Andean structural control on interseismic coupling in the North Chile subduction zone

Béjar‐Pizarro, Marta; Socquet, Anne; Armijo, Rolando; Carrizo, D.; Genrich, J. F.; Simons, M.

doi:10.1038/ngeo1802

Cited by 148 publications

(111 citation statements)

References 49 publications

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“…While models of interseismic coupling for this region exist 2,8,13 it is in the interest of consistency to produce a locking model on the same geometry as used for the coseismic slip modelling. We took the ITRF08 GPS velocities data of Métois et al 8 and performed our own corrections to fix velocities to a stable South American reference frame, and to correct for overlapping tectonic signals of shortening and sliver motion.…”

Section: Interseismic Lockingmentioning

confidence: 99%

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Gradual unlocking of plate boundary controlled initiation of the 2014 Iquique earthquake

Schurr

Asch

Hainzl

et al. 2014

Nature

318

364

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Several major earthquakes (Mw>7) have occurred in this gap since 1850 (Fig. 1); the largest until now was the Mw 7.7 Tocopilla earthquake in 2007, which broke the southern rim of this segment beneath and north of Mejillones Peninsula along a total length of 150 km. Only the downdip end of the locked zone slipped in this event, and the total slip in the rupture area was less than 2.6 m 6,7 leaving most of the past slip deficit of c. 8-9 m accumulated since 1877 3 approaches. First, we performed waveform modelling of local strong motion seismograms and teleseismic body waves to constrain the kinematic development of the rupture towards the final displacement in a joint inversion with continuous GPS data of static displacements (Fig. 1, 2a). Second, we use the backprojection technique applied to stations in North America to map the radiation of high frequency seismic waves (HFSR; 1-4 Hz) 9,10 . The latter technique is not sensitive to absolute slip amplitudes, but rather to changes in slip and rupture velocity.During the first 35-40s the rupture propagated downdip with increasing velocity, nearly reaching the coastline (Fig. 2a,b). Surprisingly, towards the end of the rupture, the area near the epicenter was reactivated. In spite of the relatively complicated kinematic history of the rupture the cumulative slip shows a simple 'bull's eye' pattern with a peak coseismic slip of (Fig. 3a). The Iquique main shock nucleated at the 4 northwestern border of a locked patch and ruptured towards its center (Fig. 2a, 3a). The downdip end of the main shock as well as for the large Mw 7.6 aftershock rupture mapped both by the HFSR and co-seismic slip agrees quite accurately with the downdip end interseismic coupling (Fig. 2a,c 3a). The accelerated downdip rupture propagation for both earthquakes closely followed the gradient towards higher locking. Therefore, the Iquique event and its largest aftershock appear to have broken the central, only partly locked segment of the Northern Chile Southern Peru seismic gap releasing part of the slip deficit accumulated here since 1877 (cf. Fig. 1).The seismicity before the Iquique earthquake also concentrates in this zone of intermediate locking at the fringe of the highly locked -high slip patch (Fig. 3a). Starting in July 2013, three foreshock clusters with increasingly larger peak magnitudes and cumulative seismic moment occurred here (Fig. 2c, 3a,c). The mainshock rupture started at the northern end of the foreshock zone, inside the region of intermediate locking (Fig. 2c, 3a). Interestingly, the second foreshock cluster (January 2014) is associated with a weak transient deformation, whereas the third cluster (March 2014) shows a very distinct transient signal. GPS displacement vectors calculated over the times spanning these foreshock clusters point towards the cluster epicentres (Extended Data Figure 4). Deformation for both transients is entirely explained by the cumulative coseismic displacement of the respective foreshock clusters (Fig. 3d inset, Extended Data Figure 4). The ar...

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Section: Interseismic Lockingmentioning

confidence: 99%

“…The Iquique rupture affected an area shown from geodetic analysis to be a zone of intermediate interseismic coupling at 18.5-21°S interrupting the otherwise fully locked Northern Chile Southern Peru gap 8,13 (Fig. 3a).…”

mentioning

confidence: 99%

Gradual unlocking of plate boundary controlled initiation of the 2014 Iquique earthquake

Schurr

Asch

Hainzl

et al. 2014

Nature

318

364

View full text Add to dashboard Cite

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“…The earthquake ruptured añ 150 km long portion of the subduction zone [Schurr et al, 2014;Ruiz et al, 2014], in an area that was partially locked before the earthquake [Bejar Pizarro et al, 2013;Metois et al, 2016]. The earthquake was preceded by a series of earthquake swarms beginning in July 2013 [Schurr et al, 2014;Ruiz et al, 2014].…”

