2014年云南盈江两次中强震发生前后震源区P波速度变化

P-wave velocity changes in the source area before and after two moderate strong earthquakes in Yingjiang, Yunnan in 2014

  • 摘要: 基于云南地震台网的地震记录,利用基于双差层析成像的时移层析成像方法,开展了2014年5月24日盈江MS5.6和5月30日MS6.1地震前后震源区地下P波速度变化的时空特征研究。结果表明:在盈江MS5.6地震后,震源区的P波速度轻微下降,在MS6.1地震后,相对于MS5.6地震,P波速度继续下降,并下降至最低,下降幅度约为1%,说明P波速度下降的幅度可能与主震的震级大小相关。另外,本研究还观测到P波速度下降与余震分布的时空变化相关,可能是由于余震的动态和静态应力变化造成震源区介质物理性质发生改变,从而导致地震波速度的变化。在两次地震发生后约五年内,震源区P波速度值上升,上升幅度小于震后总下降幅度,但这并不能表明震源区还处于愈合过程中。

     

    Abstract: The time-lapse tomography method based on double-difference tomography can obtain high-precision seismic wave velocity changes. In this study, we applied this method to the seismic data set that recorded by the Yunnan seismic network to obtain the spatiotemporal changes of P-wave velocity in the source area during the MS5.6 and MS6.1 Yingjiang earthquakes in 2014. The results showed that the spatial and temporal characteristics of the P-wave velocity of the crust at depth around the source area suggest co-seismic velocity reductions. After the MS5.6 earthquake occurred on May 24, the P-wave velocity of the crust dropped slightly. After the MS6.1 earthquake occurred on May 30, the P-wave velocity dropped definitely with an amplitude of about 1%. It showed that the amplitude of the reduction is related to the magnitude of the mainshock. We also reported that P-wave velocity is also related to the the spatio-temporal changes of aftershocks distribution. It is possible that of dynamic and static stresses changes of the aftershocks caused changes of the physical properties in the source area which leads to the velocity change. Finally, about five years after the Yingjiang earthquakes, a healing process is observed. And the rising level did not reach the previous falling level. However, this does not mean that the source area is still in the healing process.

     

/

返回文章
返回