Spatial and temporal variations in creep rate along the El Pilar fault at the Caribbean‐South American plate boundary (Venezuela), from InSAR

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 Ms 6.8 earthquake. The creep is thus interpreted as persistent aseismic slip during an interseismic period, which has a pulse‐ or transient‐like behavior.

Shallow Creep Along the 1999 Izmit Earthquake Rupture (Turkey) From GPS and High Temporal Resolution Interferometric Synthetic Aperture Radar Data (2011–2017)

“…The maximum amplitude (~10 mm in our case, whereas it was~20 mm along the Ismetpasa section) and duration of these shallow bursts (~1 month) are similar. The growing number of evidence for such creep bursts along the North Anatolian Fault, as also suggested by long time series of creepmeter measurements (Altay & Sav, 1991;Bilham et al, 2016), and along other major strike-slip faults worldwide (De Michele et al, 2011;Jolivet, Simons, et al, 2015;Khoshmanesh & Shirzaei, 2018;Pousse-Beltram et al, 2016), suggest that continuously decaying afterslip or steady interseismic creep may not be the rule for creep behavior. New mechanical models are required to account for coupling temporal variations at shallow depth and recurrent creep bursts triggering.…”

“…A recent review by Harris (2017) discussed the earthquake potential of shallow creeping continental faults using worldwide data. Reported cases include the Hayward fault (Savage & Lisowski, 1993;Schmidt et al, 2005), the Supersitition Hills fault (Bilham, 1989;Wei et al, 2009), and the Central San Andreas Fault in California (De Michele et al, 2011, Jolivet, Candela, et al, 2015, Khoshmanesh & Shirzaei, 2018, the Longitudinal Valley fault in Taiwan (Champenois et al, 2012;Thomas et al, 2014), the Ismetpasa segment of North Anatolian Fault in Turkey (Ambraseys, 1970;Bilham et al, 2016;Cakir et al, 2005;Cetin et al, 2014;Kaneko et al, 2013;Rousset et al, 2016), the Izmit and Marmara segment of the North Anatolian Fault (Cakir et al, 2012;Ergintav et al, 2014;Hussain et al, 2016), the Haiyuan fault in China (Jolivet et al, 2012, Jolivet, Simons, et al, 2015, the El-Pilar fault in Venezuela (Jouanne et al, 2011, Pousse-Beltram et al, 2016, and the Chaman fault in Pakistan (Barnhart, 2017;Fattahi & Amelung, 2016). These studies show that the spatial patterns (rate and rate-change distribution along strike and with depth) vary significantly.…”

The Transient and Intermittent Nature of Slow Slip

“…Along any fault network where regional‐scale, dense, and continuous geodetic data sets have been gathered, we have been able to observe slow slip (Figure ). The advent of continuously operating GPS networks and high‐resolution InSAR time series provoked a series of slow slip discoveries across multiple subduction zones and major continental fault networks (e.g., Cavalié et al, ; Duquesnoy et al, ; Pousse Beltran et al, ; Wallace et al, ). We have observed slow slip to exhibit a range of temporal behaviors, including periodic oscillations or episodic transients, along all kinds of plate boundaries, whether convergent, divergent, or transform and even within volcanic contexts (Cervelli et al, ; Doubre & Peltzer, ; Jolivet et al, ; Rogers & Dragert, ).…”

Multiscale Dynamics of Aseismic Slip on Central San Andreas Fault

“…Moreover, assuming a nearly-constant and continuous creep in time, one can estimate the slip deficit and determine the fault's seismic potential (e.g., Jolivet, Simons, et al, 2015;Rolandone et al, 2008). Timedependent observation of the kinematics of creeping segments, on the other hand, indicates that creep evolves as a series of transient accelerating events during interseismic period (e.g., Beltran et al, 2016;Jolivet, Candela, et al, 2015;Lockner et al, 2011;Nadeau & McEvilly, 2004;Turner et al, 2015). These transient events, known as slow slip events, can load surrounding locked patches and possibly trigger seismic events (e.g., Kato et al, 2012;Radiguet et al, 2016;Uchida et al, 2016).…”