Bolmer S. Thompson

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S. Thompson

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  • Technical Report
    A high-resolution bathymetry map for the Marguerite Bay and adjacent west Antarctic Peninsula shelf for the Southern Ocean GLOBEC Program
    (Woods Hole Oceanographic Institution, 2004-05) Bolmer, S. Thompson ; Beardsley, Robert C. ; Pudsey, C. ; Morris, P. ; Wiebe, Peter H. ; Hofmann, Eileen E. ; Anderson, John B. ; Maldonado, A.
    One objective of the U.S. Southern Ocean Global Ocean Ecosystems Dynamics (SO GLOBEC) program is to gain a better understanding of the sea floor bathymetry in the program study area. Much of Marguerite Bay and the adjacent shelf west of the Antarctic Peninsula were poorly charted when the SO GLOBEC program started in 2000. Before the first SO GLOBEC cruise, an improved local area version (ETOPO8.2A) was created from the Smith and Sandwell (1997) topo_8.2.img 2-minute digital gridded bathymetry for the study area. The first SO GLOBEC mooring cruise on the R/V Lawrence M. Gould (March 2001) showed that the 2-minute spatial resolution of ETOPO8.2A did not resolve many of the canyons and abrupt changes in topography that characterize Marguerite Bay and the inner- to mid-shelf region. It also was not particularly accurate in the more uniform terrain regions. We then decided to collect as much multibeam bathymetry data as possible during the SO GLOBEC broad-scale survey cruises on the R/VIB Nathaniel B. Palmer and combine these data with all other available multibeam and trackline bathymetry data to construct a digital bathymetry database and map for the study area. The resulting database has high-resolution data over much of the shelf and parts of Marguerite Bay gridded at 2 seconds in latitude and 6 seconds in longitude spacing between 65° to 71° S and 65° to 78° W. This technical report describes the steps taken to assemble and construct this database and how to access the data via the Internet.
  • Technical Report
    Ocean Bottom Seismometer Augmentation in the North Pacific (OBSANP) - cruise report
    (Woods Hole Oceanographic Institution, 2014-12) Stephen, Ralph A. ; Worcester, Peter F. ; Udovydchenkov, Ilya A. ; Aaron, Ernie ; Bolmer, S. Thompson ; Carey, Scott ; McPeak, Sean P. ; Swift, Stephen A. ; Dzieciuch, Matthew A.
    The Ocean Bottom Seismometer Augmentation in the North Pacific Experiment (OBSANP, June-July, 2013, R/V Melville) addresses the coherence and depth dependence of deep-water ambient noise and signals. During the 2004 NPAL Experiment in the North Pacific Ocean, in addition to predicted ocean acoustic arrivals and deep shadow zone arrivals, we observed "deep seafloor arrivals" (DSFA) that were dominant on the seafloor Ocean Bottom Seismometer (OBS) (at about 5000m depth) but were absent or very weak on the Distributed Vertical Line Array (DVLA) (above 4250m depth). At least a subset of these arrivals correspond to bottomdiffracted surface-reflected (BDSR) paths from an out-of-plane seamount. BDSR arrivals are present throughout the water column, but at depths above the conjugate depth are obscured by ambient noise and PE predicted arrivals. On the 2004 NPAL/LOAPEX experiment BDSR paths yielded the largest amplitude seafloor arrivals for ranges from 500 to 3200km. The OBSANP experiment tests the hypothesis that BDSR paths contribute to the arrival structure on the deep seafloor even at short ranges (from near zero to 4-1/2CZ). The OBSANP cruise had three major research goals: a) identification and analysis of DSFA and BDSR arrivals occurring at short (1/2CZ) ranges in the 50 to 400Hz band, b) analysis of deep sea ambient noise in the band 0.03 to 80Hz, and c) analysis of the frequency dependence of BR and SRBR paths. On OBSANP we deployed a 32 element VLA from 12 to 1000m above the seafloor, eight short-period OBSs and four long-period OBSs and carried out a 15day transmission program using a J15-3 acoustic source.
