Ground motion prediction from tremor

Annemarie S. Baltay, & Gregory C. Beroza

Published December 2013, SCEC Contribution #1795

Due to its widespread occurrence, frequency content, and location, tectonic tremor presents an exceptional opportunity to test and improve strong ground motion attenuation relations for subduction zones. We characterize the amplitude of thousands of individual tremor events to constrain the anelastic distance attenuation relationship of peak ground acceleration (PGA) and peak ground velocity (PGV) of tremor for application to strong ground motion prediction. In practice, ground motion prediction equations (GMPEs) are determined empirically with earthquake data recorded at many stations. In some areas of high earthquake hazard, such as Cascadia, the data set of recorded earthquakes for ground motion prediction is sparse. Tectonic tremor, however, occurs frequently and abundantly in many subduction zones, including Cascadia, at the down-dip limit of the rupture zone of potential megathrust earthquakes. We show that tremor can be used to constrain the anelastic attenuation parameter of GMPEs out to a distance of 150 km, which is sufficient to place important constraints on ground motion decay with distance. We measure PGA and PGV of thousands of individual 5-minute tremor windows occurring nearly continuously throughout three ETS events, and use differential measurements to estimate the anelastic attenuation term of the GMPE. PGA and PGV for tremor shows a distance decay that is similar to subduction-zone-specific GMPEs developed from both data and simulations [e.g. Atkinson and Boore, 1997]; however, the massive amount of data present in the tremor observations improves the fit of the GMPEs. This should allow us to refine distance-amplitude attenuation relationships for us in into hazard maps, and to search for regional variations and intra-subduction zone differences in ground-motion attenuation.

Baltay, A. S., & Beroza, G. C. (2013). Ground motion prediction from tremor. Geophysical Research Letters, 40(24), 6340-6345. doi: 10.1002/2013GL058506.