Tom Parsons
I conduct research aimed at improving our ability to forecast hazardous events like earthquakes and tsunamis. Specifically, I study how earthquakes trigger others, how crustal movements cause earthquake stresses, and how to convert geologic observations of earthquake and tsunami processes into quantitative forecasts of use to planners, insurers, and builders.
Professional Experience
1994-Present: Research Geophysicist, U. S. Geological Survey, Menlo Park, CA
1992-1994: National Research Council Postdoctoral Fellow
Education and Certifications
1992 – Ph.D. in Geophysics, Stanford University
1990 – M.S. in Geophysics, Stanford University
1988 – B.S. in Applied Geophysics, UCLA
Affiliations and Memberships*
Editor, AGU Advances, 2019-present
Editor in Chief, Journal of Geophysical Research, Solid Earth, 2009-2015
Editor in Chief, Tectonophysics, 2007-2009
Editorial Board, Tectonophysics, 2005-2007
Editorial Board, Geology, 1995-2000, 2005-2008
Member: Executive Committee, Working Group on California Earthquake Probabilities 2005-present
Member: SCEC Planning Committee, 2007-2009
Honors and Awards
Senior Scientist (ST): 1/15
Fellow American Geophysical Union, Elected 1/12
Fulbright Mutual Educational Exchange Grant USA-Greece: 2007-2008
Alumni Pillar of Achievement: Golden West College Outstanding Alumni Award (10/07)
Fellow Geological Society of America, Elected 10/97
Shoemaker Communication Award (10/00)
National Association of Government Communicators Gold Screen Award (12/00)
National Research Council Post-Doctoral Fellow (8/92)
Science and Products
Three-dimensional velocity structure of Siletzia and other accreted terranes in the Cascadia forearc of Washington
Stress sensitivity of fault seismicity: A comparison between limited-offset oblique and major strike-slip faults
Dipping San Andreas and Hayward faults revealed beneath San Francisco Bay, California
Geologic processes of accretion in the Cascadia subduction zone west of Washington State
Seismic-reflection evidence that the hayward fault extends into the lower crust of the San Francisco Bay Area, California
New seismic images of the cascadia subduction zone from cruise SO 108-ORWELL
More than one way to stretch: A tectonic model for extension along the plume track of the Yellowstone hotspot and adjacent Basin and Range Province
A new view into the Cascadia subduction zone and volcanic arc: Implications for earthquake hazards along the Washington margin
Three-dimensional upper crustal velocity structure beneath San Francisco Peninsula, California
Crustal and upper mantle velocity structure of the Salton Trough, southeast California
Crustal structure of the Colorado Plateau, Arizona: Application of new long-offset seismic data analysis techniques
Velocities of southern Basin and Range xenoliths: Insights on the nature of lower crustal reflectivity and composition
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.
Science and Products
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Filter Total Items: 116
Three-dimensional velocity structure of Siletzia and other accreted terranes in the Cascadia forearc of Washington
Eocene mafic crust with high seismic velocities underlies much of the Oregon and Washington forearc and acts as a backstop for accretion of marine sedimentary rocks from the obliquely subducting Juan de Fuca slab. Arc-parallel migration of relatively strong blocks of this terrane, known as Siletzia, focuses upper crustal deformation along block boundaries, which are potential sources of earthquakeAuthorsT. Parsons, R. E. Wells, M. A. Fisher, E. Flueh, Uri S. ten BrinkStress sensitivity of fault seismicity: A comparison between limited-offset oblique and major strike-slip faults
We present a new three-dimensional inventory of the southern San Francisco Bay area faults and use it to calculate stress applied principally by the 1989 M = 7.1 Loma Prieta earthquake and to compare fault seismicity rates before and after 1989. The major high-angle right-lateral faults exhibit a different response to the stress change than do minor oblique (right-lateral/thrust) faults. SeismicitAuthorsT. Parsons, R. S. Stein, R. W. Simpson, P.A. ReasenbergDipping San Andreas and Hayward faults revealed beneath San Francisco Bay, California
The San Francisco Bay area is crossed by several right-lateral strike-slip faults of the San Andreas fault zone. Fault-plane reflections reveal that two of these faults, the San Andreas and Hayward, dip toward each other below seismogenic depths at 60° and 70°, respectively, and persist to the base of the crust. Previously, a horizontal detachment linking the two faults in the lower crust beneathAuthorsT. Parsons, P. E. HartGeologic processes of accretion in the Cascadia subduction zone west of Washington State
The continental margin west of Oregon and Washington undergoes a northward transition in morphology, from a relatively narrow, steep slope west of Oregon to a broad, midslope terrace off Washington. Multichannel seismic (MCS) reflection data collected over the accretionary complex show that the morphologic transition is accompanied by significant change in accretionary style: West of Oregon the diAuthorsM. A. Fisher, E.R. Flueh, D.W. Scholl, T. Parsons, R. E. Wells, A. Tréhu, Uri S. ten Brink, C. S. WeaverSeismic-reflection evidence that the hayward fault extends into the lower crust of the San Francisco Bay Area, California
