Coastal and Marine Geohazards of the U.S. West Coast and Alaska
Coastal and marine geohazards are sudden and extreme events beneath the ocean that threaten coastal populations. Such underwater hazards include earthquakes, volcanic eruptions, landslides, and tsunamis.
Southern California
USGS aims to boost knowledge about the threat of earthquakes and underwater landslides in Southern California with modern, high-resolution seafloor imaging.
Devastating earthquakes in Japan (2011) and Chile (2010) that spawned pan-oceanic tsunamis sent a sobering reminder that U.S. coastlines are also vulnerable to natural disasters that originate in the ocean. People living near coastlines may think “out of sight, out of mind” when it comes to underwater dangers. But in tectonically active regions, such as the west coast of the Americas, the potential lurks for sudden seafloor movement to cause great damage to coastal communities. Using the power of modern mapping and seismic technology to gather detailed seafloor data can directly impact human life and cities by improving earthquake and tsunami forecasts.
For many people who live near the coastlines, underwater dangers are “out of sight, out of mind.” But in tectonically active regions, such as the west coast of the Americas, the potential lurks for a surge of underwater motion that could disrupt many communities along the coast.
The 2011 Tohoku earthquake and tsunami were vivid reminders that remote disasters can affect an entire ocean basin. Understanding how and what regions might be affected by faraway disasters is an important, yet complex problem.
In addition to remote threats, local hazards lie just off the shores of the western U.S. Such hazards include shaking by large earthquakes in subduction zones, where one tectonic plate compresses another (Cascadia, Aleutian Trench); or on strike-slip faults, where one tectonic plate moves horizontally past another (central and southern California). Related hazards include tsunamis generated by shifts in the seafloor or by underwater landslides that occur during earthquakes. Landslides can also threaten equipment on the ocean floor such as pipelines, communication cables, and oil platforms.
One barrier to measuring the true seismic risk has been the scarcity of high-resolution maps of the ocean floor. The technology for mapping large parts of the ocean floor with enough detail needed to study offshore faults has only been available for about the last 20 years, long after coastal areas had been densely developed. The USGS Coastal and Marine Geohazards team applies this technology to the seafloor off several urban regions along the west coast. For example, the San Francisco Bay Area has the highest density of active faults of any urban area in the nation; the densely populated expanse (approximately 20 million people) in southern California is threatened by the nation’s highest level of earthquake risk; and Alaska has had more large earthquakes than the rest of the U.S. combined. In addition, detailed imaging of the ocean bottom has uncovered new evidence of submarine landslides. Creating three-dimensional views of the seafloor down to depths of 12 kilometers has given scientists remarkable ways to examine how a fault works, or how fluids may follow underground paths and possibly trigger landslides.
It’s challenging to know how a fault will behave without seeing its detailed structure: its bends, connections, and branches. To discover a fault’s structure, scientists go to sea to collect streams of data that they turn into comprehensive underwater maps. This type of imaging, along with knowing the age of sediment along faults and measuring other factors such as magnetics and density, can help tell the story of when the fault last ruptured or how fast it’s moving. Since these details are seldom known or easy to calculate for offshore faults, it’s challenging to incorporate these faults into earthquake models and estimate their actual hazard risk.
Reassessing the threat of earthquake, tsunami, and landslide hazards to ports and nuclear power plants on the U.S. west coast can directly impact facility management, emergency-management planning, and plant re-licensing. The data can also affect building codes, the design of highways, bridges, and other large structures, as well as earthquake insurance rates.
Below are the current studies of the “U.S. West Coast and Alaska Marine Geohazards” Project.
Below are datsets associated with this project.
Minisparker seismic-reflection data collected between Point Sur and Morro Bay, offshore of central California, from 2011-09-12 to 2011-09-26 (USGS field activity B-05-11-CC)
Chirp seismic-reflection data collected offshore of San Diego and Los Angeles Counties, southern California, from 2011-06-08 to 2011-06-22 (USGS field activity S-7-11-SC)
Chirp seismic-reflection data collected between Oceanside and La Jolla, offshore of southern California, from 2010-06-01 to 2010-06-12 (USGS field activity S-12-10-SC)
Minisparker seismic-reflection data collected offshore of San Diego and Los Angeles Counties, southern California, from 2011-06-08 to 2011-06-22 (USGS field activity S-7-11-SC)
Minisparker seismic-reflection data collected between Oceanside and La Jolla, offshore of southern California, from 2010-06-01 to 2010-06-12 (USGS field activity S-12-10-SC)
Minisparker seismic-reflection data collected between Huntington Beach and San Diego, offshore of southern California, from 2008-04-28 to 2008-05-05 (USGS field activity B-1-08-SC)
Gravity cores from San Pablo Bay and Carquinez Strait, San Francisco Bay, California
Chirp seismic-reflection data collected in the San Pedro Basin, offshore of southern California, from 2009-07-06 to 2009-07-10 (USGS field activity S-5-09-SC)
Minisparker seismic-reflection data collected in the San Pedro Basin, offshore of southern California, from 2009-07-06 to 2009-07-10 (USGS field activity S-5-09-SC)
Marine Geophysical Data -- Point Arena to Cape Mendocino
Below are publications associated with this project.
