Abstract
In this study, Gravity Recovery and Climate Experiment (GRACE) RL05 data from January 2003 to October 2014 were used to extract the coseismic gravity changes induced by the 24 May 2013 Okhotsk Mw8.3 deep-focus earthquake using the difference and least square fitting methods. The gravity changes obtained from GRACE data agreed well with those from dislocation theory in both magnitude and spatial pattern. Positive and negative gravity changes appeared on both sides of the epicenter. The positive signature appeared on the western side, and the peak value was approximately 0.4 microgal (1 microgal = 10−8 m/s2), whereas on the eastern side, the gravity signature was negative, and the peak value was approximately −1.1 microgal. It demonstrates that deep-focus earthquakes Mw ≤ 8.5 are detectable by GRACE observations. Moreover, the coseismic displacements of 20 Global Positioning System (GPS) stations on the Earth’s surface were simulated using an elastic dislocation theory in a spherical earth model, and the results are consistent with the GPS results, especially the near-field results. We also estimated the gravity contributions from the coseismic vertical displacements and density changes, analyzed the proportion of these two gravity change factors (based on an elastic dislocation theory in a spherical earth model) in this deep-focus earthquake. The gravity effect from vertical displacement is four times larger than that caused by density redistribution.
Highlights
Since its launch in 2002, the Gravity Recovery and Climate Experiment (GRACE) satellites have collected more than 12 years of data, which are used for various purposes, such as determining changes in glacier mass [1,2,3], terrestrial water storage [4,5], and vertical deformation caused by seasonal hydrological loading [6,7,8]
We modeled the coseismic displacements at 20 Global Positioning System (GPS) stations based on the dislocation dislocation theory
The coseismic gravity signatures induced by the 2013 Okhotsk Mw8.3 earthquake are detected using different approaches: GRACE’s monthly difference method and the time series least square fitting (LSF)
Summary
Since its launch in 2002, the Gravity Recovery and Climate Experiment (GRACE) satellites have collected more than 12 years of data, which are used for various purposes, such as determining changes in glacier mass [1,2,3], terrestrial water storage [4,5], and vertical deformation caused by seasonal hydrological loading [6,7,8]. Tanaka et al [23] extracted the coseismic gravity steps using a time series analysis of GRACE’s monthly data spanning from February 2011 to June 2014 They analyzed the gravity contributions of the coseismic vertical deformations obtained via the half-space dislocation theory proposed by Okubo [24]. The coseismic gravity changes caused by the vertical deformation exceeded those caused by density changes by one order of magnitude Their results were calculated by an elastic half-space dislocation theory proposed by Okubo [24], and they did not take into account the effects of the earth’s layered structure and the curvature of the earth. We compared the results obtained by both of the two dislocation theories (based on spherical layered earth model and half-space earth model), and the results show that the elastic dislocation theory in layered earth model is necessary when calculating the deformations caused by deep-focus earthquakes
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
