Marine forearc structure at the seismogenic up-dip end of the 2014 Iquique Mw 8.1 earthquake

Petersen, Florian, Lange, Dietrich, Ma, Bo, Geersen, Jacob, Grevemeyer, Ingo, Kopp, Heidrun, Contreras-Reyes, Eduardo, Barrientos, Sergio and Tréhu, Anne M. (2020) Marine forearc structure at the seismogenic up-dip end of the 2014 Iquique Mw 8.1 earthquake [Poster] In: AGU Fall Meeting 2020, 01.-17.12.2020, Online, San Francisco, USA.

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On April 1st, the Mw 8.1 Iquique earthquake ruptured the plate boundary in the North Chilean marine forearc. The earthquake did not cause enough shallow rupture in the updip area to trigger a significant tsunami in the Pacific Ocean. The segment of South American subduction-zone affected by the Iquique earthquake was previously considered a seismic gap, as it last ruptured entirely in 1877 during an M~9 earthquake, with a rupture area possibly extending from south of Arica at 19°S to the north of the Mejillones peninsula at 23°S. The smaller magnitude of the 2014 event and the reduced rupture area that only broke the central part of the seismic gap implies a seismo-tectonic segmentation of the marine forearc. To identify the structure of the marine forearc and the subduction plate interface at the shallow seismic/aseismic transition, we use two years of Ocean Bottom Seismometer (OBS) and permanent onshore seismic data recorded eight months after the Iquique mainshock.

The high-resolution aftershocks of the 2014 Mw 8.1 Iquique earthquake from the local OBS network together with a seismic reflection image acquired in 2016 of the marine forearc allows us to discuss the structural control on the up-dip extent of seismic rupture in the North Chilean subduction-zone. Most aftershocks occur updip of a co-seismic shallow slip patch in the marine forearc in the vicinity of a large crustal normal fault. A second area of increased aftershocks at the plate interface coincidence with the crustal-scale normal fault that links to the coastal scarp. The updip limit under the marine forearc further correlates with a highly faulted upper-plate and the subduction of Iquique ridge related topography. Combining the results concerning the 2014 Iquique earthquake with information from the 1995 Antofagasta and 2007 Tocopilla earthquakes, we suggest a uniform structural control of seismic rupture that is uniformly active along the Northern Chile.

Document Type: Conference or Workshop Item (Poster)
Research affiliation: OceanRep > GEOMAR > FB4 Dynamics of the Ocean Floor > FB4-GDY Marine Geodynamics
Date Deposited: 15 Jan 2021 09:42
Last Modified: 15 Jan 2021 09:42

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