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Spatial and temporal variations in creep rate along the El Pilar fault at the Caribbean‐South American plate boundary (Venezuela), from InSAR
Author(s) -
Pousse Beltran Léa,
Pathier Erwan,
Jouanne François,
Vassallo Riccardo,
Reinoza Carlos,
Audemard Franck,
Doin Marie Pierre,
Volat Matthieu
Publication year - 2016
Publication title -
journal of geophysical research: solid earth
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.983
H-Index - 232
eISSN - 2169-9356
pISSN - 2169-9313
DOI - 10.1002/2016jb013121
Subject(s) - interferometric synthetic aperture radar , geology , creep , geodesy , slip (aerodynamics) , seismology , plate tectonics , fault (geology) , tectonics , satellite , synthetic aperture radar , remote sensing , materials science , physics , aerospace engineering , engineering , composite material , thermodynamics
Abstract In eastern Venezuela, the Caribbean‐South American plate boundary follows the El Pilar fault system. Previous studies based on three GPS campaigns (2003–2005–2013) demonstrated that the El Pilar fault accommodates the whole relative displacement between the two tectonic plates (20 mm/yr) and proposed that 50–60% of the slip is aseismic. In order to quantify the possible variations of the aseismic creep in time and space, we conducted an interferometric synthetic aperture radar (InSAR) time series analysis, using the (NSBAS) New Small BAseline Subset method, on 18 images from the Advanced Land Observing Satellite (ALOS‐1) satellite spanning the 2007–2011 period. During this 3.5 year period, InSAR observations show that aseismic slip decreases eastward along the fault: the creep rate of the western segment reaches 25.3 ± 9.4 mm/yr on average, compared to 13.4 ± 6.9 mm/yr on average for the eastern segment. This is interpreted, through slip distribution models, as being related to coupled and uncoupled areas between the surface and ~ 20 km in depth. InSAR observations also show significant temporal creep rate variations (accelerations) during the considered time span along the western segment. The transient behavior of the creep is not consistent with typical postseismic afterslip following the 1997 M s 6.8 earthquake. The creep is thus interpreted as persistent aseismic slip during an interseismic period, which has a pulse‐ or transient‐like behavior.