Lateral heterogeneity in the upper oceanic crust at Deep Sea Drilling Project Site 504

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doi: 10.1029/JB093iB06p06571
Author(s): Stephen, Ralph A.
Author Affiliation(s): Primary:
Woods Hole Oceanogr. Inst., Woods Hole, MA, United States
Volume Title: Journal of Geophysical Research
Source: Journal of Geophysical Research, 93(B6), p.6571-6584. Publisher: American Geophysical Union, Washington, DC, United States. ISSN: 0148-0227
Note: In English. Woods Hole Oceanogr. Inst., Contrib. No. 6721. 21 refs.; illus. incl. 2 tables, sketch map
Summary: The lateral variability of the upper oceanic crust can be studied by mapping the amplitude (or power) content of arrivals from a dense array of identical sources to a single receiver. In this paper we present the results from a borehole seismic experiment at Deep Sea Drilling Project site 504 in the eastern equatorial Pacific. Seismic amplitude anomalies of 20 dB and more are present with a horizontal correlation length of 1-3 km. Finite difference synthetic seismogram techniques are used to predict seismic wave propagation through realistic bathymetry, basement relief, and lateral variations within basement. A three-dimensional model of the velocity structure around the borehole can be constructed. The resultant model has horizontal gradients greater than 2.0 s-1 in the upper crust. These gradients are comparable to the vertical gradients normally associated with oceanic crust. Assuming that velocity anomalies in the upper crust reflect changes in porosity, the resultant structure provides constraints on the hydrothermal circulation at the site. In addition, the finite difference modeling indicates that polarity reversals can be generated by lateral velocity variations near the source and receiver.
Year of Publication: 1988
Research Program: DSDP Deep Sea Drilling Project
IPOD International Phase of Ocean Drilling
ODP Ocean Drilling Program
Key Words: 18 Geophysics, Solid-Earth; Boreholes; Crust; DSDP Site 504; Deep Sea Drilling Project; Discontinuities; Equatorial Pacific; Finite difference analysis; Geophysical methods; Geophysical surveys; Horizontal discontinuities; IPOD; Leg 111; Leg 137; Leg 140; Leg 148; Leg 69; Leg 70; Leg 83; Leg 92; Ocean Drilling Program; Oceanic crust; Pacific Ocean; Seismic logging; Seismic methods; Seismograms; Statistical analysis; Surveys; Synthetic seismograms; Tectonophysics; Three-dimensional models; Upper crust; Velocity structure; Well-logging
Coordinates: N011335 N011335 W0834356 W0834356
Record ID: 1988055044
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