Stress Drops on the Blanco Oceanic Transform Fault from Interstation Phase Coherence

摘要

Oceanic transform faults display a wide range of earthquake stress drops, large aseismic slip, and along-strike variation in seismic coupling. We use and further develop a phase coherence-based method to calculate and analyze stress drops of 61 M >= 5.0 events between 2000 and 2016 on the Blanco fault, off the coast of Oregon. With this method, we estimate earthquake rupture extents by examining how apparent source time functions (ASTFs) vary between stations. The variation is caused by the generation of seismic waves at different locations along the rupture, which arrive at different times depending on station location. We isolate ASTFs at a range of stations by comparing seismograms of collocated earthquakes and then use the interstation ASTF coherence to infer rupture extent and stress drop.