Bolmer
S. Thompson
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S. Thompson
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Working PaperLFASE data processing system overview(Woods Hole Oceanographic Institution, 1990-06) Little, William S. ; Bolmer, S. Thompson ; Stephen, Ralph A.This technical report provides an overview of the LFASE data processing system. This software system is made up of over twenty-five programs which are used to acquire, reduce, and analyze acoustic seismic data collected during the Low Frequency Acoustic Seismic Experiment (LFASE) (Stephen et al, 1989; Koelsch et al, 1990). This report is directed at scientific and engineering personnel who wish to understand the overall LFASE data processing system as well as the individual processing procedures which are utilized during each stage of data reduction and interpretation. The report is also directed at programmers, data processors, technicians, and other individuals who plan to work with LFASE programs and data.
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Working PaperLFASE data transcription software CGG2ROSE2 version 1.1 : program report(Woods Hole Oceanographic Institution, 1990-05) Little, William S. ; Galbraith, Nancy R. ; Bolmer, S. ThompsonSeismic data obtained using borehole seismometers during the LFASE experiment (Stephen et al, 1989; Koelsch et al, 1990) are retrieved from the seafloor instrument package and converted to a data format more suitable for analysis with existing computer systems. This report describes the computer program CGG2ROSE2 for converting LFASE optical disk files recorded in CGG format by the data acquisition computer into standard ROSE format data files on a VAX/VMS computer. CGG2ROSE2 provides features for rearranging LFASE data into smaller segments, making corrections to timing information, and replacing file header information.
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Working PaperBroadband borehole seismic system integration tests : report of the system integration tests at MPL/SIO(Woods Hole Oceanographic Institution, 1998) Goldsborough, Robert G. ; Austin, Gary ; Bolmer, S. Thompson ; Jabson, David M. ; Jonke, Patrick ; Gould, Matthew R. ; Hildebrand, John A. ; Hollinshead, C. B. ; Offield, Glen ; Orcutt, John ; Peal, Kenneth R. ; Spiess, Fred N. ; Stephen, Ralph A. ; Vernon, Frank L. ; Willoughby, David F. ; Zimmerman, RichardThis report describes a series of tests performed at SIO/MPL, Point Lorna the week of 17 November 1997 designed to achieve integration of the Broadband Borehole Seismic System (BBBSS) in preparation for the OSN Pilot Experiment cruise on RN Thompson during January 1997. Representatives from all groups were present (see appendix A), with their respective parts of the system and support equipment. It was anticipated that these tests would result in the complete integration of the various components of the borehole seismometer system in preparation for the January cruise. The system would be assembled and tested following a plan (see appendix C) that would culminate in the fully integrated borehole seismometer being wet tested off the MPL pier.
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Working PaperAmbient noise analysis and finite difference modelling of VLF borehole seismic data(Woods Hole Oceanographic Institution, 1987-03) Stephen, Ralph A. ; Swift, Stephen A. ; Bolmer, S. ThompsonThis report describes a preliminary analysis of borehole seismic data to determine VLF/Sub-bottom Seismic Noise in the Atlantic and the preliminary results of finite difference modelling for a Cape Fear environment. Noise levels were not a simple function of depth and there are indications that noise levels may depend on local geology about a given receiver position and/or on clamping. Coherency of the noise was generally poor (<0.8) and was independent of depth. There is no evidence for distinct polarizations or directionality of the noise. The lowest determined value for ambient noise power on the vertical component was 10-4 nm2/Hz in the frequency range from 5-50 Hz. The better clamped horizontal component had comparable power values. In conclusion, although the drill ship was on the site and drill pipe was in the hole, analysis of the data for a large number of windows can provide meaningful upper bounds on the ambient noise levels in the upper crust.
