USGS scientists Nicholas van der Elst and Alan Yong installing a seismometer near the 2019 Ridgecrest earthquakes in southern California in order to record its aftershocks.
Nicholas van der Elst
Nicholas Van der Elst is a scientist in the Earthquake Hazards Program.
Science and Products
Could the M7.1 Ridgecrest, CA Earthquake Sequence Trigger a Large Earthquake Nearby?
Release Date: SEPTEMBER 30, 2019 Two of the first questions that come to mind for anyone who just felt an earthquake are, “Will there be another one?” and “Will it be larger?”.
The Past Holds the Key to the Future of Aftershock Forecasting
Release Date: MAY 7, 2018 The outcomes of past aftershock sequences can be used to describe the range of possibilities for a current sequence.
Operational Earthquake Forecasting – Implementing a Real-Time System for California
It is well know that every earthquake can spawn others (e.g., as aftershocks), and that such triggered events can be large and damaging, as recently demonstrated by L’Aquila, Italy and Christchurch, New Zealand earthquakes. In spite of being an explicit USGS strategic-action priority (http://pubs.usgs.gov/of/2012/1088; page 32), the USGS currently lacks an automated system with which to...

Seismometer installation in Ridgecrest, California
USGS scientists Nicholas van der Elst and Alan Yong installing a seismometer near the 2019 Ridgecrest earthquakes in southern California in order to record its aftershocks.
Filter Total Items: 27
Onset of aftershocks: Constraints on the Rate-and-State model
Aftershock rates typically decay with time t after the mainshock according to the Omori–Utsu law, R(t)=K(c+t)−p, with parameters K, c, and p. The rate‐and‐state (RS) model, which is currently the most popular physics‐based seismicity model, also predicts an Omori–Utsu decay with p = 1 and a c‐value that depends on the size of the coseismic stress change. Because the mainshock‐induced...
Authors
Sebastian Hainzl, Morgan T. Page, Nicholas van der Elst
Testing rate‐and‐state predictions of aftershock decay with distance
We analyze aftershocks of the 2019 M 7.1 Ridgecrest mainshock and isolated M 5–6 mainshocks in southern California to test predictions made by the rate‐and‐state friction model of Dieterich (1994). Rate‐and‐state friction predicts that the seismicity rate after a stress step follows Omori decay, where the Omori c‐value, which is the saturation in aftershock rate observed at small times...
Authors
Morgan T. Page, Nicholas van der Elst, Sebastian Hainzl
Aftershock forecasting
Aftershocks can compound the impacts of a major earthquake, disrupting recovery efforts and potentially further damaging weakened buildings and infrastructure. Forecasts of the probability of aftershocks can therefore aid decision-making during earthquake response and recovery. Several countries issue authoritative aftershock forecasts. Most aftershock forecasts are based on simple...
Authors
Jeanne L. Hardebeck, Andrea L. Llenos, Andrew J. Michael, Morgan T. Page, Max Schneider, Nicholas van der Elst
a-positive: A robust estimator of the earthquake rate in incomplete or saturated catalogs
Detection thresholds in earthquake catalogs frequently change in time due to station coverage improvements and network saturation effects during active periods such as mainshock-aftershock cascades. This presents a challenge to seismicity-rate estimation; there is a tradeoff between using as low a minimum magnitude as possible to maximize data while not undercounting the rate due to...
Authors
Nicholas van der Elst, Morgan T. Page
Modern products for a vintage event: An update on the 1933 Long Beach, California, earthquake
When a notable earthquake occurs in the United States, a range of familiar real‐ and near‐real‐time products are produced by the U.S. Geological Survey (USGS) Advanced National Seismic System (ANSS), and made available via the ANSS Comprehensive Earthquake Catalog. For historical and early instrumental earthquakes, similar results and products are developed depending on data availability...
