Beichuan-Yingxiu fault in the middle sector of the central fault of Longmenshan nappe structural belt and the aftershocks extended along the direction of the fault zone, presenting a distribution of north and south segments. The residual error after relocation is ±0.35 s, the level of error is ±1.32 km, and the depth error is ±5 km. （2） There is a north-west aftershocks belt along Yingxiu-Lixian-Heishui near the main shock which is coincident with the Longmenshan tear fault. （3） The vicinity of Qingchuan （the north end of the Longmenshan fault zone） becomes the aftershocks dense areas, which are not coincident with the fact that few earthquakes occurred in this region in history.