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Investigating tropospheric effects and seasonal position variations in GPS and DORIS time-series from the Nepal Himalaya

Flouzat, Mireille and Bettinelli, Pierre and Willis, Pascal and Avouac, Jean-Philippe and Héritier, Thierry and Gautam, Umesh (2009) Investigating tropospheric effects and seasonal position variations in GPS and DORIS time-series from the Nepal Himalaya. Geophysical Journal International, 178 (3). pp. 1246-1259. ISSN 0956-540X. doi:10.1111/j.1365-246X.2009.04252.x.

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Geodetic time-series from continuous GPS (cGPS) and 1 DORIS stations across the Himalaya of central Nepal show strong seasonal fluctuations observed on the horizontal and vertical components. Because the fluctuations determined at the different stations have similar phase but different amplitudes, these observations would imply that the secular shortening across the range is modulated by a seasonal strain. Given the geographic and climatic setting, there is however a possibility that the GPS positions be biased by tropospheric effects. We process these data using two different software packages and two different analysis strategies. Our analysis shows evidence for 1-strong seasonal fluctuation of zenithal delays consistent with in situ meteorological data and two strong horizontal tropospheric gradients in particular in the EW direction, that is, parallel to the mountain front at Gumba, also detected in DORIS results. We show that the tropospheric effects cannot however be the source of the observed seasonality of horizontal strain. This study supports the view that the seasonal strain in the Himalaya is real and probably driven by seasonal surface load variations. Our study adds support to the view that seasonal variations of seismicity in the Himalaya reflects seasonal variations of geodetic strain.

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Avouac, Jean-Philippe0000-0002-3060-8442
Additional Information:© 2009 The Authors. Journal compilation © 2009 RAS. Accepted 2009 May 13. Received 2009 April 16; in original form 2009 February 9. We are most grateful to M.R. Pandey and all our collaborators, at NSC and DMG, and at CEA/DASE for their dedicated effort, which permitted the deployment, maintenance, and operation of the cGPS stations. This study has benefited from discussions with François Jouanne (LGCA, Université de Savoie, France), Christophe Vigny and Rodolphe Cattin (Ecole Normale Supérieure, ENS, Paris). We are grateful to Jeff Freymuller and Becky Bendick for constructive reviews of the manuscript. Roger Bilham A. Waldersporsf, K. Heki, and an anonymous reviewer also provided helpful comments on an earlier version of that manuscript. Part of this work was supported by the Centre National d'Etudes Spatiales (CNES). It is based on observations with DORIS embarked on SPOTs, TOPEX/Poseidon and ENVISAT satellites. This paper is IPGP contribution 2491 and Tectonic Observatory contribution 103.
Group:Caltech Tectonics Observatory, Caltech Tectonics Observatory. Indo-Asian Collision Zone, Seismological Laboratory
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Centre National d'Études Spatiales (CNES)UNSPECIFIED
Subject Keywords:Time series analysis; Satellite geodesy; Transient deformation; Ionosphere/atmosphere interactions; Hydrology; Asia
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Caltech Tectonics Observatory103
Issue or Number:3
Record Number:CaltechAUTHORS:20090828-231037041
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:15468
Deposited By: George Porter
Deposited On:15 Sep 2009 16:26
Last Modified:08 Nov 2021 23:19

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