Offshore shallow structure and sediment distribution, Point Sur to Point Arguello, central California
Discovery of an extensive deep-sea fossil serpulid reef associated with a cold seep, Santa Monica Basin, California
Practical approaches to maximizing the resolution of sparker seismic reflection data
Controls on submarine canyon head evolution: Monterey Canyon, offshore central California
The Santa Cruz Basin submarine landslide complex, southern California: Repeated failure of uplifted basin sediment
The Santa Cruz Basin (SCB) is one of several fault-bounded basins within the California Continental Borderland that has drawn interest over the years for its role in the tectonic evolution of the region, but also because it contains a record of a variety of modes of sedimentary mass transport (i.e., open slope vs. canyon-confined systems). Here, we present a suite of new high-resolution marine geo
Neotectonics of the Big Sur Bend, San Gregorio‐Hosgri fault system, central California
Slope failure and mass transport processes along the Queen Charlotte Fault Zone, western British Columbia
Multibeam echosounder (MBES) images, 3.5 kHz seismic-reflection profiles and piston cores obtained along the southern Queen Charlotte Fault Zone are used to map and date mass-wasting events at this transform margin – a seismically active boundary that separates the Pacific Plate from the North American Plate. Whereas the upper continental slope adjacent to and east (upslope) of the fault zone offs
Slope failure and mass transport processes along the Queen Charlotte Fault, southeastern Alaska
The Queen Charlotte Fault defines the Pacific–North America transform plate boundary in western Canada and southeastern Alaska for c. 900 km. The entire length of the fault is submerged along a continental margin dominated by Quaternary glacial processes, yet the geomorphology along the margin has never been systematically examined due to the absence of high-resolution seafloor mapping data. Hence
Deformation of the Pacific/North America plate boundary at Queen Charlotte Fault: The possible role of rheology
The tectonically controlled San Gabriel Channel–Lobe Transition Zone, Catalina Basin, Southern California Borderland
Strain partitioning in southeastern Alaska: Is the Chatham Strait Fault active?
Seafloor fluid seeps on Kimki Ridge, offshore southern California: Links to active strike-slip faulting
Below are news stories associated with this project.
Below are partners associated with this project.
Coastal and marine geohazards are sudden and extreme events beneath the ocean that threaten coastal populations. Such underwater hazards include earthquakes, volcanic eruptions, landslides, and tsunamis.
Southern California
USGS aims to boost knowledge about the threat of earthquakes and underwater landslides in Southern California with modern, high-resolution seafloor imaging.
Devastating earthquakes in Japan (2011) and Chile (2010) that spawned pan-oceanic tsunamis sent a sobering reminder that U.S. coastlines are also vulnerable to natural disasters that originate in the ocean. People living near coastlines may think “out of sight, out of mind” when it comes to underwater dangers. But in tectonically active regions, such as the west coast of the Americas, the potential lurks for sudden seafloor movement to cause great damage to coastal communities. Using the power of modern mapping and seismic technology to gather detailed seafloor data can directly impact human life and cities by improving earthquake and tsunami forecasts.
For many people who live near the coastlines, underwater dangers are “out of sight, out of mind.” But in tectonically active regions, such as the west coast of the Americas, the potential lurks for a surge of underwater motion that could disrupt many communities along the coast.
The 2011 Tohoku earthquake and tsunami were vivid reminders that remote disasters can affect an entire ocean basin. Understanding how and what regions might be affected by faraway disasters is an important, yet complex problem.
In addition to remote threats, local hazards lie just off the shores of the western U.S. Such hazards include shaking by large earthquakes in subduction zones, where one tectonic plate compresses another (Cascadia, Aleutian Trench); or on strike-slip faults, where one tectonic plate moves horizontally past another (central and southern California). Related hazards include tsunamis generated by shifts in the seafloor or by underwater landslides that occur during earthquakes. Landslides can also threaten equipment on the ocean floor such as pipelines, communication cables, and oil platforms.
One barrier to measuring the true seismic risk has been the scarcity of high-resolution maps of the ocean floor. The technology for mapping large parts of the ocean floor with enough detail needed to study offshore faults has only been available for about the last 20 years, long after coastal areas had been densely developed. The USGS Coastal and Marine Geohazards team applies this technology to the seafloor off several urban regions along the west coast. For example, the San Francisco Bay Area has the highest density of active faults of any urban area in the nation; the densely populated expanse (approximately 20 million people) in southern California is threatened by the nation’s highest level of earthquake risk; and Alaska has had more large earthquakes than the rest of the U.S. combined. In addition, detailed imaging of the ocean bottom has uncovered new evidence of submarine landslides. Creating three-dimensional views of the seafloor down to depths of 12 kilometers has given scientists remarkable ways to examine how a fault works, or how fluids may follow underground paths and possibly trigger landslides.
