Open AccessSeismic structures of the Calico fault zone inferred from local earthquake travel time modelling
Author(s) -
Yang Hongfeng,
Zhu Lupei,
Cochran Elizabeth S.
Publication year - 2011
Publication title -
geophysical journal international
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.302
H-Index - 168
eISSN - 1365-246X
pISSN - 0956-540X
DOI - 10.1111/j.1365-246x.2011.05055.x
Subject(s) - seismology , geology , fault (geology) , seismogram , shear (geology) , wave velocity , shear zone , seismic zone , seismic wave , low velocity zone , petrology , tectonics , induced seismicity , lithosphere
SUMMARY We analysed high‐frequency body waves of local earthquakes to image the damage zone of the Calico fault in the eastern California shear zone. We used generalized ray theory and finite difference methods to compute synthetic seismograms for a low‐velocity fault zone (FZ) to model the direct and FZ‐reflected P and S traveltimes of local earthquakes recorded by a temporary array across the fault. The low velocity zone boundaries were determined by apparent traveltime delays across the fault. The velocity contrast between the fault zone and host rock was constrained by the traveltime delays of P and S waves and differential traveltimes between the direct and FZ‐reflected waves. The dip and depth extent of the low velocity zone were constrained by a systematic analysis of direct P traveltimes of events on both sides of the fault. We found that the Calico fault has a ∼1.3‐km‐wide low velocity zone in which the P ‐ and S ‐wave velocity decreased 40 and 50 per cent, respectively, with respect to the host rock. The low velocity zone dips 70° northeast and extends 3 km in depth.