Robert Skoumal, PhD
Robert is a research geophysicist at the Earthquake Science Center in Moffett Field, California. Hisresearch focuses on improving our ability to characterize both natural and induced (“anthropogenic”) earthquakes. He is particularly interested in developing new methods to characterize small magnitude earthquakes, distinguishing between natural/induced seismicity, and seismogenic fault mapping.
Professional Experience
2020-present: Research Geophysicist, US Geological Survey (Moffett Field, CA)
2016-2020: Mendenhall Postdoctoral Fellow, US Geological Survey (Menlo Park/Moffett Field, CA)
2016: Postdoctoral Scholar, Stanford University (Stanford, CA)
2015: Geophysical Rock Properties R&D Intern, Chevron Corporation (Houston, TX)
2012-2016: Research & Teaching Assistant, Miami University (Oxford, OH)
2011: Teaching Assistant, Eckerd College (St. Petersburg, FL)
2011: NOAA Hollings Scholar (Kenai Peninsula, Alaska)
Education and Certifications
2016: Ph.D. Geology, Miami University (Oxford, OH)
Dissertation: “Characterizing induced and natural earthquake swarms using correlation algorithms”2014: M.S. Geology, Miami University (Oxford, OH)
Thesis: "Optimizing multi-station template matching through re-examination of the Youngstown, Ohio, sequence"2012: B.S. Marine Science (Geophysics) summa cum laude, Eckerd College, (St. Petersburg, FL)
Thesis: "Seasonal and interannual oceanographic variability in Kachemak Bay, Alaska"
Science and Products
Filter Total Items: 22
Low-frequency earthquakes track the motion of a captured slab fragment Low-frequency earthquakes track the motion of a captured slab fragment
Accurate tectonic models are essential for assessing seismic hazard and fault interactions. However, the plate configuration at the complex Mendocino triple junction, where the San Andreas Fault and the Cascadia subduction zone meet, remains uncertain. We analyzed fault slip associated with a recently identified zone of tectonic tremor and low-frequency earthquakes (LFEs) near the...
Authors
David R. Shelly, Amanda M. Thomas, Kathryn Z. Materna, Robert J. Skoumal
S/P amplitude ratios with Distributed Acoustic Sensing and application to earthquake focal mechanisms S/P amplitude ratios with Distributed Acoustic Sensing and application to earthquake focal mechanisms
Distributed acoustic sensing (DAS), which transforms a fiber optic cable into an array of high frequency strainmeters, has the potential to help us characterize earthquakes with a dense sampling of measurements. While earthquake focal mechanisms are frequently determined using P-wave polarities and S/P amplitude ratios with inertial seismometers, the dense sampling of DAS over...
Authors
Robert J. Skoumal, James William Atterholt, Andrew J. Barbour, Jeanne L. Hardebeck
SURF: An automated method for building nonplanar 3D fault models from earthquake hypocenters SURF: An automated method for building nonplanar 3D fault models from earthquake hypocenters
Accurately characterizing 3D fault geometry is vital for improving our understanding of earthquake behavior and informing the development of seismic hazard models. Despite their importance, subsurface fault structures tend to be poorly constrained because of limitations in observational data. Improvements to the seismic networks and earthquake detection algorithms have increased the...
Authors
Travis Vincent Alongi, Austin J. Elliott, Robert J. Skoumal, David R. Shelly, Alexandra Elise Hatem
Local, regional, and distal recordings of seismic unrest at Tau Island volcano, American Samoa Local, regional, and distal recordings of seismic unrest at Tau Island volcano, American Samoa
A seismic swarm near Taʻū Island, a volcanic island in eastern American Samoa, occurred from July to October 2022. The earliest unrest was noted as felt shaking reports in late July, and instrumentation varied in the beginning of the sequence as the U.S. Geological Survey (USGS) Hawaiian Volcano Observatory responded by installing temporary and then permanent seismometers to monitor the...
Authors
Aaron Wech, Matthew M. Haney, Jefferson Chang, A.D. Jolly, Clara Yoon, Robert J. Skoumal
Reduced injection rates and shallower depths mitigated induced seismicity in Oklahoma Reduced injection rates and shallower depths mitigated induced seismicity in Oklahoma
The proximity of wastewater disposal to the Precambrian basement is a critical factor influencing induced earthquake rates in the Central United States, but the impact of reducing injection depths has not been widely demonstrated. Beginning in 2015, state regulatory efforts in Oklahoma and Kansas mandated that wells injecting into the lower Arbuckle Group, a basal sedimentary unit, be...