Authors
Susan E. Hough, J. Luke Blair, Sonia Ellison, Robert Graves, Scott Haefner, Eric M. Thompson, Nicholas van der Elst, Morgan T. Page, David J. Wald
Fault roughness at seismogenic depths and links to earthquake behavior
Fault geometry affects the initiation, propagation, and cessation of earthquake rupture, as well as, potentially, the statistical behavior of earthquake sequences. We analyze 18,250 (−0.27
Authors
Elizabeth S. Cochran, Morgan T. Page, Nicholas van der Elst, Zachary E. Ross, Daniel T. Trugman
Aftershocks preferentially occur in previously active areas
The clearest statistical signal in aftershock locations is that most aftershocks occur close to their mainshocks. More precisely, aftershocks are triggered at distances following a power‐law decay in distance (Felzer and Brodsky, 2006). This distance decay kernel is used in epidemic‐type aftershock sequence (ETAS) modeling and is typically assumed to be isotropic, even though individual...
Authors
Morgan T. Page, Nicholas van der Elst
Prospective and retrospective evaluation of the U.S. Geological Survey public aftershock forecast for the 2019-2021 Southwest Puerto Rico Earthquake and aftershocks
The Mw 6.4 Southwest Puerto Rico Earthquake of 7 January 2020 was accompanied by a robust fore‐ and aftershock sequence. The U.S. Geological Survey (USGS) has issued regular aftershock forecasts for more than a year since the mainshock, available on a public webpage. Forecasts were accompanied by interpretive and informational material, published in English and Spanish. Informational...
Authors
Nicholas van der Elst, Jeanne L. Hardebeck, Andrew J. Michael, Sara K. McBride, Elizabeth A. Vanacore
Improvements to the Third Uniform California Earthquake Rupture Forecast ETAS Model (UCERF3‐ETAS)
We describe recent improvements to the Third Uniform California Earthquake Rupture Forecast ETAS Model (UCERF3‐ETAS), which continues to represent our most advanced and complete earthquake forecast in terms of relaxing segmentation assumptions and representing multifault ruptures, elastic‐rebound effects, and spatiotemporal clustering (the latter to represent aftershocks and otherwise...
Authors
Ned Field, Kevin R. Milner, Morgan T. Page, William J. Savran, Nicholas van der Elst
B-positive: A robust estimator of aftershock magnitude distribution in transiently incomplete catalogs
The earthquake magnitude-frequency distribution is characterized by the b-value, which describes the relative frequency of large versus small earthquakes. It has been suggested that changes in b-value after an earthquake can be used to discriminate whether that earthquake is part of a foreshock sequence or a more typical mainshock-aftershock sequence, with a decrease in b-value heralding...
Authors
Nicholas van der Elst
Potential duration of aftershocks of the 2020 southwestern Puerto Rico earthquake
AbstractAftershocks (earthquakes clustered spatially and chronologically near the occurrence of a causative earthquake) are ongoing in southwestern Puerto Rico after a series of earthquakes, which include a magnitude 6.4 earthquake that occurred near Barrio Indios, Guayanilla, on January 7, 2020, and affected the surrounding area. This report estimates the expected duration of these...
Authors
Nicholas van der Elst, Jeanne L. Hardebeck, Andrew J. Michael
The U.S. Geological Survey’s Rapid Seismic Array Deployment for the 2019 Ridgecrest Earthquake Sequence
Rapid seismic deployments following large earthquakes capture ephemeral near‐field recordings of aftershocks and ambient noise that can provide valuable data for seismological studies. The U.S. Geological Survey installed 19 temporary seismic stations following the 4 July 2019 Mw 6.4 and 6 July 2019 (UTC) Mw 7.1 earthquakes near the city of Ridgecrest, California. The stations record the...
Authors
Elizabeth S. Cochran, Emily Wolin, Daniel McNamara, Alan K. Yong, David C. Wilson, Mark Alvarez, Nicholas van der Elst, Adria Ruth McClain, Jamison Haase Steidl
Science and Products
Could the M7.1 Ridgecrest, CA Earthquake Sequence Trigger a Large Earthquake Nearby?
