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Modeling deformation induced by seasonal variations of continental water in the Himalaya region: Sensitivity to Earth elastic structure

Chanard, K. and Avouac, J. P. and Ramillien, G. and Genrich, J. (2014) Modeling deformation induced by seasonal variations of continental water in the Himalaya region: Sensitivity to Earth elastic structure. Journal of Geophysical Research. Solid Earth, 119 (6). pp. 5097-5113. ISSN 2169-9313. doi:10.1002/2013JB010451.

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Strong seasonal variations of horizontal and vertical positions are observed on GPS time series from stations located in Nepal, India, and Tibet (China). We show that this geodetic deformation can be explained by seasonal variations of continental water storage driven by the monsoon. For this purpose, we use satellite data from the Gravity Recovery and Climate Experiment to determine the time evolution of surface loading. We compute the expected geodetic deformation assuming a perfectly elastic Earth model. We consider Green's functions, describing the surface deformation response to a point load, for an elastic homogeneous half-space model and for a layered nonrotating spherical Earth model based on the Preliminary Reference Earth Model and a local seismic velocity model. The amplitude and phase of the seasonal variation of the vertical and horizontal geodetic positions can be jointly adjusted only with the layered Earth model, while an elastic half-space model fails, emphasizing the importance of using a realistic Earth elastic structure to model surface displacements induced by surface loading. We demonstrate, based on a formal inversion, that the fit to the geodetic data can be improved by adjusting the layered Earth model. Therefore, the study also shows that the modeling of geodetic seasonal variations provides a way to probe the elastic structure of the Earth, even in the absence of direct measurements of surface load variations.

Item Type:Article
Related URLs:
URLURL TypeDescription Information
Chanard, K.0000-0001-9934-9621
Avouac, J. P.0000-0002-3060-8442
Additional Information:© 2014 American Geophysical Union. Received 27 JUN 2013; Accepted 8 APR 2014; Accepted article online 12 APR 2014; Published online 6 JUN 2014. This research was funded by the Gordon and Betty Moore Foundation through the Tectonics Observatory at Caltech and by NSF grant EAR-0838495. We thank John Galetzka and all our collaborators at Laboratoire de détection et géophysique (CEA/LDG, France) and the Nepal Seismological Center and the Department of Mines and Geology (Nepal), for their contribution to the deployment, maintenance, and operation of the cGPS stations used in this study. We are indebted to Takeo Ito for introducing K.C. to the computation of the Green functions for a spherical Earth model. This is a Tectonics Observatory contribution. We also thank Jeff Freymueller and one anonymous reviewer for thorough and helpful reviews, as well as Duncan Agnew for comments on an early version of this manuscript.
Group:Caltech Tectonics Observatory, Seismological Laboratory
Funding AgencyGrant Number
Caltech Tectonics ObservatoryUNSPECIFIED
Gordon and Betty Moore FoundationUNSPECIFIED
Subject Keywords:GPS; GRACE; tectonics; geodesy; surface hydrology; Himalaya
Issue or Number:6
Record Number:CaltechAUTHORS:20140829-084652794
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Official Citation:Chanard, K., J. P. Avouac, G. Ramillien, and J. Genrich (2014), Modeling deformation induced by seasonal variations of continental water in the Himalaya region: Sensitivity to Earth elastic structure, J. Geophys. Res. Solid Earth, 119, 5097–5113, doi:10.1002/2013JB010451
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:49051
Deposited By: Tony Diaz
Deposited On:29 Aug 2014 20:43
Last Modified:10 Nov 2021 18:39

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