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  • 1
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    Investigating the final seismic swarm before the Iquique-Pisagua 2014 Mw 8.1 by comparison of continuous GPS and seismic foreshock data. (2015)
    Wiley
    Details
    Publication Date: 2015-05-07
    Description: Pre-existing networks of seismometers and continuous GPS in Northern Chile successfully captured surface motions and seismicity leading up to the April 1 st Mw 8.1. Here, we compare cGPS with predictions of seismic dislocations for the final foreshock swarm, beginning with the March 16 th Mw 6.7. Results show that the cumulative cGPS motion can be largely explained by seismic slip because evolutions of cGPS positions for most stations stay within the ranges of seismic predictions (given sensible ranges of assumed source errors). However, cGPS motions between 18 th -21st and 25 th- 31 st March outpace seismic predictions, supporting the existence of aseismic transients that were most probably the afterslip from preceding bursts of seismicity. A parameter search reveals that the March 16th Mw 6.7 cGPS displacements can be recreated with a fault plane significantly rotated anticlockwise from the strike of the plate interface, suggesting that failure was on a structure other than the plate interface.
    Print ISSN: 0094-8276
    Electronic ISSN: 1944-8007
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 2
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    Revisiting visco-elastic effects on interseismic deformation and locking degree: a case study of the Peru - North Chile subduction zone (2015)
    Wiley
    Details
    Publication Date: 2015-05-30
    Description: Viscoelastic effects potentially play an important role during all phases of the earthquake cycle in subduction zones. However, most current models neglect such effects in the interseismic deformation pattern. Here we use Finite Element Method (FEM) models to investigate the control of viscoelasticity on interseismic deformation, and to highlight the pitfalls of interpreting the data with purely elastic models for both the forward and inverse problems. Our results confirm that elastic models are prone to overestimating the interseismic locking depth, a crucial parameter for estimating the maximum possible earthquake magnitude. The application of the viscoelastic model improves the fit to the interseismic deformation, especially in the inland area. Additionally, we construct 3-D FEM models constrained by geophysical and GPS data and apply our methodology to the Peru - North Chile subduction zone. Our results indicate that viscoelastic effects contribute significantly to the observed GPS data. The signals interpreted as back-arc shortening in the elastic model can be alternatively explained by viscoelastic deformation, which, in turn, dramatically refines the interseismic locking pattern in both dip and strike directions. Our viscoelastic locking map exhibits excellent correlation with the slip distributions of previous earthquakes, especially the recent 2014 Mw 8.1 Iquique earthquake. The incorrect elastic assumptions affect the analysis of interseismic deformation with respect to slip deficit calculations. Our results thus suggest that it is necessary to thoroughly re-evaluate existing locking models that are based on purely elastic models, some of which attribute viscoelastic deformation to different sources such as microplate sliver motions.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 3
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    Separating simultaneous postseismic processes: An application of the postseismic straightening method to the Maule 2010 cGPSv (2016)
    Wiley
    Details
    Publication Date: 2016-10-14
    Description: The postseismic deformation captured with continuous Global Positioning System (cGPS) monitoring following many recent mega-thrust events has been shown to be a signal composed of two dominant processes: afterslip on the plate interface and viscoelastic relaxation of the continental and oceanic mantles in response to the coseismic stress perturbation. Following the south-central Chile 2010 Maule Mw 8.8 earthquake, the time series from the regional cGPS network show a distinct curvature in the pathway of the horizontal motion that is not easily fit by a stationary decaying pattern of afterslip in combination with viscoelastic relaxation. Here we show that with realistic assumptions about the long-term decay of the afterslip signal, the postseismic signal can be decomposed into three first-order contributing processes: plate interface re-locking, plate interface afterslip, and mantle viscoelastic relaxation. From our analyses we conclude that the plate interface recovers its interseismic locking state rapidly (model space ranges between an instant recovery and a period of 1 year); a finding that supports laboratory experimental evidence as well as some recent studies of aftershocks and postseismic surface deformation. Furthermore, re-locking is the main cause of the curvature in the cGPS signal, and this study presents a plausible range of geodetic re-locking rates following a megathrust earthquake.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 4
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    Postseismic uplift of the Andes following the 2010 Maule earthquake: Implications for mantle rheology (2017)
    Wiley
    Details
    Publication Date: 2017-02-19
    Description: Postseismic surface deformation associated with great subduction earthquakes is controlled by asthenosphere rheology, frictional properties of the fault, and structural complexity. Here, by modeling GPS displacements in the six years following the 2010 Mw 8.8 Maule earthquake in Chile, we investigate the impact of heterogeneous viscosity distribution in the South American sub-continental asthenosphere on the 3-D postseismic deformation pattern. The observed postseismic deformation is characterized by flexure of the South America plate with peak uplift in the Andean mountain range and subsidence in the hinterland. We find that, at the timescale of observation, over two orders of magnitude gradual increase in asthenosphere viscosity from the arc area towards the cratonic hinterland is needed to jointly explain horizontal and vertical displacements. Our findings present an efficient method to estimate spatial variations of viscosity, which clearly improves the fitting to the vertical signal of deformation. Lateral changes in asthenosphere viscosity can be correlated with the thermomechanical transition from weak sub-volcanic arc mantle to strong sub-cratonic mantle thus suggesting a stationary heterogeneous viscosity structure. However, we cannot rule out a transient viscosity structure (e.g. power law rheology) with the short time span of observation.
    Print ISSN: 0094-8276
    Electronic ISSN: 1944-8007
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
    Location Call Number Expected Availability
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