Ray Wells is a research geologist in the Geology, Minerals, Energy, and Geophysics Science Center. He is a structural geologist investigating the tectonic and volcanic evolution of the Pacific Northwest.
Ray Wells received his B.S. in Geological Science from Penn State, his M.S. from University of Oregon, and his Ph.D. from the University of California, Santa Cruz. He has 45 years of field experience documenting the geologic structure and earthquake hazards of the Cascadia convergent margin in Oregon and Washington, focusing primarily on the Coast Range, Seattle - Portland urban corridor, and the Columbia River Gorge.
Professional Experience
2020-current, Research Geologist, U.S. Geological Survey
2017-Research Associate, Portland State University, Portland, OR
2016-Research Geologist Emeritus, U.S. Geological Survey
1995-2013 Project Chief, Pacific Northwest Urban Corridor Geologic Mapping, USGS, Menlo Park, CA
1991-1996 Cascadia Regional Coordinator - USGS Deep Continental Surveys
1981-2016 Research Geologist, U.S. Geological Survey
1980 Geologist, Washington Division of Geology and Earth Resources
1978-1980 Research Assistant, University of California, Santa Cruz
1976-1977 Teaching Assistant, University of California, Santa Cruz
1975-1976 Geologist, U.S. Geological Survey
1974 Geological Field Assistant, Mobil Oil Corp., Tyee Basin
1972-1974 Teaching Assistant, University of Oregon
1971 Geological Field Assistant, Johns-Mannville Ltd, Stillwater Complex
Education and Certifications
Ph.D., Geology, University of California, Santa Cruz, 1982
M.S., Geology, University of Oregon, 1975
B.S., Geology, Art, Pennsylvania State University, 1972
Affiliations and Memberships*
1977 - Current, American Geophysical Union
1974 - Current, Geological Society of America
1990 - Current, Seismological Society of America
Oregon Department of Geology and Mineral Industries
Bureau of Reclamation
Portland State University
Honors and Awards
Distinguished Service Award of the Department of the Interior
2017 Geological Society of America’s Geologic Mapping Award in honor of Florence Bascom
Science and Products
Pacific Northwest Geologic Mapping: Northern Pacific Border, Cascades and Columbia
The Pacific Northwest is an area created by active and complex geological processes. On its path to the Pacific Ocean, the Columbia River slices through a chain of active volcanoes located along the western margin of the U.S. in Washington, Oregon, and northern California. These volcanoes rest above the active Cascadia subduction zone, which is the boundary where the oceanic tectonic plate dives...
U-Pb zircon data for Cenozoic clastic and volcaniclastic units deformed along the Gales Creek Fault zone, northwestern Oregon
This data release includes laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) U-Pb zircon geochronology data from four samples collected from fault-bounded bedrock units in northwestern Oregon. Samples were collected from a paleoseismic trench excavated across the Scoggins Valley strand of the Gales Creek Fault and nearby quarry. The trench is located on a ridge top saddle on t
Filter Total Items: 13
Geologic map of the greater Portland metropolitan area and surrounding region, Oregon and Washington
The Portland-Vancouver-Hillsboro Metropolitan Area (metro area) has great scenic, natural, and cultural resources and is the major economic hub of Oregon. The metro area is subject to a variety of geologic hazards. Underthrusting of the oceanic plate along the Cascadia plate boundary fault, or megathrust, deforms the leading edge of North America and produces earthquakes on the megathrust and in t
Lidar-revised geologic map of the Uncas 7.5' quadrangle, Clallam and Jefferson Counties, Washington
