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#           Underwater Landslides off Southern California      

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      By Pacific Coastal and Marine Science Center      April 27, 2022    

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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.

U.S. West Coast and Alaska Marine Geohazards

### Central & Northern CA

USGS images offshore faults in central and northern California that could trigger devastating earthquakes near densely populated areas and a nuclear power plant.

Central and Northern CA

### Southeastern AK

USGS uses sophisticated techniques to truly understand the Queen Charlotte-Fairweather (QCF) fault system’s hazard potential in southeastern Alaska.

QCF Fault System

### SoCal Seafloor Faults

USGS aims to boost our knowledge about faults on the seafloor offshore of southern California (SoCal), so they can be included in hazard assessments.

SoCal Seafloor Faults

View Media Details

Using equipment that stretched several kilometers behind their vessels, the petroleum industry ran 3D seismic surveys off Santa Barbara in the 1990s. When they released their data to the public in 2015, USGS geophysicist Jared Kluesner could finally sift through the values to create a 3D view of the Earth extending thousands of meters beneath the seafloor. This view was a vast improvement over the paper-thin slices of Earth’s crust that are constructed from 2D surveys. Tens of gigabytes of data required months of number crunching and the largest monitor that could fit on Kluesner’s desk. His “geologic Hubble telescope” allowed him to virtually explore kilometers below the seafloor in any direction, map faults, and study how fluid moves through the Earth’s crust.

### Issue

View Media Details

Underwater landslides threaten offshore structures such as seafloor pipelines, cables, and equipment for oil and gas exploration. These landslides can also trigger tsunamis that endanger coastal communities. A 1998 earthquake in Papua New Guinea triggered a landslide on the seafloor, which generated a 10-meter high tsunami that killed more than 2,000 people along the nearest shoreline.

Until recently, scientists had not looked closely for similar landslides off the Southern California coast. Previously known slides in the region are the Goleta slide in Santa Barbara Channel and the Palos Verdes debris avalanche off Palos Verdes Peninsula, each less than half a cubic kilometer in size. Underwater landslides might have triggered significant tsunamis in Santa Barbara in 1812 and Point Arguello in 1927. But inadequate seafloor mapping in the area limits what scientists know about the size, distribution, and age of potential tsunami-generated landslides. Numerous banks and ridges beneath the waters off the Southern California coast could hide undiscovered slides. 

As an example, a 2010 NOAA cruise to map the seafloor around the Santa Cruz Basin 50 to 80 kilometers from Ventura, accidentally discovered several underwater landslide scars. The scars show considerable variation in appearance, suggesting a wide range of ages for individual slides. The landslides range in size from less than 1 to more than 50 square kilometers, making this one of the largest underwater landslide complexes found off Southern California.

### What the USGS is doing

To understand the potential tsunami hazards that underwater landslides pose to Southern California, the USGS led a high-resolution 2D seismic study in Santa Cruz Basin and nearby basins in November 2014. This work should help identify what makes slopes unstable, what may trigger them to slide (active faults, sediment buildup, fluid channels beneath the seabed), and what potential exists for slides to generate local tsunamis.

To dig further into the complexities of these landslides, USGS researchers used advanced techniques to analyze 3D seismic data collected by the oil industry. These data from near the Goleta slide in Santa Barbara Basin help USGS scientists make connections between underwater landslides and natural events that make a slope fail. Researchers compare lower resolution 3D seismic images with higher resolution 2D data to link the 3D data to the landslides seen on the seafloor.

USGS scientists continue to collect more seafloor mapping data looking for changes to the seafloor and seafloor seeps, which can indicate mounting fluid pressure that could trigger landslides.

View Media Details

View Media Details

### What the USGS has learned

Recent research within Santa Cruz Basin shows landslides ranging from 6,000 to 8,000 years old.

