Geological processes at subduction zones control seismicity, plutonism and volcanism, geochemical cycling between the oceans, crust, mantle. The down-going plate experiences metamorphism, associated dehydration fluid flow alters physical properties of interface mantle wedge, as well controlling composition material descending into Any direct study slab evolution during is inhibited by prohibiti...

Global Positioning System vectors and surface tilt rates are inverted simultaneously for the rotation of western Oregon and plate locking on the southern Cascadia subduction thrust fault. Plate locking appears to be largely offshore, consistent with earlier studies, and is sufficient to allow occasional great earthquakes inferred from geology. Clockwise rotation of most of Oregon about a nearby...

Broadband vertical P-wave records are analyzed from 63 of the largest shallow subduction zone earthquakes which have occurred in the circum-Pacific in the last 45 yr. Most of the records studied come from a common instrument, the Pasadena, California, Benioff 1-90 seismometer. Propagation and instrument effects are deconvolved from the P-wave records using a damped least-squares inversion to ob...

S U M M A R Y Our understanding of mantle convection and the motion of plates depends intimately on our understanding of the viscosity structure of the mantle. While geoid and gravity observations have provided fundamental constraints on the radial viscosity structure of the mantle, the influence of short-wavelength variations in viscosity is still poorly understood. We present 2-D and 3-D fini...

Abstract Subduction zones have recurrently formed on Earth. Previous studies have, however, suggested that they are unlikely to start in the interior of a pristine ocean. Instead, seem be more likely form from another pre-existing subduction zone. One widely cited conceptual model new is polarity reversal, resulting shutdown pre-existent zone due arrival buoyant block at trench. However, dynami...