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Working PaperTests of the broadband borehole seismic system (B³S²) at Scripps IGPP and the Pinon Flat Observatory : October 1994 to June 1995(Woods Hole Oceanographic Institution, 1997-08) Stephen, Ralph A. ; Orcutt, John ; Peal, Kenneth R. ; Vernon, Frank L. ; Austin, Gary ; Bolmer, S. Thompson ; Gould, Matthew R. ; Koelsch, Donald E. ; Hollinshead, C. B. ; Offield, Glen ; Willoughby, David F.The broadband borehole seismic system (B3S2) is being developed as one component of the Ocean Seismic Network (OSN) Pilot Experiment which will be carried out at the OSN-1 Site off Hawaii in Winter 1998. The other major instruments being developed for the experiment are a Broadband Ocean Bottom Seismometer and a Shallow Buried Broadband Ocean Bottom Seismometer. B3S2 consists of four major components: 1) a borehole sonde with a re-entry guide, Teledyne 54000 broadband seismometer, and REFTEK digitizing system, 2) a seafloor acquisition and recording system (SEABASS), 3) a control vehicle for deploying the sonde in a borehole, and 4) shipboard command and control electronics. The deployment system is very similar to the SEABASS configuration used on LFASE (Stephen eta!, 1994). The purposes of the tests at Pinon Flat were: 1) to integrate the borehole sonde and seafloor and shipboard electronics which had been constructed by different groups: WHOI and SIO/IGPP; 2) test the combined subsystem in a wet borehole environment using actual cables and simulating seafloor conditions; and 3) acquire seismic ambient noise and earthquake data over approximately a three month period for comparison with known stations at the Pinon Flat Observatory.
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Working PaperSeafloor borehole array seismic system (SEABASS)(Woods Hole Oceanographic Institution, 1993-01) Stephen, Ralph A. ; Koelsch, Donald E. ; Berteaux, Henri O. ; Bocconcelli, Alessandro ; Bolmer, S. Thompson ; Cretin, J. ; Etourmy, N. ; Fabre, A. ; Goldsborough, Robert G. ; Gould, Matthew R. ; Kery, Sean M. ; Laurent, J. ; Omnes, G. ; Peal, Kenneth R. ; Swift, Stephen A. ; Turpening, R. ; Zani, A. CleoThe Seafloor Borehole Array Seismic System (SEABASS) has been developed to measure the pressure and three dimensional particle velocity of the VLF sound field (2-50HZ) below the seafloor in the deep ocean (water depths of up to 6km). The system consists off our three-component borehole seismometers (with an optional hydrophone), a borehole digitizing unit, and a seafloor control and recording package. The system can be deployed using a wire line re-entry capability from a conventional research vessel in Deep Sea Drilling Project (DSDP) and Ocean Drilling Project (ODP) boreholes. Data from below the seafloor are acquired either on-board the research vessel via coaxial tether or remotely on the seafloor in a self-contained package. If necessary the data module from the seafloor package can be released independently and recovered on the surface. This paper describes the engineering specifications of SEABASS, the tests that were carried out, and preliminary results from an actual deep sea deployment. Ambient noise levels beneath the seafloor acquired on the Low Frequency Acoustic-Seismic Experiment (LFASE) are within 20dB of levels from previous seafloor borehole seismic experiments and from land borehole measurements. The ambient noise observed on LFASE decreases by up to 12dB in the upper 100m of the seafloor in a sedimentary environment.
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Working PaperTranscription of 9-track tapes to CD-ROM(Woods Hole Oceanographic Institution, 1999-12) Bolmer, S. Thompson ; DuBois, David L. ; Hoskins, Hartley ; Sass, Warren J.The WHO! Marine Seismic community had about two thousand 9-track magnetic tapes in storage. The data stored were from marine experiments dating from the 1970's to 1990 and from computer models. The experiments included observations made with seafloor instruments and sondes in boreholes. These tapes were created on Digital Equipment Corporation (DEC) V AXNMS and other older computer operating systems. The tapes needed to be read and put into a format that contemporary UNIX operating systems could read. This report documents the logistics of transcribing this information onto CD-ROM. A search was made to find the best way to read and rewrite these 9-track tapes to new media that would have a longer shelflife and be readable on today's UNIX variants. As a result of this search, an outside company was hired to do these conversions. The tapes that were readable from this first group of 381 tapes selected for transcription are now on twenty-five CDROMs.
