Continental subduction and three-dimensional crustal structure: The northern South Island, New Zealand

摘要: The three-dimensional Vp and Vp/Vs structure of a region where subduction transitions to oblique transform faulting has been determined using arrival times from 579 local earthquakes recorded during temporary deployment, 3146 have relocated. Between 40 km 100 depth, the subducted plate is imaged as relatively low-velocity feature in uppermost mantle, reflecting continental nature crust this region. An increase amplitude northeast southwest can be related an thickness direction. Velocity variations within overlying plates show some spatial correlation. This suggests interaction between which extends well beyond interface consistent with other geophysical geological evidence that beneath Marlborough currently not accommodating much active subduction. In plate, Awatere fault major structural feature, associated zone extending 23 depth. There marked change near fault, seismic velocities being lower southeast. A high level seismicity occurs velocities, suggesting relationship two. possible explanation for elevated pore pressures caused by fluids derived dehydration crust. coincides most intense deformation, it weak.