Updip seismicity streaks and frictional segmentation of the megathrust observed in the 2014 Mw 8.1 Iquique, northern Chile, earthquake sequence
Abstract
On 1 April 2014, a Mw 8.1 megathrust earthquake ruptured the northern part of the 1877 earthquake seismic gap offshore Iquique, northern Chile. It was preceded by a two-weeks foreshock sequence including four M>6 events and spawned an intense aftershock series that included a M7.6 event south of the mainshock rupture area on April 3rd. Applying a multistage automatic event location procedure to seismic data recorded by temporary and permanent networks in the region, we detected and located 19,000 events for one month preceding and nine month following the Iquique mainshock. Whereas foreshocks skirt around the updip limit of the mainshock asperity, aftershocks define two belts of increased seismicity, updip and downdip of the main asperity offshore the Chilean coast. Aftershocks in the updip belt delineate several E-W striking seismicity streaks separated by completely aseismic regions. These streaks contain numerous repeating earthquakes, that may be driven by accelerated afterslip due to stresses induced by the mainshock rupture. Accordingly, we interpret the seismicity streaks as asperities of brittle failure in a region largely undergoing aseismic creep. In the downdip belt, aftershocks correlate with a moderate-to-low coseismic slip area and mostly flank two nearly aseismic patches of high afterslip located in the vicinity of the M7.6 event epicenter and NE of the mainshock. A depth level with only sparse seismicity at 45 km depth separates the downdip belt of aftershocks from the deepest interplate seismicity, that reaches 65 km depth in two individual clusters beneath the coastal cordillera, which show a prominent difference in dip.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.T43E0447S
- Keywords:
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- 1207 Transient deformation;
- GEODESY AND GRAVITYDE: 7215 Earthquake source observations;
- SEISMOLOGYDE: 8123 Dynamics: seismotectonics;
- TECTONOPHYSICSDE: 8170 Subduction zone processes;
- TECTONOPHYSICS