In 2000 and 2001, the Puget Sound Lidar Consortium obtained 1 pulse/m2 lidar data for about 65 percent of the Uncas 7.5' quadrangle. For a brief description of LIDAR (LIght Detection And Ranging) and this data acquisition program, see Haugerud and others (2003). This map combines geologic interpretation (mostly by Haugerud and Tabor) of the 6-ft (2-m) lidar-derived digital elevation model (DEM) wi
Lidar-revised geologic map of the Uncas 7.5' quadrangle, Clallam and Jefferson Counties, Washington
In 2000 and 2001, the Puget Sound Lidar Consortium obtained 1 pulse/m2 lidar data for about 65 percent of the Uncas 7.5' quadrangle. For a brief description of LIDAR (LIght Detection And Ranging) and this data acquisition program, see Haugerud and others (2003). This map combines geologic interpretation (mostly by Haugerud and Tabor) of the 6-ft (2-m) lidar-derived digital elevation model (DEM) wi
A tunnel runs through it — An inside view of the Tualatin Mountains, Oregon
The Tualatin Mountains form a northwest-striking ridge about 350 m high that separates Portland, Oregon, from the cities of the Tualatin Valley to the west. Known informally as the Portland Hills, the ridge is a late Cenozoic anticline, bounded by reverse faults that dip toward the anticlinal axis. The anticline is a broad, open fold consisting chiefly of Miocene Columbia River Basalt Group, with
A tunnel runs through it: an inside view of the Tualatin Mountains, Oregon
The Tualatin Mountains form a northwest-striking ridge about 350 m high that separates Portland, Oregon, from the cities of the Tualatin Valley to the west. Known informally as the Portland Hills, the ridge is a late Cenozoic anticline, bounded by reverse faults that dip toward the anticlinal axis. The anticline is a broad, open fold consisting chiefly of Miocene Columbia River Basalt Group, with
Earthquake hazards and lifelines in the Interstate 5 urban corridor: Woodburn, Oregon, to Centralia, Washington
The Interstate 5 highway (I-5) corridor, which stretches from Mexico to Canada, is both the main economic artery of the Pacific Northwest and home to the majority of Oregonians and Washingtonians. Accordingly, most regional utility and transportation systems have major components located within the I-5 corridor. For the purposes of this map, we refer to these essential systems as lifeline systems.
Earthquake hazards and lifelines in the Interstate 5 urban corridor: Cottage Grove to Woodburn, Oregon
The Interstate 5 highway (I-5) corridor, which stretches from Mexico to Canada, is both the main economic artery of the Pacific Northwest and home to the majority of Oregonians and Washingtonians. Accordingly, most regional utility and transportation systems have major components located within the I-5 corridor. For the purposes of this map, we refer to these essential systems as lifeline systems.
Earthquake Hazards and lifelines in the Interstate 5 urban corridor - Woodburn, Oregon, to Centralia, Washington
The Interstate 5 highway (I-5) corridor, which stretches from Mexico to Canada, is both the main economic artery of the Pacific Northwest and home to the majority of Oregonians and Washingtonians. Accordingly, most regional utility and transportation systems have major components located within the I-5 corridor. For the purposes of this map, we refer to these essential systems as lifeline systems.
Earthquake hazards and lifelines in the Interstate 5 Urban Corridor - Cottage Grove to Woodburn, Oregon
The Interstate 5 highway (I-5) corridor, which stretches from Mexico to Canada, is both the main economic artery of the Pacific Northwest and home to the majority of Oregonians and Washingtonians. Accordingly, most regional utility and transportation systems have major components located within the I-5 corridor. For the purposes of this map, we refer to these essential systems as lifeline systems.
