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Comparison of different earthquake catalogs for the American Samoa swarm from 1 July to 1 November 2022: (a) seismicity rate (number of events per day) versus time, with times of felt reports (Table 1) as green vertical lines, (b) largest magnitude earthquake per day versus time, (c) magnitude of all earthquakes versus time, (d) magnitude–frequency distribution (bars indicate number of events in magnitude bin, lines with dots indicate cumulative number of events), (e) Comparison of single‐station deep‐learning catalog against Comprehensive Catalog (ComCat). (a–d) The colors denote different catalogs: single‐station template‐matching (cyan), single‐station deep‐learning (blue), ComCat (red; USGS Earthquake Hazards Program, 2017), and hydroacoustic (yellow; Wech et al., 2025). (a–c) The pink background shows the early time period (1 July–12 August 2022) when no local stations were available, and the purple background shows the time period (13–19 August 2022) when local network installation was in progress before ComCat event origins were available starting 20 August 2022. (e) The green indicates deep‐learning catalog events where the times of ComCat manually picked and EQTransformer‐picked Pn arrivals (Mousavi et al., 2020) at station IU.AFI agreed within 4 s, gray shows new deep‐learning catalog events not found in ComCat, and orange shows ComCat events missing from the deep‐learning catalog.

Comparison of different earthquake catalogs for the American Samoa swarm fr... Open Access

Published: 14 February 2025
) magnitude of all earthquakes versus time, (d) magnitude–frequency distribution (bars indicate number of events in magnitude bin, lines with dots indicate cumulative number of events), (e) Comparison of single‐station deep‐learning catalog against Comprehensive Catalog (ComCat). (a–d) The colors denote
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Comparison of different earthquake catalogs for the American Samoa swarm from 1 July to 1 November 2022: (a) seismicity rate (number of events per day) versus time, with times of felt reports (Table 1) as green vertical lines, (b) largest magnitude earthquake per day versus time, (c) magnitude of all earthquakes versus time, (d) magnitude–frequency distribution (bars indicate number of events in magnitude bin, lines with dots indicate cumulative number of events), (e) Comparison of single‐station deep‐learning catalog against Comprehensive Catalog (ComCat). (a–d) The colors denote different catalogs: single‐station template‐matching (cyan), single‐station deep‐learning (blue), ComCat (red; USGS Earthquake Hazards Program, 2017), and hydroacoustic (yellow; Wech et al., 2025). (a–c) The pink background shows the early time period (1 July–12 August 2022) when no local stations were available, and the purple background shows the time period (13–19 August 2022) when local network installation was in progress before ComCat event origins were available starting 20 August 2022. (e) The green indicates deep‐learning catalog events where the times of ComCat manually picked and EQTransformer‐picked Pn arrivals (Mousavi et al., 2020) at station IU.AFI agreed within 4 s, gray shows new deep‐learning catalog events not found in ComCat, and orange shows ComCat events missing from the deep‐learning catalog.

Comparison of different earthquake catalogs for the American Samoa swarm fr... Open Access

Published: 14 February 2025
) magnitude of all earthquakes versus time, (d) magnitude–frequency distribution (bars indicate number of events in magnitude bin, lines with dots indicate cumulative number of events), (e) Comparison of single‐station deep‐learning catalog against Comprehensive Catalog (ComCat). (a–d) The colors denote
Journal Article

Status and Performance of the ShakeAlert Earthquake Early Warning System: 2019–2023 Available to Purchase

