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Janet Watt

My research focuses on characterizing onshore/offshore geologic structure, deformation, and active tectonics to address problems focused on geologic hazards and framework geologic processes. My recent work involves the development and application of integrative geophysical approaches to 3D characterization of faults and fault interactions.

I received my M.S. in Marine Science (Geological Oceanography) from Moss Landing Marine Laboratories while working at the USGS in Menlo Park, CA. As part of the Geophysical Unit of Menlo Park (GUMP), I used potential-field methods (gravity and magnetics) and 3D geologic mapping to understand earthquake and volcano hazards, and mineral and water resources in the western U.S. In 2010, I returned to my marine geology roots and joined the Pacific Coastal and Marine Science Center in Santa Cruz, CA where I currently work as a Research Geophysicist.

Selected Media and Public Outreach

November 18, 2016, CBS This Morning "California prepares for next big earthquake"

October 19, 2016, Popular Mechanics "Two dangerous Fault Lines Under San Francisco Are Connected, Study Finds"

February 1, 2016, Temblor.net Earthquake News & Blog, "Why don't the earthquakes line up with the San Andreas fault?"

January 2, 2016, CBS NEWS, "Alarming Discovery Shows Bay Area’s 2 Most Dangerous Earthquake Faults May Be Connected"

December 31, 2015, San Francisco Chronicle, "New data on 2 Bay Area faults cause worry about next big quake"

November 20, 2014, KQED Science "Using 3D Visualization, Geologists Explore the Complex Areas Where Faults Join and Split"

Science and Products

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A map illustration of the seafloor off of a coastal area, that shows the features like submarine canyons and depth.

Cascadia Subduction Zone Marine Geohazards

Societal Issue: Uncertainty related to rupture extent, slip distribution, and recurrence of past subduction megathrust earthquakes in the Pacific Northwest (northern CA, OR, WA, and southern BC) leads to ambiguity in earthquake and tsunami hazard assessments and hinders our ability to prepare for future events.
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Natural Hazards, 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, Multi-Sensor Core Logger Laboratory
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Cascadia Subduction Zone Marine Geohazards

Societal Issue: Uncertainty related to rupture extent, slip distribution, and recurrence of past subduction megathrust earthquakes in the Pacific Northwest (northern CA, OR, WA, and southern BC) leads to ambiguity in earthquake and tsunami hazard assessments and hinders our ability to prepare for future events.
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View from a dock near a calm bay with boats docked and one motoring slowly through the bay with a large outcrop in 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.
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Natural Hazards, Coastal and Marine Hazards and Resources Program, Pacific Coastal and Marine Science Center
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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.
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A building after an earthquake has crumbled the roof and brick walls, the interior is now visible.

U.S. West Coast and Alaska Marine Geohazards

Marine geohazards are sudden and extreme events beneath the ocean that threaten coastal populations. Such underwater hazards include earthquakes, volcanic eruptions, landslides, and tsunamis.
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Natural Hazards, 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
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U.S. West Coast and Alaska Marine Geohazards

Marine geohazards are sudden and extreme events beneath the ocean that threaten coastal populations. Such underwater hazards include earthquakes, volcanic eruptions, landslides, and tsunamis.
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Illustration of the seafloor off the coast with areas highlighted to show detail.

2019 Seafloor Geodesy cruise

Performed maintenance on and retrieved data from seafloor geodetic instrument arrays offshore of Oregon and northern California in 2019, a USGS-Scripps-University of Washington-University of Hawaii partnership
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Natural Hazards, Coastal and Marine Hazards and Resources Program, Pacific Coastal and Marine Science Center
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2019 Seafloor Geodesy cruise

Performed maintenance on and retrieved data from seafloor geodetic instrument arrays offshore of Oregon and northern California in 2019, a USGS-Scripps-University of Washington-University of Hawaii partnership
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Illustration of the seafloor off the coast with areas highlighted to show detail.