Field and laboratory data From an earthquake history study of scarps of the Lake Creek-Boundary Creek fault between the Elwha River and Siebert Creek, Clallam County, Washington
Fault scarps recently discovered on Airborne Laser Swath Mapping (ALSM; also known as LiDAR) imagery show Holocene movement on the Lake Creek–Boundary Creek fault on the north flank of the Olympic Mountains of northwestern Washington State. Such recent movement suggests the fault is a potential source of large earthquakes. As part of the effort to assess seismic hazard in the Puget Sound region, w
Filter Total Items: 102
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
Authors
Maureen 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 Wirth
Northward migration of the Oregon forearc on the Gales Creek fault
The Gales Creek fault (GCF) is a 60-km-long, northwest-striking dextral fault system (west of Portland, Oregon) that accommodates northward motion and uplift of the Oregon Coast Range. New geologic mapping and geophysical models confirm inferred offsets from earlier geophysical surveys and document ∼12 km of right-lateral offset of a basement high in Eocene Siletz River Volcanics since ca. 35 Ma a
Authors
Ray Wells, Richard J. Blakely, Sean Bemis
New geologic mapping of the northwestern Willamette Valley, Oregon, and its American Viticultural Areas (AVAs)—A foundation for understanding their terroir
A geologic map of the greater Portland, Oregon, metropolitan area is planned that will document the region’s complex geology (currently in review: “Geologic map of the greater Portland metropolitan area and surrounding region, Oregon and Washington,” by Wells, R.E., Haugerud, R.A., Niem, A., Niem, W., Ma, L., Evarts, R., Madin, I., and others). The map, which is planned to be published as a U.S. G
Authors
Ray E. Wells, Ralph A. Haugerud, Alan Niem, Wendy Niem, Lina Ma, Ian Madin, Russell C. Evarts
Holocene earthquakes of magnitude 7 during westward escape of the Olympic Mountains, Washington
The Lake Creek–Boundary Creek fault, previously mapped in Miocene bedrock as an oblique thrust on the north flank of the Olympic Mountains, poses a significant earthquake hazard. Mapping using 2015 light detection and ranging (lidar) confirms 2004 lidar mapping of postglacial (≥14 km along a splay fault, the Sadie Creek fault, west of Lake Crescent. Scarp morphology suggests repeated earthquake r
Authors
Alan R. Nelson, Stephen Personius, Ray Wells, Elizabeth R. Schermer, Lee-Ann Bradley, Jason Buck, Nadine G. Reitman
Evidence for distributed clockwise rotation of the crust in the northwestern United States from fault geometries and focal mechanisms
Paleomagnetic and GPS data indicate that Washington and Oregon have rotated clockwise for the past 16 Myr. Late Cenozoic and Quaternary fault geometries, seismicity lineaments, and focal mechanisms provide evidence that this rotation is accommodated by north directed thrusting and right-lateral strike-slip faulting in Washington, and SW to W directed normal faulting and right-lateral strike-slip f
Authors
Thomas M. Brocher, Ray E. Wells, Andrew P. Lamb, Craig S. Weaver
Cascadia subduction tremor muted by crustal faults
Deep, episodic slow slip on the Cascadia subduction megathrust of western North America is accompanied by low-frequency tremor in a zone of high fluid pressure between 30 and 40 km depth. Tremor density (tremor epicenters per square kilometer) varies along strike, and lower tremor density statistically correlates with upper plate faults that accommodate northward motion and rotation of forearc blo
Authors
Ray Wells, Richard J. Blakely, Aaron G. Wech, Patricia A. McCrory, Andrew Michael
Contemporary deformation in the Yakima fold and thrust belt estimated with GPS
Geodetic, geologic and palaeomagnetic data reveal that Oregon (western USA) rotates clockwise at 0.3 to 1.0° Ma−1 (relative to North America) about an axis near the Idaho–Oregon–Washington border, while northeast Washington is relatively fixed. This rotation has been going on for at least 15 Ma. The Yakima fold and thrust belt (YFTB) forms the boundary between northern Oregon and central Washingto
Authors
