Open AccessInvestigating tropospheric effects and seasonal position variations in GPS and DORIS time‐series from the Nepal Himalaya
Author(s) -
Flouzat Mireille,
Bettinelli Pierre,
Willis Pascal,
Avouac JeanPhilippe,
Héritier Thierry,
Gautam Umesh
Publication year - 2009
Publication title -
geophysical journal international
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.302
H-Index - 168
eISSN - 1365-246X
pISSN - 0956-540X
DOI - 10.1111/j.1365-246x.2009.04252.x
Subject(s) - geodetic datum , geodesy , seasonality , global positioning system , troposphere , geology , climatology , doris (gastropod) , amplitude , environmental science , meteorology , geography , statistics , physics , mathematics , computer science , virology , quantum mechanics , biology , telecommunications
SUMMARY 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.