The Fate of the Juan de Fuca Plate

Mei Xue and Richard M. Allen
University of California Berkeley

AGU Fall Meeting 2006
Eos Trans. AGU, 87(52), Fall Meet. Suppl., Abstract S51D-06

The Juan de Fuca plate is subducting beneath the northwestern United States and southwestern Canada. Although the slab has been imaged to depths of at least ~{400} km beneath Washington and at least ~{200} to 300 km beneath northern Oregon with a dip of ~60° to the east, there is little evidence for a slab east of High Cascades deeper than ~150 km beneath central and ~200 km beneath southern Oregon. To image the slab beneath Oregon, we apply tomography technique using a dataset consisting of our own OATS deployment and all other available data. For the Vs inversion, a total of 95 events with clear S and SKS phases were recorded at 45 stations and a total number of 2148 rays were used. For the Vp inversion, a total of 74 events with clear direct P phase were recorded at 46 stations, and a total number of 2043 rays were used. Our tomographic images clearly show that the Juan de Fuca plate dives into the mantle beneath Oregon and continues east of the High Cascades with a dip of ~50° reaching a depth of ~400 km. The slab does not dip more vertically than its counterparts to north and south, which have a dip of ~60° and ~65° respectively. Resolution tests suggest there is little or no velocity anomaly associated with a slab below ~400 km.

© Richard M Allen