New seafloor data revealed the Del Mar slide, just north of San Diego. The steep slope here has landslides more than 6 kilometers wide, about 8 kilometers west of Del Mar, along the edge of the continental shelf. Seismic data show the slide deposit is up to 20 meters thick and extends nearly 10 kilometers to the west. Data also reveal older slide deposits buried beneath the seafloor. A sediment core taken near the toe of the slide indicates it may be about 14,000 to16,000 years old, and that slides could recur here on a timescale of tens of thousands of years.

It’s likely that more offshore landslides are yet to be discovered.

View Media Details

View Media Details

*Marcus G. Langseth*

View Media Details

*Marcus G. Langseth*

### Contacts

#### Jared Kluesner

##### Research Geophysicist

Pacific Coastal and Marine Science Center

jkluesner@usgs.gov

831-460-7547

### Explore Search

                      - Submarine Landslides
                      - Coastal and Marine Hazards
                      - Coastal and Marine Hazards and Resources
                      - Geology
                      - Information Systems
                      - Maps and Mapping
                      - Methods and Analyses
                      - Natural Hazards
                      - Ocean
                      - Science Technology
                      - Marine Geohazards Project
                      - U.S. West Coast
                      - Southern California
                      - submarine landslides
                      - underwater landslides
                      - seafloor mapping

View All **

Below are the current studies of the “U.S. West Coast and Alaska Marine Geohazards” Project.

link

October 15, 2021

####                 Coastal and Marine Geohazards of the U.S. West Coast and Alaska              

Natural Hazards Mission Area, Coastal and Marine Hazards and Resources Program, Pacific Coastal and Marine Science Center, 3-D CT Core Imaging Laboratory, Core Preparation and Analysis Laboratory and Sample Repositories, Big Sur Landslides, Deep Sea Exploration, Mapping and Characterization, Subduction Zone Science

link

October 15, 2021

####   Coastal and Marine Geohazards of the U.S. West Coast and Alaska

Learn More

link

April 27, 2022

####                 Seafloor Faults off Southern California              

Natural Hazards Mission Area, Coastal and Marine Hazards and Resources Program, Pacific Coastal and Marine Science Center, Deep Sea Exploration, Mapping and Characterization

link

April 27, 2022

####   Seafloor Faults off Southern California

Learn More

link

April 27, 2022

####                 Offshore Faults along Central and Northern California              

Natural Hazards Mission Area, Coastal and Marine Hazards and Resources Program, Pacific Coastal and Marine Science Center

link

April 27, 2022

####   Offshore Faults along Central and Northern California

Learn More

link

April 27, 2022

####                 Underwater Landslides off Southern California              

Natural Hazards Mission Area, Coastal and Marine Hazards and Resources Program, Pacific Coastal and Marine Science Center

link

April 27, 2022

####   Underwater Landslides off Southern California

Learn More

link

November 2, 2020

####                 Earthquake Hazards in Southeastern Alaska              

Natural Hazards Mission Area, Coastal and Marine Hazards and Resources Program, Pacific Coastal and Marine Science Center, Deep Sea Exploration, Mapping and Characterization

link

November 2, 2020

####   Earthquake Hazards in Southeastern Alaska

Learn More

Below are data or web applications associated with this project.

April 27, 2022

####                 Reprocessed legacy seismic-reflection data from USGS field activity B-1-72-SC collected offshore central and southern California              

Natural Hazards Mission Area, Coastal and Marine Hazards and Resources Program, Pacific Coastal and Marine Science Center, Deep Sea Exploration, Mapping and Characterization

May 11, 2020

####                 Quaternary faults offshore of California              

Natural Hazards Mission Area, Coastal and Marine Hazards and Resources Program, Earthquake Hazards Program, Pacific Coastal and Marine Science Center

March 31, 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              

Coastal and Marine Hazards and Resources Program, Pacific Coastal and Marine Science Center

October 9, 2018

####                 Multibeam bathymetry and acoustic-backscatter data collected in 2016 in Catalina Basin, southern California and merged multibeam bathymetry datasets of the northern portion of the Southern California Continental Borderland              

Coastal and Marine Hazards and Resources Program, Pacific Coastal and Marine Science Center

Below are publications associated with this project.

