Maule 2010 and Tohoku 2011 Earthquakes Gravity Signals as seen by a Directional Analysis of GRACE Data
Hayn, Michael1; Panet, Isabelle2; Mikhailov, Valentin3; Bonvalot, Sylvain4; Frappart, Frederic4; Ramillien, Guillaume4; Seoane, Lucia4; Holschneider, Matthias5; Diament, Michel6
1Institut National de l'Information Geographique et Forestiere, Paris, FRANCE; 2Institut National de l'Information Geographique et Forestiere, Laboratoire LAREG, Universite Paris 7, Paris, FRANCE; 3Institute of Physics of the Earth, Russian Academy of Sciences, B. Gruzinskaya 10, Moscow, RUSSIAN FEDERATION; 4Observatoire Midi-Pyrénées, Laboratoire Geosciences Environnement (Université de Toulouse, CNRS, IRD, CNES), Toulouse, FRANCE; 5Institute for Mathematics, University of Potsdam, Am Neuen Palais 10, 14469 Potsdam, GERMANY; 6Univ Paris Diderot, Sorbonne Paris Cite, Institut de Physique du Globe de Paris, CNRS, Paris, FRANCE
Earthquakes cause mass shifts that can be detected from GRACE, as shown in former studies. Satellite gravity thus proved to efficiently complement ground networks in the areas of large earthquakes. This can be used in order to understand the rheological properties of the lithosphere and upper mantle and to study the seismic cycle.
Since the signal is relatively weak and the resolution is at the lower limit of the resolution range of the monthly GRACE data, sophisticated methods are needed in order to better separate the signal from the noise and to maximize the information derived from the satellite data. In this study, the investigation shall be concentrated to the recent earthquakes in Maule 2010 and Tohoku 2011.
We use directional wavelet analysis and reconstruction for investigating the signal in different directions and spatial scales. Our approach takes advantage of the directionality of the earthquake signal and of the aliasing effects in order to separate one from each other. Time analysis methods are applied to isolate the co- and postseismic signals in the time series of the wavelet transforms.