Intraslab earthquakes: dehydration of the Cascadia slab.
We simultaneously invert travel times of refracted and wide-angle reflected waves for three-dimensional compressional-wave velocity structure, earthquake locations, and reflector geometry in northwest Washington state. The reflector, interpreted to be the crust-mantle boundary (Moho) of the subducting Juan de Fuca plate, separates intraslab earthquakes into two groups, permitting a new understanding of the origins of intraslab earthquakes in Cascadia. Earthquakes up-dip of the Moho's 45-kilometer depth contour occur below the reflector, in the subducted oceanic mantle, consistent with serpentinite dehydration; earthquakes located down-dip occur primarily within the subducted crust, consistent with the basalt-to-eclogite transformation.
Preston
Leiph A
LA
Department of Earth and Space Sciences, University of Washington, Seattle, WA 98195, USA. preston@ess.washington.edu
Creager
Kenneth C
KC
Crosson
Robert S
RS
Brocher
Thomas M
TM
Trehu
Anne M
AM