Section: Introductionmentioning

confidence: 99%

“…The M w 8.1 2014 Iquique earthquake occurred within the North Chile seismic gap, which had not experienced a megathrust rupture since 1877 [Bejar Pizarro et al, 2013;Metois et al, 2016]. The earthquake ruptured añ 150 km long portion of the subduction zone [Schurr et al, 2014;Ruiz et al, 2014], in an area that was partially locked before the earthquake [Bejar Pizarro et al, 2013;Metois et al, 2016].…”

Section: Introductionmentioning

confidence: 99%

An 8 month slow slip event triggers progressive nucleation of the 2014 Chile megathrust

Socquet

Valdes

Jara

et al. 2017

Geophysical Research Letters

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145

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The mechanisms leading to large earthquakes are poorly understood and documented. Here we characterize the long‐term precursory phase of the 1 April 2014 Mw8.1 North Chile megathrust. We show that a group of coastal GPS stations accelerated westward 8 months before the main shock, corresponding to a Mw6.5 slow slip event on the subduction interface, 80% of which was aseismic. Concurrent interface foreshocks underwent a diminution of their radiation at high frequency, as shown by the temporal evolution of Fourier spectra and residuals with respect to ground motions predicted by recent subduction models. Such ground motions change suggests that in response to the slow sliding of the subduction interface, seismic ruptures are progressively becoming smoother and/or slower. The gradual propagation of seismic ruptures beyond seismic asperities into surrounding metastable areas could explain these observations and might be the precursory mechanism eventually leading to the main shock.

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“…To improve the seismic-hazard assessment for such rare events, it may be useful to incorporate other kinds of information such as crustal deformation at plate margins. In recent years, the development of Global Positioning System (GPS) and satellite radar interferometry make it possible to measure the strain buildup associated with plate coupling in many earthquakeprone regions around the world (Chlieh et al, 2004(Chlieh et al, , 2011Béjar-Pizarro et al, 2013). Recent studies have suggested that subducting plates are either locked or creeping aseismically, and that a patchwork of locked or coupled regions during the interseismic period may be related with asperities of earthquakes (Konca et al, 2008;Moreno et al, 2010;Perfettini et al, 2010;Loveless and Meade, 2011).…”

Section: Introductionmentioning

confidence: 99%

Scenario Source Models and Strong Ground Motion for Future Mega‐earthquakes: Application to Lima, Central Peru

Pulido¹,

Aguilar²,

Tavera³

et al. 2015

Bulletin of the Seismological Society of America

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The 2011 moment magnitude (M w ) 9.0 Tohoku-Oki Japan earthquake occurred in a region where giant megathrust earthquakes were not expected. This earthquake proved the difficulty in assessing seismic hazard by relying mainly on information from historical and instrumental seismicity. To help improve the seismic-hazard assessment for such rare events, we propose a methodology to estimate the slip distribution of future megathrust earthquakes based on a model of interseismic coupling distribution in subduction margins, as well as information of historical earthquakes, and apply the method to the central Peru region, Lima. The slip model obtained from geodetic data represents the large scale features of asperities within the megathrust, which is appropriate for simulation of long-period waves and tsunami modeling. For the simulation of a broadband strong ground motion, we add small scale heterogeneities to the source slip to be able to simulate high frequencies. To achieve this purpose, we propose broadband source models constructed by adding short-wavelength slip distributions obtained from a Von Karman power spectral density function, to the slip model inferred from interseismic geodetic data. Using these slip models and assuming several hypocenter locations, we calculate a set of strong ground motions for Lima and incorporate site effects obtained from microtremors surveys and geotechnical data. Our simulated average pseudospectral accelerations (period 0.3 s) are above 1:5g for wide areas in Lima, which may be critical in terms of damage of low-to midrise masonry and reinforced concrete buildings, which characterize the majority of buildings in Lima.

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Andean structural control on interseismic coupling in the North Chile subduction zone

Cited by 148 publications

References 49 publications

Gradual unlocking of plate boundary controlled initiation of the 2014 Iquique earthquake

Gradual unlocking of plate boundary controlled initiation of the 2014 Iquique earthquake

An 8 month slow slip event triggers progressive nucleation of the 2014 Chile megathrust

Scenario Source Models and Strong Ground Motion for Future Mega‐earthquakes: Application to Lima, Central Peru

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