A5075458836- Seismic Waves and Analysis
- Seismic Imaging and Inversion Techniques
- Underwater Acoustics Research
- earthquake and tectonic studies
- Geophysical Methods and Applications
- Cryospheric studies and observations
- Methane Hydrates and Related Phenomena
- Underwater Vehicles and Communication Systems
- Seismology and Earthquake Studies
- Geological and Geochemical Analysis
- Reservoir Engineering and Simulation Methods
- Landslides and related hazards
- Drilling and Well Engineering
- Hydraulic Fracturing and Reservoir Analysis
- High-pressure geophysics and materials
- Oceanographic and Atmospheric Processes
- Geology and Paleoclimatology Research
- Hydrocarbon exploration and reservoir analysis
- Winter Sports Injuries and Performance
- Ultrasonics and Acoustic Wave Propagation
- Arctic and Antarctic ice dynamics
- X-ray Diffraction in Crystallography
- Geological and Geophysical Studies
- Geological Modeling and Analysis
- Offshore Engineering and Technologies
Christ University
2025
Woods Hole Oceanographic Institution
2014-2024
University of California, San Diego
1979-2024
Institute of Astronomy
2018
Woodwell Climate Research Center
1987-2017
John Wiley & Sons (United States)
2014-2015
Hanover College
2015
Scripps Institution of Oceanography
1997-2014
University of Washington Applied Physics Laboratory
2012-2014
University of Washington
1983-2013
Seismic velocities measured in three drill holes through a gas hydrate deposit on the Blake Ridge, offshore South Carolina, indicate that substantial free exists to at least 250 meters beneath bottom-simulating reflection (BSR). Both methane and exist even where clear BSR is absent. The low reflectance, or blanking, above caused by lithologic homogeneity of sediments rather than cementation. average saturation relatively (5 7 percent porosity), which suggests earlier global estimates...
The Hawaii‐2 Observatory (H2O) is an excellent site for studying the source regions and propagation of microseisms since it located far from shorelines shallow water. During Leg 200 Ocean Drilling Program, officers JOIDES Resolution took wind wave measurements comparison with double‐frequency (DF) microseism data collected at nearby H2O. DF band can be divided into short‐period long‐period bands, SPDF LPDF, respectively. Comparison ship's weather log seismic in about 0.20 to 0.45 Hz shows a...
Abstract We construct a new seismic model for central and West Antarctica by jointly inverting Rayleigh wave phase group velocities along with P receiver functions. Ambient noise tomography exploiting data from more than 200 stations deployed over the past 18 years is used to velocity dispersion maps. Comparison between ambient maps those constructed using teleseismic earthquakes confirms accuracy of both results. These maps, together function waveforms, are 3‐D shear (Vs) crust uppermost...
Letter| April 01, 1983 Comment on "absorbing boundary conditions for acoustic and elastic wave equations," by R. Clayton B. Engquist Steven H. Emerman; Emerman Department of Geology Geophysics Woods Hole Oceanographic InstitutionWoods Hole, Massachusetts 02543 Search other works this author on: GSW Google Scholar Ralph A. Stephen Author Article Information Publisher: Seismological Society America Received: 18 Mar 1982 First Online: 03 2017 Online Issn: 1943-3573 Print 0037-1106 Copyright ©...
The finite‐difference method is a powerful technique for studying the propagation of elastic waves in boreholes. Even simple case an open borehole with vertical homogeneity, snapshot format displays clearly interaction between and rock, origin evolution phases. We present outline applied to acoustic logging problem, including boundary condition formulation liquid‐solid cylindrical interfaces which correct second order space increments. Absorbing boundaries based on formulations Reynolds...
Mode conversion for compressional to shear waves or vice versa, occurs most efficiently where the seismic wave encounters a large change in velocities over distance of less than half wavelength. In oceanic crust, interface between water sediment and volcanic basement is frequently site considerable mode conversion. We examine effect changes properties on efficiency range horizontal phase assuming that first order discontinuity. then show with aid synthetic seismograms calculated using...
A series of experiments conducted in the Philippine Sea during 2009-2011 investigated deep-water acoustic propagation and ambient noise this oceanographically geologically complex region: (i) 2009 North Pacific Acoustic Laboratory (NPAL) Pilot Study/Engineering Test, (ii) 2010-2011 NPAL Experiment, (iii) Ocean Bottom Seismometer Augmentation Experiment. The experimental goals included (a) understanding impacts fronts, eddies, internal tides on propagation, (b) determining whether methods,...
Abstract Recent studies attribute land double‐frequency (DF) microseism observations to deep water generation. Here we show that near‐coastal generation is generally the dominant source region. This determination based on at and ocean seismic stations, buoys, gravity‐wave hindcasts, beamforming results from continental arrays. Interactions between opposing wave components generate a pressure excitation pulse twice frequency excites pseudo‐Rayleigh (p Rg ) DF microseisms. p generated in...
