The Characteristics of Seismic Rotations in VTI Medium

Lixia Sun,Yongxiang Wei,Yun Wang,Wei Li

doi:10.3390/app112210845

Lixia Sun, Yongxiang Wei + Show 2 more

Open Access

https://doi.org/10.3390/app112210845

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Abstract

Under the assumptions of linear elasticity and small deformation in traditional elastodynamics, the anisotropy of the medium has a significant effect on rotations observed during earthquakes. Based on the basic theory of the first-order velocity-stress elastic wave equation, this paper simulates the seismic wave propagation of the translational and rotational motions in two-dimensional isotropic and VTI (transverse isotropic media with a vertical axis of symmetry) media under different source mechanisms with the staggered-grid finite-difference method with respect to nine different seismological models. Through comparing the similarities and differences between the translational and rotational components of the wave fields, this paper focuses on the influence of anisotropic parameters on the amplitude and phase characteristics of the rotations. We verify that the energy of S waves in the rotational components is significantly stronger than that of P waves, and the response of rotations to the anisotropic parameters is more sensitive. There is more abundant information in the high-frequency band of the rotational components. With the increase of Thomsen anisotropic parameters ε and δ, the energy of the rotations increases gradually, which means that the rotational component observation may be helpful to the study of anisotropic parameters.

Highlights

It is well known that the six-component records of ground motion include threecomponent translations and three-component rotations [1]
In order to study the mechanism of seismological rotations, many meaningful inquiries have been made by means of indirect calculation, direct observation, and numerical simulation
Ferreira et al [8] simulated the rotations recorded at the fundamental mode of surface waves with the full ray theory (FRT) for laterally smooth heterogeneous Earth models, and found that the synthetic seismograms showed good agreement with the real ones

Summary

Introduction

It is well known that the six-component records of ground motion include threecomponent translations and three-component rotations [1]. Barak et al [11] performed a synthetic seismic experiment on a simple two-layer model rotational components waswhere stronger than that on translational components, which would of a water-covered seabed, there were isolated high-velocity spheres different from be helpful to identify different of waves and separate the surface waves from the the background medium. They modes found that the energy of the Scholte waves on rotational body waves.was. We utilize the splitting form of perfectly matched absorbing layer boundary condition (SPML) [16] to weaken the boundary reflections

Synthetic Examples

Effects

Effects of Anisotropic Parameters on Rotations