HR: 0800h
AN: G51B-0089    [Abstracts]
TI: Long Baseline Tilt Meter Array to Monitor Cascadia's Slow Earthquakes
AU: * Suszek, N
EM: suszek@stripe.colorado.edu
AF: CIRES, Department of Geological Sciences University of Colorado, Boulder, CO 80309 United States
AU: Bilham, R
EM: bilham@stripe.colorado.edu
AF: CIRES, Department of Geological Sciences University of Colorado, Boulder, CO 80309 United States
AU: Flake, R
EM: flake@geology.cwu.edu
AF: Geodesy Laboratory, Department of Geological Sciences Central Washington University, Ellensburg, WA 98926 United States
AU: Melbourne, T I
EM: tim@geology.cwu.edu
AF: Geodesy Laboratory, Department of Geological Sciences Central Washington University, Ellensburg, WA 98926 United States
AU: Miller, M
EM: meghan@geology.cwu.edu
AF: Geodesy Laboratory, Department of Geological Sciences Central Washington University, Ellensburg, WA 98926 United States
AB: Five biaxial Michelson tilt meters are currently being installed in the Puget Lowlands near Seattle to monitor dynamic tilt changes accompanying episodic slow earthquakes that occur at 20-40 km depth. Each tilt meter consists of a 1-2 m deep, 500-m-long, 15-cm diameter, horizontal, half-filled water-pipe, terminated by float sensors with sub-micron water-level resolution, similar to those that have operated unattended for the past decade within the Long Valley caldera. The sensors measure water height relative to the base of a pile driven to 10 m depth. A wide-body LVDT attached to this pile outside the reservoir, senses the motion of the core attached to the float within. The voltage indicating the position of the core is sampled 16 times a second, and digitally filtered before transmission via radio modem for storage as 1-minute samples in a remote computer. The computer gathers 16-bit water height, vault temperature, air pressure and various housekeeping data once per minute using remote telemetry. Installed during 2004, the first of the tilt meters, installed in 2004, float sensors at each end, and one in the center of each pipe, permit us to examine tilt signal coherence and local noise. Each adjacent pair of sensors has a tilt resolution of 2e-9 and a range of 8 microradians. We anticipate tilt signals with durations of 0.3-30 days, and amplitudes of less than 0.1 microradian associated with slow earthquakes. Anticipated noise levels in the tilt meters are 10-1000 times lower that these expected signals, similar to or better than signal-to-noise levels from planned strain meters of the PBO array.
UR: http://www.geodesy.cwu.edu
DE: 1208 Crustal movements--intraplate (8110)
DE: 1213 Earth's interior--dynamics (8115, 8120)
DE: 1247 Terrestrial reference systems
DE: 1294 Instruments and techniques
SC: Geodesy [G]
MN: 2004 AGU Fall Meeting