Abstract Understanding deformation in ice shelves is necessary to evaluate the response of thinning. We study microseismicity associated with shelf using nine broadband seismographs deployed near a rift on Ross Ice Shelf. From December 2014 November 2016, we detect 5,948 icequakes generated by deformation. Locations were determined for 2,515 events least squares grid‐search and double‐difference algorithms. Ocean swell, infragravity waves, significant tsunami arrival do not affect...
Abstract 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 100 km RIS front and within 10 of each other show both dispersed infragravity (IG) wave swell‐generated signals resulting waves that originate North Pacific. Spectral levels 0.001 Hz have highest accelerations IG band (0.0025–0.03 Hz). Polarization analyses indicate complex frequency‐dependent particle motions, with energy...
Abstract Gravity waves impacting ice shelves illicit a suite of responses that can affect shelf integrity. Broadband seismometers deployed on the Ross Ice Shelf, complemented by near‐icefront seafloor hydrophone, establish association strong icequake activity with ocean gravity wave amplitudes ( A G ) below 0.04 Hz. The Shelf‐front seismic vertical displacement S V are well correlated , allowing estimating frequency‐dependent transfer function from amplitude to icefront T f )). is 0.6–0.7 at...
The primary goal of the Ocean Seismic Network Pilot Experiment (OSNPE) was to learn how make high quality broadband seismic measurements on ocean bottom in preparation for a permanent network. experiment also had implications development capability temporary (e.g., 1 year duration) experiments floor. Equipment installing, operating and monitoring borehole observatories deep sea tested including lead‐in package, logging probe, wire line packer control vehicle. vehicle used three modes during...
Some aspects of the dynamical behavior magma chambers, replenished from below with hotter but denser magma, have been modeled in a series laboratory experiments. In previously reported work fluids used were aqueous solutions comparable viscosity, and thus results should be applicable to basaltic which magmas do not vary greatly viscosity. that case, lower layer cools by convective heat transfer fluid above, crystallization causes density residual liquid decrease. When becomes equal upper...
Seismic anisotropy in the upper oceanic crust is observed borehole data obtained at Deep Sea Drilling Project (DSDP) site 504B on DSDP leg 92. Particle motion analysis of converted shear wave arrivals from explosive sources various azimuths reveals a set patterns which indicative hexagonally isotropic structure with horizontal symmetry axis. There are four diagnostic patterns: (1) Along axes, where vertically polarized waves (SV) generated but horizontally ( SH ) not generated, particle...
The paper examines P-wave propagation in anisotropic solids, and demonstrates the effect of anisotropy on polarizations quasi P-waves. deviation polarization from vector may be significant, but is almost same direction as group-velocity vector. Since group-velocity, or energy propagation, follows seismic ray paths, apparent difference deviations small. Consequently, it easily overlooked, hidden by noise, attributed to effects inhomogeneity.
An L-configured, three-component short period seismic array was deployed on the Ross Ice Shelf, Antarctica during November 2014. Polarization analysis of ambient noise data from these stations shows linearly polarized waves for frequency bands between 0.2 and 2 Hz. A spectral peak at about 1.6 Hz is interpreted as resonance water column used to estimate layer thickness below ice shelf. The band 4 18 dominated by Rayleigh Love propagating north that, based daily temporal variations, we...
Abstract Continuous seismic observations across the Ross Ice Shelf reveal ubiquitous ambient resonances at frequencies >5 Hz. These firn‐trapped surface wave signals arise through wind and snow bedform interactions coupled with very low velocity structures. Progressive long‐term spectral changes are associated redistribution by a January 2016 regional melt event. Modeling demonstrates high sensitivity to near‐surface (top several meters) elastic parameters. We propose that peak from in...
The fundamental objective of the Ocean Seismic Network Pilot Experiment (OSNPE)—which was carried out over a period about 4 months at site 225 km southwest Oahu, Hawaii—was to learn how make high‐quality, broadband seismic measurements in deep oceans. OSNPE results demonstrate that data quality similar quiet land stations can be acquired with seafloor seismographs, but location seismometer—whether it on seafloor, surficially buried within seabed, or borehole—has profound effect quality. At...
Seismic anisotropy in the upper 1500m. of oceanic basement has been observed by polarization analysis three‐component borehole seismometer records. The most convincing evidence for is shear wave splitting explosive sources at four azimuths. Compressional particle motion deviations suggestive are also but they may be caused lateral inhomogeneities. was not resolved travel‐time analysis. velocities and motions horizontal plane can modelled to within a standard deviation assuming perfectly...