Research scientists overlooking Iceberg Lake in Wrangell - St Elias National Park & Preserve, Alaska.
Rob Witter, Ph.D.
I conduct geological detective work that uncovers clues about the location, size, and frequency of ancient earthquakes and tsunamis. If we prepare for these hazards we can prevent future earthquakes and tsunamis from becoming future disasters.
I study prehistoric earthquakes along the Pacific-North American plate boundary. I apply aspects of geomorphology, paleoseismology, geodesy, and sea-level studies to decipher the geologic record of ancient earthquakes. Most of my work focuses on great subduction earthquakes capable of generating tsunamis. What I find out contributes to seismic and tsunami hazards assessments used to strengthen building codes and reduce tsunami risk.
Professional Experience
2011 – Present Research Geologist, U.S. Geological Survey, Alaska Science Center, Anchorage, AK
2006 – 2011 Regional Coastal Geologist, Oregon Department of Geology and Mineral Industries, Newport, OR
1999 – 2006 Senior Project Geologist, William Lettis & Associates, Inc., Walnut Creek, CA
Education and Certifications
Ph.D. 1999 University of Oregon, Eugene, OR Geoscience
B.A. 1991 Whitman College, Walla Walla, WA Biology
Science and Products
M7.1 November 30, 2018 Anchorage Earthquake
Alaska Earthquake and Tsunami Hazards
Alaska Seismic Hazard Map
Alaska-Aleutian Subduction Zone Studies
Characterizing the Active Queen Charlotte-Fairweather Fault System
Margin-wide geological and geophysical synthesis to understand the recurrence and hazards of great subduction zone earthquakes in Cascadia
Diatom Data from Coastal Environments on Montague Island, Alaska
Compiled onshore and offshore paleoseismic data along the Cascadia Subduction zone
Radiocarbon Data from Coastal Environments on Montague Island, Alaska
Data Release for the 2023 U.S. 50-State National Seismic Hazard Model - Overview
Radiocarbon Data for Tree Ring Samples from Girdwood, Alaska
Quaternary deposits of the 9-county San Francisco Bay Region: an areally continuous digital map database prepared from Knudsen and others (2000) and Witter and others (2006)
Geophysical and core sample data collected in lakes and fjords of southcentral Alaska following the 2018 Anchorage earthquake (ver. 2.0, October 2023)
Radiocarbon and Luminescence Data for Fairweather Fault Investigation, Glacier Bay National Park, Southeast Alaska
Gridded Data from Multibeam Bathymetric Surveys of Eklutna, Kenai, and Skilak Lakes, Alaska
Field reconnaissance of ground failure triggered by shaking during the 2018 M7.1 Anchorage, Alaska, earthquake
Airborne Lidar-based Digital Elevation Models of Coastal Montague Island (Alaska) Acquired September 2018
Radiocarbon, Cesium-137, Grain Size, and X-ray Fluorescence Data for Tsunami Geology Investigation, Driftwood Bay, Umnak Island, Alaska (2018)
Field and Laboratory Data From an Earthquake History Study of Scarps in the Hanging Wall of the Tacoma Fault, Mason and Pierce Counties, Washington
Research scientists overlooking Iceberg Lake in Wrangell - St Elias National Park & Preserve, Alaska.
THE ALEUTIAN CRADLE OF TSUNAMIS
(Click here to read EOS Feature: Seismic Sources in the Aleutian Cradle of Tsunamis)
Geologists climb a slope above Larsen Bay, Nagai Island, Alaska. Geologists studying coastal evidence of past Alaska-Aleutian subduction zone earthquakes and high tsunamis climb a slope above Larsen Bay on Nagai Island in the Shumagin seismic gap, Alaska.
Geologists climb a slope above Larsen Bay, Nagai Island, Alaska. Geologists studying coastal evidence of past Alaska-Aleutian subduction zone earthquakes and high tsunamis climb a slope above Larsen Bay on Nagai Island in the Shumagin seismic gap, Alaska.
USGS scientists, working with researchers from the University of Ghent, probed the floor of Eklutna Lake, Anchorage Borough, Alaska, for evidence of turbidity currents triggered by strong shaking during the 2018 Mw7.1 Anchorage earthquake.
USGS scientists, working with researchers from the University of Ghent, probed the floor of Eklutna Lake, Anchorage Borough, Alaska, for evidence of turbidity currents triggered by strong shaking during the 2018 Mw7.1 Anchorage earthquake.
Crack observed in 2018 along headscarp of 1964 Government Hill landslide.
2018 Anchorage Earthquake
Crack observed in 2018 along headscarp of 1964 Government Hill landslide.
2018 Anchorage Earthquake
Eklutna Lake dam appeared to be undamaged the day after the earthquake; overflights of the lake showed no landslides impacted the lake shoreline.
Eklutna Lake dam appeared to be undamaged the day after the earthquake; overflights of the lake showed no landslides impacted the lake shoreline.
