Focal mechanism and moment tensor in orthorhombic anisotropic media

TANG Jie1 WEN Lei1 WANG Hao1 ZHANG Wenzheng1

(1.School of Geosciences, China University of Petroleum (East China) , Qingdao, Shandong, China 266580)

【Abstract】Hydraulic fracturing zones have anisotropic characteristics on the whole. It is necessary to analyze the influences of anisotropic parameters on focal mechanism and moment tensor. This paper studies the shear–tensile focal mechanism and seismic moment tensor when the source is located in anisotropic media. It analyzes the influences of focal anisotropy on double couple (DC) components, compensated linear vector dipole (CLVD) components, and isotropic (ISO) components. The seismic response characteristics of dry and saturated orthorhombic anisotropy media are also analyzed. The effects of crack parameters and fluid parameters on seismic response are discussed. The following results are obtained based on our research. A. The moment tensor in anisotropic media can be obtained by anisotropic parameters and source quantity. B. The non-DC components caused by shear–tensile crack depend on the rupture mode, type of anisotropic media, crack parameter and section strike. High ISO components appear in dry cracked media and high CLVD components appear in water saturation media. C. Far field P-wave radiation patterns are different between isotropic and anisotropic media. The source characteristics and medium anisotropy have significant impacts on the seismic wave travel time, amplitude, and polarity.

【Keywords】 orthorhombic anisotropy; microseismic; focal mechanism; moment tensor; shear–tensile source;

【Funds】 National Natural Science Foundation of China (41504097, 41874153)

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This Article

ISSN:1000-7210

CN: 13-1095/TE

Vol 53, No. 06, Pages 1247-1255+1114

December 2018

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Article Outline

Abstract

  • 1 Introduction
  • 2 Shear-tensile source model in orthorhombic anisotropic media
  • 3 Characteristics of the source in orthorhombic anisotropic media
  • 4 Characteristics of microseismic wave field in orthorhombic anisotropic media
  • 5 Conclusions
  • References