HR: 0800h
AN: G51B-0832    [Abstracts]
TI: Broadband Array Analysis of the 2005 Episodic Tremor and Slip Event in Northern Cascadia
AU: * Wech, A
EM: wech@u.washington.edu
AF: Dept. of Earth & Space Sciences, University of Washington 310 Condon Hall, Seattle, WA 98195 United States
AU: Creager, K
EM: kcc@ess.washington.edu
AF: Dept. of Earth & Space Sciences, University of Washington 310 Condon Hall, Seattle, WA 98195 United States
AU: McCausland, W
EM: wendy@ess.washington.edu
AF: Dept. of Earth & Space Sciences, University of Washington 310 Condon Hall, Seattle, WA 98195 United States
AU: Frassetto, A
EM: andyf@geo.arizona.edu
AF: Department of Geosciences, University of Arizona Gould-Simpson Building #77 1040 E 4th St., Tucson, AZ 85721 United States
AU: Qamar, A
EM: tony@ess.washington.edu
AF: Dept. of Earth & Space Sciences, University of Washington 310 Condon Hall, Seattle, WA 98195 United States
AU: DeRosier, S
EM: sderosie@u.washington.edu
AF: Dept. of Earth & Space Sciences, University of Washington 310 Condon Hall, Seattle, WA 98195 United States
AU: Carmichael, J
EM: joshuadc@u.washington.edu
AF: Dept. of Earth & Space Sciences, University of Washington 310 Condon Hall, Seattle, WA 98195 United States
AU: Malone, S
EM: steve@ess.washington.edu
AF: Dept. of Earth & Space Sciences, University of Washington 310 Condon Hall, Seattle, WA 98195 United States
AU: Johnson, D
EM: dj@ess.washington.edu
AF: Dept. of Earth & Space Sciences, University of Washington 310 Condon Hall, Seattle, WA 98195 United States
AB: The region of Cascadia from the Olympic Mountains through southern Vancouver Island and down-dip of the subduction megathrust has repeatedly experienced episodes of slow slip. This episodic slip, which has been observed to take place over a period of two to several weeks, is accompanied by a seismic tremor signal. Based on the average recurrence interval of 14 months, the next episodic tremor and slip (ETS) event should occur within six weeks of mid-September, 2005. Indeed, it appears to have begun on September 3, as this abstract was being written. In order to record this anticipated event, we deployed an array of 11 three-component seismometers on the northern side of the Olympic Peninsula augmenting Pacific Northwest Seismographic Network stations as well as the first few EarthScope BigFoot stations and Plate Boundary Observatory borehole seismometers. This seismic array was comprised of six short-period and five broadband instruments with spacings of 500 m and 2200 m respectively. In conjunction with this Earthscope seismic deployment, we also installed a dense network of 29 temporary, continuous GPS stations across the entire Olympic Peninsula to integrate seismic and geodetic observations. One of the primary goals of this research is to utilize the broadband instrumentation in the array to investigate the possible correlation of low frequency energy with the rest of the tremor activity. ETS has been carefully investigated at high-frequency (seismic tremor at 2-6 Hz) and very low-frequency (slip occurring over weeks, observed by GPS). An important goal of this experiment is to investigate the possibility that the tremor generates intermediate, low-frequency signals. Preliminary analysis of short-period array recordings of the July, 2004 ETS event suggests that the tremor displays signs of lower-frequency energy (~0.5 Hz) correlated with its higher frequency activity. Our array should enable us to distinguish low- frequency signals originating in the direction of high-frequency tremor from noise in other directions. We will present an analysis of the low-frequency energy associated with this slip event.
DE: 1207 Transient deformation (6924, 7230, 7240)
DE: 1242 Seismic cycle related deformations (6924, 7209, 7223, 7230)
DE: 7240 Subduction zones (1207, 1219, 1240)
DE: 8170 Subduction zone processes (1031, 3060, 3613, 8413)
SC: Geodesy [G]
MN: Fall Meeting 2005