Superficial slides along Eagle River east of Eagle River Loop Road.
2018 Anchorage Earthquake
Superficial slides along Eagle River east of Eagle River Loop Road.
2018 Anchorage Earthquake
Research Geologist Peter Haeussler holding a stump from a tree that was killed in the penultimate great earthquake - the last giant earthquake before the 1964 M9.2 earthquake in southcentral Alaska.
Research Geologist Peter Haeussler holding a stump from a tree that was killed in the penultimate great earthquake - the last giant earthquake before the 1964 M9.2 earthquake in southcentral Alaska.
USGS scientists Kate Scharer, Richard Lease, and Adrian Bender excavate a marine terrace elevated tens of meters above sea level on the west side of the Fairweather Fault. Location: Icy Point, Glacier Bay National Park, Alaska.
USGS scientists Kate Scharer, Richard Lease, and Adrian Bender excavate a marine terrace elevated tens of meters above sea level on the west side of the Fairweather Fault. Location: Icy Point, Glacier Bay National Park, Alaska.
USGS scientists Richard Lease and Adrian Bender examine river terraces elevated tens of meters above the modern channel level on the west side of the Fairweather Fault. Location: Kaknau Creek, Icy Point, Glacier Bay National Park, Alaska.
USGS scientists Richard Lease and Adrian Bender examine river terraces elevated tens of meters above the modern channel level on the west side of the Fairweather Fault. Location: Kaknau Creek, Icy Point, Glacier Bay National Park, Alaska.
USGS geologists' camp overlooking Unga Village on Unga Island, Alaska.
USGS geologists' camp overlooking Unga Village on Unga Island, Alaska.
USGS Research Geologist Chris DuRoss investigates earthquake-faulted stratigraphy exposed in a hand-dug trench across the Fairweather Fault scarp. Location: Crillon Lake, Glacier Bay National Park, Alaska.
USGS Research Geologist Chris DuRoss investigates earthquake-faulted stratigraphy exposed in a hand-dug trench across the Fairweather Fault scarp. Location: Crillon Lake, Glacier Bay National Park, Alaska.
USGS scientists Adrian Bender and Peter Haeussler walk along the base of a ~10 m tall escarpment formed during past ground-rupturing earthquakes on the Fairweather Fault. Location: Crillon Lake, Glacier Bay National Park, Alaska
USGS scientists Adrian Bender and Peter Haeussler walk along the base of a ~10 m tall escarpment formed during past ground-rupturing earthquakes on the Fairweather Fault. Location: Crillon Lake, Glacier Bay National Park, Alaska
USGS Geologist Adrian Bender surveys a trace of the 1958 Fairweather Fault earthquake surface rupture. The trace forms a linear, uphill-facing, 1-2 m tall escarpment flanked by trees that were likely tilted during the 1958 earthquake. Location: Crillon Lake, Glacier Bay National Park, Alaska.
USGS Geologist Adrian Bender surveys a trace of the 1958 Fairweather Fault earthquake surface rupture. The trace forms a linear, uphill-facing, 1-2 m tall escarpment flanked by trees that were likely tilted during the 1958 earthquake. Location: Crillon Lake, Glacier Bay National Park, Alaska.
The field crew studies various areas thoughout the fault.
The field crew studies various areas thoughout the fault.
Sediment core showing sandy tsunami deposits over soil from an upland environment on Sitkalidak Island, Alaska.
Sediment core showing sandy tsunami deposits over soil from an upland environment on Sitkalidak Island, Alaska.
Soil pit exposing tsunami deposits on Sitkalidak Island, Alaska.
Soil pit exposing tsunami deposits on Sitkalidak Island, Alaska.
In the Fox Islands of Alaska, Driftwood Bay on Umnak Island faces the deep-sea trench formed by the Alaska-Aleutian subduction zone.
In the Fox Islands of Alaska, Driftwood Bay on Umnak Island faces the deep-sea trench formed by the Alaska-Aleutian subduction zone.
A geologist stands on a drift log stranded 23 m above mean tide level, overlooking the Cabin Flat study site and Driftwood Bay, Umnak Island, Alaska.
A geologist stands on a drift log stranded 23 m above mean tide level, overlooking the Cabin Flat study site and Driftwood Bay, Umnak Island, Alaska.
Geologists camped near an upland lake about 0.5 km from the shore of Driftwood Bay, Umnak Island, Alaska. Vsevidof Volcano in the background.
Geologists camped near an upland lake about 0.5 km from the shore of Driftwood Bay, Umnak Island, Alaska. Vsevidof Volcano in the background.
USGS Alaska Earthquake Hazards research team investigates a tsunami-rafted drift log high above sea level at Stardust Bay, Sedanka Island, Alaska.
USGS Alaska Earthquake Hazards research team investigates a tsunami-rafted drift log high above sea level at Stardust Bay, Sedanka Island, Alaska.
