Post-seismic crustal internal deformation in a layered earth model

Abstract

SUMMARY This study introduces a novel method for computing post-seismic crustal internal deformation in a layered earth model. The surface dislocation Love number (DLN) calculated by the reciprocity theorem was implemented as the initial value. Furthermore, numerical integration of the value from the Earth's surface to the interior was undertaken to obtain the internal DLN. This method does not require a combination of the general solution and particular solution for the calculation of internal deformation above the seismic source, thus avoiding the loss of precision. When the post-seismic deformation within a certain period is calculated, the particular solutions at the beginning and end of the considered period cancel each other. This simplifies the calculation of post-seismic internal deformation. The numerical results depict that as the degrees increase, the post-seismic DLN reaches stability in a shorter interval of time. Thus, for improved efficiency of the post-seismic internal deformation calculation, the post-seismic DLNs should be calculated within 2000 degree and integrated with the coseismic results. As an application, the post-seismic Coulomb failure stress changes (∆CFS) induced by the 2011 Tohoku-Oki earthquake in the near field around the Japanese archipelagos and two major faults in Northeast China were simulated. The results exhibit that the ∆CFS values in the near field agree well with those simulated by the method in a half-space layered earth model, thus verifying the present method. The coseismic ∆CFS on the Mishan-Dunhua fault in Northeast China, as an example, is only 0.094–0.668 KPa. However, the ∆CFS caused by the viscoelastic relaxation of the mantle within 5 yr following the 2011 Tohoku-Oki event on the same fault exceeds the coseismic results. Therefore, the cumulative effect of the viscoelastic relaxation of the mantle is deserving of attention.