Research Interests: Marine seismology and bottom interacting ocean acoustics Seismic structure of... more Research Interests: Marine seismology and bottom interacting ocean acoustics Seismic structure of oceanic crust Propagation and scattering in absorptive, anisotropic and heterogeneous elastic media Borehole seismic experiments Synthetic seismogram methods Ambient noise in the ocean
Research Interests: Marine seismology and geoacoustics Seismic structure of oceanic crust Seismic... more Research Interests: Marine seismology and geoacoustics Seismic structure of oceanic crust Seismic wave propagation in heterogeneous media Borehole seismic experiments Finite difference synthetic seismograms
Funding for the workshop was provided jointly by the National Science Foundation and the Office o... more Funding for the workshop was provided jointly by the National Science Foundation and the Office of Naval Research. The steering committee wishes to thank the staff at Woods Hole Oceanographic Institution, and particularly Christina Cuellar, for providing an excellent venue for the workshop. Brian Rasmussen, APL-UW Publications Manager, edited the summary report and constructed the CD-R interface. Steering committee members:
Ocean Drilling Project Leg 200 was the first leg in deep sea and ocean drilling history to conduc... more Ocean Drilling Project Leg 200 was the first leg in deep sea and ocean drilling history to conduct operations in the vicinity of a continuously operating broadband seafloor seismometer. In 1998 investigators from the University of Hawaii, Woods Hole Oceanographic Institution, and Incorporated Institutions for Seismology had installed a broadband, shallow buried seismometer at the site [Duennebier et al., 2002]
The Journal of the Acoustical Society of America, 2014
ABSTRACT During the 2004 Long-range Ocean Acoustic Propagation Experiment (LOAPEX), a new class o... more ABSTRACT During the 2004 Long-range Ocean Acoustic Propagation Experiment (LOAPEX), a new class of acoustic arrivals was observed on ocean bottom seismometers (OBSs) for ranges from 500 to 3200 km. The arrivals were called deep seafloor arrivals (DSFAs), because they were the dominant arrivals on the ocean bottom seismometers (OBSs), but were very weak on the deep vertical line array (Deep VLA), located above 750 m from the seafloor. Stephen et al. [JASA 134, 3307-3317 (2013)] attributed some of these arrivals to bottom-diffracted, surface-reflected (BDSR) energy that scattered from a seamount near the Deep VLA and subsequently reflected from the sea surface before arriving at the OBSs. In the Ocean Bottom Seismometer Augmentation in the North Pacific (OBSANP) Experiment in June to July 2013, we returned to the Deep VLA site with a near-seafloor Distributed Vertical Line Array (DVLA) that extended upward 1000 m from the seafloor and 12 OBSs. We transmitted to the instruments with a ship-suspended J15-3 acoustic source. The receiver locations and transmission program were designed to test the hypothesis that DSFAs correspond to BDSR energy, to further define the characteristics of the DSFAs, and to understand the conditions under which DSFAs are excited and propagate.
Research Interests: Marine seismology and bottom interacting ocean acoustics Seismic structure of... more Research Interests: Marine seismology and bottom interacting ocean acoustics Seismic structure of oceanic crust Propagation and scattering in absorptive, anisotropic and heterogeneous elastic media Borehole seismic experiments Synthetic seismogram methods Ambient noise in the ocean
Research Interests: Marine seismology and geoacoustics Seismic structure of oceanic crust Seismic... more Research Interests: Marine seismology and geoacoustics Seismic structure of oceanic crust Seismic wave propagation in heterogeneous media Borehole seismic experiments Finite difference synthetic seismograms
Funding for the workshop was provided jointly by the National Science Foundation and the Office o... more Funding for the workshop was provided jointly by the National Science Foundation and the Office of Naval Research. The steering committee wishes to thank the staff at Woods Hole Oceanographic Institution, and particularly Christina Cuellar, for providing an excellent venue for the workshop. Brian Rasmussen, APL-UW Publications Manager, edited the summary report and constructed the CD-R interface. Steering committee members:
Ocean Drilling Project Leg 200 was the first leg in deep sea and ocean drilling history to conduc... more Ocean Drilling Project Leg 200 was the first leg in deep sea and ocean drilling history to conduct operations in the vicinity of a continuously operating broadband seafloor seismometer. In 1998 investigators from the University of Hawaii, Woods Hole Oceanographic Institution, and Incorporated Institutions for Seismology had installed a broadband, shallow buried seismometer at the site [Duennebier et al., 2002]
The Journal of the Acoustical Society of America, 2014
ABSTRACT During the 2004 Long-range Ocean Acoustic Propagation Experiment (LOAPEX), a new class o... more ABSTRACT During the 2004 Long-range Ocean Acoustic Propagation Experiment (LOAPEX), a new class of acoustic arrivals was observed on ocean bottom seismometers (OBSs) for ranges from 500 to 3200 km. The arrivals were called deep seafloor arrivals (DSFAs), because they were the dominant arrivals on the ocean bottom seismometers (OBSs), but were very weak on the deep vertical line array (Deep VLA), located above 750 m from the seafloor. Stephen et al. [JASA 134, 3307-3317 (2013)] attributed some of these arrivals to bottom-diffracted, surface-reflected (BDSR) energy that scattered from a seamount near the Deep VLA and subsequently reflected from the sea surface before arriving at the OBSs. In the Ocean Bottom Seismometer Augmentation in the North Pacific (OBSANP) Experiment in June to July 2013, we returned to the Deep VLA site with a near-seafloor Distributed Vertical Line Array (DVLA) that extended upward 1000 m from the seafloor and 12 OBSs. We transmitted to the instruments with a ship-suspended J15-3 acoustic source. The receiver locations and transmission program were designed to test the hypothesis that DSFAs correspond to BDSR energy, to further define the characteristics of the DSFAs, and to understand the conditions under which DSFAs are excited and propagate.
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Papers by Ralph Stephen