USGS - science for a changing world

Pacific Coastal and Marine Science Center

U.S. West Coast and Alaska Marine Geohazards

A village near the coast of Sumatra lay in ruin after the Tsunami that struck South East Asia. Helicopters assigned to Carrier Air Wing Two (CVW-2) and Sailors from USS Abraham Lincoln (CVN 72) conducted humanitarian operations in the wake of the Tsunami that struck South East Asia. The Abraham Lincoln Carrier Strike Group was operating in the Indian Ocean off the waters of Indonesia and Thailand. U.S. Navy photo by Photographer's Mate 2nd Class Philip A. McDaniel.

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. Read more in Overview.


View looking out at USGS research vessel Snavely in Morro Bay, with Morro Rock in the background.

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.

Photograph looking north toward the Fairweather Range during 2015 mapping of the Queen Charlotte-Fairweather fault off Glacier Bay National Park and Preserve. The fault is directly beneath the vessel upon which the photographer, Danny Brothers, is standing.

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.

Graphic showing undersea features and landslides can clearly be noted.

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.

Illustration of the multibean sonar fish.

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.

Recent Publications

Corrugated megathrust revealed offshore from Costa Rica - Nature Geoscience 2018

Strain partitioning in Southeastern Alaska: Is the Chatham Strait Fault active? - Earth and Planetary Science Letters v. 481

A closer look at an undersea source of Alaskan earthquakes - Eos v. 98

Seafloor fluid seeps on Kimki Ridge, offshore southern California: Links to active strike-slip faulting - Deep Sea Research Part II: Topical Studies in Oceanography

Reducing risk where tectonic plates collide—U.S. Geological Survey subduction zone science plan - USGS Circular 1428

Multichannel minisparker and chirp seismic-reflection data of field activity 2015-651-FA; Chatham Strait and Cross Sound, southeastern Alaska from 2015-08-03 to 2015-08-21 - USGS data release

See all project-related publications


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