Research toward understanding earthquakes at ultra-low frequencies by analyzing satellite altimetry data.

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We have detected a significant subsidence of the sea level of the Pacific near the coast of Peru and Chile after the 1994 Bolivia earthquake by analyzing the TOPEX/POSEIDON satellite altimetry data. The isotropic pattern of the sea surface change indicates the existence of isotropic implosion source with time scale of less than 10 days. This finding provides the evidence for the phase change of mantle minerals as a critical factor for deep earthquakes.We presented a theory for displacement caused by a point dislocation in a radially heterogeneous spherical earth. The objective of this research was to constrain the fault model of the 1994 Bolivia earthquake by using GPS observations on the Pacific coast of the South American continent.In order to achieve well constrained fault model, we investigate the possibility of using absolute gravity values which complement the geoid height change. For that purpose, we verified the 1 microgal precision of the new generation absolute gravimeter FG5 by collocation with superconducting gravimeters.