各向异性HTI介质中的剪张源矩张量特征研究

Characteristics of moment tensor of shear-tensile source in HTI anisotropic media

水力压裂区整体上呈现各向异性特征,有必要针对水力压裂区的各向异性参数对震源机制和矩张量的影响进行深入研究和分析。研究了震源区为HTI各向异性介质情况下的剪张源震源机制与地震矩张量,分析了震源区HTI各向异性对双力偶分量(DC)、补偿线性偶极子分量(CLVD)和各向同性分量(ISO)的影响,比较了介质参数对于地震矩张量的影响。在此基础上研究了各向异性介质中剪张源的沙滩球和辐射花样。研究结果表明,各向异性介质中的矩张量参数依赖于各向异性的类型和强度以及断层面的方向等参数;含裂隙岩石的背景孔隙度、裂纹弱度等参数的变化会影响各向异性参数,进而对地震矩张量产生影响;地震矩张量中的非DC分量可能来自震源区介质各向异性的影响。

A hydraulic fracturing area is characterized by anisotropy as a whole.It is essential to analyze the effect of these anisotropic parameters on the focal mechanism and the moment tensor in a hydraulic fracturing area.Shear-tensile source focal mechanisms,and seismic moment tensors,are studied where the source region was HTI anisotropic medium.HTI anisotropy can influence double couple components(DC),the compensation of linear dipole components(CLVD),and isotropic components(ISO).The influence of media parameters on seismic moment tensors was compared,and the beach ball and radiation patterns of shear-tensile sources in anisotropic media were studied.Results indicated that the non-DC mechanism can comprise both the ISO and CLVD components,and that the amount of the ISO and CLVD components depended on the strength and symmetry of the anisotropy,and the orientation of the faulting.Changes to background porosity and crack weakness would affect the anisotropic parameters in the fractured rock,leading to influence on the moment tensor of the source.It was considered that the non-DC component of the moment tensor was likely to be generated from the anisotropy of the source area.