Robert McCaffrey, Robert W. King, Ray Wells, Matthew Lancaster, M. Meghan Miller
Identifying block structure in the Pacific Northwest, USA
We have identified block structure in the Pacific Northwest (west of 116°W between 38°N and 49°N) by clustering GPS stations so that the same Euler vector approximates the velocity of each station in a cluster. Given the total number k of clusters desired, the clustering procedure finds the best assignment of stations to clusters. Clustering is calculated for k= 2 to 14. In geographic space, clust
Authors
James C. Savage, Ray E. Wells
Great (≥Mw8.0) megathrust earthquakes and the subduction of excess sediment and bathymetrically smooth seafloor
Using older and in part flawed data, Ruff (1989) suggested that thick sediment entering the subduction zone (SZ) smooths and strengthens the trench-parallel distribution of interplate coupling. This circumstance was conjectured to favor rupture continuation and the generation of high-magnitude (≥Mw8.0) interplate thrust (IPT) earthquakes. Using larger and more accurate compilations of sediment thi
Authors
David W. Scholl, Stephe H. Kirby, Roland E. von Huene, Holly F. Ryan, Ray E. Wells, Eric L. Geist
Tectonic evolution of the Tualatin basin, northwest Oregon, as revealed by inversion of gravity data
The Tualatin basin, west of Portland (Oregon, USA), coincides with a 110 mGal gravity low along the Puget-Willamette lowland. New gravity measurements (n = 3000) reveal a three-dimensional (3-D) subsurface geometry suggesting early development as a fault-bounded pull-apart basin. A strong northwest-trending gravity gradient coincides with the Gales Creek fault, which forms the southwestern boundar
Authors
Darcy McPhee, Victoria E. Langenheim, Ray Wells, Richard J. Blakely
Preliminary geologic map of the eastern Willapa Hills, Cowlitz, Lewis, and Wahkiakum Counties, Washington
This digital map database and the PDF derived from the database were created from the analog geologic map: Wells, R.E. (1981), “Geologic map of the eastern Willapa Hills, Cowlitz, Lewis, and Wahkiakum Counties, Washington.” The geodatabase replicates the geologic mapping of the 1981 report with minor exceptions along water boundaries and also along the north and south map boundaries. Slight adjust
Authors
Ray E. Wells, Michael G. Sawlan
Geologic history of Siletzia, a large igneous province in the Oregon and Washington Coast Range: Correlation to the geomagnetic polarity time scale and implications for a long-lived Yellowstone hotspot
Siletzia is a basaltic Paleocene and Eocene large igneous province in coastal Oregon, Washington, and southern Vancouver Island that was accreted to North America in the early Eocene. New U-Pb magmatic, detrital zircon, and 40Ar/39Ar ages constrained by detailed field mapping, global nannoplankton zones, and magnetic polarities allow correlation of the volcanics with the 2012 geologic time scale.
Authors
Ray Wells, David Bukry, Richard Friedman, Douglas Pyle, Robert Duncan, Peter J. Haeussler, Joe Wooden
By
Energy and Minerals Mission Area, Natural Hazards Mission Area, Energy Resources Program, Geomagnetism Program, Groundwater and Streamflow Information Program, Mineral Resources Program, National Laboratories Program, Science and Decisions Center, Geologic Hazards Science Center, Geology, Minerals, Energy, and Geophysics Science Center
Science and Products
- Science
Pacific Northwest Geologic Mapping: Northern Pacific Border, Cascades and Columbia
The Pacific Northwest is an area created by active and complex geological processes. On its path to the Pacific Ocean, the Columbia River slices through a chain of active volcanoes located along the western margin of the U.S. in Washington, Oregon, and northern California. These volcanoes rest above the active Cascadia subduction zone, which is the boundary where the oceanic tectonic plate dives... - Data
U-Pb zircon data for Cenozoic clastic and volcaniclastic units deformed along the Gales Creek Fault zone, northwestern Oregon
