SEPM (Society for Sedimentary Geology) eBooks, Jun 19, 2019
<jats:title>Abstract</jats:title> <jats:p>Much about the offshore California Co... more <jats:title>Abstract</jats:title> <jats:p>Much about the offshore California Continental Borderland remains unknown, despite its location off the most populated area of the west coast of North America, vital importance to US interests, and potential for seismic and tsunamigenic hazards. In 2015 and 2016, Exploration Vessel (E/V) Nautilus of the Ocean Exploration Trust undertook a series of seven expeditions in that region. During those cruises, we acquired 13,075 km2 of multibeam bathymetric data, performed 58 dives with remotely operated vehicles (ROV) Hercules and Argus, totaling 500+ hours underwater (1000+ hours of video), and collected 532 geological and biological samples across this 200-km-wide, tectonically active region. Because Nautilus is equipped with state-of-the-art telepresence technology, numerous scientists based on shore actively participated in these expeditions in real time. Here, we describe the data acquired during these expeditions and present some very preliminary results. The digital data and physical samples are accessible to the scientific community via online request systems.</jats:p>
We have developed a marine seismic-reflection program that involves students in research and inst... more We have developed a marine seismic-reflection program that involves students in research and instruction and is being successfully used to train students in quantitative and structural concepts. Over 100 high-school to graduate-level students have participated in the program over the last five years (1993-98). The research target is the Palos Verdes fault, a major seismogenic strike-slip fault in the California Continental Borderland. Students have participated in cruise planning and data acquisition, processing, and interpretation, and they have produced semester reports, senior theses, and oral papers and posters at meetings. Seismic mapping of a 10-km part of the fault south of Los Angeles Harbor shows a small (300 m) restraining segment and a larger (1-2 km) releasing segment in the fault. Two small (4-m-high and 1-km-wide) bulges on the seafloor indicate shortening near the restraining segment. This evidence of Holocene strain provides information on the tectonic history of this important fault. The results help us build a case study of fault evolution and plate interaction for our classes in oceanography and geology and raise student interest in earthquakes and in the origin of local faultcontrolled features such as the Palos Verdes Hills.
ABSTRACT We describe observations, analysis and modeling of the March 11, 2001 Tohoku tsunami in ... more ABSTRACT We describe observations, analysis and modeling of the March 11, 2001 Tohoku tsunami in the far field based on field surveys conducted immediately after the event. In California, significant damage occurred in Crescent City and Santa Cruz harbors with moderate to minor damage at maritime facilities throughout the state. The largest surges coincided with low tide, however, tsunami effects persisted through the day and the highest water levels were recorded at high tide 16 - 22 hours later. New Zealand experienced similar effects; several docks and boats were damaged at Tutukaka Marina with some significant overland flooding at Port Charles. Strong currents, surges and broken mooring lines were observed at other locations and persisted throughout the tide cycle. Tide gauge records from California and New Zealand were analyzed for spectral content. Spectral analysis of tide gauge records from the event showed the long duration of the tsunami in the far-field. Preliminary results show clearly the difference in tsunami duration for open coast versus locations in natural or man made harbors. The spectral content of the tsunami signal as recorded on opposite corners of the Pacific Ocean is compared for this event and the 2010 Chilean tsunami.
Abstract Digital mosaics of swath and conventional bathymetry data reveal large, distinct near-ci... more Abstract Digital mosaics of swath and conventional bathymetry data reveal large, distinct near-circular crater structures in the inner California Continental Borderland offshore of southern California. Two have maximum crater diameters that exceed 30 km, and a third has a crater diameter of about 12.5 km. One of these, Catalina Crater, exhibits a well-defined crater morphology--raised outer rim, ring moat, and elevated central peak--that resembles an impact site. The others have a similar morphology but more disrupted by later tectonic ...