Authors
Robert J. Skoumal, Andrew J. Barbour, Justin L. Rubenstein, Margaret Elizabeth Glasgow
SKHASH: A python package for computing earthquake focal mechanisms SKHASH: A python package for computing earthquake focal mechanisms
We introduce a Python package for computing focal mechanism solutions. This algorithm, which we refer to as SKHASH, is largely based on the HASH algorithm originally written in Fortran over 20 yr ago. HASH innovated the use of suites of solutions, spanning the expected errors in polarities and takeoff angles, to estimate focal mechanism uncertainty. SKHASH benefits from new features with...
Authors
Robert Skoumal, Jeanne L. Hardebeck, Peter M. Shearer
Using corrected and imputed polarity measurements to improve focal mechanisms in a regional earthquake catalog near the Mt. Lewis Fault Zone, California Using corrected and imputed polarity measurements to improve focal mechanisms in a regional earthquake catalog near the Mt. Lewis Fault Zone, California
We utilized relative polarity measurements and machine learning techniques to better resolve focal mechanisms and stress orientations considering a catalog of ∼29,000 relocated earthquakes that occurred during 1984–2021 in the southeastern San Francisco Bay Area. Earthquake focal mechanisms are commonly produced using P wave first motion polarities, which traditionally requires events to...
Authors
Robert Skoumal, Jeanne L. Hardebeck, David R. Shelly
Using machine learning techniques with incomplete polarity datasets to improve earthquake focal mechanism determination Using machine learning techniques with incomplete polarity datasets to improve earthquake focal mechanism determination
Earthquake focal mechanisms are traditionally produced using P‐wave first‐motion polarities and commonly require well‐recorded seismicity. A recent approach that is less dependent on high signal‐to‐noise exploits similar waveforms to produce relative polarity measurements between earthquake pairs. Utilizing these relative polarity measurements, it is possible to produce composite focal...
Authors
Robert Skoumal, David R. Shelly, Jeanne L. Hardebeck
Wastewater disposal has not significantly altered the regional stress state in southern Kansas Wastewater disposal has not significantly altered the regional stress state in southern Kansas
Wastewater disposal is primarily responsible for the increased seismicity rate since ~2013 in southern Kansas. Previous work that used shear wave splitting (SWS) in southern Kansas interpreted a ~90º temporal rotation in the fast polarization direction and attributed it to increased pore pressures resulting from fluid injection. However, this interpreted rotation coincided with a change...
Authors
Robert Skoumal, Elizabeth S. Cochran
The proliferation of induced seismicity in the Permian Basin, Texas The proliferation of induced seismicity in the Permian Basin, Texas
The Permian Basin has a long history of induced earthquakes, but the seismicity rates have increased dramatically over the past two decades and included a MW 5.0 likely induced by wastewater disposal (WD) in March 2020. A detailed characterization of the proliferation of seismicity in the Permian Basin throughout this time period is needed for improving the scientific understanding of...
Authors
Robert Skoumal, Daniel T. Trugman
Characterizing stress orientations in southern Kansas Characterizing stress orientations in southern Kansas
Induced seismicity predominantly occurs along faults that are optimally oriented to the local principal compressive stress direction, and the characterization of these stress orientations is an important component of understanding seismic hazards. The seismicity rate in southern Kansas rapidly increased in 2013 primarily due to the disposal of large volumes of wastewater into the...
Authors
Robert Skoumal, Elizabeth S. Cochran, Kayla A. Kroll, Justin Rubinstein, Devin McPhillips
The induced Mw 5.0 March 2020 west Texas seismic sequence The induced Mw 5.0 March 2020 west Texas seismic sequence
On March 26, 2020, a M 5.0 earthquake occurred in the Delaware Basin, Texas, near the border between Reeves and Culberson Counties. This was the third largest earthquake recorded in Texas and the largest earthquake in the Central and Eastern United States since the three M 5.0–5.8 induced events in Oklahoma during 2016. Using multistation waveform template matching, we detect 3,940...
Authors
Robert Skoumal, Joern Kaven, Andrew J. Barbour, Charles Wicks, Michael R. Brudzinski, Elizabeth S. Cochran, Justin Rubinstein
Supporting Data for "Subduction intraslab-interface fault interactions in the 2022 Mw 6.4 Ferndale, California, earthquake sequence" Supporting Data for "Subduction intraslab-interface fault interactions in the 2022 Mw 6.4 Ferndale, California, earthquake sequence"
This data release pertains to the December 20, 2022, Mw 6.4 Ferndale, California, earthquake and complements the following publication: Shelly, D. R., D. E. Goldberg, K. Z. Materna, R. J. Skoumal, J. L. Hardebeck., C. E. Yoon, W. L. Yeck, and P. S. Earle (2024). Subduction intraslab-interface fault interactions in the 2022 Mw 6.4 Ferndale, California, earthquake sequence, Science...