Release Date: SEPTEMBER 30, 2019 Two of the first questions that come to mind for anyone who just felt an earthquake are, “Will there be another one?” and “Will it be larger?”.
The Past Holds the Key to the Future of Aftershock Forecasting
Release Date: MAY 7, 2018 The outcomes of past aftershock sequences can be used to describe the range of possibilities for a current sequence.
Operational Earthquake Forecasting – Implementing a Real-Time System for California
It is well know that every earthquake can spawn others (e.g., as aftershocks), and that such triggered events can be large and damaging, as recently demonstrated by L’Aquila, Italy and Christchurch, New Zealand earthquakes. In spite of being an explicit USGS strategic-action priority (http://pubs.usgs.gov/of/2012/1088; page 32), the USGS currently lacks an automated system with which to...

Seismometer installation in Ridgecrest, California
Seismometer installation in Ridgecrest, California
USGS scientists Nicholas van der Elst and Alan Yong installing a seismometer near the 2019 Ridgecrest earthquakes in southern California in order to record its aftershocks.
USGS scientists Nicholas van der Elst and Alan Yong installing a seismometer near the 2019 Ridgecrest earthquakes in southern California in order to record its aftershocks.
Filter Total Items: 27
Onset of aftershocks: Constraints on the Rate-and-State model
Aftershock rates typically decay with time t after the mainshock according to the Omori–Utsu law, R(t)=K(c+t)−p, with parameters K, c, and p. The rate‐and‐state (RS) model, which is currently the most popular physics‐based seismicity model, also predicts an Omori–Utsu decay with p = 1 and a c‐value that depends on the size of the coseismic stress change. Because the mainshock‐induced...
Authors
Sebastian Hainzl, Morgan T. Page, Nicholas van der Elst
Testing rate‐and‐state predictions of aftershock decay with distance
We analyze aftershocks of the 2019 M 7.1 Ridgecrest mainshock and isolated M 5–6 mainshocks in southern California to test predictions made by the rate‐and‐state friction model of Dieterich (1994). Rate‐and‐state friction predicts that the seismicity rate after a stress step follows Omori decay, where the Omori c‐value, which is the saturation in aftershock rate observed at small times...
Authors
Morgan T. Page, Nicholas van der Elst, Sebastian Hainzl
Aftershock forecasting
Aftershocks can compound the impacts of a major earthquake, disrupting recovery efforts and potentially further damaging weakened buildings and infrastructure. Forecasts of the probability of aftershocks can therefore aid decision-making during earthquake response and recovery. Several countries issue authoritative aftershock forecasts. Most aftershock forecasts are based on simple...
Authors
Jeanne L. Hardebeck, Andrea L. Llenos, Andrew J. Michael, Morgan T. Page, Max Schneider, Nicholas van der Elst
a-positive: A robust estimator of the earthquake rate in incomplete or saturated catalogs
Detection thresholds in earthquake catalogs frequently change in time due to station coverage improvements and network saturation effects during active periods such as mainshock-aftershock cascades. This presents a challenge to seismicity-rate estimation; there is a tradeoff between using as low a minimum magnitude as possible to maximize data while not undercounting the rate due to...
Authors
Nicholas van der Elst, Morgan T. Page
Modern products for a vintage event: An update on the 1933 Long Beach, California, earthquake
When a notable earthquake occurs in the United States, a range of familiar real‐ and near‐real‐time products are produced by the U.S. Geological Survey (USGS) Advanced National Seismic System (ANSS), and made available via the ANSS Comprehensive Earthquake Catalog. For historical and early instrumental earthquakes, similar results and products are developed depending on data availability...