The 2023 US 50-State National Seismic Hazard Model: Overview and implications
Seismic sources in the aleutian cradle of tsunamis
Reproducibility and variability of earthquake subsidence estimates from saltmarshes of a Cascadia estuary
Unravelling a 2300 year long sedimentary record of megathrust and intraslab earthquakes in proglacial Skilak Lake, south-central Alaska
Changing impacts of Alaska-Aleutian subduction zone tsunamis in California under future sea-level rise
Geomorphic expression and slip rate of the Fairweather fault, southeast Alaska, and evidence for predecessors of the 1958 rupture
A maximum rupture model for the central and southern Cascadia subduction zone—reassessing ages for coastal evidence of megathrust earthquakes and tsunamis
Extreme Quaternary plate boundary exhumation and strike slip localized along the southern Fairweather fault, Alaska, USA
Timing and amount of southern Cascadia earthquake subsidence over the past 1700 years at northern Humboldt Bay, California, USA
Toward an integrative geological and geophysical view of Cascadia subduction zone earthquakes
Minimal stratigraphic evidence for coseismic coastal subsidence during 2000 yr of megathrust earthquakes at the central Cascadia subduction zone
Identifying the greatest earthquakes of the past 2000 years at the Nehalem River Estuary, Northern Oregon Coast, USA
Non-USGS Publications**
**Disclaimer: The views expressed in Non-USGS publications are those of the author and do not represent the views of the USGS, Department of the Interior, or the U.S. Government.
WiggleMatch: a spreadsheet for radiocarbon wiggle-matching
Science and Products
- Science
M7.1 November 30, 2018 Anchorage Earthquake
A magnitude 7.1 earthquake struck north of Anchorage, Alaska, on November 30, 2018, at 8:29 a.m. local time (17:29:28 UTC).Alaska Earthquake and Tsunami Hazards
Alaska has more large earthquakes than the rest of the United States combined. More than three-quarters of the state’s population live in an area that can experience a magnitude 7 earthquake. Our research provides objective science that helps stakeholders prepare for and mitigate the effects of future earthquakes and tsunamis, which bolsters the economic health and well-being of Alaska and the...Alaska Seismic Hazard Map
The National Seismic Hazard Maps developed by the USGS show the spatial probability of peak earthquake-driven ground motion levels. Since the last revisions to the map for Alaska in 2007, scientists have made significant advances in understanding active faulting, fault slip rates, and fault behavior.Alaska-Aleutian Subduction Zone Studies
Our research team is exploring seismic and aseismic slip along the Alaska-Aleutian arc and studying the prehistoric record of megathrust earthquakes and tsunamis along the Alaska-Aleutian subduction zone Seismic and Aseismic Slip : Tectonic tremor and associated slow slip events represent a newly discovered part of the earthquake cycle. This research aims to understand the process generating...Characterizing the Active Queen Charlotte-Fairweather Fault System
This research aims to better characterize the earthquake potential of the southern Fairweather Fault in order to provide more accurate fault source data for the USGS National Seismic Hazard Map. Our approach interrogates lidar data and satellite imagery, applies paleoseismological methods to examine earthquake history, and leverages partnerships with USGS scientists from Colorado and California...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 - Data
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Diatom Data from Coastal Environments on Montague Island, Alaska
This dataset consists of fossil diatom counts from sediment cores collected in coastal environments on Montague Island, Alaska, and analyzed at Virginia Tech University.Compiled onshore and offshore paleoseismic data along the Cascadia Subduction zone
The USGS Powell Center Cascadia earthquake hazards working group compiled published onshore and offshore paleoseismic data along the Cascadia subduction zone, spanning sites from Vancouver Island to the Mendocino triple junction. Evidence for megathrust rupture includes coastal land-level change, tsunami inundation, onshore shaking proxies such as landslides or liquefaction, and offshore shaking pRadiocarbon Data from Coastal Environments on Montague Island, Alaska
This dataset consists of sample descriptions and radiocarbon age data from coastal environments on Montague Island, Alaska, analyzed at the National Ocean Sciences Accelerator Mass Spectrometry Facility.Data Release for the 2023 U.S. 50-State National Seismic Hazard Model - Overview
This data release contains data sets associated with the 2023 50-State National Seismic Hazard Model Update. The 2023 50-State National Seimsic Hazard Model (NSHM) Update includes an update to the NSHMs for the conterminous U.S (CONUS, last updated in 2018), Alaska (AK, last updated in 2007), and Hawaii (last updated in 2001). Data sets include inputs like seismicity catalogs used as input to theRadiocarbon Data for Tree Ring Samples from Girdwood, Alaska
