Abstract

A systematic study towards understanding the correlation between polarization direction of crustal anisotropy with seismogenic stress field at different locations of the Shillong-Mikir Plateau and its vicinity in North East India is attempted. We used data from a 17-station broadband seismic network. In our earlier work , crustal anisotropic parameters were determined using ANISOMAT + for the 17 seismic stations. In this study, we have estimated stress field around the stations using focal mechanism solutions (FMS). Some 215 FMS are obtained by waveform inversion. These solutions are used for stress tensor inversion to estimate stress field around each location. It is observed that polarization direction of crustal anisotropy is consistent with that of the maximum horizontal stress (_Ơmax) as well as the minimum horizontal stress (_Ơmin). In addition to this, two orthogonal fast polarizations in some locations are also noted. The bivariate nature of correlations helps us to understand that the major mechanisms of seismic crustal anisotropy are not only due to the regional stress, but active faults and other geological conditions play a significant role in contemporary orientation of seismic crustal anisotropy and seismogenic stress field.

摘要

试图系统研究地壳各向异性极化方向与印度东北部西隆-米基尔高原及其附近不同位置的地震应力场之间的相关性。我们使用了来自 17 个台站的宽带地震网络的数据。在我们早期的工作中，使用 ANISOMAT + 确定了 17 个地震台站的地壳各向异性参数。在本研究中，我们使用震源机制解 (FMS) 估算了台站周围的应力场。大约 215 个 FMS 是通过波形反演获得的。这些解用于应力张量反演以估计每个位置周围的应力场。观察到地壳各向异性的极化方向与最大水平应力( _Ơmax) 以及最小水平应力 ( _Ơmin )。除此之外，还注意到某些位置的两个正交快速极化。相关性的双变量性质有助于我们理解地震地壳各向异性的主要机制不仅是由于区域应力，而且活动断层和其他地质条件在地震地壳各向异性和发震应力场的当代定向中起着重要作用。