Real-time Monitoring of Slip Triangles: Tremor Activity –Average envelope seismogram amplitudes in tremor passband –Active Tremor = black triangles Arrows: GPS Short-term Velocity –50-day GPS site velocities after long-term velocity is removed –Slow Slip = large arrows pointing towards trench

January-February 2007

June-July-August 2007

April-May-June 2008

NVT Location Approach Filtered envelope waveforms STA/LTA to find NVT bursts Pick relative times of good S/N arrivals –By hand and/or automated 1D inversion for locations Analyze for patterns in space and time

NVT Migration in Southern Cascadia : Hand-picked vs. Automated

NVT Migration Along All of Cascadia (Automated) Still preliminary, but find long migrating episodes that overlap in time despite being separated by >100 km Three events are more interrelated along- strike than all events in previous few years

NVT Locations So Far Still plenty of work for us to do in the northern half Beginning to see a persistent gap at OR-CA border NVT band primarily between km slab contours Matches some aspects of slab curvature

Integrating ETS with Earth Structure and Geology ETS Periodicity Surface Wave Crust Structure Body Wave Mantle Structure Brudzinski & Allen, 2007 Arc volcanism Schmidt et al., 2008