2019 Regional geophysical surveys of northern and central Cascadia (offshore Washington and Oregon)

Geophysical data collected offshore of Washington and Oregon in 2019, a USGS-University of Washington partnership
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Natural Hazards, Coastal and Marine Hazards and Resources Program, Pacific Coastal and Marine Science Center
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2019 Regional geophysical surveys of northern and central Cascadia (offshore Washington and Oregon)

Geophysical data collected offshore of Washington and Oregon in 2019, a USGS-University of Washington partnership
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Illustration of the seafloor off the coast with areas highlighted to show detail.

2018 Regional geophysical surveys of southern Cascadia (offshore northern California and southern Oregon)

Regional geophysical surveys conducted offshore of northern California and southern Oregon in 2018, a USGS-Humboldt State University partnership
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Natural Hazards, Coastal and Marine Hazards and Resources Program, Pacific Coastal and Marine Science Center
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2018 Regional geophysical surveys of southern Cascadia (offshore northern California and southern Oregon)

Regional geophysical surveys conducted offshore of northern California and southern Oregon in 2018, a USGS-Humboldt State University partnership
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Illustration of the seafloor off the coast with areas highlighted to show detail.

2018 USGS-NOAA multibeam bathymetry surveys

Multibeam bathymetric surveys conducted offshore of Oregon and northern California in 2018, a USGS-NOAA partnership
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Natural Hazards, Coastal and Marine Hazards and Resources Program, Pacific Coastal and Marine Science Center
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2018 USGS-NOAA multibeam bathymetry surveys

Multibeam bathymetric surveys conducted offshore of Oregon and northern California in 2018, a USGS-NOAA partnership
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Illustration model of the Cascadia Subduction Zone

Margin-wide geological and geophysical synthesis to understand the recurrence and hazards of great subduction zone earthquakes in Cascadia

The Cascadia Subduction Zone, located in the U.S. Pacific Northwest and southwestern British Columbia, has hosted magnitude ≥8.0 megathrust earthquakes in the geologic past, a future earthquake is imminent, and the potential impacts could cripple the region. Subduction zone earthquakes represent some of the most devastating natural hazards on Earth. Despite substantial knowledge gained from deca
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John Wesley Powell Center for Analysis and Synthesis
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Margin-wide geological and geophysical synthesis to understand the recurrence and hazards of great subduction zone earthquakes in Cascadia

The Cascadia Subduction Zone, located in the U.S. Pacific Northwest and southwestern British Columbia, has hosted magnitude ≥8.0 megathrust earthquakes in the geologic past, a future earthquake is imminent, and the potential impacts could cripple the region. Subduction zone earthquakes represent some of the most devastating natural hazards on Earth. Despite substantial knowledge gained from deca
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Geophysical properties, geochronologic, and geochemical data of sediment cores collected from San Pablo Bay, California, October 17-20, 2016

Geophysical properties (P-wave velocity, gamma ray density, and magnetic susceptibility), geochronologic (radiocarbon, excess Lead-210, and Cesium-137), and geochemical data (organic carbon content and 60 element contents) are reported for select vibracores collected aboard the S/V Retriever October 17-20, 2016 in San Pablo Bay, California. Geophysical properties were measured with a Geotek Multi-
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Natural Hazards, Coastal and Marine Hazards and Resources Program, Pacific Coastal and Marine Science Center, Multi-Sensor Core Logger Laboratory

Composite multibeam bathymetry surface and data sources of the southern Cascadia Margin offshore Oregon and northern California

Bathymetry data from various sources, including newly released 2018 and 2019 multibeam data collected by the National Oceanic and Atmospheric Administration (NOAA) and the U.S. Geological Survey (USGS), were combined to create a composite 30-m resolution multibeam bathymetry surface of the southern Cascadia Margin offshore of Oregon and northern California. The bathymetry data are available as a 3
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Natural Hazards, Coastal and Marine Hazards and Resources Program, Pacific Coastal and Marine Science Center

Geophysical and core sample data collected offshore San Francisco, California, during field activity 2019-649-FA from 2019-10-11 to 2019-10-18

