U.S. West Coast and Alaska Marine Geohazards
Science Center Objects
Marine geohazards are sudden and extreme events beneath the ocean that threaten coastal populations. Such underwater hazards include earthquakes, volcanic eruptions, landslides, and tsunamis.
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.
View of John Muir School on Pacific Avenue in Long Beach, California, showing damage from the March 10, 1933 Long Beach earthquake. Photo taken 8 days after the earthquake.
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.
Sonar-generated image showing underwater topography and the potential for landslides near the head of Resurrection Bay, Alaska. The terrain looks three times as steep as it occurs naturally. The arrow points to underwater landslide debris from the collapse of a fan-delta following the great Alaskan earthquake of 1964. The town of Seward, which suffered much damage and lost lives due to the quake, had been built on this fan-delta (just above and to the left of the arrow).
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.
Mapping along the Queen Charlotte-Fairweather fault required several days aboard the Alaska Department of Fish and Game research vessel Solstice. Here, the boat sits in a marina near Cordova, Alaska.
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 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.
See the USGS Interactive Map of 2014 Fault Sources. This database contains information on faults and associated folds in the United States that are believed to be sources of M>6 earthquakes during 2014.
Sam Johnson explaining details of the Hosgri fault zone at USGS offices in Santa Cruz.
USGS geophysicist Jared Kluesner points at a three-dimensional cross-section of seismic data about 40 kilometers across and several kilometers deep located in the Santa Barbara Channel. This imaging deep below the seafloor allows scientists to visualize and map faults better.
Below are the current studies of the “U.S. West Coast and Alaska Marine Geohazards” Project.
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Date published: November 2, 2020Status: Active
Earthquake Hazards in Southeastern Alaska
Over the last 100 years, the Queen Charlotte-Fairweather fault system has produced large-magnitude earthquakes affecting both Canada and the U.S. To fill in missing details about its offshore location and structure, USGS uses sophisticated techniques to truly understand the fault’s hazard potential.
Contacts: Danny Brothers -
Date published: August 3, 2020Status: Active
Underwater Landslides off Southern California
An earthquake can trigger a landslide along the ocean floor, which can then set off a tsunami. Without modern, high-resolution imaging of the seafloor, many historical slides and threats from future slides remain undetected.
Contacts: Jared Kluesner -
Date published: July 27, 2020Status: Active
Seafloor Faults off Southern California
More than 22 million people live along Southern California’s coast, and many more migrate there every year. Faults and earthquake threats in this region have been heavily studied on land. USGS aims to boost our knowledge about faults on the seafloor, so they can be included in hazard assessments.
Contacts: Danny Brothers -
Date published: June 23, 2020Status: Active
Hazards: EXPRESS
Marine geohazards including earthquakes, landslides, and tsunamis lie offshore of densely populated areas of California, Oregon, and Washington. One goal of EXPRESS is to improve assessments of these hazards.
Contacts: Danny Brothers, Nancy Prouty -
Date published: May 1, 2020Status: Active
Offshore Faults along Central and Northern California
From Point Conception to Cape Mendocino, seafloor faults have been, in the past, mapped in varying ways and without enough detail to assess their earthquake potential. To provide this important information, USGS uses advanced technology to image offshore faults that could trigger devastating earthquakes near densely populated areas and a nuclear power plant.
Contacts: Janet Watt
Below are publications associated with this project.
Focused fluid flow and methane venting along the Queen Charlotte fault, offshore Alaska (USA) and British Columbia (Canada)
Fluid seepage along obliquely deforming plate boundaries can be an important indicator of crustal permeability and influence on fault-zone mechanics and hydrocarbon migration. The ~850-km-long Queen Charlotte fault (QCF) is the dominant structure along the right-lateral transform boundary that separates the Pacific and North American tectonic...
Prouty, Nancy G.; Brothers, Daniel; Kluesner, Jared; Barrie, J. Vaughn; Andrews, Brian D.; Lauer, Rachel; Greene, Gary; Conrad, James E.; Lorenson, Thomas; Law, Michael D.; Sahy, Diana; Conway, Kim; McGann, Mary; Dartnell, PeterMorphology, structure, and kinematics of the San Clemente and Catalina faults based on high-resolution marine geophysical data, southern California Inner Continental Borderland
Catalina Basin, located within the southern California Inner Continental Borderland (ICB), is traversed by two active submerged fault systems that are part of the broader North America-Pacific plate boundary: the San Clemente fault (along with a prominent splay, the Kimki fault) and the Catalina fault. Previous studies have suggested that the San...