Angela I. Lux, Deborah Smith, Maren Böse, Jeffrey J. McGuire, Jessie K. Saunders, Minh Huynh, Igor Stubailo, Jennifer Andrews, Gabriel Lotto, Brendan Crowell, Stephen Crane, Richard M. Allen, Douglas Given, Renate Hartog, Thomas Heaton, Allen Husker, Julien Marty, Leland O’Driscoll, Harold Tobin, Sara K. McBride, Douglas Toomey
Published: 16 August 2024
Bulletin of the Seismological Society of America (2024) 114 (6): 3041–3062.
DOI: https://doi.org/10.1785/0120230259
... (ComCat; Guy et al. , 2015 ; U.S. Geological Survey, Earthquake Hazards Program, 2017 ), which contains the earthquake location and magnitude determined using complete waveform data. M 4.5 and larger is the threshold used for public alerting and was deliberately set below the level where damage is likely...
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View PDF for article title, Status and Performance of the ShakeAlert Earthquake Early Warning System: 2019–2023
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Comparison of frequency–magnitude distributions from the ComCat preferred magnitudes (MCC) and MP derived from seismic potency. For small earthquakes, the ComCat preferred magnitude MCC underestimates MP, resulting in a lower apparent b‐value for MCC than for MP (dashed lines). The distribution of MP is truncated around ∼2.7 because the ComCat catalog we analyze only includes events with MCC 2.0 or greater. MCC values in the 2–3 range are systematically corrected to higher values when converting to MP.

Comparison of frequency–magnitude distributions from the ComCat preferred m... Open Access

Published: 24 September 2024
Figure 4. Comparison of frequency–magnitude distributions from the ComCat preferred magnitudes ( M CC ) and M P derived from seismic potency. For small earthquakes, the ComCat preferred magnitude M CC underestimates M P , resulting in a lower apparent b ‐value
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Comparison of the number of stations with either P or S picks for the 2605 ComCat events (USGS Earthquake Hazards Program, 2017) provided by PRSN (University of Puerto Rico, 1986), with 997 before and 1608 during the sequence, located within the volume in Table 1, that were missed by EQT (Mousavi et al., 2020). These 2D histograms count the number of missed events belonging to each “number of stations” bin; diagonal black dashed lines indicate the same number of stations on both axes. (a) ComCat‐only station comparison: number of missed events with analyst picks on stations with continuous data from Table S1 (horizontal axis), against the number of missed events with analyst picks on all available stations (vertical axis). (b) EQT‐ComCat station comparison: number of missed events with analyst picks from ComCat on stations with continuous data from Table S1 (horizontal axis), against the number of missed events with EQT picks within 15 s of event origin time (vertical axis). Events inside the red dashed rectangle had EQT picks on two or fewer stations. (c) Breakdown of the 2605 missed ComCat events by the number of stations (0, 1, 2, 3, 4, and 5+) containing EQT picks. The color version of this figure is available only in the electronic edition.

Comparison of the number of stations with either P or S picks for the 2... Available to Purchase

Published: 06 July 2023
Figure 4. Comparison of the number of stations with either P or S picks for the 2605 ComCat events ( USGS Earthquake Hazards Program, 2017 ) provided by PRSN ( University of Puerto Rico, 1986 ), with 997 before and 1608 during the sequence, located within the volume in Table  1 , that were
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Comparisons of (a) gCent centroid depth and (b) magnitude to ComCat and Global CMT catalog values. gCent centroid depths are shifted by the elevation of their centroid location to reflect depth relative to mean sea level (MSL). Vertical bars in panel (a) indicate fixed depths in the ComCat (10 and 35 km) and Global CMT (12 km) catalogs. The red and black curves in panel (b) are log fits to distribution of ComCat and Global CMT magnitudes that show variation from the 1:1 comparison. The color version of this figure is available only in the electronic edition.

Comparisons of (a) gCent centroid depth and (b) magnitude to ComCat and Glo... Available to Purchase

Published: 15 September 2022
Figure 9. Comparisons of (a) gCent centroid depth and (b) magnitude to ComCat and Global CMT catalog values. gCent centroid depths are shifted by the elevation of their centroid location to reflect depth relative to mean sea level (MSL). Vertical bars in panel (a) indicate fixed depths
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Recent Alaska earthquakes ( USGS ComCat, 2022 ); refer to Figures 1 and ... Open Access

Published: 01 November 2024
Table 1. Recent Alaska earthquakes ( USGS ComCat, 2022 ); refer to Figures 1 and 2 for locations Date M Name Tectonic setting and focal mechanism 28/7/21 8.2 Chignik Interface, reverse 19/10/20 7.6 Shumagin Islands Intraslab, strike-slip 21/7/20 7.8 Shumagin
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Frequency–magnitude distributions for different ComCat‐preferred magnitude types of western U.S. earthquakes (1950–2024). For small earthquakes, local and duration magnitudes (ML and MD) predominate, whereas for larger events, moment magnitudes Mw, body‐wave magnitudes Mb, or occasionally surface‐wave magnitudes Ms are usually preferred if available. A small fraction of events, mostly small ones, have unknown, helicorder or another nonstandard magnitude type (MU). The composite distribution combining all of the preferred magnitude types is shown in black for reference.