The U.S. Geological Survey (USGS) collected geophysical and core sample data aboard the R/V Bold Horizon in 2019 on cruise 2019-649-FA offshore San Francisco, California. The data were collected to assess sand and gravel resources in Federal and State waters for potential use in future beach nourishment projects along stretches of the coast where critical erosion hotspots have been identified. Thi
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Natural Hazards, Coastal and Marine Hazards and Resources Program, Pacific Coastal and Marine Science Center

Geophysical and sampling data collected offshore Oceanside, southern California during field activity 2017-686-FA from 2017-10-23 to 2017-10-31

This data release contains geophysical and sediment sample data that were collected aboard the R/V Snavely in 2017 on U.S. Geological Survey cruise 2017-686-FA offshore Oceanside, southern California. The goal of the survey was to provide high-resolution imaging, magnetic anomaly profiles and sediment analysis to characterize the surface and subsurface properties of the study area such as unconsol
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Natural Hazards, Coastal and Marine Hazards and Resources Program, Pacific Coastal and Marine Science Center, Sediment Lab Suite and Carbon Analysis Laboratory

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. Sub-bottom acoustic pe
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Natural Hazards, Coastal and Marine Hazards and Resources Program, Pacific Coastal and Marine Science Center

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

Magnetotelluric data from San Pablo Bay, California

This dataset consists of 14 magnetotelluric (MT) stations collected in 2015 near San Pablo Bay, California along a east-northeast profile. The U.S. Geological Survey acquired these data to understand the fault geometry of the Hayward Fault and the Rodgers Creek Fault.
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Geology, Minerals, Energy, and Geophysics Science Center

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 deformation and sediment dyn
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Natural Hazards, Coastal and Marine Hazards and Resources Program, Pacific Coastal and Marine Science Center

California State Waters Map Series Data Catalog--Point Sur to Point Arguello

As part of the USGS's California State Waters Mapping Project, a 50-m grid of sediment thickness for the seafloor within the 3-nautical mile limit between Point Sur and Point Arguello was generated from seismic-reflection data collected between 2008 and 2014, and supplemented with geologic structure (fault and fold) information following the methodology of Wong (2012). Water depths determined from
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Natural Hazards, Coastal and Marine Hazards and Resources Program, Pacific Coastal and Marine Science Center

Marine magnetic data from Point Sur to Piedras Blancas, central California, 2011

This dataset includes marine magnetic data collected by the U.S. Geological Survey (USGS) in 2011 during field activity B-05-11-CC between Point Sur and Piedras Blancas, central California.
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Natural Hazards, Coastal and Marine Hazards and Resources Program, Pacific Coastal and Marine Science Center

Chirp seismic-reflection data: San Pablo Bay, California

This data release includes chirp seismic-reflection data collected in 2014 aboard the USGS R/V Snavely in San Pablo Bay, part of northern San Francisco Bay. These data were acquired to image the shallow geologic structure, particularly that related to the Hayward and Rodgers Creek Faults. Approximately 200 km of marine seismic-reflection data were collected along primarily northeast and northwest-
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Natural Hazards, Coastal and Marine Hazards and Resources Program, Pacific Coastal and Marine Science Center

California State Waters Map Series Data Catalog--Offshore of Aptos, California

Data catalog for California State Waters Map Series--Offshore of Aptos, California.
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Natural Hazards, Coastal and Marine Hazards and Resources Program, Pacific Coastal and Marine Science Center

Offshore geology and geomorphology from Point Piedras Blancas to Pismo Beach, San Luis Obispo County, California

Marine geology and geomorphology were mapped along the continental shelf and upper slope between Point Piedras Blancas and Pismo Beach, California. The map area is divided into the following three (smaller) map areas, listed from north to south: San Simeon, Morro Bay, and Point San Luis. Each smaller map area consists of a geologic map and the corresponding geophysical data that support the geolog

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Pacific Coastal and Marine Science Center