Walton, Maureen A. L.; Brothers, Daniel; Conrad, James E.; Maier, Katherine L.; Roland, Emily C.; Kluesner, Jared; Dartnell, PeterStructural controls on slope failure within the western Santa Barbara Channel based on 2D and 3D seismic imaging
The Santa Barbara Channel, offshore California, contains several submarine landslides and ample evidence for incipient failure. This region hosts active thrust and reverse faults that accommodate several mm/yr of convergence, yet the relationships between tectonic deformation and slope failure remain unclear. We present 3‐D and 2‐D multichannel...
Kluesner, Jared; Brothers, Daniel; Wright, Alexis L; Johnson, SamuelSubmarine canyons, slope failures and mass transport processes in southern Cascadia
The marine turbidite record along the southern Cascadia Subduction Zone has been used to interpret paleoseismicity and suggest a shorter recurrence interval for large (>M7) earthquakes along this portion of the margin; however, the sources and pathways of these turbidity flows are poorly constrained. We examine the spatial distribution of...
Hill, Jenna C.; Watt, Janet; Brothers, Daniel; Kluesner, JaredSubduction megathrust heterogeneity characterized from 3D seismic data
Megathrust roughness and structural complexity are thought to be controls on earthquake slip at subduction zones because they result in heterogeneity in shear strength and resolved stress. However, because active megathrust faults are difficult to observe, the causes and scales of complexity are largely unknown. Here we measured the in situ...
Kirkpatrick, James D.; Edwards, Joel H.; Verdecchia, Alessandro; Kluesner, Jared; Harrington, Rebecca M.; Silver, EliControls on sediment distribution in the coastal zone of the central California transform continental margin, USA
We use >10,000 km of high-resolution seismic-reflection data together with multibeam bathymetry to document complex and highly variable post-Last Glacial Maximum (LGM) sediment distribution and thickness in the coastal zone (~10 m isobath to 5.6 km offshore) along a ~800 km section of central California's transform...
Johnson, Samuel; Beeson, Jeffrey W.; Watt, Janet; Sliter, Ray; Papesh, AntoinettePlate boundary localization, slip-rates and rupture segmentation of the Queen Charlotte Fault based on submarine tectonic geomorphology
Linking fault behavior over many earthquake cycles to individual earthquake behavior is a primary goal in tectonic geomorphology, particularly across an entire plate boundary. Here, we examine the 1150-km-long, right-lateral Queen Charlotte-Fairweather fault system using comprehensive multibeam bathymetry data acquired along the Queen Charlotte...
Brothers, Daniel; Miller, Nathaniel C.; Vaughn Barrie; Haeussler, Peter; H. Gary Greene; Andrews, Brian D.; Olaf Zielke; Dartnell, PeterRecent sandy deposits at five northern California coastal wetlands—Stratigraphy, diatoms, and implications for storm and tsunami hazards
A recent geological record of inundation by tsunamis or storm surges is evidenced by deposits found within the first few meters of the modern surface at five wetlands on the northern California coast. The study sites include three locations in the Crescent City area (Marhoffer Creek marsh, Elk Creek wetland, and Sand Mine marsh), O’rekw marsh in...
Eileen Hemphill-Haley; Kelsey, Harvey M.; Nicholas Graehl; Casso, Michael; Dylan Caldwell; Casey Loofbourrow; Michelle Robinson; Jessica Vermeer; Edward SouthwickOffshore shallow structure and sediment distribution, Punta Gorda to Point Arena, Northern California
This publication consists of two map sheets that display shallow geologic structure, along with sediment distribution and thickness, for an approximately 150-km-long offshore section of the northern California coast between Punta Gorda and Point Arena. Each map sheet includes three maps at scales of either 1:100,000 or 1:200,000, and together the...
Beeson, Jeffrey W.; Johnson, Samuel Y.Offshore shallow structure and sediment distribution, Point Sur to Point Arguello, central California
This publication consists of three map sheets that display shallow geologic structure, along with sediment distribution and thickness, for an about 225-km-long offshore section of the central California coast between Point Sur and Point Arguello. Each map sheet includes three maps, at scales of either 1:150,000 or 1:200,000, as well as a set of...
