Coseismic changes of gravitational potential energy induced by global earthquakes based on spherical‐Earth elastic dislocation theory

Abstract

We compute the coseismic gravitational potential energy Eg change using the spherical‐Earth elastic dislocation theory and either the fault model treated as a point source or the finite fault model. The rate of the accumulative Eg loss produced by historical earthquakes from 1976 to 2016 (about 42,000 events) using the Global Centroid Moment Tensor Solution catalogue is estimated to be on the order of −2.1 × 1020 J/a, or −6.7 TW (1 TW = 1012 W), amounting to 15% in the total terrestrial heat flow. The energy loss is dominated by the thrust faulting, especially the megathrust earthquakes such as the 2004 Sumatra earthquake (Mw 9.0) and the 2011 Tohoku‐Oki earthquake (Mw 9.1). It is notable that the very deep focus events, the 1994 Bolivia earthquake (Mw 8.2) and the 2013 Okhotsk earthquake (Mw 8.3), produced significant overall coseismic Eg gain according to our calculation. The accumulative coseismic Eg is mainly lost in the mantle of the Earth and also lost in the core of the Earth but with a relatively smaller magnitude. By contrast, the crust of the Earth gains gravitational potential energy cumulatively because of the coseismic deformations. We further investigate the tectonic signature in the coseismic crustal Eg changes in some complex tectonic zone, such as Taiwan region and the northeastern margin of the Tibetan Plateau. We found that the coseismic Eg change is consistent with the regional tectonic character.

Seismic Contributions to Secular Changes in Global Geodynamic Parameters

“…where k and h represent the dislocation Love numbers, and F eq is the scale factor for each earthquake which is a function of rupture area, and rupture slip, which can be deduced from a finite fault model. We briefly summarize the formula of coseismic changes in geodynamic parameters, and more details can be found in Xu et al (2014), Xu and Chao (2017);Xu (2021).…”

“…Earthquake-induced mass redistribution can perturb global geodynamic parameters according to linear and angular momentum conservation. We summarized the formulas used to compute coseismic changes in geodynamic parameters below, including polar motion excitation component x and y (χ x and χ y ), variation in length of day (ΔLOD) and oblateness of Earth (ΔJ 2 ), and changes in the total moment of inertia (ΔT); for details see Xu et al (2014), Xu and Chao (2017);Xu (2021).…”

“…Here, we take the coseismic and postseismic excitation as the seismic excitation. The function of global geodynamic parameters induced by an earthquake is mathematically described as follows: where, 𝐴𝐴 𝐴𝐴 𝑒𝑒𝑒𝑒 𝑐𝑐𝑐𝑐 represents coseismic excitation of global geodynamic parameters (Xu et al, 2014;Xu & Chao, 2017 based on the spherical-Earth dislocation theory (Sun et al, 2009), and the formulas used to calculate them are given in Appendix A. t denotes the timing of each earthquake, and H(t) is the Heaviside function. The long-term coseismic contribution is cumulatively superimposed from individual earthquakes.…”

GRAFT: A Model for Evaluating Actuator Systems in Terms of Force Production

“…There are hundreds, perhaps thousands, of papers, surveys, and proposed ideas discussing a very wide range of issues relating to Earth, astronomy, and IoT knowledge [39][40][41][42]. However, as we searched extensively for related works to ours, we found that no previous work discussed the computation of net force produced by actuators on Earth conceptually as described in this paper.…”

Seismic Effects on the Secular Drift of the Earth's Rotational Pole

“…We cannot rule out that possibility a priori, but to believe that is qualitatively to deny the long‐term geodynamic evolution of the Earth. That would be inconsistent with the finding of the decreasing trend of the coseismic gravitational energy change: Governed by the second law of thermodynamics, typically only a small fraction of natural energy transport winds up in doing mechanical work elsewhere while the majority dissipates into heat (Chao et al, ; Chao & Ding, ; Xu & Chao, ). Moreover, there is no telling where the compensating mass changes would occur relative to each other or more importantly whether or not their effect would happen to cancel each other out for the particular geodynamic quantity in question, in our case the polar motion excitation which depends critically on the latitude and longitude.…”