Andrea L. Llenos David R. Shelly Allison M. Shumway 20251119 tabular digital data USGS Data Release na Golden, CO USGS Llenos, A.L., Shelly, D.R., and Shumway, A.M., 2025, Earthquake magnitude conversion and sensitivity catalogs for the central and eastern United States: U.S. Geological Survey data release, https://doi.org/10.5066/P13XZCBA. https://doi.org/10.5066/P13XZCBA Andrea L. Llenos David R. Shelly Allison M. Shumway 2025 publication Seismological Research Letters on-line Albany, CA Seismological Society of America Llenos, A.L., Shelly, D.R., and Shumway, A.M., 2025, Magnitude conversion relations create substantial differences in seismic hazard models: Seismological Research Letters, https://doi.org/10.1785/0220250231. https://doi.org/10.1785/0220250231 Earthquake catalogs are essential data inputs for seismic hazard modeling. Because earthquake magnitudes are reported in a variety of types (e.g., local magnitudes, moment magnitudes), magnitude conversion relationships must be used to convert the different magnitude types present in a catalog to a uniform magnitude type to avoid biases in the hazard computation. However, these conversion relationships are often uncertain and have been shown to sometimes perform poorly. In a corresponding journal publication, we investigate the sensitivity of the gridded seismicity component of the U.S. Geological Survey National Seismic Hazard Model (NSHM) to the catalog conversion equations in the eastern United States. In the 2023 NSHM, magnitudes of various types were converted to moment magnitudes using equations developed by the Central and Eastern United States Seismic Source Characterization for Nuclear Facilities (CEUS-SSCn; U.S. Department of Energy and others, 2012), based on least squares regressions made using data from a catalog containing events up through 2008. We recompute these equations using events in the Advanced National Seismic System Comprehensive Earthquake Catalog (U.S. Geological Survey Earthquake Hazards Program, 2017) with multiple magnitudes from 2000 through 2023 using orthogonal regression methods, which account for uncertainties in both dependent and independent regression variables (observed moment magnitude and alternative magnitude type, respectively). In some cases, we find large differences between the CEUS-SSCn conversion and the newly computed ones, especially at smaller magnitudes. We compare the spatial distribution of annual rates using three different models: 1) the 2023 NSHM conversions, 2) our updated conversions, and 3) no conversions. We find that the choice of conversions leads to substantial differences in the rate forecasts, which can greatly impact the seismic hazard model, particularly in regions with low seismicity rates like the eastern U.S. where the hazard is dominated by gridded seismicity rather than a fault model. This data release includes seismicity catalogs used by Llenos and others (2025) to (1) compute new magnitude conversion equations and (2) perform a gridded seismicity sensitivity analysis. References Llenos, A.L., Shelly, D.R., and Shumway, A.M., 2025, Magnitude conversion relations create substantial differences in seismic hazard models: Seismological Research Letters, https://doi.org/10.1785/0220250231. U.S. Geological Survey, Earthquake Hazards Program, 2017, Advanced National Seismic System Comprehensive Catalog of Earthquake Events and Products: U.S. Geological Survey data release, https://doi.org/10.5066/F7MS3QZH. U.S. Department of Energy, Electric Power Research Institute, and U.S. Nuclear Regulatory Commission, 2012, Central and Eastern United States Seismic Source Characterization for Nuclear Facilities: NUREG-2115, 6 volumes, 3798 p. This data release includes seismicity catalogs used by Llenos and others (2025) to (1) compute new magnitude conversion equations and (2) perform a gridded seismicity sensitivity analysis. See READ_ME.txt files for additional information. 2025 publication date Complete None planned -100.0000 -60.0000 53.0000 23.0000 USGS Thesaurus earthquakes hazards seismology USGS Metadata Identifier USGS:67bfb9d1d34e8876fcbfca21 http://geonames.usgs.gov/ USA Hawaii Alaska Common geographic areas eastern United States none 2023 None. These data are marked with a Creative Common CC0 1.0 Universal License. These data are in the public domain and do not have any use constraints. Users are advised to read the dataset's metadata thoroughly to understand appropriate use and data limitations. Allison M. Shumway U.S. Geological Survey - Rocky Mountain Region Research Geophysicist mailing