July 10, 2020

####                 Morphology, structure, and kinematics of the San Clemente and Catalina faults based on high-resolution marine geophysical data, southern California Inner Continental Borderland              

Natural Hazards Mission Area, Coastal and Marine Hazards and Resources Program, Pacific Coastal and Marine Science Center, Deep Sea Exploration, Mapping and Characterization

June 29, 2020

####                 Structural controls on slope failure within the western Santa Barbara Channel based on 2D and 3D seismic imaging              

Natural Hazards Mission Area, Coastal and Marine Hazards and Resources Program, Pacific Coastal and Marine Science Center, Deep Sea Exploration, Mapping and Characterization

May 20, 2020

####                 Submarine canyons, slope failures and mass transport processes in southern Cascadia              

Natural Hazards Mission Area, Coastal and Marine Hazards and Resources Program, Pacific Coastal and Marine Science Center, Subduction Zone Science

March 19, 2019

####                 Discovery of an extensive deep-sea fossil serpulid reef associated with a cold seep, Santa Monica Basin, California              

Natural Hazards Mission Area, Coastal and Marine Hazards and Resources Program, Pacific Coastal and Marine Science Center

June 30, 2018

####                 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

Ecosystems Mission Area, Natural Hazards Mission Area, Coastal and Marine Hazards and Resources Program, Pacific Coastal and Marine Science Center, Wetland and Aquatic Research Center , Woods Hole Coastal and Marine Science Center

January 1, 2018

####                 The tectonically controlled San Gabriel Channel–Lobe Transition Zone, Catalina Basin, Southern California Borderland              

Pacific Coastal and Marine Science Center

April 19, 2017

####                 The California Seafloor and Coastal Mapping Program – Providing science and geospatial data for California's State Waters              

Natural Hazards Mission Area, Coastal and Marine Hazards and Resources Program, Pacific Coastal and Marine Science Center, Deep Sea Exploration, Mapping and Characterization

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.

U.S. West Coast and Alaska Marine Geohazards

### Central & Northern CA

USGS images offshore faults in central and northern California that could trigger devastating earthquakes near densely populated areas and a nuclear power plant.

Central and Northern CA

### Southeastern AK

USGS uses sophisticated techniques to truly understand the Queen Charlotte-Fairweather (QCF) fault system’s hazard potential in southeastern Alaska.

QCF Fault System

### SoCal Seafloor Faults

USGS aims to boost our knowledge about faults on the seafloor offshore of southern California (SoCal), so they can be included in hazard assessments.

SoCal Seafloor Faults

View Media Details

Using equipment that stretched several kilometers behind their vessels, the petroleum industry ran 3D seismic surveys off Santa Barbara in the 1990s. When they released their data to the public in 2015, USGS geophysicist Jared Kluesner could finally sift through the values to create a 3D view of the Earth extending thousands of meters beneath the seafloor. This view was a vast improvement over the paper-thin slices of Earth’s crust that are constructed from 2D surveys. Tens of gigabytes of data required months of number crunching and the largest monitor that could fit on Kluesner’s desk. His “geologic Hubble telescope” allowed him to virtually explore kilometers below the seafloor in any direction, map faults, and study how fluid moves through the Earth’s crust.

### Issue

View Media Details

Underwater landslides threaten offshore structures such as seafloor pipelines, cables, and equipment for oil and gas exploration. These landslides can also trigger tsunamis that endanger coastal communities. A 1998 earthquake in Papua New Guinea triggered a landslide on the seafloor, which generated a 10-meter high tsunami that killed more than 2,000 people along the nearest shoreline.

