The relation of crustal scattering to seismicity in southern California

Dense regional array recordings of 377 teleseismic events are used to map g eographic variability in upper crustal P to S scattering in southern Califo rnia. Scattered-wave energy is sensitive to short-wavelength heterogeneity and maps of scattering potential offer a powerful complement to travel time tomography in characterizing seismic crustal heterogeneity. The scale leng th of resolved scattering variability is commensurate with the scale length s of surface fault-trace length and microseismicity variations, and both ma pped faults and seismicity are concentrated in regions of strong scattering . Fault-proximal scattering averaged across-strike of predominately strike- slip fault zones is highly correlated with microseismicity levels and is pr edictive of the pattern of microseismicity variation but not of absolute sc ale. North-south profiles through the Transverse Ranges reveal coincident s trong gradients in microseismicity and scattering, whereas mapped segment b ounds along the San Andreas fault zone from San Francisco to the Salton Sea coincide with strong along-strike gradients in the level of scattering. Th e overall correlation of microseismicity and scattering potential is consis tent with structural control of aftershock and background microseismicity p roduction, strain energy control of scattering, or both. Prior evidence for fault offset in the pattern of scattering intensity [Revenaugh and Reasone r, 1997] favors the former.