This dataset consists of sample details and radiocarbon age data of tree-ring samples collected near Girdwood, Alaska, and analyzed at the National Ocean Sciences Accelerator Mass Spectrometry Facility.Quaternary deposits of the 9-county San Francisco Bay Region: an areally continuous digital map database prepared from Knudsen and others (2000) and Witter and others (2006)
This digital map database provides an areally continuous representation of the Quaternary surficial deposits of the San Francisco Bay region merged from the database files from Knudsen and others (2000) and Witter and others (2006). The more detailed mapping by Witter and others (2006) of the inner part of the region (compiled at a scale of 1:24,000), is given precedence over the less detailed mapGeophysical and core sample data collected in lakes and fjords of southcentral Alaska following the 2018 Anchorage earthquake (ver. 2.0, October 2023)
This dataset includes sub-bottom seismic and sediment core data collected during USGS field activities 2021-612-FA, 2020-625-FA, and 2020-615-FA. Sub-bottom data include Chirp seismic in SEG-Y format with associated navigation tracklines. Core data include photo and computed tomography (CT) scans, and various mineralogical, radiometric, and other sampling data. Users are advised to read the metadaRadiocarbon and Luminescence Data for Fairweather Fault Investigation, Glacier Bay National Park, Southeast Alaska
This dataset is comprised of two tables with age data along the Fairweather fault in Glacier Bay National Park. The tables are: (1) radiocarbon dates analyzed at the National Ocean Sciences Accelerator Mass Spectrometry Facility (NOSAMS), and (2) infrared stimulated luminescence ages determined by the Utah State University (USU) Luminescence Laboratory.Gridded Data from Multibeam Bathymetric Surveys of Eklutna, Kenai, and Skilak Lakes, Alaska
This dataset provides bathymetry data collected in 2015 for Eklutna, Kenai, and Skilak Lakes, Alaska. The data release consists of a grid for each lake (4 m, 9 m, and 7 m respectively), derived from processed and cleaned multibeam data. Depths were corrected using conductivity, temperature, and depth profiles collected during the surveys, and the data were cleaned of spurious returns.Field reconnaissance of ground failure triggered by shaking during the 2018 M7.1 Anchorage, Alaska, earthquake
These data present geolocated photographs, GPS tracks, and field-mapped ground failures collected during the USGS reconnaissance of ground failures following the 2018 M7.1 Anchorage Earthquake.Airborne Lidar-based Digital Elevation Models of Coastal Montague Island (Alaska) Acquired September 2018
This dataset provides a digital elevation model mosaic derived from airborne lidar data acquired in 2018 from September 2-3 over eight separate areas along Alaska's Montague Island coast, between Prince William Sound and the Gulf of Alaska.Radiocarbon, Cesium-137, Grain Size, and X-ray Fluorescence Data for Tsunami Geology Investigation, Driftwood Bay, Umnak Island, Alaska (2018)
These files provide the complete data release for the paper entitled, "Frequent large tsunamis spanned locked/creeping parts of the Aleutian megathrust." The data set consists of nine tables that include radiocarbon dates, cesium-137 activity, grain size measurements, and scanning X-ray fluorescence element intensity counts. - Maps
Field and Laboratory Data From an Earthquake History Study of Scarps in the Hanging Wall of the Tacoma Fault, Mason and Pierce Counties, Washington
As part of the effort to assess seismic hazard in the Puget Sound region, we map fault scarps on Airborne Laser Swath Mapping (ALSM, an application of LiDAR) imagery (with 2.5-m elevation contours on 1:4,000-scale maps) and show field and laboratory data from backhoe trenches across the scarps that are being used to develop a latest Pleistocene and Holocene history of large earthquakes on the Taco - Multimedia
Filter Total Items: 26Panorama of Iceberg Lake
Research scientists overlooking Iceberg Lake in Wrangell - St Elias National Park & Preserve, Alaska.
Research scientists overlooking Iceberg Lake in Wrangell - St Elias National Park & Preserve, Alaska.
The Aleutian Cradle of TsunamisTHE ALEUTIAN CRADLE OF TSUNAMIS
(Click here to read EOS Feature: Seismic Sources in the Aleutian Cradle of Tsunamis)
Geologists climb a slope above Larsen Bay, AlaskaGeologists climb a slope above Larsen Bay, Nagai Island, Alaska. Geologists studying coastal evidence of past Alaska-Aleutian subduction zone earthquakes and high tsunamis climb a slope above Larsen Bay on Nagai Island in the Shumagin seismic gap, Alaska.
Geologists climb a slope above Larsen Bay, Nagai Island, Alaska. Geologists studying coastal evidence of past Alaska-Aleutian subduction zone earthquakes and high tsunamis climb a slope above Larsen Bay on Nagai Island in the Shumagin seismic gap, Alaska.
Evidence of turbidity currents in Eklutna LakeUSGS scientists, working with researchers from the University of Ghent, probed the floor of Eklutna Lake, Anchorage Borough, Alaska, for evidence of turbidity currents triggered by strong shaking during the 2018 Mw7.1 Anchorage earthquake.
