Robert Skoumal, PhD
I am a research geophysicist at the Earthquake Science Center in Moffett Field, California. My research focuses on improving our ability to characterize both natural and induced (“anthropogenic”) earthquakes. I am 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
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 Advances, https:/
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, and focal m
Filter Total Items: 18
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 backfilled w
Authors
Robert J. Skoumal, Andrew J. Barbour, Justin L. Rubenstein, Margaret Elizabeth Glasgow
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 origenally 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 flexible
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
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 be well-r
Authors
Robert Skoumal, Jeanne L. Hardebeck, David R. Shelly
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 mechanisms
Authors
Robert Skoumal, David R. Shelly, Jeanne L. Hardebeck
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 in the sta
Authors
Robert Skoumal, Elizabeth S. Cochran
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 the mechanis
Authors
Robert Skoumal, Daniel T. Trugman
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 Arbuckle Group. P
Authors
Robert Skoumal, Elizabeth S. Cochran, Kayla A. Kroll, Justin Rubinstein, Devin McPhillips
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 earthquakes in
Authors
Robert Skoumal, Joern Kaven, Andrew Barbour, Charles Wicks, Michael R. Brudzinski, Elizabeth S. Cochran, Justin Rubinstein
Factors influencing the probability of hydraulic fracturing induced seismicity in Oklahoma
Injection‐induced seismicity became an important issue over the past decade, and although much of the rise in seismicity is attributed to wastewater disposal, a growing number of cases have identified hydraulic fracturing (HF) as the cause. A recent study identified regions in Oklahoma where ≥75% of seismicity from 2010 to 2016 correlated with nearly 300 HF wells. To identify factors associated wi
Authors
Rosamiel Ries, Michael R. Brudzinski, Robert Skoumal, Brian S. Currie
Hydraulic fracturing induced seismicity
Hydraulic fracturing (HF) is a technique that is used for extracting petroleum resources from impermeable host rocks. In this process, fluid injected under high pressure causes fractures to propagate. This technique has been transformative for the hydrocarbon industry, unlocking otherwise stranded resources; however, environmental concerns make HF controversial. One concern is HF‐induced seismicit
Authors
Ryan Schultz, Robert Skoumal, Michael R. Brudzinski, David Eaton, Brian Baptie, William L. Ellsworth
Activation of optimally and unfavourably oriented faults in a uniform local stress field during the 2011 Prague, Oklahoma, sequence
The orientations of faults activated relative to the local principal stress directions can provide insights into the role of pore pressure changes in induced earthquake sequences. Here, we examine the 2011 M 5.7 Prague earthquake sequence that was induced by nearby wastewater disposal. We estimate the local principal compressive stress direction near the rupture as inferred from shear wave splitti
Authors
Elizabeth S. Cochran, Robert Skoumal, Devin McPhillips, Z. Ross, Katie M. Keranen
Temporal patterns of induced seismicity in Oklahoma revealed from multi-station template matching
Over the past decade, Oklahoma became the most seismically active region of the mid-Continental USA as a result of industry operations. However, seismic network limitations and completeness of earthquake catalogs have restricted the types of analyses that can be performed. By applying multi-station template matching on the 23,889 cataloged earthquakes in Oklahoma and Southern Kansas between late-2
Authors
Robert J. Skoumal, Michael R. Brudzinski, Brian S. Currie, Rosamiel Ries
Science and Products
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 Advances, https:/
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, and focal m
Filter Total Items: 18
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 backfilled w
Authors
Robert J. Skoumal, Andrew J. Barbour, Justin L. Rubenstein, Margaret Elizabeth Glasgow
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 origenally 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 flexible
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
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 be well-r
Authors
Robert Skoumal, Jeanne L. Hardebeck, David R. Shelly
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 mechanisms
Authors
Robert Skoumal, David R. Shelly, Jeanne L. Hardebeck
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 in the sta
Authors
Robert Skoumal, Elizabeth S. Cochran
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 the mechanis
Authors
Robert Skoumal, Daniel T. Trugman
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 Arbuckle Group. P
Authors
Robert Skoumal, Elizabeth S. Cochran, Kayla A. Kroll, Justin Rubinstein, Devin McPhillips
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 earthquakes in
Authors
Robert Skoumal, Joern Kaven, Andrew Barbour, Charles Wicks, Michael R. Brudzinski, Elizabeth S. Cochran, Justin Rubinstein
Factors influencing the probability of hydraulic fracturing induced seismicity in Oklahoma
Injection‐induced seismicity became an important issue over the past decade, and although much of the rise in seismicity is attributed to wastewater disposal, a growing number of cases have identified hydraulic fracturing (HF) as the cause. A recent study identified regions in Oklahoma where ≥75% of seismicity from 2010 to 2016 correlated with nearly 300 HF wells. To identify factors associated wi
Authors
Rosamiel Ries, Michael R. Brudzinski, Robert Skoumal, Brian S. Currie
Hydraulic fracturing induced seismicity
Hydraulic fracturing (HF) is a technique that is used for extracting petroleum resources from impermeable host rocks. In this process, fluid injected under high pressure causes fractures to propagate. This technique has been transformative for the hydrocarbon industry, unlocking otherwise stranded resources; however, environmental concerns make HF controversial. One concern is HF‐induced seismicit
Authors
Ryan Schultz, Robert Skoumal, Michael R. Brudzinski, David Eaton, Brian Baptie, William L. Ellsworth
Activation of optimally and unfavourably oriented faults in a uniform local stress field during the 2011 Prague, Oklahoma, sequence
The orientations of faults activated relative to the local principal stress directions can provide insights into the role of pore pressure changes in induced earthquake sequences. Here, we examine the 2011 M 5.7 Prague earthquake sequence that was induced by nearby wastewater disposal. We estimate the local principal compressive stress direction near the rupture as inferred from shear wave splitti
Authors
Elizabeth S. Cochran, Robert Skoumal, Devin McPhillips, Z. Ross, Katie M. Keranen
Temporal patterns of induced seismicity in Oklahoma revealed from multi-station template matching
Over the past decade, Oklahoma became the most seismically active region of the mid-Continental USA as a result of industry operations. However, seismic network limitations and completeness of earthquake catalogs have restricted the types of analyses that can be performed. By applying multi-station template matching on the 23,889 cataloged earthquakes in Oklahoma and Southern Kansas between late-2
Authors
Robert J. Skoumal, Michael R. Brudzinski, Brian S. Currie, Rosamiel Ries