This data release includes laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) U-Pb zircon geochronology data from four samples collected from fault-bounded bedrock units in northwestern Oregon. Samples were collected from a paleoseismic trench excavated across the Scoggins Valley strand of the Gales Creek Fault and nearby quarry. The trench is located on a ridge top saddle on t - Maps
Filter Total Items: 13
Geologic map of the greater Portland metropolitan area and surrounding region, Oregon and Washington
The Portland-Vancouver-Hillsboro Metropolitan Area (metro area) has great scenic, natural, and cultural resources and is the major economic hub of Oregon. The metro area is subject to a variety of geologic hazards. Underthrusting of the oceanic plate along the Cascadia plate boundary fault, or megathrust, deforms the leading edge of North America and produces earthquakes on the megathrust and in tLidar-revised geologic map of the Uncas 7.5' quadrangle, Clallam and Jefferson Counties, Washington
In 2000 and 2001, the Puget Sound Lidar Consortium obtained 1 pulse/m2 lidar data for about 65 percent of the Uncas 7.5' quadrangle. For a brief description of LIDAR (LIght Detection And Ranging) and this data acquisition program, see Haugerud and others (2003). This map combines geologic interpretation (mostly by Haugerud and Tabor) of the 6-ft (2-m) lidar-derived digital elevation model (DEM) wiLidar-revised geologic map of the Uncas 7.5' quadrangle, Clallam and Jefferson Counties, Washington
In 2000 and 2001, the Puget Sound Lidar Consortium obtained 1 pulse/m2 lidar data for about 65 percent of the Uncas 7.5' quadrangle. For a brief description of LIDAR (LIght Detection And Ranging) and this data acquisition program, see Haugerud and others (2003). This map combines geologic interpretation (mostly by Haugerud and Tabor) of the 6-ft (2-m) lidar-derived digital elevation model (DEM) wiA tunnel runs through it — An inside view of the Tualatin Mountains, Oregon
The Tualatin Mountains form a northwest-striking ridge about 350 m high that separates Portland, Oregon, from the cities of the Tualatin Valley to the west. Known informally as the Portland Hills, the ridge is a late Cenozoic anticline, bounded by reverse faults that dip toward the anticlinal axis. The anticline is a broad, open fold consisting chiefly of Miocene Columbia River Basalt Group, withA tunnel runs through it: an inside view of the Tualatin Mountains, Oregon
The Tualatin Mountains form a northwest-striking ridge about 350 m high that separates Portland, Oregon, from the cities of the Tualatin Valley to the west. Known informally as the Portland Hills, the ridge is a late Cenozoic anticline, bounded by reverse faults that dip toward the anticlinal axis. The anticline is a broad, open fold consisting chiefly of Miocene Columbia River Basalt Group, withEarthquake hazards and lifelines in the Interstate 5 urban corridor: Woodburn, Oregon, to Centralia, Washington
The Interstate 5 highway (I-5) corridor, which stretches from Mexico to Canada, is both the main economic artery of the Pacific Northwest and home to the majority of Oregonians and Washingtonians. Accordingly, most regional utility and transportation systems have major components located within the I-5 corridor. For the purposes of this map, we refer to these essential systems as lifeline systems.Earthquake hazards and lifelines in the Interstate 5 urban corridor: Cottage Grove to Woodburn, Oregon
The Interstate 5 highway (I-5) corridor, which stretches from Mexico to Canada, is both the main economic artery of the Pacific Northwest and home to the majority of Oregonians and Washingtonians. Accordingly, most regional utility and transportation systems have major components located within the I-5 corridor. For the purposes of this map, we refer to these essential systems as lifeline systems.Earthquake Hazards and lifelines in the Interstate 5 urban corridor - Woodburn, Oregon, to Centralia, Washington
The Interstate 5 highway (I-5) corridor, which stretches from Mexico to Canada, is both the main economic artery of the Pacific Northwest and home to the majority of Oregonians and Washingtonians. Accordingly, most regional utility and transportation systems have major components located within the I-5 corridor. For the purposes of this map, we refer to these essential systems as lifeline systems.Earthquake hazards and lifelines in the Interstate 5 Urban Corridor - Cottage Grove to Woodburn, Oregon
