RV SONNE SO244 Leg II [SO244/2] Cruise Report / Fahrtbericht, Antofagasta, 27.11.2015 – Antofagasta, 13.12.2015, SO244-2 – GeoSEA: Geodetic Earthquake Observatory on the Seafloor
Year: 2016
Type: report
Abstract: RV SONNE cruise SO244-2 sailed offshore northern Chile from Nov. 27 to\nDec. 13, 2015 to install the seafloor geodetic network GeoSEA (Geodetic\nEarthquake Observatory on the SEAfloor) on the marine forearc and outer rise of the\nSouth American subduction system around 21°S. This segment of the Nazca-South\nAmerican plate boundary has last ruptured in an earthquake in 1877 and was\nidentified as a seismic gap prior to the 2014 Iquique/Pisagua earthquake (Mw=8.1).\nThe southern portion of the segment remains unbroken by a recent earthquake and\nis currently in the latest stage of the interseismic phase of the seismic cycle. Seafloor\ngeodetic measurements provide a way to monitor crustal deformation at high\nresolution comparable to the satellite-based GPS technique upon which terrestrial\ngeodesy is largely based. The GeoSEA Network consists of autonomous seafloor\ntransponders installed on 4 m high tripods, which were lowered to the seabed on the\ndeep-sea cable of RV SONNE. The transponders within an array intercommunicate\nvia acoustic signals for a period of up to 3.5 years. An additional component of the\nnetwork is GeoSURF, a self-steering autonomous surface vehicle (Wave Glider),\nwhich monitors system health and is capable to upload the seafloor data to the sea\nsurface and to transfer it via satellite. We have chosen three areas on the middle and\nlower slope and the outer rise for the set-up of three sub-arrays. The array in Area 1\non the middle continental slope consists of 8 transponders located in pairs on four\ntopographic ridges, which are surface expressions of faults at depth. Area 2 is\nlocated on the outer rise seaward of the trench where 5 stations monitor extension\nacross plate-bending related normal faults. The third area is located at water depth\n>5000 m on the lower continental slope where an array of 10 stations measures\ndiffuse strain build-up. Data from all networks and all stations were successfully\nuploaded to GeoSURF and/or a HPT modem lowered into the water from RV\nSONNE. The seabed installation of a total of 23 transponders was completed by\nDecember 07, when we proceeded to deploy a total of 14 ocean bottom\nseismometers (OBS) on the forearc between 19.2°-21.6°S. These instruments will be\nrecovered by RV LANGSETH in Spring/Summer 2016.
Author: Kopp, Heidrun
Language: English
Subfield: Geophysics
Field: Earth and Planetary Sciences
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W2559893552