Johnson, Samuel Y.; Hartwell, Stephen R.; Watt, Janet T.; Beeson, Jeffrey W.; Dartnell, PeterDiscovery of an extensive deep-sea fossil serpulid reef associated with a cold seep, Santa Monica Basin, California
Multi-beam mapping of the Santa Monica Basin in the eastern Pacific has revealed the existence of a number of elevated bathymetric features, or mounds, harboring cold seep communities. During 2013-2014, mounds at ~600 m water depth were observed for the first time and sampled by Monterey Bay Aquarium Research Institute’s ROV Doc Ricketts. Active...
Georgieva, Magdalena N; Paull, Charles K.; Little, Crispin TS; McGann, Mary; Sahy, Diana; Condon, Daniel; Lundsten, Lonny; Pewsey, Jack; Caress, David W; Vrijenhoek, Robert CThe 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,...
Brothers, Daniel S.; Maier, Katherine L.; Kluesner, Jared W.; Conrad, James E.; Chaytor, JasonBelow are datsets associated with this project.
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Date published: January 22, 2021
Multichannel minisparker, multichannel boomer, and chirp seismic-reflection data of USGS field activity 2017-612-FA collected in Puget Sound and Lake Washington in February of 2017
High-resolution multichannel minisparker, multichannel boomer and chirp seismic-reflection data were collected by the U.S. Geological Survey and the University of Washington in February of 2017 west of Seattle in Puget Sound and in Lake Washington, Washington. Data were collected aboard University of Washington's R/V Clifford A. Barnes during USGS field activity 2017-612-FA.
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Date published: January 22, 2021
Chirp sub-bottom data of USGS field activity K0211PS collected in Puget Sound, Washington in April of 2011
High-resolution chirp sub-bottom data were collected by the U.S. Geological Survey in April 2011 south of Bainbridge Island and west of Seattle in Puget Sound, Washington. Data were collected aboard R/V Karluk during field activity K0211PS using an Edgetech SB-512i sub-bottom profiler. Sub-bottom acoustic penetration spans several tens of meters and is variable by location.
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Date published: July 6, 2020
Multichannel minisparker seismic-reflection and chirp sub-bottom data of USGS field activity 2018-645-FA collected in the Santa Barbara Channel in July of 2018
High-resolution multichannel minisparker seismic-reflection and chirp sub-bottom data were collected by the USGS in July of 2018 between Point Conception and Coal Oil Point in the Santa Barbara Channel, California. Data were collected aboard USGS R/V Parke Snavely during field activity 2018-645-FA. Data were acquired to support the USGS geologic hazards projects to aid hazard assessment...
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Date published: June 25, 2020
Multibeam bathymetry, acoustic backscatter, and multichannel minisparker seismic-reflection data of USGS field activity 2016-666-FA collected in the Santa Barbara Basin in September and October of 2016
High-resolution multichannel minkisparker seismic-reflection profiles were collected by the USGS in September and October of 2016 from the northern portion of the Santa Barbara Basin offshore southern California. Data were collected aboard USGS R/V Parke Snavely and NOAA R/V Shearwater during field activity 2016-666-FA. Data were acquired to support USGS geologic hazards...
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Date published: April 30, 2020
Quaternary faults offshore of California
A comprehensive map of Quaternary faults has been generated for offshore of California. The Quaternary fault map includes mapped geometries and attribute information for offshore fault systems located in California State and Federal waters. The polyline shapefile has been compiled from previously published mapping where relatively dense, high-resolution marine geophysical data exist. The data...
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Date published: April 30, 2020
Quaternary faults offshore of California
A comprehensive map of Quaternary faults has been generated for offshore of California. The Quaternary fault map includes mapped geometries and attribute information for offshore fault systems located in California State and Federal waters. The polyline shapefile has been compiled from previously published mapping where relatively dense, high-resolution marine geophysical data exist. The data...
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Date published: March 31, 2020
Minisparker and chirp seismic-reflection data of field activity 2014-645-FA; offshore Santa Barbara, southern California from 2014-11-12 to 2014-11-25
USGS collected high-resolution multichannel minisparker and single-channel chirp seismic-reflection data in November 2014, in the offshore Catalina and Santa Cruz basins, which are surrounded by several of the southern California Channel Islands. The survey was designed to image areas of the seafloor associated with movement on the numerous faults offshore of southern California.