Authors
Susan E. Hough, J. Luke Blair, Sonia Ellison, Robert Graves, Scott Haefner, Eric M. Thompson, Nicholas van der Elst, Morgan T. Page, David J. Wald
Fault roughness at seismogenic depths and links to earthquake behavior
Fault geometry affects the initiation, propagation, and cessation of earthquake rupture, as well as, potentially, the statistical behavior of earthquake sequences. We analyze 18,250 (−0.27
Authors
Elizabeth S. Cochran, Morgan T. Page, Nicholas van der Elst, Zachary E. Ross, Daniel T. Trugman
Aftershocks preferentially occur in previously active areas
The clearest statistical signal in aftershock locations is that most aftershocks occur close to their mainshocks. More precisely, aftershocks are triggered at distances following a power‐law decay in distance (Felzer and Brodsky, 2006). This distance decay kernel is used in epidemic‐type aftershock sequence (ETAS) modeling and is typically assumed to be isotropic, even though individual...
Authors
Morgan T. Page, Nicholas van der Elst
Prospective and retrospective evaluation of the U.S. Geological Survey public aftershock forecast for the 2019-2021 Southwest Puerto Rico Earthquake and aftershocks
The Mw 6.4 Southwest Puerto Rico Earthquake of 7 January 2020 was accompanied by a robust fore‐ and aftershock sequence. The U.S. Geological Survey (USGS) has issued regular aftershock forecasts for more than a year since the mainshock, available on a public webpage. Forecasts were accompanied by interpretive and informational material, published in English and Spanish. Informational...
Authors
Nicholas van der Elst, Jeanne L. Hardebeck, Andrew J. Michael, Sara K. McBride, Elizabeth A. Vanacore
Improvements to the Third Uniform California Earthquake Rupture Forecast ETAS Model (UCERF3‐ETAS)
We describe recent improvements to the Third Uniform California Earthquake Rupture Forecast ETAS Model (UCERF3‐ETAS), which continues to represent our most advanced and complete earthquake forecast in terms of relaxing segmentation assumptions and representing multifault ruptures, elastic‐rebound effects, and spatiotemporal clustering (the latter to represent aftershocks and otherwise...
Authors
Ned Field, Kevin R. Milner, Morgan T. Page, William J. Savran, Nicholas van der Elst
B-positive: A robust estimator of aftershock magnitude distribution in transiently incomplete catalogs
The earthquake magnitude-frequency distribution is characterized by the b-value, which describes the relative frequency of large versus small earthquakes. It has been suggested that changes in b-value after an earthquake can be used to discriminate whether that earthquake is part of a foreshock sequence or a more typical mainshock-aftershock sequence, with a decrease in b-value heralding...
Authors
Nicholas van der Elst
Potential duration of aftershocks of the 2020 southwestern Puerto Rico earthquake
AbstractAftershocks (earthquakes clustered spatially and chronologically near the occurrence of a causative earthquake) are ongoing in southwestern Puerto Rico after a series of earthquakes, which include a magnitude 6.4 earthquake that occurred near Barrio Indios, Guayanilla, on January 7, 2020, and affected the surrounding area. This report estimates the expected duration of these...
Authors
Nicholas van der Elst, Jeanne L. Hardebeck, Andrew J. Michael
The U.S. Geological Survey’s Rapid Seismic Array Deployment for the 2019 Ridgecrest Earthquake Sequence
Rapid seismic deployments following large earthquakes capture ephemeral near‐field recordings of aftershocks and ambient noise that can provide valuable data for seismological studies. The U.S. Geological Survey installed 19 temporary seismic stations following the 4 July 2019 Mw 6.4 and 6 July 2019 (UTC) Mw 7.1 earthquakes near the city of Ridgecrest, California. The stations record the...
Authors
Elizabeth S. Cochran, Emily Wolin, Daniel McNamara, Alan K. Yong, David C. Wilson, Mark Alvarez, Nicholas van der Elst, Adria Ruth McClain, Jamison Haase Steidl