2008年以来荣昌地区地震重新定位及地震丛集原因初探

Earthquake relocation and a preliminary study on the causes of seismic clustering in Rongchang, Chongqing since 2008

摘要:

通过对荣昌地区地震重新定位，结合当地注水资料，对该地区2008年以来地震丛集的原因进行初步研究。收集了2007～2011年6月间荣昌台记录的131个远震，计算了这些地震的接收函数，用H-Kappa叠加方法得到台站下方及附近的莫霍面深度，并用线性反演方法反演了该区s波速度结构。利用接收函数反演得到的速度结构，采用双差定位方法对荣昌及其邻区2008—2011年8月间肘。≥1．0地震进行了重新定位，得到了408个地震的精确位置。重定位结果显示地震的水平震中分布与华蓥山断裂走向一致，另外在通过2010年舭．7地震震中且垂直于华蓥山断裂的剖面中，地震分布所勾画的发震断层轮廓显示地震的发震断层倾向为sE，倾角约70。左右，这与华蓥山断裂的产状（50。L75。）较为一致。分析了注水点与地震分布的空间关系及注水量与地震频度的关系，认为注水井位置距离2008年以来的几次4级地震震中较远，震源深度主要分布在6—7kin，且注水量与地震频度的对应关系不显著，地震丛集性原因尚待更多研究。

Abstract:

In this paper, a preliminary study of the causes of the earthquake clustering in Rongchang, especially since 2008, was made by relocating earthquakes and analyzing the data of fluid injection in this area. First, 131 records （from 2007 to June 2011） of teleseismic events at Rongchang station were used to extract receiver function, and the Moho depth and S-wave velocity structure beneath this station were estimated by using H-Kappa stacking method and linear inversion method, respectively. Then, hypoDD was applied to relocate the earthquakes in this region, with the velocity model obtained from receiver function inversion. The result shows that, the distribution of the epicenters is consistent with the strike of the Huayinshan fault; the profile across the ）144.7 earthquake 2010 and perpendicular to the strike of Huayinshan fault illustrates the seismogenic structure dip to SE, the angle is about 70~, which is in accordance with the attitude of the Huayinshan fault. Lastly, neither the large separation between fluid injection well and ccntroid of earthquake sequence nor unclear connection between fluid injection rate and earthquake frequency supports the induced seismicity hypothesis.[著者文摘]