David Shelly
I use seismic waveforms, typically recorded at or near the surface, to infer physical processes associated with active faulting. Recent interests include earthquake swarms (and associated fluid-faulting interactions) and tectonic tremor.
I earned my Ph.D. from Stanford University in 2007, focused on understanding the mechanism of "non-volcanic tremor" in the Nankai subudction zone. After finishing my Ph.D., I was a Miller Postdoctoral Fellow at UC Berkeley and a Mendenhall Postdoctoral Fellow in the USGS Earthquake Science Center. From 2010-2018 I was a Research Geophysicist with the USGS Volcano Science Center (California and Yellowstone Volcano Observatories) in Menlo Park, California. I am now a member of the Geologic Hazards Science Center in Golden, Colorado.
I'm working maximize the information we can obtain from seismic records of faulting processes. This information is then combined with other available constraints (e.g. geodetic, geologic, geochemical) to understand what these seismic signals can tell us about physical (tectonic, hydrothermal, and/or magmatic) processes in the subsurface.
Professional Experience
2018-present - Research Geophysicist, Geologic Hazards Science Center, U.S. Geological Survey, Golden, CO
2010-2018 - Research Geophysicist, Volcano Science Center, U.S. Geological Survey, Menlo Park, CA
2008-2010 - Mendenhall Postdoctoral Fellow, Earthquake Science Center, U.S. Geological Survey, Menlo Park, CA
2007-2008 - Miller Postdoctoral Fellow, Department of Earth and Planetary Science, University of California, Berkeley
Education and Certifications
2007 - Ph.D., Geophysics, Stanford University, Stanford, CA
2000 - B.A. Mathematics-Physics, Whitman College, Walla Walla, WA
Honors and Awards
2015 - Editor’s Citation for Excellence in Refereeing, Geophysical Research Letters
2014 - Kavli Fellow, National Academy of Sciences
2012 - Macelwane Medal, presented by the American Geophysical Union for significant contributions to the geophysical sciences by an outstanding early career scientist.
2012 - Fellow, American Geophysical Union
2010 - Editor’s Citation for Excellence in Refereeing, Geophysical Research Letters
Science and Products
Filter Total Items: 25
Identification of low-frequency earthquakes on the San Andreas fault with deep learning
Low-frequency earthquakes are a seismic manifestation of slow fault slip. Their emergent onsets, low amplitudes, and unique frequency characteristics make these events difficult to detect in continuous seismic data. Here, we train a convolutional neural network to detect low-frequency earthquakes near Parkfield, CA using the catalog of Shelly (2017), https://doi.org/10.1002/2017jb014047...
Authors
A. M. Thomas, A. Inbal, J. Searcy, David R. Shelly, R. Bürgmann
Geological constraints on the mechanisms of slow earthquakes
The recognition of slow earthquakes in geodetic and seismological data has transformed the understanding of how plate motions are accommodated at major plate boundaries. Slow earthquakes, which slip more slowly than regular earthquakes but faster than plate motion velocities, occur in a range of tectonic and metamorphic settings. They exhibit spatiotemporal associations with large...
Authors
James D. Kirkpatrick, Åke Fagereng, David R. Shelly
Post-1978 tumescence at Long Valley Caldera, California: A geophysical perspective
Long Valley Caldera has been restless since at least 1978. Prominent symptoms of this unrest include earthquake swarms and tumescence (inflation) centered on the resurgent dome. Over the years, interpretations of physical processes underlying this unrest have varied considerably. Results from a collection of geophysical studies infer the presence and/or active intrusion of magma in the...
Authors
David P. Hill, Emily K. Montgomery-Brown, David R. Shelly, Ashton F. Flinders, Stephanie Prejean
Geodetic measurements of slow slip events southeast of Parkfield, CA
Tremor and low-frequency earthquakes are presumed to be indicative of surrounding slow, aseismic slip that is often below geodetic detection thresholds. This study uses data from borehole seismometers and long-baseline laser strainmeters to observe both the seismic and geodetic signatures of episodic tremor and slip on the Parkfield region of the San Andreas Fault near Cholame, CA. The...
Authors
Brent G. Delbridge, Joshua D. Carmichael, Robert M. Nadeau, David R. Shelly, Roland Burgmann
A high-resolution seismic catalog for the initial 2019 Ridgecrest Earthquake sequence: Foreshocks, aftershocks, and faulting complexity
I use template matching and precise relative relocation techniques to develop a high-resolution earthquake catalog for the initial portion of the 2019 Ridgecrest earthquake sequence, from July 4-16, encompassing the foreshock sequence and the first 10+ days of aftershocks following the Mw 7.1 mainshock. Using 13,525 routinely cataloged events as waveform templates, I detect and precisely...
Authors
David R. Shelly
Anatomy of a caldera collapse: Kīlauea 2018 summit seismicity sequence in high resolution
The 2018 Kīlauea eruption and caldera collapse generated intense cycles of seismicity tied to repeated large seismic (Mw ~5) collapse events associated with magma withdrawal from beneath the summit. To gain insight into the underlying dynamics and aid eruption response, we applied waveform-based earthquake detection and double-difference location as the eruption unfolded. Here, we...
