HR: 15:25h
AN: S43D-07    [Abstracts]
TI: Imaging Subduction, Episodic Tremor and Slip in the Pacific Northwest: Cascadia Arrays For Earthscope (CAFE)
AU: * Abers, G A
EM: abers@bu.edu
AF: Boston University Department of Earth Sciences, 675 Commonwealth Av, Boston, MA 02215, United States
AU: Rondenay, S
EM: rondenay@mit.edu
AF: MIT Department of Earth, Atmospheric and Planetary Sci., 77 Massachusetts Av., Cambridge, MA 02139,
AU: Creager, K C
EM: kcc@ess.washington.edu
AF: University of Washington, Dept. Earth & Space Sciences, Seattle, WA 98195, United States
AU: Malone, S D
EM: steve@ess.washington.edu
AF: University of Washington, Dept. Earth & Space Sciences, Seattle, WA 98195, United States
AU: Zhang, Z
EM: zhuzhang@bu.edu
AF: Boston University Department of Earth Sciences, 675 Commonwealth Av, Boston, MA 02215, United States
AU: Wech, A G
EM: wech@u.washington.edu
AF: University of Washington, Dept. Earth & Space Sciences, Seattle, WA 98195, United States
AU: Sweet, J R
EM: jrsweet@u.washington.edu
AF: University of Washington, Dept. Earth & Space Sciences, Seattle, WA 98195, United States
AU: Melbourne, T I
EM: tim@geology.cwu.edu
AF: Central Washington Univ., Department of Geology 400 E University Way, Ellensburg, WA 98926, United States
AU: Hacker, B R
EM: hacker@geol.ucsb.edu
AF: University of California, Santa Barbara, Geological Sciences, Santa Barbara, CA 93106, United States
AB: Subduction delivers fluids into the Earth's mantle by transport of hydrated crust downward in subducting plates. These fluids are released at depth and may be responsible for a wide variety of phenomena including weakened thrust faults, episodic tremor and slip (ETS), intraslab earthquakes, forearc serpentinization, and arc magmatism. Cascadia is the volcanic arc associated with the youngest subducting plate, and hence a primary EarthScope target. In 2006 we launched Cascadia Arrays For Earthscope (CAFE), an EarthScope effort utilizing Flexible Array, Transportable Array, and PBO facilities, and integrating these data with complementary constraints from geodynamics and geochemistry. Seismic imaging, the emphasis of this presentation, is employed to illuminate (i) the descending oceanic plate, from where fluids are expelled by metamorphism, and (ii) the mantle wedge, where fluids migrate to produce hydrous phases such as serpentine or, beneath the volcanic arc, primary magmas, and (iii) the interface between them where ETS may be produced. The experiment traverses a section of the Cascadia system where earthquakes extend to nearly 100 km depth, thus permitting an investigation of the relationship between the release of fluids and the generation of Wadati-Benioff-zone earthquakes, and crosses regions of ETS excitation. The basic experiment has four components: (1) a 47-element broadband imaging array of Flexible Array instruments integrated with Bigfoot; (2) three small-aperture seismic arrays with 15 additional short-period instruments near known sources of ETS; (3) analysis of the PBO and PANGA GPS data sets to define the details of episodic slip events; and (4) integrative modeling. Sixty-two seismographs were deployed in July 2006; here we present a first look at the experiment and the data collected. Initial data recovery has been excellent, with approximately 12 months of continuous data recovered as of this writing, most delivered to the IRIS DMC. This time window includes an ETS episode in Jan. 2007. Given the success of this deployment, we expect to make good progress toward understanding the relationship between subduction, ETS, and fluid cycling.
DE: 7215 Earthquake source observations (1240)
DE: 7240 Subduction zones (1207, 1219, 1240)
DE: 8170 Subduction zone processes (1031, 3060, 3613, 8413)
DE: 8185 Volcanic arcs
SC: Seismology [S]
MN: 2007 Fall Meeting