High resolution earthquake relocations and focal mechanisms with preferred fault planes for the 2020 Maacama sequence High resolution earthquake relocations and focal mechanisms with preferred fault planes for the 2020 Maacama sequence
This page contains results from analysis of 2020 Maacama earthquake sequence, including the detected and relocated earthquake catalog along with associated focal mechanisms and preferred fault planes as derived in: Shelly, D. R., R. J. Skoumal, and J. L. Hardebeck, Fracture-mesh faulting in the swarm-like 2020 Maacama sequence revealed by high-precision earthquake detection, location...
SURF - Seismicity Utilized for Reconstructing Faults - Python Package SURF - Seismicity Utilized for Reconstructing Faults - Python Package
SURF is an algorithm to generate 3D fault models. This algorithm utilizes open-source, well known and documented packages, to generate fault models that require very few user input parameters.
Science and Products
Filter Total Items: 22
Low-frequency earthquakes track the motion of a captured slab fragment Low-frequency earthquakes track the motion of a captured slab fragment
Accurate tectonic models are essential for assessing seismic hazard and fault interactions. However, the plate configuration at the complex Mendocino triple junction, where the San Andreas Fault and the Cascadia subduction zone meet, remains uncertain. We analyzed fault slip associated with a recently identified zone of tectonic tremor and low-frequency earthquakes (LFEs) near the...
Authors
David R. Shelly, Amanda M. Thomas, Kathryn Z. Materna, Robert J. Skoumal
S/P amplitude ratios with Distributed Acoustic Sensing and application to earthquake focal mechanisms S/P amplitude ratios with Distributed Acoustic Sensing and application to earthquake focal mechanisms
Distributed acoustic sensing (DAS), which transforms a fiber optic cable into an array of high frequency strainmeters, has the potential to help us characterize earthquakes with a dense sampling of measurements. While earthquake focal mechanisms are frequently determined using P-wave polarities and S/P amplitude ratios with inertial seismometers, the dense sampling of DAS over...
Authors
Robert J. Skoumal, James William Atterholt, Andrew J. Barbour, Jeanne L. Hardebeck
SURF: An automated method for building nonplanar 3D fault models from earthquake hypocenters SURF: An automated method for building nonplanar 3D fault models from earthquake hypocenters
Accurately characterizing 3D fault geometry is vital for improving our understanding of earthquake behavior and informing the development of seismic hazard models. Despite their importance, subsurface fault structures tend to be poorly constrained because of limitations in observational data. Improvements to the seismic networks and earthquake detection algorithms have increased the...
Authors
Travis Vincent Alongi, Austin J. Elliott, Robert J. Skoumal, David R. Shelly, Alexandra Elise Hatem
Local, regional, and distal recordings of seismic unrest at Tau Island volcano, American Samoa Local, regional, and distal recordings of seismic unrest at Tau Island volcano, American Samoa
A seismic swarm near Taʻū Island, a volcanic island in eastern American Samoa, occurred from July to October 2022. The earliest unrest was noted as felt shaking reports in late July, and instrumentation varied in the beginning of the sequence as the U.S. Geological Survey (USGS) Hawaiian Volcano Observatory responded by installing temporary and then permanent seismometers to monitor the...
Authors
Aaron Wech, Matthew M. Haney, Jefferson Chang, A.D. Jolly, Clara Yoon, Robert J. Skoumal
Reduced injection rates and shallower depths mitigated induced seismicity in Oklahoma Reduced injection rates and shallower depths mitigated induced seismicity in Oklahoma
The proximity of wastewater disposal to the Precambrian basement is a critical factor influencing induced earthquake rates in the Central United States, but the impact of reducing injection depths has not been widely demonstrated. Beginning in 2015, state regulatory efforts in Oklahoma and Kansas mandated that wells injecting into the lower Arbuckle Group, a basal sedimentary unit, be...
Authors
Robert J. Skoumal, Andrew J. Barbour, Justin L. Rubenstein, Margaret Elizabeth Glasgow
SKHASH: A python package for computing earthquake focal mechanisms SKHASH: A python package for computing earthquake focal mechanisms
We introduce a Python package for computing focal mechanism solutions. This algorithm, which we refer to as SKHASH, is largely based on the HASH algorithm originally written in Fortran over 20 yr ago. HASH innovated the use of suites of solutions, spanning the expected errors in polarities and takeoff angles, to estimate focal mechanism uncertainty. SKHASH benefits from new features with...
Authors
Robert Skoumal, Jeanne L. Hardebeck, Peter M. Shearer
Using corrected and imputed polarity measurements to improve focal mechanisms in a regional earthquake catalog near the Mt. Lewis Fault Zone, California Using corrected and imputed polarity measurements to improve focal mechanisms in a regional earthquake catalog near the Mt. Lewis Fault Zone, California
We utilized relative polarity measurements and machine learning techniques to better resolve focal mechanisms and stress orientations considering a catalog of ∼29,000 relocated earthquakes that occurred during 1984–2021 in the southeastern San Francisco Bay Area. Earthquake focal mechanisms are commonly produced using P wave first motion polarities, which traditionally requires events to...