  • Presentation
    Three-dimensional numerical modeling of bottom-diffracted surface-reflected arrivals in the North Pacific [poster]
    ( 2015-12-15) Stephen, Ralph A. ; Udovydchenkov, Ilya A. ; Bolmer, S. Thompson ; Komatitsch, Dimitri ; Tromp, Jeroen ; Casarotti, Emanuele ; Xie, Zhinan ; Worcester, Peter F.
    Bottom-diffracted surface-reflected (BDSR) arrivals were first identified in the 2004 Long-range Ocean Acoustic Propagation Experiment (Stephen et al, 2013, JASA, v.134, p.3307-3317). The BDSR mechanism provides a means for acoustic signals and noise from distant sources to appear with significant strength on the deep seafloor. At depths deeper than the conjugate depth ambient noise and PE- predicted arrivals are sufficiently quiet that BDSR paths, scattered from small seamounts, can be the largest amplitude arrivals observed. The Ocean Bottom Seismometer Augmentation in the North Pacific (OBSANP) Experiment in June-July 2013 was designed to further define the characteristics of the BDSRs and to understand the conditions under which BDSRs are excited and propagate. The reciprocal of the BDSR mechanism also plays a role in T-phase excitation. To further understand the BDSR mechanism, the SPECFEM3D code was extended to handle high-frequency, deep water bottom scattering problems with actual bathymetry and a typical sound speed profile in the water column. The model size is 38km x 27km x 6.5km. The source is centered at 10Hz with a 5Hz bandwidth. Work supported by NSF and ONR.
  • Technical Report
    Ocean Bottom Seismometer Augmentation of the Philippine Sea Experiment (OBSAPS) cruise report
    (Woods Hole Oceanographic Institution, 2011-09) Stephen, Ralph A. ; Kemp, John N. ; McPeak, Sean P. ; Bolmer, S. Thompson ; Carey, Scott ; Aaron, Ernie ; Campbell, Richard L. ; Moskovitz, Brianne ; Calderwood, John ; Cohen, Ben ; Worcester, Peter F. ; Dzieciuch, Matthew A.
    The Ocean Bottom Seismometer Augmentation to the Philippine Sea Experiment (OBSAPS, April-May, 2011, R/V Revelle) addresses the coherence and depth dependence of deep-water ambient noise and signals. During the 2004 NPAL Experiment in the North Pacific Ocean, in addition to predicted ocean acoustic arrivals and deep shadow zone arrivals, we observed "deep seafloor arrivals" that were dominant on the seafloor Ocean Bottom Seismometer (OBS) (at about 5000m depth) but were absent or very weak on the Distributed Vertical Line Array (DVLA) (above 4250m depth). These "deep seafloor arrivals" (DSFA) are a new class of arrivals in ocean acoustics possibly associated with seafloor interface waves. The OBSAPS cruise had three major research goals: a) identification and analysis of DSFAs occurring at short (1/2CZ) ranges in the 50 to 400Hz band, b) analysis of deep sea ambient noise in the band 0.03 to 80Hz, and c) analysis of the frequency dependence of BR and SRBR paths as a function of frequency. On OBSAPS we deployed a fifteen element VLA from 12 to 852m above the seafloor, four short-period OBSs and two long-period OBSs and carried out an 11.5day transmission program using a J15-3 acoustic source.
  • Technical Report
    User's guide for PLOT_FINDIF
    (Woods Hole Oceanographic Institution, 2006-02) Bolmer, S. Thompson ; Stephen, Ralph A.
    PLOT_FINDIF is a MATLAB script which is used to plot output from the Woods Hole Oceanographic Institution (WHOI) Time Domain Finite Difference (TDFD) program called "Geoacoustic_TDFD" Both Geoacoustic_TDFD and PLOT_FINDIF are available from the ONR Ocean Acoustics Library ( This script will plot both the snapshot and time series output from Geoacoustic_TDFD. To run this script you must have a MATLAB license and the complete suite of 32 m-files contained in the PLOT_FINDIF package. This code has been tested with MATLAB versions 6 and 7.
