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Andrea Llenos

I am a research geophysicist whose research focuses on developing earthquake rate models for seismic hazard forecasts. I use statistical methods to characterize earthquake rate changes in catalogs, investigating the impacts these variations have on short-term earthquake forecasts as well as long-term seismic hazard models. 

Professional Experience

Research Geophysicist, US Geological Survey, Geologic Hazards Science Center, Golden, CO. 2020-present

Research Geophysicist (term), US Geological Survey, Earthquake Science Center, Menlo Park/Moffett Field, CA . 2015-2020

Mendenhall Postdoctoral Fellow, US Geological Survey, Earthquake Science Center, Menlo Park, CA. 2011-2015

Postdoctoral Scholar, Stanford University, Stanford, CA. 2010-2011

Graduate Research Assistant, Woods Hole Oceanographic Institution, Woods Hole, MA. 2004-2010

Visiting Researcher, Institute of Statistical Mathematics, Tokyo, Japan. 2008, 2009

Undergraduate Research Assistant, Dept. of Geo. Sci., Brown University, Providence, RI. 2002-2004

NSF-REU Intern, University of Alaska Fairbanks, Geophysical Institute, Fairbanks, AK. 2003

Undergraduate Research Assistant, Planetary Geosci., Brown University, Providence, RI. 2001

Fellowships and Awards

Excellent Reviewer Award for Earth, Planets and Space. 2019

Editors' Citation for Excellence in Refereeing for Geophysical Research Letters. 2016

USGS Mendenhall Postdoctoral Fellowship. 2011-2013

National Defense Science and Engineering Graduate Fellowship. 2005-2008

Hollister Fellowship, Woods Hole Oceanographic Institution. 2004-2005

Outstanding Student Award (in Mechanical Engineering). 2004

Undergraduate Research and Academics Award (in Geological Science). 2004

Education and Certifications

  • PhD, 2010, Marine Geophysics, MIT/Woods Hole Oceanographic Institution Joint Program in Oceanography

  • ScB, 2004, Geology-Physics/Mathematics (with honors), Brown University, magna cum laude

  • ScB, 2004, Engineering (Mechanical), Brown University

Science and Products

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Understanding Fluid Injection Induced Seismicity

Fluid injection induced seismicity has been reported since the 1960s. There are currently more than 150,000 injection wells associated with oil and gas production in 34 states in the conterminous US. Pore pressure disturbance caused by injection is generally considered the culprit for injection induced seismicity, but, not all injection causes seismicity. It is not well understood what mechanical
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John Wesley Powell Center for Analysis and Synthesis
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Understanding Fluid Injection Induced Seismicity

Fluid injection induced seismicity has been reported since the 1960s. There are currently more than 150,000 injection wells associated with oil and gas production in 34 states in the conterminous US. Pore pressure disturbance caused by injection is generally considered the culprit for injection induced seismicity, but, not all injection causes seismicity. It is not well understood what mechanical
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2017 One-Year Seismic Hazard Forecast for the Central and Eastern United States from Induced and Natural Earthquakes

We produced a one-year 2017 seismic hazard forecast for the central and eastern United States from induced and natural earthquakes that replaces the one-year 2016 forecast, and evaluated the 2016 seismic hazard forecast to improve future assessments. The 2016 forecast indicated high seismic hazard (greater than 1% probability of damaging ground shaking in 1 year) in portions of Oklahoma/Kansas, th
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Earthquake Hazards

2016 One-Year Seismic Hazard Forecast for the Central and Eastern United States from Induced and Natural Earthquakes

A one-year seismic hazard forecast for the Central and Eastern United States (CEUS), based on induced and natural earthquakes, has been produced by the U.S. Geological Survey. The model assumes that earthquake rates calculated from several different time windows will remain relatively stationary and can be used to forecast earthquake hazard and damage intensity for the year 2016. This assessment
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Earthquake Hazards
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Modeling the occurrence of M ∼ 5 caldera collapse-related earthquakes in Kīlauea volcano, Hawai'i

During the 2018 Kīlauea eruption and caldera collapse, M ∼ 5 caldera collapse earthquakes occurred almost daily from mid-May until the beginning of August. While caldera collapses happen infrequently, the collapse-related seismicity damaged nearby structures, and so these events should be included in a complete seismic hazard assessment. Here, we present an approach to forecast the seismic hazard
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Natural Hazards, Earthquake Hazards, Earthquake Science Center, Geologic Hazards Science Center

Regionally Optimized Background Earthquake Rates from ETAS (ROBERE) for probabilistic seismic hazard assessment

We use an epidemic‐type aftershock sequence (ETAS) based approach to develop a regionally optimized background earthquake rates from ETAS (ROBERE) method for probabilistic seismic hazard assessment. ROBERE fits parameters to the full seismicity catalog for a region with maximum‐likelihood estimation, including uncertainty. It then averages the earthquake rates over a suite of catalogs from which f
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Natural Hazards, Earthquake Hazards, Earthquake Science Center

#EarthquakeAdvisory: Exploring discourse between government officials, news media and social media during the Bombay Beach 2016 Swarm

Communicating probabilities of natural hazards to varied audiences is a notoriously difficult task. Many of these challenges were encountered during the 2016 Bombay Beach, California, swarm of ~100 2≤M≤4.3 earthquakes, which began on 26 September 2016 and lasted for several days. The swarm’s proximity to the southern end of the San Andreas fault caused concern that a larger earthquake could be tri
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Natural Hazards, Earthquake Hazards, Earthquake Science Center