USGS scientists, working with researchers from the University of Ghent, probed the floor of Eklutna Lake, Anchorage Borough, Alaska, for evidence of turbidity currents triggered by strong shaking during the 2018 Mw7.1 Anchorage earthquake.
Ground crack at Sunset Park, Anchorage, AKCrack observed in 2018 along headscarp of 1964 Government Hill landslide.
2018 Anchorage Earthquake
Crack observed in 2018 along headscarp of 1964 Government Hill landslide.
2018 Anchorage Earthquake
Eklutna Dam after 2018 Anchorage earthquakeEklutna Lake dam appeared to be undamaged the day after the earthquake; overflights of the lake showed no landslides impacted the lake shoreline.
Eklutna Lake dam appeared to be undamaged the day after the earthquake; overflights of the lake showed no landslides impacted the lake shoreline.
Eagle River landslides, Eagle River, AKSuperficial slides along Eagle River east of Eagle River Loop Road.
2018 Anchorage Earthquake
Superficial slides along Eagle River east of Eagle River Loop Road.
2018 Anchorage Earthquake
Scientist holding dead tree stumpResearch Geologist Peter Haeussler holding a stump from a tree that was killed in the penultimate great earthquake - the last giant earthquake before the 1964 M9.2 earthquake in southcentral Alaska.
Research Geologist Peter Haeussler holding a stump from a tree that was killed in the penultimate great earthquake - the last giant earthquake before the 1964 M9.2 earthquake in southcentral Alaska.
Investigating a marine terrace along the Fairweather FaultInvestigating a marine terrace along the Fairweather FaultUSGS scientists Kate Scharer, Richard Lease, and Adrian Bender excavate a marine terrace elevated tens of meters above sea level on the west side of the Fairweather Fault. Location: Icy Point, Glacier Bay National Park, Alaska.
USGS scientists Kate Scharer, Richard Lease, and Adrian Bender excavate a marine terrace elevated tens of meters above sea level on the west side of the Fairweather Fault. Location: Icy Point, Glacier Bay National Park, Alaska.
River terraces elevated along the Fairweather FaultRiver terraces elevated along the Fairweather FaultUSGS scientists Richard Lease and Adrian Bender examine river terraces elevated tens of meters above the modern channel level on the west side of the Fairweather Fault. Location: Kaknau Creek, Icy Point, Glacier Bay National Park, Alaska.
USGS scientists Richard Lease and Adrian Bender examine river terraces elevated tens of meters above the modern channel level on the west side of the Fairweather Fault. Location: Kaknau Creek, Icy Point, Glacier Bay National Park, Alaska.
Geologists' camp on Unga Island, AlaskaUSGS geologists' camp overlooking Unga Village on Unga Island, Alaska.
USGS geologists' camp overlooking Unga Village on Unga Island, Alaska.
Investigating a trench across the Fairweather FaultInvestigating a trench across the Fairweather FaultUSGS Research Geologist Chris DuRoss investigates earthquake-faulted stratigraphy exposed in a hand-dug trench across the Fairweather Fault scarp. Location: Crillon Lake, Glacier Bay National Park, Alaska.
USGS Research Geologist Chris DuRoss investigates earthquake-faulted stratigraphy exposed in a hand-dug trench across the Fairweather Fault scarp. Location: Crillon Lake, Glacier Bay National Park, Alaska.
Walking along the Fairweather Fault scarpUSGS scientists Adrian Bender and Peter Haeussler walk along the base of a ~10 m tall escarpment formed during past ground-rupturing earthquakes on the Fairweather Fault. Location: Crillon Lake, Glacier Bay National Park, Alaska
USGS scientists Adrian Bender and Peter Haeussler walk along the base of a ~10 m tall escarpment formed during past ground-rupturing earthquakes on the Fairweather Fault. Location: Crillon Lake, Glacier Bay National Park, Alaska
Surveying the Fairweather Fault traceUSGS Geologist Adrian Bender surveys a trace of the 1958 Fairweather Fault earthquake surface rupture. The trace forms a linear, uphill-facing, 1-2 m tall escarpment flanked by trees that were likely tilted during the 1958 earthquake. Location: Crillon Lake, Glacier Bay National Park, Alaska.
USGS Geologist Adrian Bender surveys a trace of the 1958 Fairweather Fault earthquake surface rupture. The trace forms a linear, uphill-facing, 1-2 m tall escarpment flanked by trees that were likely tilted during the 1958 earthquake. Location: Crillon Lake, Glacier Bay National Park, Alaska.
Alaska field crew next to a trenchThe field crew studies various areas thoughout the fault.
The field crew studies various areas thoughout the fault.
Sediment core showing tsunami deposits on Sitkalidak Island, AlaskaSediment core showing tsunami deposits on Sitkalidak Island, AlaskaSediment core showing sandy tsunami deposits over soil from an upland environment on Sitkalidak Island, Alaska.