E/V Nautilus cruise NA075 returned to the Southern California Continental Borderland, an area tha... more E/V Nautilus cruise NA075 returned to the Southern California Continental Borderland, an area that remains largely unexplored. Part of the broader North America-Pacific plate boundary, this region extends ~300 km west of the San Andreas Fault and displays an unusually rugged physiography. During the cruise, the multibeam sonar mapped ~5,200 km2 of seafloor, and ROVs Hercules and Argus were deployed for 16 dives to explore geological and biological targets (Figure 1) and collect samples
We assess tsunami hazards in San Diego Bay, California, using newly identified offshore tsunami s... more We assess tsunami hazards in San Diego Bay, California, using newly identified offshore tsunami sources and recently available high resolution bathymetric/topographic data. Using MOST (Titov and Synolakis, J Waterways Port Coastal Ocean Eng ASCE 124(4):57-171, 1998), we simulate locally, regionally and distant-generated tsunamis. Local tsunami source models use more realistic fault and landslide data than previous efforts. With the exception of the Alaska-Aleutian Trench, modeling results suggest that local sources are responsible for the largest waves within the San Diego Bay and Mission Bay. Because San Diego Bay is relatively well protected by North Island and the Silver Strand, the wave heights predicted are consistently smaller inside the harbor than outside. However, historical accounts, recent tsunamis and our predictions show that San Diego Bay is vulnerable to strong tsunami induced currents. More specifically, large currents are expected inside the harbor for various distant and local tsunami sources with estimated flow velocities exceeding 100 cm/s. Such currents have been damaging to harbor facilities, such as wharves and piers, and may cause boats to break from moorings and ram into adjacent harbor structures, as observed in recent historic tsunamis. More recently, following the M w 8.8 February 27, 2010 Chile earthquake, tsunami-currents damaged docks/piers in Shelter Island confirming our findings. We note that the first generation of inundation maps in use in San Diego County by emergency management was based on much larger ''worst case but realistic scenarios'' (Synolakis et al. 2002a), which reflected the understanding of offshore hazards pervasive ten years ago. Large inundation and overland flow depths were observed primarily in local tsunami source simulations. In
For more information on this work, visit www.tsunami.ca.gov ABSTRACT: At 2:55 AM PDT, a little ov... more For more information on this work, visit www.tsunami.ca.gov ABSTRACT: At 2:55 AM PDT, a little over four hours after the Chilean earthquake origin time, the West Coast Alaska Tsunami Warning Center placed the entire California coast in a Tsunami Advisory. The Advisory forecast tsunami amplitudes ranging from approximately 0.3 to 1.4 meters and strong currents in bays and harbors. Hourly conference calls were held with the county operational areas and most counties cleared beaches and limited access to harbor areas. The highest amplitudes were predicted for San Luis Obispo County and areas south. The tsunami initially arrived at San Diego at 12:02pm on February 27, and moved progressively up the coast over the next hour and a half. Peak amplitudes at tide gauge locations in the state ranges from 0.12 meters to a high of 0.91 meters at Santa Barbara. At most locations, the strongest surges were recorded within the first two hours but for some locations, like Crescent City and Santa Ba...
SEPM (Society for Sedimentary Geology) eBooks, Jun 19, 2019
<jats:title>Abstract</jats:title> <jats:p>Much about the offshore California Co... more <jats:title>Abstract</jats:title> <jats:p>Much about the offshore California Continental Borderland remains unknown, despite its location off the most populated area of the west coast of North America, vital importance to US interests, and potential for seismic and tsunamigenic hazards. In 2015 and 2016, Exploration Vessel (E/V) Nautilus of the Ocean Exploration Trust undertook a series of seven expeditions in that region. During those cruises, we acquired 13,075 km2 of multibeam bathymetric data, performed 58 dives with remotely operated vehicles (ROV) Hercules and Argus, totaling 500+ hours underwater (1000+ hours of video), and collected 532 geological and biological samples across this 200-km-wide, tectonically active region. Because Nautilus is equipped with state-of-the-art telepresence technology, numerous scientists based on shore actively participated in these expeditions in real time. Here, we describe the data acquired during these expeditions and present some very preliminary results. The digital data and physical samples are accessible to the scientific community via online request systems.</jats:p>
We have developed a marine seismic-reflection program that involves students in research and inst... more We have developed a marine seismic-reflection program that involves students in research and instruction and is being successfully used to train students in quantitative and structural concepts. Over 100 high-school to graduate-level students have participated in the program over the last five years (1993-98). The research target is the Palos Verdes fault, a major seismogenic strike-slip fault in the California Continental Borderland. Students have participated in cruise planning and data acquisition, processing, and interpretation, and they have produced semester reports, senior theses, and oral papers and posters at meetings. Seismic mapping of a 10-km part of the fault south of Los Angeles Harbor shows a small (300 m) restraining segment and a larger (1-2 km) releasing segment in the fault. Two small (4-m-high and 1-km-wide) bulges on the seafloor indicate shortening near the restraining segment. This evidence of Holocene strain provides information on the tectonic history of this important fault. The results help us build a case study of fault evolution and plate interaction for our classes in oceanography and geology and raise student interest in earthquakes and in the origin of local faultcontrolled features such as the Palos Verdes Hills.
