Contreras-Reyes, Eduardo

Hannemann, Katrin

Kopp, Heidrun

Lange, Dietrich

Petersen, Florian

OceanRep

Geophysical Research AbstractsVol. 19, EGU2017-7833, 2017EGU General Assembly 2017© Author(s) 2017. CC Attribution 3.0 License.Deformation offshore Northern Chile monitored by a seafloor geodeticnetwork (GeoSEA)Katrin Hannemann (1), Dietrich Lange (1), Heidrun Kopp (1), Florian Petersen (1), and Eduardo Contreras-Reyes(2)(1) RD4 Dynamics of the Ocean Floor, GEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, Germany, (2)Departamento de Geofísica, Universidad de Chile, Santiago de Chile, ChileThe Nazca-South American plate boundary around 21◦S has last ruptured in an earthquake in 1877 and was iden-tified as a seismic gap prior to the 2014 Iquique earthquake (Mw=8.1). The southern portion of this segment isstill unbroken. The geodetic monitoring of the Chilean subduction zone is crucial to understand the deformationprocesses in this area. Most geodetic measurements rely on GPS and are therefore limited to onshore campaigns. InDecember 2015, we installed the GeoSEA (Geodetic Earthquake Observatory on the SEAfloor) array around 21◦Sof the Nazca-South American plate boundary with RV SONNE to extend the geodetic observations to the offshoreareas. The GeoSEA array consists of autonomous acoustic seafloor transponders mounted on 4 m high tripods.These transponders are able to continuously measure the two-way travel time of acoustic signals between stationpairs (baselines) and the properties of the sea water (sound speed, temperature and pressure) at each transponder.These measurements are used to retrieve the distances between the transponders and give insights into the defor-mation of the seafloor. At the Chilean subduction zone, we installed in total 23 transponders in 3 subarrays withinterstation distances of up to 2500 m. On the middle continental slope in 2300 m water depth, an array consistingof 8 transponders measures across crustal faults seen in AUV mapping. A second array of 5 stations located onthe outer rise monitors extension across normal plate-bending faults. The deepest deployment in ∼5000 m waterdepth located on the lower continental slope with 10 stations is designed to measure diffuse strain build-up. Thetransponders are intended to monitor the seafloor deformation for 3.5 years. In November 2016 during a cruise ofRV Langseth, the first 11 months of data were successfully uploaded via an acoustic modem. Furthermore, an ad-ditional component of the network, GeoSURF, a self-steering autonomous vehicle (wave glider), was successfullyused to monitor system health and to upload parts of the data from the seafloor stations. The first 11 months ofdata show a good signal quality and the baseline precision is ± 5 mm. The data reveals no deformation above theresolution limits of the individual distance measurements.

Deformation offshore Northern Chile monitored by a seafloor geodetic network (GeoSEA) 2014

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