Sediment core showing sandy tsunami deposits over soil from an upland environment on Sitkalidak Island, Alaska.
Soil pit on Sitkalidak Island, AlaskaSoil pit exposing tsunami deposits on Sitkalidak Island, Alaska.
Soil pit exposing tsunami deposits on Sitkalidak Island, Alaska.
Driftwood Bay, Umnak Island, AlaskaIn the Fox Islands of Alaska, Driftwood Bay on Umnak Island faces the deep-sea trench formed by the Alaska-Aleutian subduction zone.
In the Fox Islands of Alaska, Driftwood Bay on Umnak Island faces the deep-sea trench formed by the Alaska-Aleutian subduction zone.
Geologist on a log 23 m above mean tide level in the Cabin Flat areaGeologist on a log 23 m above mean tide level in the Cabin Flat areaA geologist stands on a drift log stranded 23 m above mean tide level, overlooking the Cabin Flat study site and Driftwood Bay, Umnak Island, Alaska.
A geologist stands on a drift log stranded 23 m above mean tide level, overlooking the Cabin Flat study site and Driftwood Bay, Umnak Island, Alaska.
Camp near Driftwood Bay, Umnak Island, AlaskaGeologists camped near an upland lake about 0.5 km from the shore of Driftwood Bay, Umnak Island, Alaska. Vsevidof Volcano in the background.
Geologists camped near an upland lake about 0.5 km from the shore of Driftwood Bay, Umnak Island, Alaska. Vsevidof Volcano in the background.
USGS team looking at a tsunami-rafted log above Stardust Bay, AlaskaUSGS team looking at a tsunami-rafted log above Stardust Bay, AlaskaUSGS Alaska Earthquake Hazards research team investigates a tsunami-rafted drift log high above sea level at Stardust Bay, Sedanka Island, Alaska.
USGS Alaska Earthquake Hazards research team investigates a tsunami-rafted drift log high above sea level at Stardust Bay, Sedanka Island, Alaska.
- Publications
Filter Total Items: 46
The 2023 US 50-State National Seismic Hazard Model: Overview and implications
The US National Seismic Hazard Model (NSHM) was updated in 2023 for all 50 states using new science on seismicity, fault ruptures, ground motions, and probabilistic techniques to produce a standard of practice for public policy and other engineering applications (defined for return periods greater than ∼475 or less than ∼10,000 years). Changes in 2023 time-independent seismic hazard (both increaseAuthorsMark D. Petersen, Allison Shumway, Peter M. Powers, Edward H. Field, Morgan P. Moschetti, Kishor Jaiswal, Kevin R. Milner, Sanaz Rezaeian, Arthur Frankel, Andrea L. Llenos, Andrew J. Michael, Jason M. Altekruse, Sean Kamran Ahdi, Kyle Withers, Charles Mueller, Yuehua Zeng, Robert E. Chase, Leah M. Salditch, Nicolas Luco, Kenneth S. Rukstales, Julie A Herrick, Demi Leafar Girot, Brad T. Aagaard, Adrian Bender, Michael Blanpied, Richard W. Briggs, Oliver S. Boyd, Brandon Clayton, Christopher DuRoss, Eileen L. Evans, Peter J. Haeussler, Alexandra Elise Hatem, Kirstie Lafon Haynie, Elizabeth H. Hearn, Kaj M. Johnson, Zachary Alan Kortum, N. Simon Kwong, Andrew James Makdisi, Henry (Ben) Mason, Daniel McNamara, Devin McPhillips, P. Okubo, Morgan T. Page, Fred Pollitz, Justin Rubinstein, Bruce E. Shaw, Zheng-Kang Shen, Brian Shiro, James Andrew Smith, William J. Stephenson, Eric M. Thompson, Jessica Ann Thompson Jobe, Erin Wirth, Robert C. WitterSeismic sources in the aleutian cradle of tsunamis
No abstract available.AuthorsRobert C. Witter, Richard W. Briggs, Tina Dura, Simon E. Engelhart, Alan NelsonReproducibility and variability of earthquake subsidence estimates from saltmarshes of a Cascadia estuary
We examine fossil foraminiferal assemblages from 20 sediment cores to assess sudden relative sea-level (RSL) changes across three mud-over-peat contacts at three salt marshes in northern Humboldt Bay, California (~44.8°N, -124.2°W). We use a validated foraminiferal-based Bayesian transfer function to evaluate the variability of subsidence stratigraphy at a range of 30-6000 m across an estuary. WeAuthorsJason Scott Padgett, Simon E. Engelhart, Harvey M. Kelsey, Robert C. Witter, Niamh CahillUnravelling a 2300 year long sedimentary record of megathrust and intraslab earthquakes in proglacial Skilak Lake, south-central Alaska