ABSTRACT We describe observations, analysis and modeling of the March 11, 2001 Tohoku tsunami in ... more ABSTRACT We describe observations, analysis and modeling of the March 11, 2001 Tohoku tsunami in the far field based on field surveys conducted immediately after the event. In California, significant damage occurred in Crescent City and Santa Cruz harbors with moderate to minor damage at maritime facilities throughout the state. The largest surges coincided with low tide, however, tsunami effects persisted through the day and the highest water levels were recorded at high tide 16 - 22 hours later. New Zealand experienced similar effects; several docks and boats were damaged at Tutukaka Marina with some significant overland flooding at Port Charles. Strong currents, surges and broken mooring lines were observed at other locations and persisted throughout the tide cycle. Tide gauge records from California and New Zealand were analyzed for spectral content. Spectral analysis of tide gauge records from the event showed the long duration of the tsunami in the far-field. Preliminary results show clearly the difference in tsunami duration for open coast versus locations in natural or man made harbors. The spectral content of the tsunami signal as recorded on opposite corners of the Pacific Ocean is compared for this event and the 2010 Chilean tsunami.
Abstract Digital mosaics of swath and conventional bathymetry data reveal large, distinct near-ci... more Abstract Digital mosaics of swath and conventional bathymetry data reveal large, distinct near-circular crater structures in the inner California Continental Borderland offshore of southern California. Two have maximum crater diameters that exceed 30 km, and a third has a crater diameter of about 12.5 km. One of these, Catalina Crater, exhibits a well-defined crater morphology--raised outer rim, ring moat, and elevated central peak--that resembles an impact site. The others have a similar morphology but more disrupted by later tectonic ...
E/V Nautilus cruise NA075 returned to the Southern California Continental Borderland, an area tha... more E/V Nautilus cruise NA075 returned to the Southern California Continental Borderland, an area that remains largely unexplored. Part of the broader North America-Pacific plate boundary, this region extends ~300 km west of the San Andreas Fault and displays an unusually rugged physiography. During the cruise, the multibeam sonar mapped ~5,200 km2 of seafloor, and ROVs Hercules and Argus were deployed for 16 dives to explore geological and biological targets (Figure 1) and collect samples
We assess tsunami hazards in San Diego Bay, California, using newly identified offshore tsunami s... more We assess tsunami hazards in San Diego Bay, California, using newly identified offshore tsunami sources and recently available high resolution bathymetric/topographic data. Using MOST (Titov and Synolakis, J Waterways Port Coastal Ocean Eng ASCE 124(4):57-171, 1998), we simulate locally, regionally and distant-generated tsunamis. Local tsunami source models use more realistic fault and landslide data than previous efforts. With the exception of the Alaska-Aleutian Trench, modeling results suggest that local sources are responsible for the largest waves within the San Diego Bay and Mission Bay. Because San Diego Bay is relatively well protected by North Island and the Silver Strand, the wave heights predicted are consistently smaller inside the harbor than outside. However, historical accounts, recent tsunamis and our predictions show that San Diego Bay is vulnerable to strong tsunami induced currents. More specifically, large currents are expected inside the harbor for various distant and local tsunami sources with estimated flow velocities exceeding 100 cm/s. Such currents have been damaging to harbor facilities, such as wharves and piers, and may cause boats to break from moorings and ram into adjacent harbor structures, as observed in recent historic tsunamis. More recently, following the M w 8.8 February 27, 2010 Chile earthquake, tsunami-currents damaged docks/piers in Shelter Island confirming our findings. We note that the first generation of inundation maps in use in San Diego County by emergency management was based on much larger ''worst case but realistic scenarios'' (Synolakis et al. 2002a), which reflected the understanding of offshore hazards pervasive ten years ago. Large inundation and overland flow depths were observed primarily in local tsunami source simulations. In
For more information on this work, visit www.tsunami.ca.gov ABSTRACT: At 2:55 AM PDT, a little ov... more For more information on this work, visit www.tsunami.ca.gov ABSTRACT: At 2:55 AM PDT, a little over four hours after the Chilean earthquake origin time, the West Coast Alaska Tsunami Warning Center placed the entire California coast in a Tsunami Advisory. The Advisory forecast tsunami amplitudes ranging from approximately 0.3 to 1.4 meters and strong currents in bays and harbors. Hourly conference calls were held with the county operational areas and most counties cleared beaches and limited access to harbor areas. The highest amplitudes were predicted for San Luis Obispo County and areas south. The tsunami initially arrived at San Diego at 12:02pm on February 27, and moved progressively up the coast over the next hour and a half. Peak amplitudes at tide gauge locations in the state ranges from 0.12 meters to a high of 0.91 meters at Santa Barbara. At most locations, the strongest surges were recorded within the first two hours but for some locations, like Crescent City and Santa Ba...
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