Authors
David R. Shelly, Weston Thelen
Snowmelt-triggered earthquake swarms at the margin of Long Valley Caldera, California
Fluids are well known to influence earthquakes, yet rarely are earthquakes convincingly linked to precipitation. Weak modulation or limited data often leads to ambiguous interpretations. In contrast, here we find that shallow seismicity in the Sierra Nevada range near Long Valley Caldera is strongly modulated by snowmelt. Over 33 years, shallow seismicity rates were ~37 times higher...
Authors
Emily K. Montgomery-Brown, David R. Shelly, Paul A. Hsieh
A 15-year catalog of more than 1 million low-frequency earthquakes: Tracking tremor and slip along the deep San Andreas Fault
Low-frequency earthquakes (LFEs) are small, rapidly recurring slip events that occur on the deep extensions of some major faults. Their collective activation is often observed as a semi-continuous signal known as tectonic (or non-volcanic) tremor. This manuscript presents a catalog of more than 1 million LFEs detected along the central San Andreas Fault from 2001-2016. These events have...
Authors
David R. Shelly
Deep fluid pathways beneath Mammoth Mountain, California, illuminated by migrating earthquake swarms
Although most volcanic seismicity is shallow (within several kilometers of the surface), some volcanoes exhibit deeper seismicity (10 to 30+ km) that may reflect active processes such as magma resupply and volatile transfer. One such volcano is Mammoth Mountain, California, which has also recently exhibited high rates of CO2 discharge at the surface. We perform high-resolution earthquake...
Authors
Alicia J. Hotovec-Ellis, David R. Shelly, David P. Hill, Andrew M. Pitt, Phillip B. Dawson, Bernard A. Chouet
Seismic evidence for significant melt beneath the Long Valley Caldera, California, USA
A little more than 760 ka ago, a supervolcano on the eastern edge of California (United States) underwent one of North America's largest Quaternary explosive eruptions. Over this ~6-day-long eruption, pyroclastic flows blanketed the surrounding ~50 km with more than 1400 km3 of the now-iconic Bishop Tuff, with ashfall reaching as far east as Nebraska. Collapse of the volcano's magma...
Authors
Ashton F. Flinders, David R. Shelly, Phillip B. Dawson, David P. Hill, Barbara Tripoli, Yang Shen
Imaging a crustal low-velocity layer using reflected seismic waves from the 2014 earthquake swarm at Long Valley Caldera, California: The magmatic system roof?
The waveforms generated by the 2014 Long Valley Caldera earthquake swarm recorded at station MLH show clear reflected waves that are often stronger than direct P and S waves. With waveform analyses, we discover that these waves are reflected at the top of a low-velocity body, which may be residual magma from the ∼767 ka caldera-forming eruption. The polarity of the reflection compared to...
Authors
Nori Nakata, David R. Shelly
Kinematics of the 2015 San Ramon, California earthquake swarm: Implications for fault zone structure and driving mechanisms
Earthquake swarms represent a sudden increase in seismicity that may indicate a heterogeneous fault-zone, the involvement of crustal fluids and/or slow fault slip. Swarms sometimes precede major earthquake ruptures. An earthquake swarm occurred in October 2015 near San Ramon, California in an extensional right step-over region between the northern Calaveras Fault and the Concord–Mt...
Authors
Lian Xue, Roland Bürgmann, David R. Shelly, Christopher Johnson, Taka'aki Taira
Science and Products
Filter Total Items: 25
Identification of low-frequency earthquakes on the San Andreas fault with deep learning
Low-frequency earthquakes are a seismic manifestation of slow fault slip. Their emergent onsets, low amplitudes, and unique frequency characteristics make these events difficult to detect in continuous seismic data. Here, we train a convolutional neural network to detect low-frequency earthquakes near Parkfield, CA using the catalog of Shelly (2017), https://doi.org/10.1002/2017jb014047...
Authors
A. M. Thomas, A. Inbal, J. Searcy, David R. Shelly, R. Bürgmann
Geological constraints on the mechanisms of slow earthquakes
The recognition of slow earthquakes in geodetic and seismological data has transformed the understanding of how plate motions are accommodated at major plate boundaries. Slow earthquakes, which slip more slowly than regular earthquakes but faster than plate motion velocities, occur in a range of tectonic and metamorphic settings. They exhibit spatiotemporal associations with large...
Authors
James D. Kirkpatrick, Åke Fagereng, David R. Shelly
Post-1978 tumescence at Long Valley Caldera, California: A geophysical perspective
Long Valley Caldera has been restless since at least 1978. Prominent symptoms of this unrest include earthquake swarms and tumescence (inflation) centered on the resurgent dome. Over the years, interpretations of physical processes underlying this unrest have varied considerably. Results from a collection of geophysical studies infer the presence and/or active intrusion of magma in the...
