Hess Deep Rift Valley Structure from Seismic Tomography

Sean M. Wiggins, LeRoy M. Dorman, Bruce D. Cornuelle, and John A. Hildebrand

Scripps Institution of Oceanography, University of California, San Diego, La Jolla

The Hess Deep rift valley, at approximately 2° 14' N, 101° 33' W, displays exposures of young, lower crustal and upper mantle rocks formed at the nearby, fast-spreading East Pacific Rise. A seismic refraction experiment was conducted across the Hess Deep rift valley to provide P-wave travel times between sea floor explosions and Ocean-Bottom Seismometers. These travel time data were analyzed using an iterative, damped least-squares, inverse method to produce a velocity model of the subsurface structure. The resulting velocity contrasts were interpreted as lithologies originating at different depths and/or alteration of the preexisting rock units. Petrologic and bathymetric data from previous studies were used, along with the seismic interpretation, to produce a geologic model. The model supports low-angle detachment faulting with serpentinization of peridotite as the preferred mechanism for creating the distribution and exposure of lower crustal and upper mantle rocks within the Hess Deep.

Last Revised: 18 Apr 1996