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Date published: March 27, 2020
Multichannel minisparker and chirp seismic reflection data of USGS field activity 2016-616-FA collected in the Catalina Basin offshore southern California in February 2016
This data release contains 25 multichannel minisparker seismic reflection (MCS) profiles and 41 chirp sub-bottom profiles collected in February of 2016 from the Catalina Basin offshore southern California by PCMSC in cooperation with the University of Washington. We collected data on R/V Thompson on USGS cruise 2016-616-FA. We collected MCS profiles to image the fault and channel...
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Date published: February 25, 2020
Archive of boomer subbottom data collected offshore Eureka, California during USGS field activity W-1-96-NC from 1996-06-29 to 1996-07-07
This data release contains boomer subbottom data collected in June and July of 1996 on the shelf and slope offshore Eureka, California. Subbottom acoustic penetration spans up to several tens of meters, and is variable by location. This data release contains digital SEG-Y data. The data were collected aboard the R/V Wecoma using a Huntec Hydrosonde Deep-Tow system.
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Date published: February 20, 2020
Multichannel sparker seismic reflection data of USGS field activity 2018-658-FA collected between Cape Blanco and Cape Mendocino from 2018-10-04 to 2018-10-18
This data release contains processed high-resolution multichannel sparker seismic-reflection (MCS) data that were collected aboard Humboldt State University’s R/V Coral Sea in October of 2018 on U.S. Geological Survey cruise 2018-658-FA on the shelf and slope between Cape Blanco, Oregon, and Cape Mendocino, California. MCS data were collected to characterize quaternary deforma
Below are news stories associated with this project.
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Date published: June 22, 2020
Earthquakes, Landslides, and Tsunamis: Mapping Geohazards in the Cascadia Subduction Zone
The geologic research and mapping in the offshore areas is foundational to understanding how to manage resources and improve public safety in subduction zone areas.
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Date published: June 22, 2020
Special Issue of Sound Waves Focuses on Deep-Sea Research
2019 was a big year for deep-sea expeditions, and USGS was pleased to be a partner supporting our Nation in advancing our knowledge about these remote and unexplored areas of the Earth. In honor of National Ocean Month, we highlight USGS research from the deep sea.
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Date published: June 22, 2020
EXPRESS: Expanding Pacific Research and Exploration of Submerged Systems - Interagency Collaborative Efforts Explore Deep Ocean Areas
As state and national interest in offshore renewable energy development and substantial commercial and recreational fishing activities grows, managing offshore habitats becomes increasingly challenging. In response, USGS and BOEM have joined NOAA and several non-Federal partners to initiate...
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Date published: September 7, 2018
USGS-NOAA cruise maps Cascadia subduction zone to assess earthquake hazards
From July 31 to August 23, a joint USGS-NOAA cruise mapped seafloor depths, texture, and gas seeps in the Cascadia subduction zone offshore of Washington, Oregon, and northern California.
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Date published: August 6, 2018
Scientists complete mission to map fast-moving fault off Alaska: Data will help coastal communities prepare for risks from earthquakes and tsunamis
Researchers from NOAA, U.S. Geological Survey and their partners have completed the first high-resolution, comprehensive mapping of one of the fastest moving underwater tectonic faults in the world, located in southeastern Alaska. This information will help communities in coastal Alaska and Canada better understand and prepare for the risks from earthquakes and tsunamis that can occur when faults suddenly move.
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Date published: March 12, 2018
Laboratory collaboration to study earthquake hazards off southeast Alaska and western Canada
Studying the Queen Charlotte-Fairweather fault
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Date published: February 19, 2018
USGS fields tsunami questions after earthquake off Kodiak, Alaska
USGS geophysicist Eric Geist fielded questions about tsunamis after a magnitude 7.9 earthquake off southern Alaska prompted a tsunami watch for the U.S. west coast.
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Date published: February 16, 2018
Workshops on subduction-zone science to reduce risk for communities
The USGS Pacific Coastal and Marine Science Center hosted two back-to-back subduction-zone workshops in Santa Cruz, California, from February 5–8, 2018.
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Date published: February 14, 2018
USGS research featured on the cover of Eos
USGS research on a big earthquake fault off Alaska and Canada is featured on the cover of Eos, a journal of Earth and space science news published by the American Geophysical Union.
Below are partners associated with this project.