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Working PaperProgress report on the development of the seafloor borehole array seismic system (phase II) : July 14, 1992 to January 31, 1996(Woods Hole Oceanographic Institution, 1996-06) Stephen, Ralph A. ; Peal, Kenneth R. ; Bolmer, S. Thompson ; Gould, Matthew R. ; Koelsch, Donald E. ; Orcutt, John A. ; Vernon, Frank L. ; Offield, G. ; Willoughby, David F. ; Hollinshead, C. B. ; Spiess, Fred N. ; Hildebrand, John A. ; Zimmerman, Richard ; Austin, GaryThe Seafloor Borehole Array Seismic System (SEABASS) was originally developed to record autonomously on the seafloor the signals received on a four-sonde three-component borehole geophone array in the VLF band (2-50Hz)(Stephen eta!., 1994). The system is designed to use the wireline re-entry capability (Spiess, 1993; Spiess eta!., 1992) to install and retrieve the seafloor instrumentation (Figures 1 and 2). Following the successful demonstration of this technology on the LFASE (Low Frequency Acoustic-Seismic Experiment) project in September 1989, it was decided to extend the capability to broadband (1000sec-5Hz) borehole seismometers which could be used for permanent seafloor seismic observatories in the Ocean Seismic Network (Orcutt and Stephen, 1993; Purdy and Dziewonski, 1988; Purdy and Orcutt, 1995; Stephen, 1995; Sutton and Barstow, 1990; Sutton eta!., 1988; Sutton eta!., 1965). The Broadband Borehole Seismic System (B3S2) is the prototype system for permanent broadband borehole seismic observatories on the seafloor. It has three major components: i) a broadband borehole seismometer, the Teledyne 54000, modified for seafloor operations by Scripps-IGPP; ii) the re-entry system provided by Scripps-MPL; and iii) the seafloor recording system developed by WHO I. Because of the similarity of the seafloor recording system to SEABASS we have named this new system SEABASS-ll. This report discusses the development of SEABASS-Il at WHOI in the period from July 14, 1992 to January 31, 1996. The motivation for the project and a work statement are contained in WHOI proposals 7016 and 7016.1. This report is a collection of documentation prepared while the work was being carried out. Some of the issues discussed in early memos were subsequently changed. Modifications and further testing of SEABASS-ll, as well as final system integration tests with the borehole andreentry systems (both of which are also still being modified and tested) have still to be carried out in preparation for the OSN Pilot Experiment Cruise in Spring 1997. This is a preliminary report only and presents work in progress. It will be useful to the engineering team as a historical reference of the sequence of events in the development of SEABASS-ll but it should not be considered as a technical manual for the instrumentation.
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Working PaperLFASE borehole array data acquisition and reduction summary(Woods Hole Oceanographic Institution, 1991-09) Bolmer, S. Thompson ; Swift, Stephen A. ; Stephen, Ralph A.On the Low Frequency Acoustic - Seismic Experiment (LFASE), carried out at DSDP hole 534A in August, 1989, WHOI was responsible for acquiring data from a twelve channel borehole seismic array. Data were acquired both on-board while tethered to the array and autonomously in a seafloor package. Seismic source data (explosives and airguns) and ambient noise data were recorded. This report describes the nature of data acquired, reviews the data reduction procedure from field format to ROSE data format, and includes examples of the data. A total of918.6 Mbytes of data were acquired (769 Mbytes in the shipboard recording mode and 149.6 Mbytes in the seafloor recording mode). Approximately 85 explosive shots, 2000 airgun shots, and 10 hours of ambient noise data were recorded.