Seismic hazards in subduction settings typically arise from megathrust, intraslab and crustal earthquake sources. Despite the frequent occurrence of intraslab earthquakes in subduction zones and their potential threat to communities, their long-term recurrence behaviour is barely studied. Sedimentary sequences in lakes may register ground shaking from different seismic sources. This study investigAuthorsNore Praet, Maarten Van Daele, Jasper Moernaut, Thomas Mestdagh, Thomas Vandorpe, Britta J.L. Jensen, Robert C. Witter, Peter J. Haeussler, Marc De BatistChanging impacts of Alaska-Aleutian subduction zone tsunamis in California under future sea-level rise
The amplification of coastal hazards such as distant-source tsunamis under future relative sea-level rise (RSLR) is poorly constrained. In southern California, the Alaska-Aleutian subduction zone has been identified as an earthquake source region of particular concern for a worst-case scenario distant-source tsunami. Here, we explore how RSLR over the next century will influence future maximum neaAuthorsTina Dura, Andra Garner, Robert Weiss, Robert E. Kopp, Simon E. Engelhart, Robert C. Witter, Richard W. Briggs, Charles Mueller, Alan Nelson, Benjamin P. HortonGeomorphic expression and slip rate of the Fairweather fault, southeast Alaska, and evidence for predecessors of the 1958 rupture
Active traces of the southern Fairweather fault were revealed by light detection and ranging (lidar) and show evidence for transpressional deformation between North America and the Yakutat block in southeast Alaska. We map the Holocene geomorphic expression of tectonic deformation along the southern 30 km of the Fairweather fault, which ruptured in the 1958 moment magnitude 7.8 earthquake. DigitalAuthorsRobert C. Witter, Adrian Bender, Katherine Scharer, Christopher DuRoss, Peter J. Haeussler, Richard O. LeaseA maximum rupture model for the central and southern Cascadia subduction zone—reassessing ages for coastal evidence of megathrust earthquakes and tsunamis
A new history of great earthquakes (and their tsunamis) for the central and southern Cascadia subduction zone shows more frequent (17 in the past 6700 yr) megathrust ruptures than previous coastal chronologies. The history is based on along-strike correlations of Bayesian age models derived from evaluation of 554 radiocarbon ages that date earthquake evidence at 14 coastal sites. We reconstruct aAuthorsAlan Nelson, Christopher DuRoss, Robert C. Witter, Harvey M. Kelsey, Simon E. Engelhart, Shannon A. Mahan, Harrison J. Gray, Andrea D. Hawkes, Benjamin P. Horton, Jason S. PadgettExtreme Quaternary plate boundary exhumation and strike slip localized along the southern Fairweather fault, Alaska, USA
The Fairweather fault (southeastern Alaska, USA) is Earth’s fastest-slipping intracontinental strike-slip fault, but its long-term role in localizing Yakutat–(Pacific–)North America plate motion is poorly constrained. This plate boundary fault transitions northward from pure strike slip to transpression where it comes onshore and undergoes a <25°, 30-km-long restraining double bend. To the east, aAuthorsRichard O. Lease, Peter J. Haeussler, Robert C. Witter, Daniel F. Stockli, Adrian Bender, Harvey Kelsey, Paul O'SullivanTiming and amount of southern Cascadia earthquake subsidence over the past 1700 years at northern Humboldt Bay, California, USA
Stratigraphic, lithologic, foraminiferal, and radiocarbon analyses indicate that at least four abrupt mud-over-peat contacts are recorded across three sites (Jacoby Creek, McDaniel Creek, and Mad River Slough) in northern Humboldt Bay, California, USA (∼44.8°N, −124.2°W). The stratigraphy records subsidence during past megathrust earthquakes at the southern Cascadia subduction zone ∼40 km north ofAuthorsJason S. Padgett, Simon E. Engelhart, Harvey M. Kelsey, Robert C. Witter, Niamh Cahill, Eileen Hemphill-HaleyToward 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 eventAuthorsMaureen A. L. Walton, Lydia M. Staisch, Tina Dura, Jessie Kathleen Pearl, Brian L. Sherrod, Joan S. Gomberg, Simon E. Engelhart, Anne Trehu, Janet Watt, Jonathan P. Perkins, Robert C. Witter, Noel Bartlow, Chris Goldfinger, Harvey Kelsey, Ann Morey, Valerie J. Sahakian, Harold Tobin, Kelin Wang, Ray Wells, Erin WirthByNatural Hazards Mission Area, 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, Deep Sea Exploration, Mapping and Characterization, Subduction Zone ScienceMinimal stratigraphic evidence for coseismic coastal subsidence during 2000 yr of megathrust earthquakes at the central Cascadia subduction zone
