Vertical Seismic Profile at Site 765 and Seismic Reflectors in the Argo Abyssal Plain

Bolmer, S. Thompson; Buffler, Richard T.; Hoskins, Hartley; Stephen, Ralph A.; Swift, Stephen A.

doi:10.2973/odp.proc.sr.123.136.1992

Cited by 4 publications

(3 citation statements)

References 16 publications

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“…The experiment will be conducted in a similar manner to other VSPs on ODP Legs 118, 123, 148, and 164 (Swift et al, 1991, Bolmer et al, 1992Swift et al, 1996;Holbrook et al, 1996). A water gun and an airgun will be floated from the aft port crane and the Schlumberger three-component tool will be used as the borehole receiver.…”

Section: Conventional Vertical Seismic Profilingmentioning

confidence: 99%

Hammer Drilling and NERO

Casey¹,

Pettigrew²,

Miller³

1998

ODP Scientific Prospectus

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This Scientific Prospectus is based on precruise JOIDES panel discussions and scientific input from the designated Co-Chief Scientists on behalf of the drilling proponents. The operational plans within reflect JOIDES Planning Committee and thematic panel priorities. During the course of the cruise, actual site operations may indicate to the Co-Chief Scientists and the Operations Manager that it would be scientifically or operationally advantageous to amend the plan detailed in this prospectus. It should be understood that any proposed changes to the plan presented here are contingent upon approval of the Director of the Ocean Drilling Program in consultation with the Science and Operations Committees (successors to the Planning Committee) and the Pollution Prevention and Safety Panel.Technical Editor: Karen K. Graber Leg 179 Scientific ProspectusPage 3 ABSTRACTLeg 179 is a two-part drilling program; first we will test the hammer drill-in casing system recently developed under the direction of the Ocean Drilling Program (ODP), then we will drill and case a hole for the Ninetyeast Ridge Observatory (NERO) project. The sea trials for the hammer drill-in casing system will take place near ODP Site 735, in the rift mountains of the Southwest IndianRidge. We will evaluate the operational characteristics of the components of the hammer drill-in casing system, as well as the complete system. This test will also address operational limits of the system in terms of water depth, topography, and surface slope. Time permitting, we will recover cores through the cased reentry hole, to as great a depth as possible. Fifteen days on site have been allocated for these tests. Successful completion of the NERO project will fill a major gap in the global coverage of seismic, magnetic, and general geophysical monitoring. Currently, geophysical observatories are only present on continents and islands; thus, data collection is incomplete.Establishing a cased reentry hole into basement at ODP Site 757 will be the first step toward the installation of a Geophysical Ocean Bottom Observatory. This observatory will be part of the future network of seafloor observatories proposed in the International Ocean Network (ION) program for studying global geodynamics and earthquakes. A borehole observatory at NinetyeastRidge will enhance investigation of the dynamics of the Indian plate. This plate has a complex geologic history characterized by high intraplate seismicity and may contain a diffuse plate boundary between the Central Indian Ridge and the Indonesian Arc. A seismometer will be installed in the hole at a later date. Several additional seismic experiments are planned for the NERO site during and after drilling operations. These include (1) a vertical seismic profile, (2) a seismic-while-drilling experiment, 3) and a two-ship offset seismic experiment (OSE) using the German research vessel Sonne, which will shoot several seismic profiles of varying azimuth and along circles with different radii about the hole. Shots in the OSE will be reco...

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Section: Conventional Vertical Seismic Profilingmentioning

confidence: 99%

Hammer Drilling and NERO

Casey¹,

Pettigrew²,

Miller³

1998

ODP Scientific Prospectus

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“…Seismic signals were received by a Geospace wall-lock seismometer, which contained three pairs of 4.5-Hz geophones (Bolmer et al, 1992). Each pair is wired in series and orthogonally configured with two components in the plane normal to the borehole and one parallel to the borehole.…”

Section: Data Acquisitionmentioning

confidence: 99%

Seismic Velocities at Site 891 from a Vertical Seismic Profile Experiment

Moore¹,

Dellinger²,

M.E.³

1995

Proceedings of the Ocean Drilling Program, 146 Part 1 Scientific Results

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A vertical seismic profile experiment carried out at Ocean Drilling Program Site 891 ties the regional seismic reflection data to the drilled and logged section and provides additional velocity data near the frontal thrust. The depth of the frontal thrust is confirmed to be between 425 and 440 mbsf at a two-way traveltime of 4.05 s. Compressional P-wave velocities in the upper 275 mbsf as determined by a walkaway VSP (1883 m/s) are consistent with those measured by in situ wireline sonic logs. Sonic log velocities between 310 and 400 mbsf are bounded by the walkaway VSP (1883 to 1835 m/s) and zero-offset VSP (2193 m/ s) velocities. Below the depth of the drill hole, the walkaway VSP velocities are significantly lower than those determined by stacking velocity analyses on nearby multichannel seismic lines. Shear wave velocities in the upper section, as measured by the walkaway VSP, are about 340 m/s.

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“…There have been many examples of the importance of normal incidence and offset VSP's on the DSDP and ODP programs including the origin of mid-sediment reflectors (from interference effects in thin layers) [Bolmer, et al, 1992], the nature of Layer 2/Layer 3 boundary in oceanic crust [Detrick, et al, 1994], and the investigations of gas hydrate deposits [Holbrook, et al, 1996]. In these cases and others it has been very useful to acquire VSP's using sources with similar bandwidth to the seismic sources in order to resolve the interference and multi-path effects that often affect the character of reflections on seismic record sections.…”

Section: Validating Surface Seismic -Interference and Multi-path Effectsmentioning

confidence: 99%