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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.  To gain insight into these processes, I have worked to develop new techniques for earthquake detection, source location, and focal mechanism dete

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.

Other Recognitions

2015 - Editor’s Citation for Excellence in Refereeing, Geophysical Research Letters

2014 - Kavli Fellow, National Academy of Sciences

2010 - Editor’s Citation for Excellence in Refereeing, Geophysical Research Letters

Publications

Hill, D.P., E. Montgomery-Brown, D. R. Shelly, A. Flinders, and S. P. Prejean (2020), Post-1978 Tumescence at Long Valley Caldera, California: a Geophysical Perspective, Journal of Volcanology and Geothermal Research, https://doi.org/10.

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, Unversity 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

  • 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

    2011 - Presidential Early Career Awards for Scientists and Engineers (PECASE) recipient, the highest honor bestowed by the United States government on science and engineering professionals in the early stages of their independent research careers.

    2011 - Charles F. Richter Early Career Award, Seismological Society of America, awarded to one early career scientist annually for outstanding contributions to the Society

    2008 - Inaugural recipient of the Keiiti Aki Young Scientist Award, American Geophysical Union Seismology Section, given to recognize the scientific accomplishments of a junior scientist who makes outstanding contributions to the advancement of seismology.

Science and Products

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
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Geologic Hazards Science Center

A High-Resolution Seismic Catalog for the Initial 2019 Ridgecrest Earthquake Sequence

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 locate a
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Earthquake Hazards, Geologic Hazards Science Center

High resolution earthquake catalogs from the 2018 Kilauea eruption sequence

The 2018 Kilauea 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 augment these ra
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Earthquake Hazards, Geologic Hazards Science Center
Schematic cross section of the magmatic and hydrothermal systems underlying Yellowstone Caldera
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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
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Natural Hazards, Earthquake Hazards, Volcano Hazards, Earthquake Science Center, Volcano Science Center

Earthquake-derived seismic velocity changes during the 2018 caldera collapse of Kīlauea volcano

The 2018 Kīlauea caldera collapse produced extraordinary sequences of seismicity and deformation, with 62 episodic collapse events which significantly altered the landscape of the summit region. Despite decades of focused scientific studies at Kīlauea, detailed information about the internal structure of the volcano is limited. Recently developed techniques in seismic interferometry can be used to
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Volcano Hazards, Volcano Science Center

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 as trainin
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Volcano Hazards, Volcano Science Center

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 seismic events t
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Natural Hazards, Geologic Hazards Science Center

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 crust. Geol
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Volcano Hazards, Volcano Science Center

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 observed oc
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Natural Hazards, Geologic Hazards Science Center

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 locate a
By
Natural Hazards, Earthquake Hazards, Geologic Hazards Science Center

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 augment these r
By
Natural Hazards, Geologic Hazards Science Center

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 during very we
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Volcano Hazards, Volcano Science Center

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 detection
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Volcano Hazards, Volcano Science Center

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 reservoir crea
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Volcano Hazards, Volcano Science Center

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 been de
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Volcano Hazards, Volcano Science Center
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What causes earthquake swarms at Yellowstone?

Earthquake swarms are common at Yellowstone, but why do they occur?  Are they driven by magma migration?  Water?  Steady creep along faults?  All...

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How Big Was That Earthquake?

Earthquake magnitudes may seem straightforward, but a lot goes into their calculation, and multiple methods can be used.  These methods must account...

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Science and Products