Denver Federal Center

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Denver CO 80225 United States 303-273-8402 ashumway@usgs.gov Work was accomplished by the U.S. Geological Survey Geology with funding from the U.S. Nuclear Regulatory Commission. See READ_ME.txt files for additional information. The following report provides information on quality assessment for the data set: Llenos, A.L., Shelly, D.R., and Shumway, A.M., 2025, Magnitude conversion relations create substantial differences in seismic hazard models: Seismological Research Letters, https://doi.org/10.1785/0220250231. See individual data sets for appropriate logical consistency reports. Data sets include seismicity catalogs in the eastern U.S. from 1/1/2000 to 12/31/2023. U.S. Geological Survey 2017 application/service https://earthquake.usgs.gov/earthquakes/search/ Digital and/or Hardcopy 2025 observed Advanced National Seismic System Comprehensive Catalog Seismicity catalogs used to compute new magnitude conversion equations were output from searches of the Advanced National Seismic System Comprehensive Catalog of Earthquake Events. Mark D. Petersen and others. 20231221 tabular digital data https://doi.org/10.5066/P9GNPCOD Digital and/or Hardcopy 2023 publication date Seismicity catalog used for the 2023 50-state NSHM for the conterminous U.S. The 2023 50-state NSHM for the conterminous U.S. seismicity catalog was used as the starting point for the seismicity catalogs used by Llenos and others (2025) for the sensitivity analysis. # Seismicity Catalogs for Development of Magnitude Conversion Equations To develop relationships converting various magnitude types to moment magnitude (Mw or mw), we used events from the area of investigation (25-50º latitude, -100º to –65º longitude) with multiple magnitude types in the Advanced National Seismic System Comprehensive Catalog (U.S. Geological Survey, Earthquake Hazards Program, 2017; ComCat) from 1 January 2000 through 31 December 2023. To make such a search more tractable, we used an internal database implementation of ComCat, provisionally termed “FlatCat” (Hearne and others, 2024). However, all magnitudes retrieved using FlatCat are also publicly available in the standard ComCat. For this study we developed nine separate seismicity catalogs: (1) md vs. mblg - Catalog of events with both md and mblg magnitudes available for comparison File name: catalog_all-mb_lg_noOtt_vs_mdtest2000_2023_Eastof100_pref2.txt (2) ml vs. mblg - Catalog of events with both ml and mblg magnitudes available for comparison File name: catalog_all-mb_lg_noOtt_vs_mltest2000_2023_Eastof100_pref2.txt (3) mblg (Canada) vs. mblg (US) - Catalog of events with both mblg (reported from the Canadian seismic network) and mblg (reported from the US seismic network) available for comparison File name: catalog_all-mb_lg_noOtt_vs_ott_mb_lgtest2000_2023_Eastof100_pref2.txt (4) mblg vs. mw - Catalog of events with both mblg and mw magnitudes available for comparison File name: catalog_all-mw_vs_mb_lg_noOtttest2000_2023_Eastof100_pref2.txt (5) ml vs ms -Catalog of events with both ml and ms magnitudes available for comparison File name: catalog_all-ml_vs_mdtest2000_2023_Eastof100_pref2.txt (6) mb vs. mw - Catalog of events with both mb and mw magnitudes available for comparison File name: catalog_all-mw_vs_mbtest2000_2023_Eastof100_pref2.txt (7) md vs. Mw - Catalog of events with both md and mw magntudes available for comparison File name: catalog_all-mw_vs_mdtest2000_2023_Eastof100_pref2.txt (8) ml vs. mw - Catalog of events with both ml and mw magnitudes available for comparison File name: catalog_all-mw_vs_mltest2000_2023_Eastof100_pref2.txt (9) ms vs. mw - Catalog of events with both ms and mw magnitudes available for comparison File name: catalog_all-mw_vs_mstest2000_2023_Eastof100_pref2.txt A description of each column in the seismicity catalog files is listed below: Column 1: Event-ID (event ID) Column 2: OriginTime (year-month-day hour:minute:second) Column 3: Lat (latitude, degree north) Column 4: Lon (longitude, degree east) Column 5: Depth (km) Column 6: Mag1type (magnitude 1 type) Column 7: Mag1 (magnitude 1 value) Column 8: Mag2type (magnitude 2 type) Column 9: Mag2 (magnitude 2 value) # References Hearne and others (2024) Three relational databases in support of model development for earthquake hazard products. Abstract presented at the SSA 2024 Annual Meeting. Seismological Research Letters 95(2B): 1113–1465, https://doi.org/10.1785/0220240136. U.S. Geological Survey, Earthquake Hazards Program (2017) Advanced National Seismic System Comprehensive Catalog of Earthquake Events and Products. Data release. Reston, VA: U.S. Geological Survey. DOI: 10.5066/F7MS3QZH. Also available at https://earthquake.usgs.gov/earthquakes/search/. 2025 David R Shelly USGS - ROCKY MOUNTAIN REGION Research Geophysicist mailing and physical