  • Working Paper
    LFASE 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.
  • Working Paper
    LFASE data transcription software CGG2ROSE2 version 1.1 : program report
    (Woods Hole Oceanographic Institution, 1990-05) Little, William S. ; Galbraith, Nancy R. ; Bolmer, S. Thompson
    Seismic 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.
  • Technical Report
    A graphical user interface for processing data from the high resolution profiler (HRP)
    (Woods Hole Oceanographic Institution, 1998-03) Montgomery, Ellyn T. ; Bolmer, S. Thompson
    The High Resolution Profiler (HRP) is one of the only oceanographic instruments that is capable of measuring turbulent velocity and temperature fluctuations in the abyssal ocean. It is a unique device, and consequently specialized communications, data conversion and analysis software are employed to examine the data it collects. This document describes a major upgrade of the software and hardware systems used to process data from the HRP. The bulk of the conversion occurred in 1996 prior to the Brazil Basin Tracer Release Experiment (BBTRE). During the upgrade process, a Graphical User Interface (GUI) was designed and implemented for accomplishing routine HRP data processing tasks.
  • Article
    Deep seafloor arrivals : an unexplained set of arrivals in long-range ocean acoustic propagation
    (Acoustical Society of America, 2009-08) Stephen, Ralph A. ; Bolmer, S. Thompson ; Dzieciuch, Matthew A. ; Worcester, Peter F. ; Andrew, Rex K. ; Buck, Linda J. ; Mercer, James A. ; Colosi, John A. ; Howe, Bruce M.
    Receptions, from a ship-suspended source (in the band 50–100 Hz) to an ocean bottom seismometer (about 5000 m depth) and the deepest element on a vertical hydrophone array (about 750 m above the seafloor) that were acquired on the 2004 Long-Range Ocean Acoustic Propagation Experiment in the North Pacific Ocean, are described. The ranges varied from 50 to 3200 km. In addition to predicted ocean acoustic arrivals and deep shadow zone arrivals (leaking below turning points), “deep seafloor arrivals,” that are dominant on the seafloor geophone but are absent or very weak on the hydrophone array, are observed. These deep seafloor arrivals are an unexplained set of arrivals in ocean acoustics possibly associated with seafloor interface waves.
  • Article
    Phase change in subducted lithosphere, impulse, and quantizing Earth surface deformations
    (Copernicus Publications on behalf of the European Geosciences Union, 2015-09-23) Bowin, Carl O. ; Yi, W. ; Rosson, Rick D. ; Bolmer, S. Thompson
    The new paradigm of plate tectonics began in 1960 with Harry H. Hess's 1960 realization that new ocean floor was being created today and is not everywhere of Precambrian age as previously thought. In the following decades an unprecedented coming together of bathymetric, topographic, magnetic, gravity, seismicity, seismic profiling data occurred, all supporting and building upon the concept of plate tectonics. Most investigators accepted the premise that there was no net torque amongst the plates. Bowin (2010) demonstrated that plates accelerated and decelerated at rates 10−8 times smaller than plate velocities, and that globally angular momentum is conserved by plate tectonic motions, but few appeared to note its existence. Here we first summarize how we separate where different mass sources may lie within the Earth and how we can estimate their mass. The Earth's greatest mass anomalies arise from topography of the boundary between the metallic nickel–iron core and the silicate mantle that dominate the Earth's spherical harmonic degree 2 and 3 potential field coefficients, and overwhelm all other internal mass anomalies. The mass anomalies due to phase changes in olivine and pyroxene in subducted lithosphere are hidden within the spherical harmonic degree 4–10 packet, and are an order of magnitude smaller than those from the core–mantle boundary. Then we explore the geometry of the Emperor and Hawaiian seamount chains and the 60° bend between them that aids in documenting the slow acceleration during both the Pacific Plate's northward motion that formed the Emperor seamount chain and its westward motion that formed the Hawaiian seamount chain, but it decelerated at the time of the bend (46 Myr). Although the 60° change in direction of the Pacific Plate at of the bend, there appears to have been nary a pause in a passive spreading history for the North Atlantic Plate, for example. This, too, supports phase change being the single driver for plate tectonics and conservation of angular momentum. Since mountain building we now know results from changes in momentum, we have calculated an experimental deformation index value (1–1000) based on a world topographic grid at 5 arcmin spacing and displayed those results for viewing.