Authors
David P. Hill, Emily K. Montgomery-Brown, David R. Shelly, Ashton F. Flinders, Stephanie Prejean
Geodetic measurements of slow slip events southeast of Parkfield, CA
Tremor and low-frequency earthquakes are presumed to be indicative of surrounding slow, aseismic slip that is often below geodetic detection thresholds. This study uses data from borehole seismometers and long-baseline laser strainmeters to observe both the seismic and geodetic signatures of episodic tremor and slip on the Parkfield region of the San Andreas Fault near Cholame, CA. The...
Authors
Brent G. Delbridge, Joshua D. Carmichael, Robert M. Nadeau, David R. Shelly, Roland Burgmann
A high-resolution seismic catalog for the initial 2019 Ridgecrest Earthquake sequence: Foreshocks, aftershocks, and faulting complexity
I use template matching and precise relative relocation techniques to develop a high-resolution earthquake catalog for the initial portion of the 2019 Ridgecrest earthquake sequence, from July 4-16, encompassing the foreshock sequence and the first 10+ days of aftershocks following the Mw 7.1 mainshock. Using 13,525 routinely cataloged events as waveform templates, I detect and precisely...
Authors
David R. Shelly
Anatomy of a caldera collapse: Kīlauea 2018 summit seismicity sequence in high resolution
The 2018 Kīlauea eruption and caldera collapse generated intense cycles of seismicity tied to repeated large seismic (Mw ~5) collapse events associated with magma withdrawal from beneath the summit. To gain insight into the underlying dynamics and aid eruption response, we applied waveform-based earthquake detection and double-difference location as the eruption unfolded. Here, we...
Authors
David R. Shelly, Weston Thelen
Snowmelt-triggered earthquake swarms at the margin of Long Valley Caldera, California
Fluids are well known to influence earthquakes, yet rarely are earthquakes convincingly linked to precipitation. Weak modulation or limited data often leads to ambiguous interpretations. In contrast, here we find that shallow seismicity in the Sierra Nevada range near Long Valley Caldera is strongly modulated by snowmelt. Over 33 years, shallow seismicity rates were ~37 times higher...
Authors
Emily K. Montgomery-Brown, David R. Shelly, Paul A. Hsieh
A 15-year catalog of more than 1 million low-frequency earthquakes: Tracking tremor and slip along the deep San Andreas Fault
Low-frequency earthquakes (LFEs) are small, rapidly recurring slip events that occur on the deep extensions of some major faults. Their collective activation is often observed as a semi-continuous signal known as tectonic (or non-volcanic) tremor. This manuscript presents a catalog of more than 1 million LFEs detected along the central San Andreas Fault from 2001-2016. These events have...
Authors
David R. Shelly
Deep fluid pathways beneath Mammoth Mountain, California, illuminated by migrating earthquake swarms
Although most volcanic seismicity is shallow (within several kilometers of the surface), some volcanoes exhibit deeper seismicity (10 to 30+ km) that may reflect active processes such as magma resupply and volatile transfer. One such volcano is Mammoth Mountain, California, which has also recently exhibited high rates of CO2 discharge at the surface. We perform high-resolution earthquake...
Authors
Alicia J. Hotovec-Ellis, David R. Shelly, David P. Hill, Andrew M. Pitt, Phillip B. Dawson, Bernard A. Chouet
Seismic evidence for significant melt beneath the Long Valley Caldera, California, USA
A little more than 760 ka ago, a supervolcano on the eastern edge of California (United States) underwent one of North America's largest Quaternary explosive eruptions. Over this ~6-day-long eruption, pyroclastic flows blanketed the surrounding ~50 km with more than 1400 km3 of the now-iconic Bishop Tuff, with ashfall reaching as far east as Nebraska. Collapse of the volcano's magma...
Authors
Ashton F. Flinders, David R. Shelly, Phillip B. Dawson, David P. Hill, Barbara Tripoli, Yang Shen
Imaging a crustal low-velocity layer using reflected seismic waves from the 2014 earthquake swarm at Long Valley Caldera, California: The magmatic system roof?
The waveforms generated by the 2014 Long Valley Caldera earthquake swarm recorded at station MLH show clear reflected waves that are often stronger than direct P and S waves. With waveform analyses, we discover that these waves are reflected at the top of a low-velocity body, which may be residual magma from the ∼767 ka caldera-forming eruption. The polarity of the reflection compared to...
Authors
Nori Nakata, David R. Shelly
Kinematics of the 2015 San Ramon, California earthquake swarm: Implications for fault zone structure and driving mechanisms
Earthquake swarms represent a sudden increase in seismicity that may indicate a heterogeneous fault-zone, the involvement of crustal fluids and/or slow fault slip. Swarms sometimes precede major earthquake ruptures. An earthquake swarm occurred in October 2015 near San Ramon, California in an extensional right step-over region between the northern Calaveras Fault and the Concord–Mt...
Authors
Lian Xue, Roland Bürgmann, David R. Shelly, Christopher Johnson, Taka'aki Taira