Authors
Robert Skoumal, Jeanne L. Hardebeck, David R. Shelly
Using machine learning techniques with incomplete polarity datasets to improve earthquake focal mechanism determination Using machine learning techniques with incomplete polarity datasets to improve earthquake focal mechanism determination
Earthquake focal mechanisms are traditionally produced using P‐wave first‐motion polarities and commonly require well‐recorded seismicity. A recent approach that is less dependent on high signal‐to‐noise exploits similar waveforms to produce relative polarity measurements between earthquake pairs. Utilizing these relative polarity measurements, it is possible to produce composite focal...
Authors
Robert Skoumal, David R. Shelly, Jeanne L. Hardebeck
Wastewater disposal has not significantly altered the regional stress state in southern Kansas Wastewater disposal has not significantly altered the regional stress state in southern Kansas
Wastewater disposal is primarily responsible for the increased seismicity rate since ~2013 in southern Kansas. Previous work that used shear wave splitting (SWS) in southern Kansas interpreted a ~90º temporal rotation in the fast polarization direction and attributed it to increased pore pressures resulting from fluid injection. However, this interpreted rotation coincided with a change...
Authors
Robert Skoumal, Elizabeth S. Cochran
The proliferation of induced seismicity in the Permian Basin, Texas The proliferation of induced seismicity in the Permian Basin, Texas
The Permian Basin has a long history of induced earthquakes, but the seismicity rates have increased dramatically over the past two decades and included a MW 5.0 likely induced by wastewater disposal (WD) in March 2020. A detailed characterization of the proliferation of seismicity in the Permian Basin throughout this time period is needed for improving the scientific understanding of...
Authors
Robert Skoumal, Daniel T. Trugman
Characterizing stress orientations in southern Kansas Characterizing stress orientations in southern Kansas
Induced seismicity predominantly occurs along faults that are optimally oriented to the local principal compressive stress direction, and the characterization of these stress orientations is an important component of understanding seismic hazards. The seismicity rate in southern Kansas rapidly increased in 2013 primarily due to the disposal of large volumes of wastewater into the...
Authors
Robert Skoumal, Elizabeth S. Cochran, Kayla A. Kroll, Justin Rubinstein, Devin McPhillips
The induced Mw 5.0 March 2020 west Texas seismic sequence The induced Mw 5.0 March 2020 west Texas seismic sequence
On March 26, 2020, a M 5.0 earthquake occurred in the Delaware Basin, Texas, near the border between Reeves and Culberson Counties. This was the third largest earthquake recorded in Texas and the largest earthquake in the Central and Eastern United States since the three M 5.0–5.8 induced events in Oklahoma during 2016. Using multistation waveform template matching, we detect 3,940...
Authors
Robert Skoumal, Joern Kaven, Andrew J. Barbour, Charles Wicks, Michael R. Brudzinski, Elizabeth S. Cochran, Justin Rubinstein
Supporting Data for "Subduction intraslab-interface fault interactions in the 2022 Mw 6.4 Ferndale, California, earthquake sequence" Supporting Data for "Subduction intraslab-interface fault interactions in the 2022 Mw 6.4 Ferndale, California, earthquake sequence"
This data release pertains to the December 20, 2022, Mw 6.4 Ferndale, California, earthquake and complements the following publication: Shelly, D. R., D. E. Goldberg, K. Z. Materna, R. J. Skoumal, J. L. Hardebeck., C. E. Yoon, W. L. Yeck, and P. S. Earle (2024). Subduction intraslab-interface fault interactions in the 2022 Mw 6.4 Ferndale, California, earthquake sequence, Science...
High resolution earthquake relocations and focal mechanisms with preferred fault planes for the 2020 Maacama sequence High resolution earthquake relocations and focal mechanisms with preferred fault planes for the 2020 Maacama sequence
This page contains results from analysis of 2020 Maacama earthquake sequence, including the detected and relocated earthquake catalog along with associated focal mechanisms and preferred fault planes as derived in: Shelly, D. R., R. J. Skoumal, and J. L. Hardebeck, Fracture-mesh faulting in the swarm-like 2020 Maacama sequence revealed by high-precision earthquake detection, location...
SURF - Seismicity Utilized for Reconstructing Faults - Python Package SURF - Seismicity Utilized for Reconstructing Faults - Python Package
SURF is an algorithm to generate 3D fault models. This algorithm utilizes open-source, well known and documented packages, to generate fault models that require very few user input parameters.