  • Working Paper
    Broadband 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, Richard
    This 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.
  • Article
    Three-dimensional bottom diffraction in the North Pacific
    (Acoustical Society of America, 2019-09-30) Stephen, Ralph A. ; Bolmer, S. Thompson ; Worcester, Peter F. ; Dzieciuch, Matthew A. ; Udovydchenkov, Ilya A.
    A significant aspect of bottom-interaction in deep water acoustic propagation, from point sources to point receivers, is the diffraction (or scattering) of energy from discrete seafloor locations along repeatable, deterministic paths in three-dimensions. These bottom-diffracted surface-reflected (BDSR) paths were first identified on the North Pacific acoustic laboratory experiment in 2004 (NPAL04) for a diffractor located on the side of a small seamount. On the adjacent deep seafloor, ambient noise and propagation in the ocean sound channel were sufficiently quiet that the BDSRs were the dominant arrival. The ocean bottom seismometer augmentation in the North Pacific (OBSANP) experiment in June–July 2013 studied BDSRs at the NPAL04 site in more detail. BDSRs are most readily identified by the arrival time of pulses as a function of range to the receiver for a line of transmissions. The diffraction points for BDSRs occur on the relatively featureless deep seafloor as well as on the sides of small seamounts. Although the NPAL04 and OBSANP experiments had very different geometries the same diffractor location is consistent with observed arrivals in both experiments within the resolution of the analysis. On OBSANP the same location excites BDSRs for 77.5, 155, and 310 Hz transmissions.
  • Technical Report
    Notes for Geoacoustic_TDFD
    (Woods Hole Oceanographic Institution, 2006-02) Stephen, Ralph A. ; Bolmer, S. Thompson
    These notes were written to help users run the WHOI TDFD (Time Domain Finite Difference) elastic wave equation code that was prepared for distribution through the ONR Ocean Acoustics Library ( The code and documentation are based on materials that were developed for a Numerical Wave Propagation class given at MIT in the Fall of 2000. The code used is the full two-dimensional time-domain finite-difference code developed at WHOI over the past 25 years, but in order to reduce the number of variables to a manageable size, we consider a two dimensional, isotropic problem with fixed parameters in time and space. For example, the source waveform in time for both beam and point sources is a RICKER wavelet, time units have been normalized to periods (defined at the peak frequency for pressure in water), space units have been normalized to water speed and density of 1! .5km/sec and 1000kg/m3) and the domain size has been fixed at 72 x 12 water wavelengths.
  • Article
    Ross ice shelf vibrations
    (John Wiley & Sons, 2015-09-16) Bromirski, Peter D. ; Diez, Anja ; Gerstoft, Peter ; Stephen, Ralph A. ; Bolmer, S. Thompson ; Wiens, Douglas A. ; Aster, Richard C. ; Nyblade, Andrew A.