The Interstate 5 highway (I-5) corridor, which stretches from Mexico to Canada, is both the main economic artery of the Pacific Northwest and home to the majority of Oregonians and Washingtonians. Accordingly, most regional utility and transportation systems have major components located within the I-5 corridor. For the purposes of this map, we refer to these essential systems as lifeline systems.Field and laboratory data From an earthquake history study of scarps of the Lake Creek-Boundary Creek fault between the Elwha River and Siebert Creek, Clallam County, Washington
Fault scarps recently discovered on Airborne Laser Swath Mapping (ALSM; also known as LiDAR) imagery show Holocene movement on the Lake Creek–Boundary Creek fault on the north flank of the Olympic Mountains of northwestern Washington State. Such recent movement suggests the fault is a potential source of large earthquakes. As part of the effort to assess seismic hazard in the Puget Sound region, w - Publications
Filter Total Items: 102
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 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 WirthNorthward migration of the Oregon forearc on the Gales Creek fault
The Gales Creek fault (GCF) is a 60-km-long, northwest-striking dextral fault system (west of Portland, Oregon) that accommodates northward motion and uplift of the Oregon Coast Range. New geologic mapping and geophysical models confirm inferred offsets from earlier geophysical surveys and document ∼12 km of right-lateral offset of a basement high in Eocene Siletz River Volcanics since ca. 35 Ma aAuthorsRay Wells, Richard J. Blakely, Sean BemisNew geologic mapping of the northwestern Willamette Valley, Oregon, and its American Viticultural Areas (AVAs)—A foundation for understanding their terroir
A geologic map of the greater Portland, Oregon, metropolitan area is planned that will document the region’s complex geology (currently in review: “Geologic map of the greater Portland metropolitan area and surrounding region, Oregon and Washington,” by Wells, R.E., Haugerud, R.A., Niem, A., Niem, W., Ma, L., Evarts, R., Madin, I., and others). The map, which is planned to be published as a U.S. GAuthorsRay E. Wells, Ralph A. Haugerud, Alan Niem, Wendy Niem, Lina Ma, Ian Madin, Russell C. EvartsHolocene earthquakes of magnitude 7 during westward escape of the Olympic Mountains, Washington
The Lake Creek–Boundary Creek fault, previously mapped in Miocene bedrock as an oblique thrust on the north flank of the Olympic Mountains, poses a significant earthquake hazard. Mapping using 2015 light detection and ranging (lidar) confirms 2004 lidar mapping of postglacial (≥14 km along a splay fault, the Sadie Creek fault, west of Lake Crescent. Scarp morphology suggests repeated earthquake rAuthorsAlan R. Nelson, Stephen Personius, Ray Wells, Elizabeth R. Schermer, Lee-Ann Bradley, Jason Buck, Nadine G. ReitmanEvidence for distributed clockwise rotation of the crust in the northwestern United States from fault geometries and focal mechanisms
Paleomagnetic and GPS data indicate that Washington and Oregon have rotated clockwise for the past 16 Myr. Late Cenozoic and Quaternary fault geometries, seismicity lineaments, and focal mechanisms provide evidence that this rotation is accommodated by north directed thrusting and right-lateral strike-slip faulting in Washington, and SW to W directed normal faulting and right-lateral strike-slip fAuthorsThomas M. Brocher, Ray E. Wells, Andrew P. Lamb, Craig S. WeaverCascadia subduction tremor muted by crustal faults
Deep, episodic slow slip on the Cascadia subduction megathrust of western North America is accompanied by low-frequency tremor in a zone of high fluid pressure between 30 and 40 km depth. Tremor density (tremor epicenters per square kilometer) varies along strike, and lower tremor density statistically correlates with upper plate faults that accommodate northward motion and rotation of forearc bloAuthorsRay Wells, Richard J. Blakely, Aaron G. Wech, Patricia A. McCrory, Andrew MichaelContemporary deformation in the Yakima fold and thrust belt estimated with GPS
