11 research outputs found
Observing and modeling the spectrum of a slow slip event
We estimate and model the normalized moment rate power spectrum of large slow slip events in Cascadia. We estimate the spectrum using data from GPSâderived slip inversions, borehole strain records, and beamformingâbased tremor amplitudes. The normalized power spectrum initially decreases with frequency but then may flatten at periods of 1 to 10 days before decaying as frequency urn:x-wiley:jgrb:media:jgrb52668:jgrb52668-math-0001 at higher frequencies, where nm is between 1.1 and 1.4 when estimated from tremor and between 0.4 and 1.5 when estimated from strain. We explore one way to understand the observed spectrum: by modeling a monthâlong slow slip event as the sum of a steady background moment rate and a population of subevents. The subevents represent the wide variety of observed slow earthquakes, ranging from 0.5âsâlong tremor to 3âhrâlong rapid tremor reversals. We parameterize the subevents' magnitude distribution and momentâduration scaling, and we examine how the subevent population determines the slow slip spectrum. There are not enough data to rigorously test the subevent model, but we show that the data are consistent with a single continuum of slow earthquakes whose moments scale linearly with their duration, as has been proposed previously