Frequency–magnitude distributions for different ComCat‐preferred magnitude ... Open Access

Published: 24 September 2024
Figure 1. Frequency–magnitude distributions for different ComCat‐preferred magnitude types of western U.S. earthquakes (1950–2024). For small earthquakes, local and duration magnitudes ( M L and M D ) predominate, whereas for larger events, moment magnitudes M w , body
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Mislocations between gCent centroid locations, ComCat epicenters, and Global CMT centroid locations. (a) Map illustrating ComCat epicenter locations relative to gCent centroid locations. (b) Map illustrating Global CMT centroid locations relative to gCent centroid locations. Dots in panels (a) and (b) indicate the location of the gCent centroid. (c,d) Polar plots showing the azimuth and distance of mislocation between the (c) gCent and ComCat epicenter and (d) Global CMT. All points that are in panels (c) and (d) are reported relative to the gCent location. Polar plots divided by region are shown in Figure S1. The color version of this figure is available only in the electronic edition.

Mislocations between gCent centroid locations, ComCat epicenters, and Globa... Available to Purchase

Published: 15 September 2022
Figure 8. Mislocations between gCent centroid locations, ComCat epicenters, and Global CMT centroid locations. (a) Map illustrating ComCat epicenter locations relative to gCent centroid locations. (b) Map illustrating Global CMT centroid locations relative to gCent centroid locations. Dots
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Performance and alerting contours for the largest aftershock (M 5.3). (a) Epicenter location error for EPIC (blue) and bEPIC (yellow) in kilometers. (b) Magnitude estimates from EPIC and bEPIC compared with the ComCat magnitude (gray dashed line). (c) Comparison of the expected modified Mercalli intensity (MMI) 4 alerting contour between EPIC and bEPIC based on the alert location and magnitude histories from panels (a) and (b). This is compared with the expected alerting contour based on the static ComCat location and magnitude (black polygon). The pink squares are stations included in the ShakeAlert network.

Performance and alerting contours for the largest aftershock ( M  5.3). (a)... Open Access

Published: 26 March 2025
Figure 5. Performance and alerting contours for the largest aftershock ( M  5.3). (a) Epicenter location error for EPIC (blue) and bEPIC (yellow) in kilometers. (b) Magnitude estimates from EPIC and bEPIC compared with the ComCat magnitude (gray dashed line). (c) Comparison of the expected
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Earthquake locations. (a) USGS ComCat mainshock (large red circle), foreshock (yellow), and 5687 aftershocks (until 1 April 2023). First‐day aftershock lateral extent as a proxy suggests a rupture length of ∼25–30 km. The aftershock region rapidly expanded north and south (orange) and then east (cyan and dark gray). (b) In red, HYPOINVERSE absolute locations of 1446 events (foreshock, mainshock, and aftershocks) show tighter distribution than the same events from the USGS (gray circles). Triangles show temporary seismic stations. The mainshock moved ∼15 km south‐southeast and is now consistent with aftershocks. (c) VELEST absolute locations with a VELEST‐derived 1D velocity model (Fig. 5). Otherwise as panel (b). (d) hypoDD relative locations of 1401 events with the VELEST 1D model. Colors indicate temporal distribution, as in the upper left. Note: Tight relative locations from absolute and cross‐correlation differential travel times. Foreshock size is exaggerated (2×) for visibility. The color version of this figure is available only in the electronic edition.