This article presents deep seismic-reflection data from an experiment across San Francisco Peninsula in 1995 using large (125 to 500 kg) explosive sources. Shot gathers show a mostly nonreflective upper crust in both the Franciscan and Salinian terranes (juxtaposed across the San Andreas fault), an onset of weak lower-crustal reflectivity beginning at about 6-sec two-way travel time (TWTT) and briAuthorsT. ParsonsNew seismic images of the cascadia subduction zone from cruise SO 108-ORWELL
In April and May 1996, a geophysical study of the Cascadia continental margin off Oregon and Washington was conducted aboard the German R/V Sonne. This cooperative experiment by GEOMAR and the USGS acquired wide-angle reflection and refraction seismic data, using ocean-bottom seismometers (OBS) and hydrophones (OBH), and multichannel seismic reflection (MCS) data. The main goal of this experimentAuthorsE.R. Flueh, M. A. Fisher, J. Bialas, J.R. Childs, D. Klaeschen, Nina Kukowski, T. Parsons, D.W. Scholl, Uri S. ten Brink, A.M. Trehu, N. VidalMore than one way to stretch: A tectonic model for extension along the plume track of the Yellowstone hotspot and adjacent Basin and Range Province
The eastern Snake River Plain of southern Idaho poses a paradoxical problem because it is nearly aseismic and unfaulted although it appears to be actively extending in a SW-NE direction continuously with the adjacent block-faulted Basin and Range Province. The plain represents the 100-km-wide track of the Yellowstone hotspot during the last ???16-17 m.y., and its crust has been heavily intruded byAuthorsT. Parsons, G. A. Thompson, R.P. SmithA new view into the Cascadia subduction zone and volcanic arc: Implications for earthquake hazards along the Washington margin
In light of suggestions that the Cascadia subduction margin may pose a significant seismic hazard for the highly populated Pacific Northwest region of the United States, the U.S. Geological Survey (USGS), the Research Center for Marine Geosciences (GEOMAR), and university collaborators collected and interpreted a 530-km-long wide-angle onshore-offshore seismic transect across the subduction zone aAuthorsT. Parsons, A.M. Trehu, J. H. Luetgert, K. Miller, F. Kilbride, R. E. Wells, M. A. Fisher, E. Flueh, Uri S. ten Brink, N.I. ChristensenThree-dimensional upper crustal velocity structure beneath San Francisco Peninsula, California
This paper presents new seismic data from, and crustal models of the San Francisco Peninsula. In much of central California the San Andreas fault juxtaposes the Cretaceous granitic Salinian terrane on its west and the Late Mesozoic/Early Tertiary Franciscan Complex on its east. On San Francisco Peninsula, however, the present-day San Andreas fault is completely within a Franciscan terrane, and theAuthorsT. Parsons, M.L. ZobackCrustal and upper mantle velocity structure of the Salton Trough, southeast California
This paper presents data and modelling results from a crustal and upper mantle wide-angle seismic transect across the Salton Trough region in southeast California. The Salton Trough is a unique part of the Basin and Range province where mid-ocean ridge/transform spreading in the Gulf of California has evolved northward into the continent. In 1992, the U.S. Geological Survey (USGS) conducted the fiAuthorsT. Parsons, J. McCarthyCrustal structure of the Colorado Plateau, Arizona: Application of new long-offset seismic data analysis techniques
The Colorado Plateau is a large crustal block in the southwestern United States that has been raised intact nearly 2 km above sea level since Cretaceous marine sediments were deposited on its surface. Controversy exists concerning the thickness of the plateau crust and the source of its buoyancy. Interpretations of seismic data collected on the plateau vary as to whether the crust is closer to 40AuthorsT. Parsons, J. McCarthy, W. M. Kohler, C.J. Ammon, H. M. Benz, J.A. Hole, E.E. CrileyVelocities of southern Basin and Range xenoliths: Insights on the nature of lower crustal reflectivity and composition
To reconcile differences between the assessments of crustal composition in the southern Basin and Range province on the basis of seismic refraction and reflection data and lower-crustal xenoliths, we measured velocities of xenoliths from the Cima volcanic field in southern California. Lower-crustal samples studied included gabbro, microgabbro, and pyroxenite. We find that the mafic xenolith velociAuthorsThomas E. Parsons, Nikolas I. Christensen, Howard G. WilshireNon-USGS Publications**
1992, by Parsons, T. et al., Department of Geophysics, Stanford University1992, by Parsons, T., et al., Department of Geophysics, Stanford University1991, by Howie, J.M., et al., Department of Geophysics, Stanford University1991, by Parsons, T., and Thompson, G.A., Department of Geophysics, Stanford University**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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*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