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Abstract:
Anisotropy is an important characteristic of the Earth’s materials that has long been confirmed in the analysis of the Earth’s free oscillations due to Love and Rayleigh waves, as well as wide azimuth and long offset seismic data acquisition in exploration seismology. Anisotropy in the Earth is generally occurred in the specific form of transverse isotropy in which the material properties are symmetric with respect to a direction known as symmetry axis, usually assumed to be aligned with the local vertical. Besides the common consequences of seismic anisotropy including, variations of seismic velocities with a direction and shear wave splitting, it also affects on the moment tensor interpretation. Here we proposed the new analytical solution for the three-dimensional transient dislocation Green’s tensor in a transversely isotropic half-space and use this formulation for synthesizing the theoretical seismogram due to a ramp-type moment tensor source. Synthetic examples conducted for some sedimentary rocks reveal the effects of anisotropy on the amplitude of seismic waves and their travel time from the source to the receiver. We also illustrate how the apparent non-double couple components of moment tensor due to anisotropy, can change the polarity of P-wave at different source-receiver epicental distances and azimuth. Another important and interesting feature of this formulation is the fact that it also contains the long-term static solution, showing the total co-seismic deformation after the Earthquake.
