Present-day deformation along the El Pilar Fault in eastern Venezuela: Evidence of creep along a major transform boundary

Jouanne, François; Audemard, Franck; Beck, Christian; Welden, Aurélien van; Ollarves, Reinaldo; Reinoza, Carlos

doi:10.1016/j.jog.2010.11.003

Cited by 27 publications

(59 citation statements)

References 42 publications

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“…It should be noted that the step width estimation is limited at its lower boundary not only by the spatial resolution of the InSAR velocity map, which is 30 m, but also by the prior interferogram filtering done on the basis of 6 pixel size windows, which is 180 m (see section 3). Taking that limit into account, it is likely that in some places the creep could reach the surface, which is supported by field observations [ Audemard , ; Jouanne et al ., ].…”

Section: Insar Inversion Resultsmentioning

confidence: 99%

“…Although the beginnings and endings of each phase are not well constrained due to the low temporal sampling, the two phases can be defined as Phase I between June 2007 and June 2009, with an average velocity of 15.2 ± 6.4 mm/yr, and Phase II from June 2009 to February 2011, during which time average velocity significantly increased and reached 30.2 ± 18.0 mm/yr. Such an acceleration has been already observed in the field based on measurements of local displacement markers during the 2002–2003 period following the 1997 earthquake [ Audemard , ; Jouanne et al ., ]. Velocities during the Phase II locally are higher than the relative plate motions [ Pérez et al ., ; Weber et al ., ; DeMets et al ., ].…”

Section: Insar Inversion Resultsmentioning

confidence: 99%

“…For instance, it is possible that at other periods the western segment could return to a lower steady state value while the eastern segment could undergo acceleration. Nevertheless, GNSS campaigns (2003–2005–2013) show a consistent segmentation pattern (a western segment creeping faster than the eastern segment) [ Jouanne et al ., ; Reinoza et al ., ].…”

Section: Discussionmentioning

confidence: 99%

“…The bend of Guarapiche (localized in Figure ) is discretized separately. We fixed a threshold for the maximum of slip magnitude in the lower part at 20 mm/yr in agreement with GPS far field velocities [ Pérez et al ., ; DeMets et al ., ; Jouanne et al ., ; Reinoza et al ., ]. We also apply a threshold on the upper part of 70 mm/yr.…”

Section: Slip Distribution Modelmentioning

confidence: 99%

“…Denser and longer geodetic time series would also improve our knowledge about the creeping process, for instance, by distinguishing the nature of the creep: e.g., afterslip induced by the latest seismic event in 1997 ( M s 6.8) which has transitioned into a persistent interseismic slip or an afterslip which is still occurring. We would like to understand the local observation of slip acceleration in 2002 [ Jouanne et al ., ] and the inconsistency between the return periods evaluated in trenches at 400 years [ Audemard , ] and the return period estimated at up to 200 years, assuming a geological slip rate of 20 mm/yr and a characteristic slip of 1 to 4 m slip (coseismic slip and afterslip) [ Pérez et al ., ; Jouanne et al ., ]. Finally, higher spatial resolution can also help to detect asperities that may trigger events like the M s 6.8 in 1997 [e.g., Chaussard et al ., , ; Jolivet et al ., ].…”

Section: Introductionmentioning

confidence: 99%

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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

et al. 2016

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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.

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Section: Insar Inversion Resultsmentioning

confidence: 99%

Section: Insar Inversion Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Slip Distribution Modelmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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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

et al. 2016

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A geodetic plate motion and Global Strain Rate Model

Kreemer

Blewitt

Klein

2014

Geochem. Geophys. Geosyst.

782

785

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We present a new global model of plate motions and strain rates in plate boundary zones constrained by horizontal geodetic velocities. This Global Strain Rate Model (GSRM v.2.1) is a vast improvement over its predecessor both in terms of amount of data input as in an increase in spatial model resolution by factor of $2.5 in areas with dense data coverage. We determined 6739 velocities from time series of (mostly) continuous GPS measurements; i.e., by far the largest global velocity solution to date. We transformed 15,772 velocities from 233 (mostly) published studies onto our core solution to obtain 22,511 velocities in the same reference frame. Care is taken to not use velocities from stations (or time periods) that are affected by transient phenomena; i.e., this data set consists of velocities best representing the interseismic plate velocity. About 14% of the Earth is allowed to deform in 145,086 deforming grid cells (0.25 longitude by 0.2 latitude in dimension). The remainder of the Earth's surface is modeled as rigid spherical caps representing 50 tectonic plates. For 36 plates we present new GPS-derived angular velocities. For all the plates that can be compared with the most recent geologic plate motion model, we find that the difference in angular velocity is significant. The rigid-body rotations are used as boundary conditions in the strain rate calculations. The strain rate field is modeled using the Haines and Holt method, which uses splines to obtain an self-consistent interpolated velocity gradient tensor field, from which strain rates, vorticity rates, and expected velocities are derived. We also present expected faulting orientations in areas with significant vorticity, and update the no-net rotation reference frame associated with our global velocity gradient field.Finally, we present a global map of recurrence times for M w 57.5 characteristic earthquakes.

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Geodetic exploration of strain along the El Pilar Fault in northeastern Venezuela

et al. 2015

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We use Global Navigation Satellite Systems observations in northeastern Venezuela to constrain the El Pilar Fault (EPF) kinematics and to explore the effects of the variable elastic properties of the surrounding medium and of the fault geometry on inferred slip rates and locking depth. The velocity field exhibits an asymmetric velocity gradient on either side of the EPF. We use five different approaches to explore possible models to explain this asymmetry. First, we infer a 1.6 km locking depth using a classic elastic half-space dislocation model. Second, we infer a 1.5 km locking depth and a 0.33 asymmetry coefficient using a heterogeneous asymmetric model, including contrasting material properties on either side of a vertical fault, suggesting that the igneous-metamorphic terranes on the northern side are~2 times more rigid than the sedimentary southern side. Third, we use a three-dimensional elastostatic model to evaluate the presence of a compliant zone, suggesting a 30% reduction of rigidity in the upper 3 km at the depth of a 1 to 5 km wide fault zone. Fourth, we evaluate the distribution of fault slip, revealing a widespread partial creep pattern in the eastern upper segment, while the upper western segment exhibits a partially locked area, which coincides with the rupture surface of the 1797 and 1929 earthquakes. To supplement these models, we upgrade the previously published displacement simulation method using nonvertical dislocations with data acquired between 2003 and 2013. The localized aseismic displacement pattern associated with creeping or partially creeping fault segments could explain the low level of historic seismicity.

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Present-day deformation along the El Pilar Fault in eastern Venezuela: Evidence of creep along a major transform boundary

Cited by 27 publications

References 42 publications

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

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

A geodetic plate motion and Global Strain Rate Model

Geodetic exploration of strain along the El Pilar Fault in northeastern Venezuela

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