Ensembles of ETAS models provide optimal operational earthquake forecasting during swarms: Insights from the 2015 San Ramon, California swarm

Earthquake swarms, typically modeled as time-varying changes in background seismicity that are driven by external processes such as fluid flow or aseismic creep, present challenges for operational earthquake forecasting. While the time decay of aftershock sequences can be estimated with the modified Omori law, it is difficult to forecast the temporal behavior of seismicity rates during a swarm.
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Natural Hazards, Earthquake Hazards, Earthquake Science Center

Improving earthquake forecasts during swarms with a duration model

Earthquake swarms present a challenge for operational earthquake forecasting because they are driven primarily by transient external processes, such as fluid flow, the behavior and duration of which are difficult to predict. In this study, we develop a swarm duration model to estimate how long a swarm is likely to last based on actuarial statistics of previous swarms in a given region. We demonstr
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Natural Hazards, Earthquake Hazards, Earthquake Science Center

Updated California aftershock parameters

Reasenberg and Jones (1989) introduced a statistical model for aftershock rate following a mainshock along with estimates of “generic” California parameter values based on past aftershock sequences. The Reasenberg and Jones (1989) model has been used for decades to issue aftershock forecasts following M≥5 mainshocks in California. Here, we update the “generic” parameters for California through a f
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Natural Hazards, Earthquake Hazards, Earthquake Science Center

2018 one‐year seismic hazard forecast for the central and eastern United States from induced and natural earthquakes

This article describes the U.S. Geological Survey (USGS) 2018 one‐year probabilistic seismic hazard forecast for the central and eastern United States from induced and natural earthquakes. For consistency, the updated 2018 forecast is developed using the same probabilistic seismicity‐based methodology as applied in the two previous forecasts. Rates of earthquakes across the United States M≥3.0 gre
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Natural Hazards, Earthquake Hazards, Geologic Hazards Science Center

Forecasting the (un)productivity of the 2014 M 6.0 South Napa aftershock sequence

The 24 August 2014 Mw 6.0 South Napa mainshock produced fewer aftershocks than expected for a California earthquake of its magnitude. In the first 4.5 days, only 59 M≥1.8 aftershocks occurred, the largest of which was an M 3.9 that happened a little over two days after the mainshock. We investigate the aftershock productivity of the South Napa sequence and compare it with other M≥5.5 California st
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Natural Hazards, Earthquake Hazards, Earthquake Science Center

2017 One‐year seismic‐hazard forecast for the central and eastern United States from induced and natural earthquakes

We produce a one‐year 2017 seismic‐hazard forecast for the central and eastern United States from induced and natural earthquakes that updates the 2016 one‐year forecast; this map is intended to provide information to the public and to facilitate the development of induced seismicity forecasting models, methods, and data. The 2017 hazard model applies the same methodology and input logic tree as t
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Natural Hazards, Earthquake Hazards, Geologic Hazards Science Center

Seismic‐hazard forecast for 2016 including induced and natural earthquakes in the central and eastern United States

The U.S. Geological Survey (USGS) has produced a one‐year (2016) probabilistic seismic‐hazard assessment for the central and eastern United States (CEUS) that includes contributions from both induced and natural earthquakes that are constructed with probabilistic methods using alternative data and inputs. This hazard assessment builds on our 2016 final model (Petersen et al., 2016) by adding sensi
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Natural Hazards, Earthquake Hazards, Geologic Hazards Science Center

Characterizing potentially induced earthquake rate changes in the Brawley Seismic Zone, southern California

The Brawley seismic zone (BSZ), in the Salton trough of southern California, has a history of earthquake swarms and geothermal energy exploitation. Some earthquake rate changes may have been induced by fluid extraction and injection activity at local geothermal fields, particularly at the North Brawley Geothermal Field (NBGF) and at the Salton Sea Geothermal Field (SSGF). We explore this issue by
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Natural Hazards, Earthquake Hazards, Earthquake Science Center

2016 one-year seismic hazard forecast for the Central and Eastern United States from induced and natural earthquakes

The U.S. Geological Survey (USGS) has produced a 1-year seismic hazard forecast for 2016 for the Central and Eastern United States (CEUS) that includes contributions from both induced and natural earthquakes. The model assumes that earthquake rates calculated from several different time windows will remain relatively stationary and can be used to forecast earthquake hazard and damage intensity for
By
Natural Hazards, Earthquake Hazards, Geologic Hazards Science Center

Pre-USGS Publications

Segall, P., A. L. Llenos, S.-H. Yun, A. M. Bradley, and E. M. Syracuse (2013), Time-dependent dike propagation from joint inversion of seismicity and deformation data, J. Geophys. Res. Solid Earth, 118, doi: 10.1002/2013JB010251.
Llenos, A. L., and J. J. McGuire (2011), Detecting aseismic strain transients from seismicity data, J. Geophys. Res., 116, B06305, doi: 10.1029/2010JB007537.
Llenos, A. L., J. J. McGuire, and Y. Ogata (2009), Modeling seismic swarms triggered by aseismic transients, Earth Planet. Sci. Lett., 281, 59-69, doi:10.1016/j.epsl.2009.02.011.
Llenos, A. L., and J. J. McGuire (2007), Influence of fore-arc structure on the extent of great subduction zone earthquakes, J. Geophys. Res., 112, B09301, doi: 10.1029/2007JB004944.

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