Obtaining Accurate Earthquake Location with Cabled Seismic Networks on the Juan de Fuca Spreading Center
Date: 4/24/2019
Time: 06:00 PM
Room: Grand Ballroom
Background seismicity at mid-ocean ridges result from tectonic extension, magmatic inflation and hydrothermal cooling, and intense seismic swarms accompany volcanic spreading events. Because most of the earthquakes are small, long-term local seismic networks are required to characterize background seismicity and capture infrequent spreading events. In the Northeast Pacific Ocean, two regional cabled observatories extend to the Juan de Fuca Ridge (JdFR). Since 2011, the Ocean Networks Canada (ONC) observatory has monitored seismicity on the Endeavour segment starting with a single station that expanded to 4 in 2016. Since late 2014, the Oceanic Observatories Initiative (OOI) Cabled Array has hosted a 7-station seismic network at the summit of Axial Seamount.
Axial Seamount lies at the intersection of the JdFR and Cobb-Eickelberg hotspot chain, rises ~0.8 km above the rest of the JdFR, and erupted in 1998, 2011 and 2015. Over 100,000 earthquakes were located beneath the summit caldera leading up to and during the 2015 eruption. The Endeavour segment is a typical intermediate spreading rate ridge and supports particularly vigorous hydrothermal system. It has not erupted for at least 25 years and the last non-eruptive spreading event occurred in 2005.
We are developing catalogs of accurate earthquake locations at both sites. At Axial Seamount, we have obtained a 3D S-wave velocity model by inverting earthquake data using LOTOS, to complement an existing 3D tomographic P-wave model. Using the 3D velocity models in a non-linear location algorithm (NLLoc) improves locations and reveals faults beneath the caldera that were previously unseen. At the Endeavour we are developing a one-station location technique that uses waveform polarization and P , S and sea-surface reflected PW times. 3D P- and S-wave velocity models already exist from a previous tomography experiment and will be used to accurately locate the seismicity.
Presenting Author: Christian Baillard
Authors
Christian Baillard baillard@uw.edu University of Washington, Seattle, Washington, United States Presenting Author
Corresponding Author
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William S D Wilcock wilcock@uw.edu University of Washington, Seattle, Washington, United States |
Adrien F Arnulf aarnulf@ig.utexas.edu Institute for Geophysics, University of Texas, Austin, Texas, United States |
Maya Tolstoy tolstoy@ldeo.columbia.edu Lamont-Doherty Earth Observatory, Palisades, New York, United States |
Felix Waldhauser felixw@ldeo.columbia.edu Lamont-Doherty Earth Observatory, Palisades, New York, United States |
Martin Heesemann mheesema@uvic.ca Ocean Networks Canada, University of Victoria, Victoria, British Columbia, Canada |
Joseph J Farrugia jfarrugia@uvic.ca Ocean Networks Canada, University of Victoria, Victoria, British Columbia, Canada |
Obtaining Accurate Earthquake Location with Cabled Seismic Networks on the Juan de Fuca Spreading Center
Category
Advances in Ocean Floor Seismology