It’s challenging to know how a fault will behave without seeing its detailed structure: its bends, connections, and branches. To discover a fault’s structure, scientists go to sea to collect streams of data that they turn into comprehensive underwater maps. This type of imaging, along with knowing the age of sediment along faults and measuring other factors such as magnetics and density, can help tell the story of when the fault last ruptured or how fast it’s moving. Since these details are seldom known or easy to calculate for offshore faults, it’s challenging to incorporate these faults into earthquake models and estimate their actual hazard risk.
Reassessing the threat of earthquake, tsunami, and landslide hazards to ports and nuclear power plants on the U.S. west coast can directly impact facility management, emergency-management planning, and plant re-licensing. The data can also affect building codes, the design of highways, bridges, and other large structures, as well as earthquake insurance rates.
Below are the current studies of the “U.S. West Coast and Alaska Marine Geohazards” Project.
Below are datsets associated with this project.
Minisparker seismic-reflection data collected between Point Sur and Morro Bay, offshore of central California, from 2011-09-12 to 2011-09-26 (USGS field activity B-05-11-CC)
Chirp seismic-reflection data collected offshore of San Diego and Los Angeles Counties, southern California, from 2011-06-08 to 2011-06-22 (USGS field activity S-7-11-SC)
Chirp seismic-reflection data collected between Oceanside and La Jolla, offshore of southern California, from 2010-06-01 to 2010-06-12 (USGS field activity S-12-10-SC)
Minisparker seismic-reflection data collected offshore of San Diego and Los Angeles Counties, southern California, from 2011-06-08 to 2011-06-22 (USGS field activity S-7-11-SC)
Minisparker seismic-reflection data collected between Oceanside and La Jolla, offshore of southern California, from 2010-06-01 to 2010-06-12 (USGS field activity S-12-10-SC)
Minisparker seismic-reflection data collected between Huntington Beach and San Diego, offshore of southern California, from 2008-04-28 to 2008-05-05 (USGS field activity B-1-08-SC)
Gravity cores from San Pablo Bay and Carquinez Strait, San Francisco Bay, California
Chirp seismic-reflection data collected in the San Pedro Basin, offshore of southern California, from 2009-07-06 to 2009-07-10 (USGS field activity S-5-09-SC)
Minisparker seismic-reflection data collected in the San Pedro Basin, offshore of southern California, from 2009-07-06 to 2009-07-10 (USGS field activity S-5-09-SC)
Marine Geophysical Data -- Point Arena to Cape Mendocino
Below are publications associated with this project.
Offshore shallow structure and sediment distribution, Point Sur to Point Arguello, central California
Discovery of an extensive deep-sea fossil serpulid reef associated with a cold seep, Santa Monica Basin, California
Practical approaches to maximizing the resolution of sparker seismic reflection data
Controls on submarine canyon head evolution: Monterey Canyon, offshore central California
The Santa Cruz Basin submarine landslide complex, southern California: Repeated failure of uplifted basin sediment
The Santa Cruz Basin (SCB) is one of several fault-bounded basins within the California Continental Borderland that has drawn interest over the years for its role in the tectonic evolution of the region, but also because it contains a record of a variety of modes of sedimentary mass transport (i.e., open slope vs. canyon-confined systems). Here, we present a suite of new high-resolution marine geo
Neotectonics of the Big Sur Bend, San Gregorio‐Hosgri fault system, central California
Slope failure and mass transport processes along the Queen Charlotte Fault Zone, western British Columbia
Multibeam echosounder (MBES) images, 3.5 kHz seismic-reflection profiles and piston cores obtained along the southern Queen Charlotte Fault Zone are used to map and date mass-wasting events at this transform margin – a seismically active boundary that separates the Pacific Plate from the North American Plate. Whereas the upper continental slope adjacent to and east (upslope) of the fault zone offs
Slope failure and mass transport processes along the Queen Charlotte Fault, southeastern Alaska
The Queen Charlotte Fault defines the Pacific–North America transform plate boundary in western Canada and southeastern Alaska for c. 900 km. The entire length of the fault is submerged along a continental margin dominated by Quaternary glacial processes, yet the geomorphology along the margin has never been systematically examined due to the absence of high-resolution seafloor mapping data. Hence
Deformation of the Pacific/North America plate boundary at Queen Charlotte Fault: The possible role of rheology
The tectonically controlled San Gabriel Channel–Lobe Transition Zone, Catalina Basin, Southern California Borderland
Strain partitioning in southeastern Alaska: Is the Chatham Strait Fault active?
Seafloor fluid seeps on Kimki Ridge, offshore southern California: Links to active strike-slip faulting
Below are news stories associated with this project.
Below are partners associated with this project.