Materials of the International Conference
50th Anniversary of the International Geophysical Year
and Electronic Geophysical Year

16-19 September 2007 • Suzdal, Russia

Monitoring of subduction zones dynamics using modern satellite systems

M. Diament1, V. Mikhailov1, 2, I. Panet1, 3, O. de Viron1, and N. Tcybin4

1Institut de Physique du Globe de Paris & University, Paris, France

2Institute of Physics of the Earth, Russian Academy of Sciences, Moscow, Russia

3Institut Gèographique National, Laboratoire de Recherche en Gèodèsie, ENSG, Marne-la-Vallèe, France

4State research Institute of Aviation Systems, Moscow, Russia

Abstract

The GRACE satellite mission has been measuring the Earth's gravity field and its temporal variations since April 2002. Although these variations are mainly due to mass transfer within the geofluid envelops, they also result from mass displacements associated with phenomena including glacial isostatic adjustment and earthquakes. However, these last contributions are difficult to isolate because of the presence of noise and of geofluid signals, and because of GRACE's coarse spatial resolution ($>$400 km half-wavelength). In this paper, we show that a wavelet analysis on the sphere helps to retrieve earthquake signatures from GRACE geoid products. Using a wavelet analysis of GRACE geoids products, we show that the geoid variations caused by the December 2004 (Mw = 9.2) and March 2005 (Mw = 8.7) Sumatra earthquakes can be detected. At GRACE resolution, the December 2004 earthquake produced a strong co-seismic decrease of the gravity field in the Andaman Sea, followed by relaxation in the area affected by both the Andaman 2004 and the Nias 2005 earthquakes. We find two characteristic timescales for the relaxation, with a fast variation occurring in the vicinity of the Central Andaman ridge. We discuss our co-seismic observations in terms of density changes of crustal and upper mantle rocks, and of the vertical displacements in the Andaman Sea. We interpret the post-seismic signal in terms of the visco-elastic response of the Earth's mantle. The transient component of the relaxation may indicate the presence of hot, viscous material beneath the active Central Andaman Basin.

Citation: M. Diament, V. Mikhailov, I. Panet, O. de Viron, and N Tcybin (2007), Monitoring of subduction zones dynamics using modern satellite systems, in: Materials of the International Conference '50th Anniversary of the International Geophysical Year and Electronic Geophysical Year', GC RAS, Moscow, doi:10.2205/2007-IGY50conf.

© 2007 Geophysical Center RAS and authors


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