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Nicholas van der Elst

Nicholas Van der Elst is a scientist in the Earthquake Hazards Program.

Science and Products

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Map showing regional faults and Coso field near Ridgecrest

Could the M7.1 Ridgecrest, CA Earthquake Sequence Trigger a Large Earthquake Nearby?

Release Date: SEPTEMBER 30, 2019Two 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?”.
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Natural Hazards, Earthquake Hazards, Earthquake Science Center, Geologic Hazards Science Center
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Could the M7.1 Ridgecrest, CA Earthquake Sequence Trigger a Large Earthquake Nearby?

Release Date: SEPTEMBER 30, 2019Two 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?”.
Learn More
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Map showing aftershocks of 7.8 earthquake in Oaxaca, Mexico

The Past Holds the Key to the Future of Aftershock Forecasting

Release Date: MAY 7, 2018The outcomes of past aftershock sequences can be used to describe the range of possibilities for a current sequence.
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Natural Hazards, Earthquake Hazards
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The Past Holds the Key to the Future of Aftershock Forecasting

Release Date: MAY 7, 2018The outcomes of past aftershock sequences can be used to describe the range of possibilities for a current sequence.
Learn More
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USGS science for a changing world logo

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 forecast s...
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John Wesley Powell Center for Analysis and Synthesis
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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 forecast s...
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Filter Total Items: 15

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 a larger
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Natural Hazards, Earthquake Hazards, Earthquake Science Center

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 aftershocks by
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Natural Hazards, Earthquake Hazards, Earthquake Science Center

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 aftershoc
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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

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

Developing earthquake forecast templates for fast and effective communication

No abstract available.
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Western Geographic 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

Turing-style tests for UCERF3 synthetic catalogs

Epidemic-Type Aftershock Sequence (ETAS) catalogs generated from the 3rd Uniform California Earthquake Rupture Forecast (UCERF3) model are unique in that they are the first to combine a complex, fault-based long-term forecast with short-term earthquake clustering statistics. We present Turing-style tests to examine whether these synthetic catalogs can successfully imitate observed earthquake behav
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Natural Hazards, Earthquake Hazards, Earthquake Science Center

Accounting for orphaned aftershocks in the earthquake background rate

Aftershocks often occur within cascades of triggered seismicity in which each generation of aftershocks triggers an additional generation, and so on. The rate of earthquakes in any particular generation follows Omori's law, going approximately as 1/t. This function decays rapidly, but is heavy-tailed, and aftershock sequences may persist for long times at a rate that is difficult to discriminate f
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Natural Hazards, Earthquake Hazards, Earthquake Science Center

Tidal triggering of earthquakes suggests poroelastic behavior on the San Andreas Fault

Tidal triggering of earthquakes is hypothesized to provide quantitative information regarding the fault's stress state, poroelastic properties, and may be significant for our understanding of seismic hazard. To date, studies of regional or global earthquake catalogs have had only modest successes in identifying tidal triggering. We posit that the smallest events that may provide additional evidenc
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Natural Hazards, Earthquake Hazards, Earthquake Science Center

Three ingredients for Improved global aftershock forecasts: Tectonic region, time-dependent catalog incompleteness, and inter-sequence variability

Following a large earthquake, seismic hazard can be orders of magnitude higher than the long‐term average as a result of aftershock triggering. Because of this heightened hazard, emergency managers and the public demand rapid, authoritative, and reliable aftershock forecasts. In the past, U.S. Geological Survey (USGS) aftershock forecasts following large global earthquakes have been released on an
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Natural Hazards, Earthquake Hazards, Earthquake Science Center

Fortnightly modulation of San Andreas tremor and low-frequency earthquakes

Earth tides modulate tremor and low-frequency earthquakes (LFEs) on faults in the vicinity of the brittle−ductile (seismic−aseismic) transition. The response to the tidal stress carries otherwise inaccessible information about fault strength and rheology. Here, we analyze the LFE response to the fortnightly tide, which modulates the amplitude of the daily tidal stress over a 14-d cycle. LFE rate i
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Natural Hazards, Earthquake Hazards, Earthquake Science Center

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