    Broadband seismic stations were deployed across the Ross Ice Shelf (RIS) in November 2014 to study ocean gravity wave-induced vibrations. Initial data from three stations 100 km from the RIS front and within 10 km of each other show both dispersed infragravity (IG) wave and ocean swell-generated signals resulting from waves that originate in the North Pacific. Spectral levels from 0.001 to 10 Hz have the highest accelerations in the IG band (0.0025–0.03 Hz). Polarization analyses indicate complex frequency-dependent particle motions, with energy in several frequency bands having distinctly different propagation characteristics. The dominant IG band signals exhibit predominantly horizontal propagation from the north. Particle motion analyses indicate retrograde elliptical particle motions in the IG band, consistent with these signals propagating as Rayleigh-Lamb (flexural) waves in the ice shelf/water cavity system that are excited by ocean wave interactions nearer the shelf front.
  • Working Paper
    Ambient 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. Thompson
    This 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.
  • Article
    Third-party borehole seismic experiments during the Ocean Drilling Program
    (Copernicus Publications on behalf of the German Research Centre for Geosciences, 2007-11) Stephen, Ralph A. ; Swift, Stephen A. ; Bolmer, S. Thompson ; Hoskins, Hartley
    The first borehole seismic experiments on DSDP and ODP were two-ship Oblique Seismic Experiments (Stephen, 1979; Stephen, et al., 1979, 1980; Swift, et al., 1988). By recording on the drill ship and shooting explosives out to ranges of 8 km, the upper 1.5 km of the upper crust (Layer 2) adjacent to the borehole could be imaged (Fig. 1; Stephen and Harding, 1983), Azimuthal anisotropy (Stephen, 1981, 1985) and lateral heterogeneity (Stephen, 1988; Swift and Stephen, 1989) could also be studied by shooting circles of shots at a fixed range from the borehole,
  • Technical Report
    Analysis of Deep Seafloor Arrivals observed on NPAL04
    (Woods Hole Oceanographic Institution, 2012-12) Stephen, Ralph A. ; Bolmer, S. Thompson ; Udovydchenkov, Ilya A. ; Dzieciuch, Matthew A. ; Worcester, Peter F. ; Andrew, Rex K. ; Mercer, James A. ; Colosi, John A. ; Howe, Bruce M.
    This report gives an overview of the analysis that was done on Deep Seafloor Arrivals since they were initially presented in Stephen et al (2009). All of the NPAL04/LOAPEX (North Pacific Acoustic Laboratory, 2004/ Long Range Ocean Acoustic Propagation Experiment) data on three ocean bottom seismometers (OBSs) at ~5,000m depth and the deepest element of the deep vertical line array (DVLA) at 4250m depth has been analyzed. A distinctive pattern of late arrivals was observed on the three OBSs for transmissions from T500 to T2300. The delays of these arrivals with respect to the parabolic equation predicted (PEP) path were the same for all ranges from 500 to 2300km, indicating that the delay was introduced near the receivers. At 500km range the same arrival was observed throughout the water column on the DVLA. We show that arrivals in this pattern converted from a PEP path to a bottom-diffracted surface reflected (BDSR) path at an off-geodesic seamount.
  • Technical Report
    Site synthesis report of DSPP sites 417 and 418
    (Woods Hole Oceanographic Institution, 1989-06) Swift, Stephen A. ; Bolmer, S. Thompson ; Stephen, Ralph A.
    This document summarizes information relevent to planning, execution, and interpretation of results from a study of the interaction of sound in the 2-30Hz band with deep ocean seafloor using sea-surface sources, seafloor receivers, and borehole seismometers emplaced by wireline re-entry at Deep Sea Drilling Project sites 417 and 418 in the western North Atlantic. We summarize published scientific results from borehole sampling of water, sediment, and rock, from wire line logging, and from borehole seismic experiments. We present new results from analysis of total power recorded by receivers clamped in basement during the borehole seismic experiment on DSDP Leg 102. We document non-drilling investigations of the site and the nature and location of re-entry cones and transponders. We describe the physical oceanography of the region and the speed of sound in water. We provide an extensive bibliography on published results from scientific investigations at 417/418. This document was completed prior to 1989 surveys of sites 417 and 418.
  • Working Paper
    Tests 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.
  • Working Paper
    Seafloor 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. Cleo
    The 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.