Detection of a half-microgal coseismic gravity change after the Ms7.0 Lushan earthquake

Abstract

Because only a small near-field coseismic gravity change signal remains after removal of noise from the accuracy of observations and the time and spatial resolution of the earth's surface gravity observation system, it is difficult to verify simulations of dislocation theory. In this study, it is shown that the GS15 gravimeter, located 99. 5 km from the epicenter of the Ms7. 0 Lushan earthquake on April 20, 2013 at 08 : 04 UTC+8, showed the influence of the earthquake from 2013-04-16 to 2013-04-26 after a time calibration, tide corrections, drift correction, period correction and relaxation correction were applied to its data. The post-seismic relaxation process of the spring in the gravimeter took approximately 430 minutes and showed a 2. 5×10−8 ms−2 gravity change. After correcting for the relaxation process, it is shown that a coseismic gravity change of approximately +0. 59±0. 4×10–8 ms–2 was observed by the GS15 gravimeter; this agrees with the simulated gravity change of approximately 0. 31×10–8 ms–2. The rate of the coseismic gravity change and the coseismic vertical displacement, as measured by one-second and one-day sampling interval GPS units, is also consistent with the theoretical rate of change. Therefore, the GS15 gravimeter at the Pixian Station observed a coseismic gravity change after the Ms7. 0 Lushan earthquake. This and similar measurements could be applied to test and confirm the theory used for these simulations.

Keywords

• GS15 gravimeter
• coseismic gravity change
• the Ms7. 0 Lushan earthquake