Earthquake locations. (a) USGS ComCat mainshock (large red circle), foresho... Available to Purchase

Published: 04 April 2024
Figure 4. Earthquake locations. (a) USGS ComCat mainshock (large red circle), foreshock (yellow), and 5687 aftershocks (until 1 April 2023). First‐day aftershock lateral extent as a proxy suggests a rupture length of ∼25–30 km. The aftershock region rapidly expanded north and south (orange
Journal Article

Assessment of Seismic Hazard Potential for a Geothermal Field: A Case Study in West Texas Open Access

Victor Salles, Guo‐Chin Dino Huang, Katerine Vallejo, Peter Eichhubl, Shuvajit Bhattacharya, Alexandros Savvaidis
Published: 15 May 2025
The Seismic Record (2025) 5 (2): 185–194.
DOI: https://doi.org/10.1785/0320250006
... the magnitude detection threshold compared to public catalogs (e.g., U.S. Geological Survey ComCat with 35 events in the same period). Manual review and relocation using NonLinLoc and hierarchical clustering with GrowClust3D revealed seven seismic clusters: four clusters align with mapped Quaternary faults...
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View PDF for article title, Assessment of Seismic Hazard Potential for a Geothermal Field: A Case Study in West Texas
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Number of picks comparison between the ComCat catalog (horizontal axis; USGS Earthquake Hazards Program, 2017) and EQT‐REAL‐HypoSVI catalog (vertical axis), displayed as a 2D histogram counting the number of common events belonging to both catalogs and located within the region in Table 1. The comparison for all picks (first column) is divided into two categories: picks for events with origin times within the analyst complete times in Table 4 (second column) and picks for remaining events with origin times during analyst incomplete times (third column). In each row, the number of picks are compared for (a) only P picks, (b) only S picks, and (c) all P and S picks; note the different axes scales. The color version of this figure is available only in the electronic edition.

Number of picks comparison between the ComCat catalog (horizontal axis; US... Available to Purchase

Published: 06 July 2023
Figure 5. Number of picks comparison between the ComCat catalog (horizontal axis; USGS Earthquake Hazards Program, 2017 ) and EQT‐REAL‐HypoSVI catalog (vertical axis), displayed as a 2D histogram counting the number of common events belonging to both catalogs and located within the region
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Detection performance comparison between the deep learning–enhanced catalog (EQT‐REAL‐HypoSVI locations, with local magnitude, without false detections; Fig. 2d), against the ComCat catalog (USGS Earthquake Hazards Program, 2017) provided by PRSN (University of Puerto Rico, 1986), during the southwestern Puerto Rico seismic sequence (SWPRSS) from 28 December 2019 22:00:00 to 1 January 2023 00:00:00 UTC. Figure S7 shows a similar plot from before the SWPRSS, spanning 1 January 2018 00:00:00 to 28 December 2019 22:00:00 UTC. This analysis includes only events inside the volume defined in Table 1. In panels (a) and (b), detection categories are shown by these colors: blue for ComCat events also detected by EQT, cyan for new EQT‐detected events not in ComCat, and red for ComCat events missed by EQT. (a) Binned magnitude–frequency distribution. Venn diagram shows the relative fraction of events in each detection category. (b) Magnitude of events in each detection category as a function of time. (c) Number of events per day (histogram, left vertical axis), and cumulative seismic moment computed from local magnitudes (blue line, right vertical axis) as a function of time.

Detection performance comparison between the deep learning–enhanced catalog... Available to Purchase

Published: 06 July 2023
Figure 3. Detection performance comparison between the deep learning–enhanced catalog (EQT‐REAL‐HypoSVI locations, with local magnitude, without false detections; Fig.  2d ), against the ComCat catalog ( USGS Earthquake Hazards Program, 2017 ) provided by PRSN ( University of Puerto Rico, 1986
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Catalog magnitude (Comprehensive Earthquake Catalog [ComCat]) versus hypocentral distance density plot, in which the legend reports the number of recordings (count) per magnitude–distance combination. The color version of this figure is available only in the electronic edition.