Until recently, scientists had not looked closely for similar landslides off the Southern California coast. Previously known slides in the region are the Goleta slide in Santa Barbara Channel and the Palos Verdes debris avalanche off Palos Verdes Peninsula, each less than half a cubic kilometer in size. Underwater landslides might have triggered significant tsunamis in Santa Barbara in 1812 and Point Arguello in 1927. But inadequate seafloor mapping in the area limits what scientists know about the size, distribution, and age of potential tsunami-generated landslides. Numerous banks and ridges beneath the waters off the Southern California coast could hide undiscovered slides. 

As an example, a 2010 NOAA cruise to map the seafloor around the Santa Cruz Basin 50 to 80 kilometers from Ventura, accidentally discovered several underwater landslide scars. The scars show considerable variation in appearance, suggesting a wide range of ages for individual slides. The landslides range in size from less than 1 to more than 50 square kilometers, making this one of the largest underwater landslide complexes found off Southern California.

### What the USGS is doing

To understand the potential tsunami hazards that underwater landslides pose to Southern California, the USGS led a high-resolution 2D seismic study in Santa Cruz Basin and nearby basins in November 2014. This work should help identify what makes slopes unstable, what may trigger them to slide (active faults, sediment buildup, fluid channels beneath the seabed), and what potential exists for slides to generate local tsunamis.

To dig further into the complexities of these landslides, USGS researchers used advanced techniques to analyze 3D seismic data collected by the oil industry. These data from near the Goleta slide in Santa Barbara Basin help USGS scientists make connections between underwater landslides and natural events that make a slope fail. Researchers compare lower resolution 3D seismic images with higher resolution 2D data to link the 3D data to the landslides seen on the seafloor.

USGS scientists continue to collect more seafloor mapping data looking for changes to the seafloor and seafloor seeps, which can indicate mounting fluid pressure that could trigger landslides.

View Media Details

View Media Details

### What the USGS has learned

Recent research within Santa Cruz Basin shows landslides ranging from 6,000 to 8,000 years old.

New seafloor data revealed the Del Mar slide, just north of San Diego. The steep slope here has landslides more than 6 kilometers wide, about 8 kilometers west of Del Mar, along the edge of the continental shelf. Seismic data show the slide deposit is up to 20 meters thick and extends nearly 10 kilometers to the west. Data also reveal older slide deposits buried beneath the seafloor. A sediment core taken near the toe of the slide indicates it may be about 14,000 to16,000 years old, and that slides could recur here on a timescale of tens of thousands of years.

It’s likely that more offshore landslides are yet to be discovered.

View Media Details

View Media Details

*Marcus G. Langseth*

View Media Details

*Marcus G. Langseth*

### Contacts

#### Jared Kluesner

##### Research Geophysicist

Pacific Coastal and Marine Science Center

jkluesner@usgs.gov

831-460-7547

### Explore Search

                      - Submarine Landslides
                      - Coastal and Marine Hazards
                      - Coastal and Marine Hazards and Resources
                      - Geology
                      - Information Systems
                      - Maps and Mapping
                      - Methods and Analyses
                      - Natural Hazards
                      - Ocean
                      - Science Technology
                      - Marine Geohazards Project
                      - U.S. West Coast
                      - Southern California
                      - submarine landslides
                      - underwater landslides
                      - seafloor mapping

View All **

Below are the current studies of the “U.S. West Coast and Alaska Marine Geohazards” Project.

link

October 15, 2021

####                 Coastal and Marine Geohazards of the U.S. West Coast and Alaska              

Natural Hazards Mission Area, Coastal and Marine Hazards and Resources Program, Pacific Coastal and Marine Science Center, 3-D CT Core Imaging Laboratory, Core Preparation and Analysis Laboratory and Sample Repositories, Big Sur Landslides, Deep Sea Exploration, Mapping and Characterization, Subduction Zone Science

link

October 15, 2021

####   Coastal and Marine Geohazards of the U.S. West Coast and Alaska

Learn More

link

April 27, 2022

####                 Seafloor Faults off Southern California              

Natural Hazards Mission Area, Coastal and Marine Hazards and Resources Program, Pacific Coastal and Marine Science Center, Deep Sea Exploration, Mapping and Characterization

