Finite-fault simulations for rotations and strains in the near-fault subjected to layered reduced micropolar half-space

Abstract

The unmatched seismic theoretical rotations from the experimental data led the researchers to develop the reduced micropolar theory in seismology. The study here mainly focuses on the finite-fault simulations for rotations and strains in the near-fault region for a causative strike-slip fault of the \(M_w\) 6.5 event. Firstly, the parametric investigation is performed on additional material parameters, viz. micropolar couple modulus and microinertia density to the rotations and strains. Secondly, the seismic source parameters such as rupture velocity, slip velocity, burial fault depth, earthquake magnitude, hypocenter location and slip amplitude are varied to see the effect of these parameters on rotations and strains seismograms. The results in different scenarios are compared to the classical elastic medium and reduced micropolar medium. The rotations obtained using reduced micropolar theory are comparatively high to the rotations of classical elastic theory. Although, the obtained displacements in both theories are almost the same. The normal strains in both theories are equivalent, while the shear strains differ as the shear strains in reduced micropolar theory are asymmetric and rotation dependent. The increment in the value of microinertia density increases the rotations, however, the converse is true in the case of micropolar couple modulus. The parametric analysis results demonstrate that near-fault ground rotations and strains are highly sensitive to changes in the seismic source parameters. For instance, modelling the medium homogeneous decreases the amplitude and duration of seismograms sharply compared to layered media. Finally, peak ground contours of displacements, rotations and strains are presented for different hypocenter locations using grid point simulation, and it is found that a change of hypocenter location alters the spatial distribution of peak values of these quantities in the near-fault region of the surface plane. Nevertheless, the maximum limit of peak values over the entire ground surface is near equal for the different hypocentral locations.