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Fred F Pollitz

Fred Pollitz is a research geophysicist with the U.S. Geological Survey. He received his Ph.D in Geophysics (long-period seismology) from Princeton University in 1989, advised by Tony Dahlen.

As a postdoctoral researcher he switched focus to crustal deformation studies, motivated initially through collaboration with Dr. Selwyn Sacks at the Carnegie Institution of Washington.  With the USGS since 2000, he has continued to work on problems related to crustal deformation and long-period seismology.

Education:

B.Sc. in Mathematics, Massachusetts Institute of Technology, Cambridge, MA USA (1984)

B.Sc. in Geophysics, Massachusetts Institute of Technology, Cambridge, MA USA (1984)

Ph.D. in Geophysics, Princeton University, Princeton, NJ USA (1989)

Professional Experience:

1997 to 2000:  Postdoctoral Researcher, University of California, Davis
1995 to 1997:  Isaac Newton Trust Postdoctoral Fellow, University of Cambridge, England
1993 to 1995:  Alexander von Humboldt Postdoctoral Fellow, Geophysical Institute, Karlsruhe, Germany
1992 to 1993:  CNRS Research Associate, Laboratoire de Sismologie, Institut de Physique du Globe, Paris
1989 to 1991:  Postdoctoral Fellow, Department of Terrestrial Magnetism, Carnegie Institution of Washington

Honors and Offices:

2010 - First author of two of the 20 most cited `earthquake’ papers of the period
           2000-2010
           (http://www.sciencewatch.com/ana/st/earthquakes2/papers10yr/)
2002 - 2013 - Associate Editor, Bulletin of the Seismological Society of America
1998 - 2001 - Associate Editor, Journal of Geophysical Research

Science and Products

Earthquake geology inputs for the U.S. National Seismic Hazard Model (NSHM) 2023, version 1.0

This Data Release contains preliminary versions of two related databases: 1) A fault sections database ("NSHM2023_FaultSections_v1"), which depicts the geometry of faults capable of hosting independent earthquakes, and 2) An earthquake geology site information database ("NSHM2023_EQGeoDB_v1"), which contains fault slip-rate constraints at points. These databases were prepared in anticipation of up
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Geologic Hazards Science Center
Filter Total Items: 25

Coseismic slip and early afterslip of the M6.0 August 24, 2014 South Napa, California, earthquake

We employ strong motion seismograms and static offsets from the Global Positioning System, Interferometric Synthetic Aperture Radar, and other measurements in order to derive a coseismic slip and afterslip model of the M6.0 24 August 2014 South Napa earthquake. This earthquake ruptured an ∼13‐km‐long portion of the West Napa fault with predominantly right‐lateral strike slip. In the kinematic seis
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Natural Hazards, Earthquake Hazards, Earthquake Science Center

Fault slip associated with the 2 September 2017 M 5.3 Sulphur Peak, Idaho, earthquake and aftershock sequence

The 2 September 2017 M 5.3 Sulphur Peak, Idaho, earthquake is one of the largest earthquakes in southern Idaho since the 1983 M 6.9 Borah Peak earthquake. It was followed by a vigorous aftershock sequence for nearly two weeks that included five events above M 4.5. The coseismic and early postseismic deformation was measured with both Interferometric Synthetic Aperture Radar and Global Positioning
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Natural Hazards, Earthquake Hazards, Earthquake Science Center

Induced seismicity reduces seismic hazard?

Earthquakes caused by human activities have been observed for decades. Often these are related to industrial activities pumping fluids into deep geologic formations, like with wastewater disposal. The simplest theory connecting these processes to earthquakes is straightforward: injection leads to fluid pressure changes that either reduce the strength of preexisting faults or generate new faults. I
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Natural Hazards, Earthquake Hazards, Earthquake Science Center

Sea level rise in the Samoan Islands escalated by viscoelastic relaxation after the 2009 Samoa‐Tonga earthquake

The Samoan islands are an archipelago hosting a quarter million people mostly residing in three major islands, Savai'i and Upolu (Samoa), and Tutuila (American Samoa). The islands have experienced sea level rise by 2–3 mm/year during the last half century. The rate, however, has dramatically increased following the Mw 8.1 Samoa‐Tonga earthquake doublet (megathrust + normal faulting) in September 2
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Natural Hazards, Earthquake Hazards, Earthquake Science Center

Surface imaging functions for elastic reverse time migration

Reverse time migration is often used to interpret acoustic or three‐component seismic recordings by creating an image of subsurface seismic reflectors. Here I describe elastic reverse time migration imaging functions that are cast as waveform misfit sensitivity kernels of contrasts in material parameters across hypothetical seismic discontinuities, that is, specular reflectors. The proposed “surfa
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Natural Hazards, Earthquake Hazards, Earthquake Science Center