Colorado School of Mines, 1711 Illinois St

Golden CO 80401 303-273-8659 dshelly@usgs.gov # Seismicity Catalogs for Sensitivity Analysis For each update of the National Seismic Hazard Model (NSHM), seismicity catalogs are developed as input to the smoothed seismicity model. Development of the seismicity catalogs includes: - reformatting and combining pre-existing input catalogs; - deleting duplicates, explosions, and mining-related events; - flagging induced events in the central and eastern U.S. (CEUS); and - delivering a final uniform moment magnitude (Mw) catalog for further processing (i.e., declustering and smoothing). Mueller (2019) outlines the full set of catalog processing steps in further detail. For this study we developed three separate seismicity catalogs: (1) 2023 NSHM - Events between January 1, 2000 and December 31, 2022 and east of -100 degrees west longitude from the central and eastern U.S. seismicity catalog used for the 2023 50-state NSHM update (Petersen and others, 2023). File name: emm_pn_2023_nshm.csv (2) No Magnitude Conversions - Same catalog as listed above (i.e., 2023) but during the magnitude conversion process, magnitude conversions were turned off. Therefore, the original magnitude value was assumed to be equal to the Mw value. File name: emm_pn_no_mag_conversions.csv (3) New Magnitude Conversions - Same catalog as listed above (i.e., 2023) but during the magnitude conversion process, the new magnitude conversions developed as part of this study were used to convert from original magnitude type to Mw. File name: emm_pn_new_mag_conversions.csv A description of each column in the seismicity catalog files is listed below: Column 1: Mw (nonspecific moment magnitude) Column 2: lon (longitude, degree east) Column 3: lat (latitude, degree north) Column 4: depth (km) Column 5: year Column 6: month Column 7: day Column 8: hour Column 9: min (minute) Column 10: sec (second) Column 11: sigma_m (magnitude uncertainty) Column 12: M_we (expected value of Mw) Column 13: N (counting factor) Column 14: comment (comment field that includes contributing input catalog, original magnitude, original magnitude type, event ID, etc.) # References Mueller CS (2019) Earthquake catalogs for the USGS National Seismic Hazard Maps. Seismological Research Letters 90(1): 251–261, https://doi.org/10.1785/0220170108. Petersen and others (2023) Data Release for the 2023 U.S. 50-State National Seismic Hazard Model: Overview: U.S. Geological Survey data release, https://doi.org/10.5066/P9GNPCOD. 2025 Allison M Shumway USGS - ROCKY MOUNTAIN REGION Research Geophysicist mailing and physical

Colorado School of Mines, 1711 Illinois St

Golden CO 80401 303-273-8402 ashumway@usgs.gov This data release includes seismicity catalogs used by Llenos and others (2025) to (1) compute new magnitude conversion equations and (2) perform a gridded seismicity sensitivity analysis. Llenos, A.L., Shelly, D.R., and Shumway, A.M., 2025, Earthquake magnitude conversion and sensitivity catalogs for the central and eastern United States: U.S. Geological Survey data release, https://doi.org/10.5066/P13XZCBA. U.S. Geological Survey - ScienceBase mailing address

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Lakewood CO 80215 USA 1-888-275-8747 sciencebase@usgs.gov Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Although this information product, for the most part, is in the public domain, it also contains copyrighted materials as noted in the text. Permission to reproduce copyrighted items must be secured from the copyright owner whenever applicable. The data have been approved for release and publication by the U.S. Geological Survey (USGS). Although the data have been subjected to rigorous review and are substantially complete, the USGS reserves the right to revise the data pursuant to further analysis and review. Furthermore, the data are released on the condition that neither the USGS nor the U.S. Government may be held liable for any damages resulting from authorized or unauthorized use. Although the data have been processed successfully on computer systems at the U.S. Geological Survey, no warranty expressed or implied is made regarding the display or utility of the data on any other system, or for general or scientific purposes, nor shall the act of distribution constitute any such warranty. The U.S. Geological Survey shall not be held liable for improper or incorrect use of the data described and/or contained herein. Users of the data are advised to read all metadata and associated documentation thoroughly to understand appropriate use and data limitations. Digital Data https://doi.org/10.5066/P13XZCBA None. 20251119 GS-HAZ Metadata USGS - physical

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Golden CO 80401 (303) 273-8500 ghsc_metadata@usgs.gov FGDC Content Standards for Digital Geospatial Metadata FGDC-STD-001-1998 local time