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Dual megathrust slip behaviors of the 2014 Iquique earthquake sequence

Meng, Lingsen and Huang, Hui and Bürgmann, Roland and Ampuero, Jean Paul and Strader, Anne (2015) Dual megathrust slip behaviors of the 2014 Iquique earthquake sequence. Earth and Planetary Science Letters, 411 . pp. 177-187. ISSN 0012-821X. doi:10.1016/j.epsl.2014.11.041.

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The transition between seismic rupture and aseismic creep is of central interest to better understand the mechanics of subduction processes. A Mw 8.2 earthquake occurred on April 1st, 2014 in the Iquique seismic gap of northern Chile. This event was preceded by a long foreshock sequence including a 2-week-long migration of seismicity initiated by a Mw 6.7 earthquake. Repeating earthquakes were found among the foreshock sequence that migrated towards the mainshock hypocenter, suggesting a large-scale slow-slip event on the megathrust preceding the mainshock. The variations of the recurrence times of the repeating earthquakes highlight the diverse seismic and aseismic slip behaviors on different megathrust segments. The repeaters that were active only before the mainshock recurred more often and were distributed in areas of substantial coseismic slip, while repeaters that occurred both before and after the mainshock were in the area complementary to the mainshock rupture. The spatiotemporal distribution of the repeating earthquakes illustrates the essential role of propagating aseismic slip leading up to the mainshock and illuminates the distribution of postseismic afterslip. Various finite fault models indicate that the largest coseismic slip generally occurred down-dip from the foreshock activity and the mainshock hypocenter. Source imaging by teleseismic back-projection indicates an initial down-dip propagation stage followed by a rupture-expansion stage. In the first stage, the finite fault models show an emergent onset of moment rate at low frequency (<0.1 Hz<0.1 Hz), while back-projection shows a steady increase of high frequency power (>0.5 Hz>0.5 Hz). This indicates frequency-dependent manifestations of seismic radiation in the low-stress foreshock region. In the second stage, the rupture expands in rich bursts along the rim of a semi-elliptical region with episodes of re-ruptures, suggesting delayed failure of asperities. The high-frequency rupture remains within an area of local high trench-parallel gravity anomaly (TPGA), suggesting the presence of subducting seamounts that promote high-frequency generation. Our results highlight the complexity of the interactions between large-scale aseismic slow-slip and dynamic ruptures of megathrust earthquakes.

Item Type:Article
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URLURL TypeDescription DOIArticle
Meng, Lingsen0000-0003-2428-0548
Bürgmann, Roland0000-0002-3560-044X
Ampuero, Jean Paul0000-0002-4827-7987
Additional Information:© 2014 Elsevier B.V. Received 22 August 2014; Received in revised form 24 November 2014; Accepted 26 November 2014; Available online 19 December 2014. The IRIS ( and GFZ ( data centers were used to access the broadband and strong-motion seismograms of the GSN (Global Seismic Network) and IPOC (Integrated Plate boundary Observatory Chile) network, respectively. The Chilean earthquake catalog was acquired from the Centro Sismologico Nacional (CSN). We thank Chen Ji for providing the slip model of the Mw 7.6 aftershock. We thank Jack Loveless for providing the Trench Parallel Gravity Anomaly (TPGA) code. The Global Marine Gravity Version 23.1 ( was used to compute the TPGA. We appreciate the valuable discussions with Chen Ji, Paul Davis, Yuji Yagi, An Yin, Javier Ruiz and Gilles Peltzer. H. Huang was supported by the National Natural Science Foundation of China (Grants: 41374048 and 41174038).
Group:Seismological Laboratory
Funding AgencyGrant Number
National Natural Science Foundation of China41374048
National Natural Science Foundation of China41174038
Subject Keywords:Chile; subduction; foreshock; slow slip; repeating earthquakes; back-projection
Record Number:CaltechAUTHORS:20150309-081809231
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Official Citation:Lingsen Meng, Hui Huang, Roland Bürgmann, Jean Paul Ampuero, Anne Strader, Dual megathrust slip behaviors of the 2014 Iquique earthquake sequence, Earth and Planetary Science Letters, Volume 411, 1 February 2015, Pages 177-187, ISSN 0012-821X, (
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:55621
Deposited By: Tony Diaz
Deposited On:10 Mar 2015 01:41
Last Modified:10 Nov 2021 20:47

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