Shallow microearthquakes near Chongqing, China triggered by the Rayleigh waves of the 2015 M7.8 Gorkha, Nepal earthquake

We present a case of remotely triggered seismicity in Southwest China by the 2015/04/25 M7.8 Gorkha, Nepal earthquake. A local magnitude ML3.8 event occurred near the Qijiang district south of Chongqing city approximately 12 min after the Gorkha mainshock. Within 30km of this ML3.8 event there are 62 earthquakes since 2009 and only 7 ML>3events, which corresponds to a likelihood of 0.3% for a ML>3
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Natural Hazards, Earthquake Hazards, Earthquake Science Center

Proceedings of the 11th United States-Japan natural resources panel for earthquake research, Napa Valley, California, November 16–18, 2016

The UJNR Panel on Earthquake Research promotes advanced research toward a more fundamental understanding of the earthquake process and hazard estimation. The Eleventh Joint meeting was extremely beneficial in furthering cooperation and deepening understanding of problems common to both Japan and the United States.The meeting included productive exchanges of information on approaches to systematic
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Natural Hazards, Earthquake Hazards, Earthquake Science Center

Viscoelastic lower crust and mantle relaxation following the 14–16 April 2016 Kumamoto, Japan, earthquake sequence

The 2016 Kumamoto, Japan, earthquake sequence, culminating in the Mw=7.0 16 April 2016 main shock, occurred within an active tectonic belt of central Kyushu. GPS data from GEONET reveal transient crustal motions from several millimeters per year up to ∼3 cm/yr during the first 8.5 months following the sequence. The spatial pattern of horizontal postseismic motions is shaped by both shallow aftersl
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Natural Hazards, Earthquake Hazards, Earthquake Science Center

Connecting crustal seismicity and earthquake-driven stress evolution in Southern California

Tectonic stress in the crust evolves during a seismic cycle, with slow stress accumulation over interseismic periods, episodic stress steps at the time of earthquakes, and transient stress readjustment during a postseismic period that may last months to years. Static stress transfer to surrounding faults has been well documented to alter regional seismicity rates over both short and long time scal
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Natural Hazards, Earthquake Hazards, Earthquake Science Center

A note on adding viscoelasticity to earthquake simulators

Here, I describe how time‐dependent quasi‐static stress transfer can be implemented in an earthquake simulator code that is used to generate long synthetic seismicity catalogs. Most existing seismicity simulators use precomputed static stress interaction coefficients to rapidly implement static stress transfer in fault networks with typically tens of thousands of fault patches. The extension to qu
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Natural Hazards, Earthquake Hazards, Earthquake Science Center

Geodetic slip model of the 3 September 2016 Mw 5.8 Pawnee, Oklahoma, earthquake: Evidence for fault‐zone collapse

The 3 September 2016 Mw 5.8 Pawnee earthquake in northern Oklahoma is the largest earthquake ever recorded in Oklahoma. The coseismic deformation was measured with both Interferometric Synthetic Aperture Radar and Global Positioning System (GPS), with measureable signals of order 1 cm and 1 mm, respectively. We derive a coseismic slip model from Sentinel‐1A and Radarsat 2 interferograms and GPS st
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Natural Hazards, Earthquake Hazards, Earthquake Science Center

Implications of the earthquake cycle for inferring fault locking on the Cascadia megathrust

GPS velocity fields in the Western US have been interpreted with various physical models of the lithosphere-asthenosphere system: (1) time-independent block models; (2) time-dependent viscoelastic-cycle models, where deformation is driven by viscoelastic relaxation of the lower crust and upper mantle from past faulting events; (3) viscoelastic block models, a time-dependent variation of the block
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Natural Hazards, Earthquake Hazards, Earthquake Science Center

Pre-USGS Publications

Han, L., Peng, Z., Johnson, C. W., Pollitz, F.F., Wang, B., Li, L., Wang, B., Wu, J., Li, Q., and Wei, H., "Shallow microearthquakes near Chongqing, China triggered by the Rayleigh waves of the 2015 M7.8 Gorkha, Nepal earthquake", Earth Planet. Sci. Lett., 479, 231-240, 2017.

STATIC1D

These programs solve the equations of static equilibrium in a spherically layered isotropic medium using a decomposition into spheroidal and toroidal motions.

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Earthquake Hazards

Direct Green's Function Synthetic Seismograms

These programs are an implementation of the Direct Green’s Function method described by Friederich and Dalkolmo (1995) and Dalkolmo (1993).

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Earthquake Hazards

VISCO1D

VISCO1D-v3 is a program package to calculate quasi-static deformation on a layered spherical Earth from a specified input source (fault plane parameters) at specified points on the surface or at depth.

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Earthquake Hazards

Science and Products