Nicholas van der Elst
Nicholas Van der Elst is a scientist in the Earthquake Hazards Program.
Science and Products
Filter Total Items: 20
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
Authors
Morgan T. Page, Nicholas van der Elst
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
Authors
Nicholas van der Elst
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
Authors
Andrew Delorey, Nicholas van der Elst, Paul Johnson
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
Authors
Morgan T. Page, Nicholas van der Elst, Jeanne L. Hardebeck, Karen Felzer, Andrew J. Michael
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
Authors
Nicholas van der Elst, Andrew Delorey, David R. Shelly, Paul Johnson
Induced earthquake magnitudes are as large as (statistically) expected
A major question for the hazard posed by injection-induced seismicity is how large induced earthquakes can be. Are their maximum magnitudes determined by injection parameters or by tectonics? Deterministic limits on induced earthquake magnitudes have been proposed based on the size of the reservoir or the volume of fluid injected. However, if induced earthquakes occur on tectonic faults oriented f
Authors
Nicholas van der Elst, Morgan T. Page, Deborah A. Weiser, Thomas Goebel, S. Mehran Hosseini
Larger aftershocks happen farther away: nonseparability of magnitude and spatial distributions of aftershocks
Aftershocks may be driven by stress concentrations left by the main shock rupture or by elastic stress transfer to adjacent fault sections or strands. Aftershocks that occur within the initial rupture may be limited in size, because the scale of the stress concentrations should be smaller than the primary rupture itself. On the other hand, aftershocks that occur on adjacent fault segments outside
Authors
Nicholas van der Elst, Bruce E. Shaw
Complex faulting associated with the 22 December 2003 Mw 6.5 San Simeon California, earthquake, aftershocks and postseismic surface deformation
We use data from two seismic networks and satellite interferometric synthetic aperture radar (InSAR) imagery to characterize the 22 December 2003 Mw 6.5 San Simeon earthquake sequence. Absolute locations for the mainshock and nearly 10,000 aftershocks were determined using a new three-dimensional (3D) seismic velocity model; relative locations were obtained using double difference. The mainshock l
Authors
Marcia K. McLaren, Jeanne L. Hardebeck, Nicholas van der Elst, Jeffrey R. Unruh, Gerald W. Bawden, J. Luke Blair
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Filter Total Items: 20
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 behavAuthorsMorgan T. Page, Nicholas van der ElstAccounting 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 fAuthorsNicholas van der ElstTidal 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 evidencAuthorsAndrew Delorey, Nicholas van der Elst, Paul JohnsonThree 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 anAuthorsMorgan T. Page, Nicholas van der Elst, Jeanne L. Hardebeck, Karen Felzer, Andrew J. MichaelFortnightly 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 iAuthorsNicholas van der Elst, Andrew Delorey, David R. Shelly, Paul JohnsonInduced earthquake magnitudes are as large as (statistically) expected
A major question for the hazard posed by injection-induced seismicity is how large induced earthquakes can be. Are their maximum magnitudes determined by injection parameters or by tectonics? Deterministic limits on induced earthquake magnitudes have been proposed based on the size of the reservoir or the volume of fluid injected. However, if induced earthquakes occur on tectonic faults oriented fAuthorsNicholas van der Elst, Morgan T. Page, Deborah A. Weiser, Thomas Goebel, S. Mehran HosseiniLarger aftershocks happen farther away: nonseparability of magnitude and spatial distributions of aftershocks
Aftershocks may be driven by stress concentrations left by the main shock rupture or by elastic stress transfer to adjacent fault sections or strands. Aftershocks that occur within the initial rupture may be limited in size, because the scale of the stress concentrations should be smaller than the primary rupture itself. On the other hand, aftershocks that occur on adjacent fault segments outsideAuthorsNicholas van der Elst, Bruce E. ShawComplex faulting associated with the 22 December 2003 Mw 6.5 San Simeon California, earthquake, aftershocks and postseismic surface deformation
We use data from two seismic networks and satellite interferometric synthetic aperture radar (InSAR) imagery to characterize the 22 December 2003 Mw 6.5 San Simeon earthquake sequence. Absolute locations for the mainshock and nearly 10,000 aftershocks were determined using a new three-dimensional (3D) seismic velocity model; relative locations were obtained using double difference. The mainshock lAuthorsMarcia K. McLaren, Jeanne L. Hardebeck, Nicholas van der Elst, Jeffrey R. Unruh, Gerald W. Bawden, J. Luke Blair