Geodetic, geologic and palaeomagnetic data reveal that Oregon (western USA) rotates clockwise at 0.3 to 1.0° Ma−1 (relative to North America) about an axis near the Idaho–Oregon–Washington border, while northeast Washington is relatively fixed. This rotation has been going on for at least 15 Ma. The Yakima fold and thrust belt (YFTB) forms the boundary between northern Oregon and central WashingtoAuthorsRobert McCaffrey, Robert W. King, Ray Wells, Matthew Lancaster, M. Meghan MillerIdentifying block structure in the Pacific Northwest, USA
We have identified block structure in the Pacific Northwest (west of 116°W between 38°N and 49°N) by clustering GPS stations so that the same Euler vector approximates the velocity of each station in a cluster. Given the total number k of clusters desired, the clustering procedure finds the best assignment of stations to clusters. Clustering is calculated for k= 2 to 14. In geographic space, clustAuthorsJames C. Savage, Ray E. WellsGreat (≥Mw8.0) megathrust earthquakes and the subduction of excess sediment and bathymetrically smooth seafloor
Using older and in part flawed data, Ruff (1989) suggested that thick sediment entering the subduction zone (SZ) smooths and strengthens the trench-parallel distribution of interplate coupling. This circumstance was conjectured to favor rupture continuation and the generation of high-magnitude (≥Mw8.0) interplate thrust (IPT) earthquakes. Using larger and more accurate compilations of sediment thiAuthorsDavid W. Scholl, Stephe H. Kirby, Roland E. von Huene, Holly F. Ryan, Ray E. Wells, Eric L. GeistTectonic evolution of the Tualatin basin, northwest Oregon, as revealed by inversion of gravity data
The Tualatin basin, west of Portland (Oregon, USA), coincides with a 110 mGal gravity low along the Puget-Willamette lowland. New gravity measurements (n = 3000) reveal a three-dimensional (3-D) subsurface geometry suggesting early development as a fault-bounded pull-apart basin. A strong northwest-trending gravity gradient coincides with the Gales Creek fault, which forms the southwestern boundarAuthorsDarcy McPhee, Victoria E. Langenheim, Ray Wells, Richard J. BlakelyPreliminary geologic map of the eastern Willapa Hills, Cowlitz, Lewis, and Wahkiakum Counties, Washington
This digital map database and the PDF derived from the database were created from the analog geologic map: Wells, R.E. (1981), “Geologic map of the eastern Willapa Hills, Cowlitz, Lewis, and Wahkiakum Counties, Washington.” The geodatabase replicates the geologic mapping of the 1981 report with minor exceptions along water boundaries and also along the north and south map boundaries. Slight adjustAuthorsRay E. Wells, Michael G. SawlanGeologic history of Siletzia, a large igneous province in the Oregon and Washington Coast Range: Correlation to the geomagnetic polarity time scale and implications for a long-lived Yellowstone hotspot
Siletzia is a basaltic Paleocene and Eocene large igneous province in coastal Oregon, Washington, and southern Vancouver Island that was accreted to North America in the early Eocene. New U-Pb magmatic, detrital zircon, and 40Ar/39Ar ages constrained by detailed field mapping, global nannoplankton zones, and magnetic polarities allow correlation of the volcanics with the 2012 geologic time scale.AuthorsRay Wells, David Bukry, Richard Friedman, Douglas Pyle, Robert Duncan, Peter J. Haeussler, Joe WoodenByEnergy and Minerals Mission Area, Natural Hazards Mission Area, Energy Resources Program, Geomagnetism Program, Groundwater and Streamflow Information Program, Mineral Resources Program, National Laboratories Program, Science and Decisions Center, Geologic Hazards Science Center, Geology, Minerals, Energy, and Geophysics Science Center - News
*Disclaimer: Listing outside positions with professional scientific organizations on this Staff Profile are for informational purposes only and do not constitute an endorsement of those professional scientific organizations or their activities by the USGS, Department of the Interior, or U.S. Government