Fahrtbericht / Cruise Report SO244/1 - GeoSEA: Geodetic Earthquake Observatory on the Seafloor, Antofagasta (Chile) - Antofagasta (Chile), 30.10.2015 - 24.11.2015

Behrmann, Jan, Klaucke, Ingo, Stipp, Michael and Geersen, Jacob, eds . (2016) Fahrtbericht / Cruise Report SO244/1 - GeoSEA: Geodetic Earthquake Observatory on the Seafloor, Antofagasta (Chile) - Antofagasta (Chile), 30.10.2015 - 24.11.2015 GEOMAR Report, N. Ser. 033 . GEOMAR Helmholtz-Zentrum für Ozeanforschung, Kiel. DOI 10.3289/GEOMAR_REP_NS_33_2016.

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Abstract

The majority of M>8.5 active plate boundary earthquakes has hypocenters located beneath the
oceans in subduction zones. Post-hoc analysis shows that most of the surface deformation
related to co-seismic stress release takes place on the seafloor, in many cases unleashing major
tsunamis. The structure and morphology of the seafloor and shallow subbottom thus stores
crucial information on sub-seafloor processes, such as permanent deformation by seismic slip or
aseismic creep within the overriding plate and earthquake and tsunami generation.

We have mapped the seafloor seaward of the Northern Chilean coast between about 19°S and
22°S down to the Northern Chile deep sea trench, using the ship-based Multibeam Echosounder
EM122, Parasound, and AUV (autonomous underwater vehicle) – in selected subareas - at
sufficient resolution to identify active tectonic fault structures and submarine mass wasting
structures, to quantitatively assess young and active deformation of the overriding plate in the
area, and quantify the extent of recent catastrophic downslope mass movements of sediment.
Furthermore, the investigations serve as a site survey for the deployment of the GeoSEA
seafloor geodetic array, to be installed immediately after completion of this cruise.

The investigations were made timely by the 1st April 2014 Pisagua M=8.2 earthquake, that
ruptured the plate interface in the northern part of the area of investigation. The central and
southern parts are located in the last remaining locked seimotectonic segment along the Chilean
active margin. In addition to providing the first data base for geomorphological and tectonic
interpretation of geo-processes at the seafloor, the bathymetric mapping done during SO244
Leg 1 will provide an important data reference for possible post-earthquake surveys once this
seismotectonic segment will have broken in the future.

Document Type: Report (Cruise Report)
Keywords: RV Sonne, Fahrtbericht, Cruise Report, SO244/1, GeoSEA: Geodetic Earthquake Observatory on the Seafloor, Northern Chile
Research affiliation: OceanRep > GEOMAR > FB4 Dynamics of the Ocean Floor > FB4-GDY Marine Geodynamics
DOI etc.: 10.3289/GEOMAR_REP_NS_33_2016
ISSN: 2193-8113
Projects: GeoSEA
Expeditions/Models:
Date Deposited: 30 Nov 2016 08:28
Last Modified: 14 Dec 2016 09:31
URI: http://eprints.uni-kiel.de/id/eprint/34973

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