link

April 27, 2022

####   Seafloor Faults off Southern California

Learn More

link

April 27, 2022

####                 Offshore Faults along Central and Northern California              

Natural Hazards Mission Area, Coastal and Marine Hazards and Resources Program, Pacific Coastal and Marine Science Center

link

April 27, 2022

####   Offshore Faults along Central and Northern California

Learn More

link

April 27, 2022

####                 Underwater Landslides off Southern California              

Natural Hazards Mission Area, Coastal and Marine Hazards and Resources Program, Pacific Coastal and Marine Science Center

link

April 27, 2022

####   Underwater Landslides off Southern California

Learn More

link

November 2, 2020

####                 Earthquake Hazards in Southeastern Alaska              

Natural Hazards Mission Area, Coastal and Marine Hazards and Resources Program, Pacific Coastal and Marine Science Center, Deep Sea Exploration, Mapping and Characterization

link

November 2, 2020

####   Earthquake Hazards in Southeastern Alaska

Learn More

Below are data or web applications associated with this project.

April 27, 2022

####                 Reprocessed legacy seismic-reflection data from USGS field activity B-1-72-SC collected offshore central and southern California              

Natural Hazards Mission Area, Coastal and Marine Hazards and Resources Program, Pacific Coastal and Marine Science Center, Deep Sea Exploration, Mapping and Characterization

May 11, 2020

####                 Quaternary faults offshore of California              

Natural Hazards Mission Area, Coastal and Marine Hazards and Resources Program, Earthquake Hazards Program, Pacific Coastal and Marine Science Center

March 31, 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              

Coastal and Marine Hazards and Resources Program, Pacific Coastal and Marine Science Center

October 9, 2018

####                 Multibeam bathymetry and acoustic-backscatter data collected in 2016 in Catalina Basin, southern California and merged multibeam bathymetry datasets of the northern portion of the Southern California Continental Borderland              

Coastal and Marine Hazards and Resources Program, Pacific Coastal and Marine Science Center

Below are publications associated with this project.

July 10, 2020

####                 Morphology, structure, and kinematics of the San Clemente and Catalina faults based on high-resolution marine geophysical data, southern California Inner Continental Borderland              

Natural Hazards Mission Area, Coastal and Marine Hazards and Resources Program, Pacific Coastal and Marine Science Center, Deep Sea Exploration, Mapping and Characterization

June 29, 2020

####                 Structural controls on slope failure within the western Santa Barbara Channel based on 2D and 3D seismic imaging              

Natural Hazards Mission Area, Coastal and Marine Hazards and Resources Program, Pacific Coastal and Marine Science Center, Deep Sea Exploration, Mapping and Characterization

May 20, 2020

####                 Submarine canyons, slope failures and mass transport processes in southern Cascadia              

Natural Hazards Mission Area, Coastal and Marine Hazards and Resources Program, Pacific Coastal and Marine Science Center, Subduction Zone Science

March 19, 2019

####                 Discovery of an extensive deep-sea fossil serpulid reef associated with a cold seep, Santa Monica Basin, California              

Natural Hazards Mission Area, Coastal and Marine Hazards and Resources Program, Pacific Coastal and Marine Science Center

June 30, 2018

####                 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

Ecosystems Mission Area, Natural Hazards Mission Area, Coastal and Marine Hazards and Resources Program, Pacific Coastal and Marine Science Center, Wetland and Aquatic Research Center , Woods Hole Coastal and Marine Science Center

January 1, 2018

####                 The tectonically controlled San Gabriel Channel–Lobe Transition Zone, Catalina Basin, Southern California Borderland              

Pacific Coastal and Marine Science Center

April 19, 2017

####                 The California Seafloor and Coastal Mapping Program – Providing science and geospatial data for California's State Waters              

Natural Hazards Mission Area, Coastal and Marine Hazards and Resources Program, Pacific Coastal and Marine Science Center, Deep Sea Exploration, Mapping and Characterization