HR: 0800h
AN: T21A-0349    [Abstracts]
TI: Frequency Content of Subduction Zone Tremor and Similarities to Volcanic Tremor
AU: * Sit, S
EM: stefany.m.sit@lawrence.edu
AF: Lawrence University, PO Box 599, Appleton, WI 54912, United States
AU: Brudzinski, M R
EM: brudzimr@muohio.edu
AF: Miami University, 114 Shideler Hall, Oxford, OH 45056, United States
AB: Non-Volcanic Tremor (NVT) signals have been correlated in space and time with slow slip movements across several subduction zones in a process known as Episodic Tremor and Slip (ETS). Currently, the process responsible for ETS is unknown, however two possible models have been proposed. The first attributes tremor to temporal strain release caused by episodic slip along the plate interface, while the second suggests that tremor is fluid-related and can occur away from the interface. This study investigates patterns within the frequency domain of NVT in Cascadia and southern Mexico to help constrain the possible models. NVT signals from Cascadia have been collected from a mixture of seismometers including those of the Earthscope Tranportable Array and a host of permanent regional networks that span the subduction zone. A recently deployed network of 8 broadband stations provides the data for analysis along the Oaxaca segment of southern Mexico. Fast Fourier Transforms (FFT) were performed on successive hour-long segments during entire ETS events and showed a range of activity from 1 Hz to up to at least 10 Hz, along with a series of dominant peaks within the domain. Additionally, spectrograms constructed for selected time frames showed discrete banding at specific frequencies verifying the peaks seen with FFT are continuous, stable features. At both subduction zones, we find that primary peaks occur in the 1-4 Hz range, secondary peaks in the 2-7 Hz range, and additional smaller peaks in the 5-9 Hz range. Peaks seen in NVT are not as well-defined as many traditional volcanic tremor signals, but this may be due to superposition of several sharper peaks. Nevertheless, at stations where NVT amplitudes are most prominent, we observe both harmonic and inharmonic peaking common in volcanic tremor. The similarities between the frequency content of NVT and traditional volcanic tremor support a fluid-related model for ETS.
DE: 7215 Earthquake source observations (1240)
DE: 7240 Subduction zones (1207, 1219, 1240)
DE: 7280 Volcano seismology (8419)
DE: 8123 Dynamics: seismotectonics
DE: 9350 North America
SC: Tectonophysics [T]
MN: 2007 Fall Meeting