Catalog magnitude (Comprehensive Earthquake Catalog [ComCat]) versus hypoce... Available to Purchase

Published: 08 December 2020
Figure 2. Catalog magnitude (Comprehensive Earthquake Catalog [ComCat]) versus hypocentral distance density plot, in which the legend reports the number of recordings (count) per magnitude–distance combination. The color version of this figure is available only in the electronic edition.
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Map view of model input events from ComCat (M≥2.5, accessed 4 September 2019) from one week preceding to one week following the M 7.1 earthquake (circles). Events that occurred up to and including the M 7.1 are plotted as dark circles, and those that occurred in the week following are light circles. UCERF3 faults traces are drawn as thick black lines, and the extent of the dipping Airport Lake fault surface is outlined in dotted gray lines. The M 7.1 epicenter (largest dark circle) occurred inside the polygon for the Airport Lake fault, whereas the M 6.4 (second largest dark circle) occurred outside of all UCERF3 fault polygons.

Map view of model input events from ComCat ( M ≥ 2.5 , accessed 4 Sep... Available to Purchase

Published: 04 March 2020
Figure 2. Map view of model input events from ComCat ( M ≥ 2.5 , accessed 4 September 2019) from one week preceding to one week following the M  7.1 earthquake (circles). Events that occurred up to and including the M  7.1 are plotted as dark circles, and those that occurred
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Central Oklahoma earthquake characteristics from the USGS COMCAT online system. (a) Earthquakes from the NEIC COMCAT system from 2005 through February 2015. Plot showing cumulative-moment release (top panel). Timeline showing earthquake magnitude versus time (bottom panel). (b) The number of magnitude 4 earthquakes per year from 1990 through 2015.

Central Oklahoma earthquake characteristics from the USGS COMCAT online sys... Available to Purchase

Published: 01 June 2015
Figure 2. Central Oklahoma earthquake characteristics from the USGS COMCAT online system. (a) Earthquakes from the NEIC COMCAT system from 2005 through February 2015. Plot showing cumulative-moment release (top panel). Timeline showing earthquake magnitude versus time (bottom panel). (b
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Shift in location from initial single‐event location from USGS COMCAT to the Hypocentroidal Decomposition (HD) location with typical error ellipses. Not all relocated events are shown to enhance clarity.

Shift in location from initial single‐event location from USGS COMCAT to ... Available to Purchase

Published: 14 September 2016
Figure 3. Shift in location from initial single‐event location from USGS COMCAT to the Hypocentroidal Decomposition ( HD ) location with typical error ellipses. Not all relocated events are shown to enhance clarity.
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Double‐difference earthquake relocations (circles) for aftershocks up to 4 June 2024, using differential travel times from the USGS ComCat (USGS, 2017) picks and singular value decomposition (Waldhauser and Ellsworth, 2000), and vertical profile along A–A′ from west‐northwest to east‐southeast, perpendicular to the N11E focal plane of the mainshock’s focal mechanism available in ComCat (refer to Fig. 1). Topographic profile from 10 m National Elevation Dataset (see Data and Resources) and approximate fault locations and dips from Drake et al. (1996). Surficial fault dips projected to ∼500 m depth; faults may become gentler and merge at depth.

Double‐difference earthquake relocations (circles) for aftershocks up to 4 ... Open Access

Published: 01 October 2024
Figure 5. Double‐difference earthquake relocations (circles) for aftershocks up to 4 June 2024, using differential travel times from the USGS ComCat ( USGS, 2017 ) picks and singular value decomposition ( Waldhauser and Ellsworth, 2000 ), and vertical profile along A–A′ from west‐northwest
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Spatial event density. Comparison of our cataloged events (red circles) and the historic Comprehensive Catalog (ComCat; cyan circles). Events in our new 2‐yr catalog (red circles and red hashes on left and bottom) occur in different locations than the majority of events from the 33‐yr ComCat (cyan circles and cyan hashes on top and right). The highest event density on record in the basin is related to the newly detected Hugo sequence in mid‐eastern Colorado.

Spatial event density. Comparison of our cataloged events (red circles) and... Available to Purchase

Published: 23 May 2018
Figure 5. Spatial event density. Comparison of our cataloged events (red circles) and the historic Comprehensive Catalog (ComCat; cyan circles). Events in our new 2‐yr catalog (red circles and red hashes on left and bottom) occur in different locations than the majority of events from the 33‐yr