Velocity Bounds on the Seismic Structure of Mesozoic Crust and Uppr Mantle in the Southwest Pacific Basin from Downhole Observations at Deep-Sea Drilling Project Hole-595B

Citation:
Whitmarsh, RB, Orcutt JA, Jordan TH, Adair RG, Shearer PM.  1987.  Velocity Bounds on the Seismic Structure of Mesozoic Crust and Uppr Mantle in the Southwest Pacific Basin from Downhole Observations at Deep-Sea Drilling Project Hole-595B. Initial Reports of the Deep Sea Drilling Project. 91:437-444.

Date Published:

Mar

Abstract:

The Marine Seismic System (MSS) was deployed during Leg 91 of the Deep Sea Drilling Project in order to assess the reduction in noise levels achievable through burying a seismic inertial sensor within the basaltic crust. The noise levels were significantly reduced and the usual coupling problems experienced by ocean bottom seismographs were essentially eliminated. This contribution reports on the results of early analyses of data collected while shooting two roughly orthogonal refraction lines. The data were processed at Scripps Institution of Oceanography and topographic corrections were applied to reduce the effects of roughness in the seafloor topography. The data were first corrected to the seafloor and the remaining correlations with topography were attenuated by a correction for the height of the seafloor above a datum. The corrections reduced traveltime scatter and significantly tightened extremal envelopes on acceptable velocity functions. The best constrained solutions were achieved over moderate topography while the presence of substantial seamounts always introduced scatter presumably due to unknown features off the ship's track. Velocity anisotropy was discovered within the oceanic upper mantle and the velocity structure of this old crust was found to berather "normal."

Notes:

n/a

Website

DOI:

10.2973/dsdp.proc.91.111.1987