California State Waters Map Series — Offshore of San Gregorio, California

In 2007, the California Ocean Protection Council initiated the California Seafloor Mapping Program (CSMP), designed to create a comprehensive seafloor map of high-resolution bathymetry, marine benthic habitats, and geology within the 3-nautical-mile limit of California's State Waters. The CSMP approach is to create highly detailed seafloor maps through collection, integration, interpretation, and
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Pacific Coastal and Marine Science Center

California State Waters Map Series — Offshore of San Gregorio, California

In 2007, the California Ocean Protection Council initiated the California Seafloor Mapping Program (CSMP), designed to create a comprehensive seafloor map of high-resolution bathymetry, marine benthic habitats, and geology within the 3-nautical-mile limit of California's State Waters. The CSMP approach is to create highly detailed seafloor maps through collection, integration, interpretation, and
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Pacific Coastal and Marine Science Center
Map shows location of a fault that runs through a bay, with a line drawn to show the location of the cross section.
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Illustrative map of the deep ocean off a coastal area showing depth of the water with lines and dots where data was collected.
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Map showing offshore geology
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Photo looking down on the rocky coastline of Oregon from high up on a cliff, with breaking ocean waves on rocks.
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Filter Total Items: 52

Mass wasting along the Cascadia subduction zone: Implications for abyssal turbidite sources and the earthquake record

The only submarine records of large (>Mw7) prehistoric earthquakes along the Cascadia subduction zone are derived from sequences of deep sea turbidites interpreted to represent synchronous, shaking-induced failures along the continental slope. However, the spatial correlation of these deposits along the margin is complicated and the chronological constraints involve significant uncertainties, rais
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Pacific Coastal and Marine Science Center

Marine paleoseismic evidence for seismic and aseismic slip along the Hayward-Rodgers Creek fault system in northern San Pablo Bay

Distinguishing between seismic and aseismic fault slip in the geologic record is difficult, yet fundamental to estimating the seismic potential of faults and the likelihood of multi-fault ruptures. We integrated chirp sub-bottom imaging with targeted cross-fault coring and core analyses of sedimentary proxy data to characterize vertical deformation and slip behavior within an extensional fault ben
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Natural Hazards, Coastal and Marine Hazards and Resources Program, Pacific Coastal and Marine Science Center, Core Preparation and Analysis Laboratory and Sample Repositories, Multi-Sensor Core Logger Laboratory

Toward an integrative geological and geophysical view of Cascadia subduction zone earthquakes

The Cascadia subduction zone (CSZ) is an exceptional geologic environment for recording evidence of land level changes, tsunamis, and ground motion that reveals at least 19 great megathrust earthquakes over the past 10 kyr. Such earthquakes are among the most impactful natural hazards on Earth, transcend national boundaries, and can have global impact. Reducing the societal impacts of future event
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Natural Hazards, Coastal and Marine Hazards and Resources Program, National Cooperative Geologic Mapping Program, Geosciences and Environmental Change Science Center, Pacific Coastal and Marine Science Center, Core Preparation and Analysis Laboratory and Sample Repositories

Systematic characterization of morphotectonic variability along the Cascadia convergent margin: Implications for shallow megathrust behavior and tsunami hazards

Studies of recent destructive megathrust earth­quakes and tsunamis along subduction margins in Japan, Sumatra, and Chile have linked forearc mor­phology and structure to megathrust behavior. This connection is based on the idea that spatial varia­tions in the frictional behavior of the megathrust influence the tectono-morphological evolution of the upper plate. Here we present a comprehen­sive exa
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Natural Hazards, Coastal and Marine Hazards and Resources Program, Pacific Coastal and Marine Science Center

Submarine 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 sediment storage, downslope transport, and slope failures a
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Natural Hazards, Coastal and Marine Hazards and Resources Program, Pacific Coastal and Marine Science Center

Cascadia Margin cold seeps: Subduction zone fluids, gas hydrates, and chemosynthetic habitats

