天水地震区S波偏振异常

THF POLARIZED ANOMALY OF S WAVE IN TIANSHUI EARTHQUAKE AREA

摘要:

本文给出中国大陆西部天水地区地壳测深研究工作中S波激发与接收,S波有效观测窗口,S波分裂和偏振异常特征与介质地震各向异性以及区域构造应力场作用主方向关系的研究试验结果。结果表明,利用普通钻井爆炸震源,震源位于含水层以下,能够激发出较强的S波。采用三个分量拾震器,不但能够较好地接收到莫霍界面上反射的S波波列,而且在不同的观测距离观测到不同深度界面反射的S波。天水地区试验结果给出M面反射S波最佳观测窗口为170公里左右,并存在着明显的S波分裂与偏振异常。超前S波偏振优势方向为近东西方向,与该区震源机制解研究得到的最大主压应力方向(P轴方向)基本一致。而晚到S波偏振优势方向为近南北向,与该区现今最大主压应力方向垂直。

Abstract:

The experiment results about the excitation and reception,effect measurement window,splitting,relationship between polarized anomaly,anisotropy and principal stress direction of S waves in Tianshui earthquake area have been given in this article.A common hypocenter of the explosion located under the water-bearing bed can excites stronger S waves.The S waves can be received not only from Moho but also from other interface using three component geophone.The optimal window of Sm in this experiment is about 170kin and the obvious S-splitting and polarization anomaly exist there.The predominant polarized direction of faster S-wave is near E-W which is basically agree with the maximum principal compressive stress direction (P-axis),the slower S-wave is near N-S which across modern maximum principal compressive stress direction.