2012 IRIS Workshop

Zooming-In on Cascadia Episodic Tremor and Slip with an Array of Arrays

T. Thomas: University of Washington, J.E. Vidale: University of Washington, A. Ghosh: University of California Santa Cruz, K.C. Creager: University of Washington, H. Houston: University of Washington,

The Array of Arrays (AofA) seismic experiment in Cascadia just completed its final deployment, during which we recorded the 2011 Episodic Tremor and Slip (ETS) event beneath Cascadia. We now have the 2010 and 2011 ETS events recorded in their entirety by eight seismic arrays of between 11-20 seismometers each. Using a beam-forming method, we get unprecedented views of short-term tremor migration and behavior, allowing observations of tremor bursts and streaks in conjunction with amplitudes across short distance and time. We observe an eight-hour period of the 2010 ETS event beneath the AofA where it is highly resolvable and appears very active in terms of migration and energy release. Periods of high-amplitude tremor coincide with either tight (~20 km across) tremor bursts or long (up to 40 km) bursts, delineating the variability in sizes and shapes of slow slip patches on the subduction interface. Occasionally, tremor appears to “streak” between separate bursts, possibly showing a

Full-resolution graphics file in original format: 0086.ai