Applications of satellite gravity missions in co-seismic gravity and geoid changes

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This project is mainly about theoretical research on the following aspects: 1. to investigate whether or not co-seismic geoid and gravity changes detectable from space, i.e., the satellite gravity missions. In this study, global deformations caused by large earthquakes are considered with taking satellite spatial resolution into account. Then based on the result, a method to determine Dislocation Love Numbers using the data observed by satellite gravity missions are presented. 2. New theory on co-seismic strain changes for a spherical earth is presented. The effects of the Earth's curvature and radial heterogeneity are also investigated through comparing the co-seismic deformations caused by dislocations in half-space and homogeneous spherical earth models, a homogeneous sphere and a layer spherical model. It was learnt that both the effects are large. 3. The sub-micro gal co-seismic gravity changes caused by the 2002 Hokkaido earthquake were successfully detected by superconducting gravity network, and is well explained by Sun and Okubo's dislocation theory. 4. This project also investigated co-seismic displacement, gravity and geoid changes caused by the 2004 Sumatra earthquake. The above results have been presented in Japanese Geodetic Conferences, The Japanese Geosciences Union Assembly, the Dynamic Planet Conference, and America Geophysical Union Assembly. In summary, there are 9 papers have been published in internal and international journals, such as, Journal of Geophysical Research, Geophysical Research Letter, Science, and so on.