Priority Geographic Area: The outer continental shelf and upper continental slope from Canada/U.S. border offshore Washington State to the Mendocino Fracture Zone (Northern California), entirely within the U.S. Exclusive Economic Zone (EEZ), from the outermost shelf to at least 2000 m water depth (Figure 1). Description of Priority Area: Since 2015, over a thousand water column gas plumes originat
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Ecosystems, Wetland and Aquatic Research Center

Mapping, exploration, and characterization of the California continental margin and associated features from the California-Oregon border to Ensenada, Mexico

Priority Geographic Area: Both within and outside US Exclusive Economic Zone (EEZ). California continental margin. This area includes and continues south of the geographic area captured in the Watt et al. white paper. Description of Priority Area: The California continental margin, from the narrow shelf to abyssal depths, contains diverse seafloor features that influence benthic community types, b
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Ecosystems, Wetland and Aquatic Research Center

Controls 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 continental margin. Sediment thickness ranges from 0 (seafloor bedrock) to 64 m wit
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Natural Hazards, Coastal and Marine Hazards and Resources Program, Pacific Coastal and Marine Science Center

Plate 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 Fault (QCF) offshore southeastern Alaska and western
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Natural Hazards, Coastal and Marine Hazards and Resources Program, Alaska Science Center, Pacific Coastal and Marine Science Center, Woods Hole Coastal and Marine Science Center, Core Preparation and Analysis Laboratory and Sample Repositories, Multi-Sensor Core Logger Laboratory

Santa Rosa's past and future earthquakes

Santa Rosa is no stranger to earthquakes. This northern California city was damaged several times in the late 19th and early 20th centuries by shaking from earthquakes, culminating in the devastating earthquake of 1906, whose rupture passed 20 miles to the west of the city on the San Andreas Fault. Then in 1969, Santa Rosa was again strongly shaken and buildings were damaged by a pair of nearby, m
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Natural Hazards, Earthquake Hazards, Earthquake Science Center

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 figures that contain representative high-resolution s
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Natural Hazards, Coastal and Marine Hazards and Resources Program, Pacific Coastal and Marine Science Center

Neotectonics of the Big Sur Bend, San Gregorio‐Hosgri fault system, central California

The right‐lateral San Gregorio‐Hosgri fault system (SGHF) extends mainly offshore for about 400 km along the central California coast and is a major structure in the distributed transform margin of western North America. We mapped a poorly known 64‐km‐long section of the SGHF offshore Big Sur between Piedras Blancas and Point Sur using high‐resolution bathymetry, seismic reflection, and marine mag
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Coastal and Marine Hazards and Resources Program, Pacific Coastal and Marine Science Center
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Research Expedition Collects Cores, Geophysical Data from Cascadia Subduction Zone

To better understand the geophysical characteristics and seismic history of the Cascadia Subduction Zone, USGS researchers conduct fieldwork at sea to...

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Unlocking plate motions of the Cascadia subduction zone with seafloor geodesy

Seeking understanding of the fundamental constraints on plate motions, rates of convergence, and shallow strain accumulation across one of the United...

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PCMSC scientists invited to present at the National Seismic Hazard Map Workshop

USGS Pacific Coastal and Marine Science Center research geologist Jenna Hill to present recent offshore work on the Cascadia Subduction Zone.

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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...

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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...

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Mystery Gap: Connecting Earthquake Faults near San Francisco, California, Requires Many Approaches

New USGS mapping studies in San Pablo Bay, California, show that two of the region’s earthquake faults—the Hayward and Rodgers Creek faults—connect...

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CBS This Morning features USGS scientists studying link between earthquake faults near San Francisco, California

News from USGS Pacific Coastal and Marine Science Center

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Coring the Hayward-Rodgers Creek fault zone in San Pablo Bay, California, to unravel the history of faulting beneath the bay

News from USGS Pacific Coastal and Marine Science Center

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Link between two earthquake faults near San Francisco, California, revealed by detailed sub-seafloor mapping

News from USGS Pacific Coastal and Marine Science Center

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