New Method for Computing Postseismic Deformations in a Realistic Gravitational Viscoelastic Earth Model

Abstract

AbstractAfter extensive development of the dislocation theories regarding static deformations that are due to earthquakes, coseismic deformations can be well explained by the present elastic dislocation theories. However, it is difficult to separate and interpret the contributions from interseismic and postseismic deformations, because various mechanisms are involved, including the coupling of the fault interface, aftershock activity, porous‐elastic rebound, and viscoelastic relaxation. It is only possible to infer the dominant mechanism for an earthquake via multiobservation of postseismic deformations in regions that have a dense geodetic network. Accurately simulating a process in a realistic Earth model is a unique way to overcome this difficulty. Here, we present a new robust, accurate, and antioscillational method for modeling the postseismic deformations that are due to viscoelastic relaxation in a realistic gravitational spherical Earth model with linear viscoelastic rheological models. The viscoelastic dislocation Love numbers are evaluated by comparing the results of Sun and Okubo (1993, https://doi.org/10.1029/95JB03536), those of Tanaka et al. (2006 https://doi.org/10.1111/j.1365-246X.2005.02821.x, 2007, https://doi.org/10.1111/j.1365-246X.2007.03486.x), and our newly derived analytical results. The satisfactory consistency between our new results and previous ones demonstrates that our proposed method is highly accurate. This robust and accurate forward modeling approach is helpful for investigating and separating the major mechanism of the postseismic deformations and will greatly benefit the inverse investigation of the ground viscoelastic parameters from geodetic observations.