Lithology and microfossil biostratigraphy beneath the marshes of a central Oregon estuary limit geophysical models of Cascadia megathrust rupture during successive earthquakes by ruling out >0.5 m of coseismic coastal subsidence for the past 2000 yr. Although the stratigraphy in cores and outcrops includes as many as 12 peat-mud contacts, like those commonly inferred to record subsidence during meAuthorsAlan Nelson, Andrea D. Hawkes, Yuki Sawai, Ben P. Hotron, Robert C. Witter, Lee-Ann Bradley, Niamh CahillIdentifying the greatest earthquakes of the past 2000 years at the Nehalem River Estuary, Northern Oregon Coast, USA
We infer a history of three great megathrust earthquakes during the past 2000 years at the Nehalem River estuary based on the lateral extent of sharp (≤3 mm) peat-mud stratigraphic contacts in cores and outcrops, coseismic subsidence as interpreted from fossil diatom assemblages and reconstructed with foraminiferal assemblages using a Bayesian transfer function, and regional correlation of 14C-modAuthorsAlan R. Nelson, Andrea D. Hawkes, Yuki Sawai, Simon E. Engelhart, Robert C. Witter, Wendy C. Grant-Walter, Lee-Ann Bradley, Tina Dura, Niamh Cahill, Benajamin P. HortonNon-USGS Publications**
Engelhart, S. E., Horton, B. P., Nelson, A. R., Hawkes, A. D., Witter, R. C., Wang, K., Wang P.-L., and Vane, C. H., 2013, Testing the use of microfossils to reconstruct great earthquakes at Cascadia, Geology, doi:10.1130/G34544.1.Engelhart, S. E., B. P. Horton, C. H. Vane, A. R. Nelson, R. C. Witter, S. R. Brody, and A. D. Hawkes, 2013, Modern foraminifera, δ13C, and bulk geochemistry of central Oregon tidal marshes and their application in paleoseismology, Palaeogeography, Palaeoclimatology, Palaeoecology, doi:10.1016/j.palaeo.2013.02.032.Kelson, K., R. C. Witter, A. Tassara, I. Ryder, C. Ledezma, G. Montalva, D. Frost, N. Sitar, R. Moss, and L. Johnson, 2012, Coseismic tectonic surface deformation during the 2012 Maule, Chile, Mw 8.8 earthquake, Earthquake Spectra, v. 28, n. S1, p. 39-54.Pilarczyk, J. E., Horton, B. P., Witter, R. C., Vane, C. H., Chagué-Goff, C., Goff, J., 2012, Sedimentary and foraminiferal evidence of the 2011 Tohoku-oki tsunami on the Sendai coastal plain, Japan. Sedimentary Geology. doi:10.1016/j.sedgeo.2012.08.011.Richmond, B., W. Szczucinski, C.Chague-Goff, K. Goto, D. Sugawara, R. Witter, D.R. Tappin, B. Jaffe, S. Fujino, Y. Nishimura, and J. Goff, 2012, Erosion, deposition and landscape change on the Sendai coastal plain, Japan, resulting from the March 11, 2011 Tohoku-oki tsunami, Sedimentary Geology, doi:10.1016/j.sedgeo.2012.08.005.Witter, R.C., Y.J. Zhang, K. Wang, C. Goldfinger, and G.R. Priest, 2012, Coseismic slip on the southern Cascadia megathrust implied by tsunami deposits in an Oregon lake and earthquake-triggered marine turbidites, Journal of Geophysical Research, 117, B10303, doi:10.1029/2012JB009404.Allan, J., P. Komar, P. Ruggiero, and R.C. Witter, 2012, The March 2011 Tohoku tsunami and its impacts along the U.S. West Coast, Journal of Coastal Research, Journal of Coastal Research, v. 28, n. 5, p. 1142-1153, doi:10.2112/jcoastres-d-11-00115.1.Witter, R. C., B. Jaffe, Y. Zhang, and G. R. Priest, 2012, Reconstructing Hydrodynamic Flow Parameters of the 1700 Tsunami at Cannon Beach, Oregon, USA, Natural Hazards, doi:10.1007/s11069-011-9912-7.Horton, B. P., Sawai, Y., Hawkes, A. D., and Witter, R. C., 2011, Sedimentology and paleontology of a tsunami deposit accompanying the great Chilean earthquake of February 2010: Marine Micropaleontology, v. 79, no. 3-4, p. 132–138, doi:10.1016/j.marmicro.2011.02.001Zhang, Y. J., R. C. Witter, and G. R. Priest, 2011, Tsunami-tide interaction in 1964 Prince William Sound tsunami, Ocean Modelling, v. 40, p. 246–259, doi:10.1016/j.ocemod.2011.09.005**Disclaimer: The views expressed in Non-USGS publications are those of the author and do not represent the views of the USGS, Department of the Interior, or the U.S. Government.
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WiggleMatch: a spreadsheet for radiocarbon wiggle-matching
This spreadsheet enables statistical and visual wiggle-matching of sequential radiocarbon ages from a tree-ring chronology to the IntCal20 calibration curve. It will calculate and plot an optimal fit of the samples to the calibration curve and the user can then incrementally move the wiggle-match in time to see the effect in both goodness-of-fit statistics and visually on a graph. This is useful w - News