The “Database of Central and Eastern North American Seismic Velocity Structure” involves the compilation of one-dimensional (1D) seismic velocity-depth functions for central and eastern North America (CENA). The present database is an update of the report by Chulick and Mooney (2002) who present a compilation and statistical analysis of 1D seismic velocity-depth functions for North America and its margins. All seismic velocity-depth functions are extracted from peer-reviewed journal articles, with 86% derived from active-source seismic refraction profiles and the remaining 14% from receiver functions or local earthquake tomography models. No reanalysis of the original seismic field data was undertaken. The database of Chulick and Mooney (2002) covered a much larger region than central and eastern North America. In 2013 the USGS focused on augmenting the Chulick and Mooney (2002) database to update the coverage specifically for central and eastern North America. This augmented compilation was done to help characterize the seismic site response at the locations of nuclear power facilities and was a deliverable specified by a USGS-Nuclear Regulatory Commission Inter-agency Work Agreement, which can be found at https://www.nrc.gov/docs/ML1428/ML14280A412.pdf. Each seismic velocity-depth function is specified by its unique latitude and longitude and consists of the published crustal model for the subsurface Earth layers at that location, with each layer specified by compressional-wave velocity, shear-wave velocity, thickness, and depth. Each entry also includes other information, such as: elevation, geologic province, age of last significant thermo-tectonic activity, and the principal seismic methodology used to determine the velocity-depth function. Chulick, G.S., and Mooney, W.D., 2002, Seismic Structure of the Crust and Uppermost Mantle of North America and Adjacent Oceanic Basins: A Synthesis, Bulletin of the Seismological Society of America, vol.92, no.6, p.2478–2492.

The U.S. Geological Survey acquired high-resolution P- and S-wave seismic data across the Frijoles Fault strand of the San Gregorio Fault Zone (SGFZ) at northern Año Nuevo, California in 2012. SGFZ is a right-lateral fault system that is mainly offshore, and prior studies provide highly variable slip estimates, which indicates uncertainty about the seismic hazard it poses. Therefore, the primary goal of the seismic survey was to better understand the structure and geometry of the onshore section of the Frijoles Fault strand of the SGFZ. We deployed 118 geophones (channels) at 5-m spacing along a linear profile centered on the mapped surface trace of the Frijoles Fault and co-located active P- and S-wave sources at ~1-m offset from the geophones. Channel numbers increase from west to east along the profile. We generated P-waves using either a seisgun (www.utep.edu/science/ssf/Manuals/betsy_seisgun.pdf, accessed August 2022) or an accelerated weight-drop and S-waves by horizontally striking an aluminum block on both sides with a sledgehammer. We first deployed vertical-component geophones (40-Hz, SercelTM L40A, sensitivity of 22.34 volts/meter/second) to record P-wave sources, after which we replaced the vertical-component geophones with horizontal-component geophones (4.5-Hz, SercelTM L28-LBH, sensitivity of 31.3 volts/meter/second) to record S-wave sources. Refraction cables connected all geophones to two 60-channel Geometrics Stratavisor NX-60TM seismographs with 24-bit analog-to-digital converters. Each shot was recorded at a 0.5-ms sampling rate for two seconds, with data recording at 100 ms before the actual time of the shot. This data release provides the metadata needed to utilize the seismic data. Data Format and Files We combined each seismic trace for a given shot time into a shot gather, and the traces in each shot gather are ordered by channel numbers (1-118) based on the position of the geophones along the profile. Furthermore, we assigned a unique field number (FFID) to each shot gather, and we combined the shot gathers recorded from both seismographs into two SEG-Y files (Barry et al., 1975), 78023.segy (channels 1 to 60) and marine.segy (channels 61 to 118), which are stored in big-Endian, 4-byte IBM-floating-point format (format code 1). Data samples are in millivolts and can be converted to velocity using the geophone sensitivity values. Metadata for all profiles are contained in two text files and one xml file: PIE12.setup.csv, PIE12.location.csv, and PIE12Metadata.xml. The setup file describes the identification of shots recorded by the two seismographs, channel number, recording stations (geophones), and the source type for both SEG-Y files. The location file describes the channel number, latitude, and longitude of all geophone locations. Reference Barry, K.M., Cavers, D.A., and Kneale, C.W., 1975, Recommended standards for digital tape formats: Geophysics, vol. 40, no. 2, p. 344-352, doi: 10.1190/1.1440530.

The Seismicity Catalog Collection is a compilation data on over four million earthquakes dating from 2150 BC to 1996 AD from NOAA's National Geophysical Data Center and U.S. Geological Survey's National Earthquake Information Center. The data include information on epicentral time of origin, location, magnitudes, depth and other earthquake-related parameters. This database is static and is no longer being updated.

This data release complements Murray et al. (2023) which presents a framework for incorporating earthquake magnitude estimates based on real-time Global Navigation Satellite System (GNSS) data into the ShakeAlert® earthquake early warning system for the west coast of the United States. Murray et al. (2023) assess the impact of time-dependent noise in GNSS real-time position estimates on the reliability of earthquake magnitudes estimated using such data. To do so they derived peak ground displacement (PGD) estimates from time series of background noise in GNSS real-time positions. These noise-only PGD measurements were used as input to a published empirical relationship to compute magnitude for hypothetical earthquakes that are each defined by an epicentral location and origin time. The data files provided here give the locations of GNSS stations used in the study, the hypothetical epicenters and origin times, and the PGD for each GNSS station for four time windows following each hypothetical origin time. We also provide the epicenters and origin times used to simulate the impact of noisy PGD data in terms of the annual number of spuriously large magnitude estimates that would be generated in the geographic region spanned by California, Oregon, and Washington, United States, due to noise alone. Finally, we include the estimated magnitudes for the annual simulations along with the number of GNSS stations for which the measured PGD exceeding a threshold value that was defined empirically to eliminate unreliable magnitude estimates.

VS30, the time-averaged shear-wave velocity (VS) to a depth of 30 meters, is a key index adopted by the earthquake engineering community to account for seismic site conditions. VS30 is typically based on geophysical measurements of VS derived from invasive and noninvasive techniques at sites of interest. Owing to cost considerations, as well as logistical and environmental concerns, VS30 data are sparse or not readily available for most areas. Where data are available, VS30 values are often assembled in assorted formats that are accessible from disparate and (or) impermanent Websites. To help remedy this situation, we compiled VS30 measurements obtained by studies funded by the U.S. Geological Survey (USGS) and other governmental agencies. Thus far, we have compiled VS30 values for 4,369 sites in the United States, along with metadata for each measurement from government-sponsored reports, online databases, and scientific and engineering journals. Most of the data in our VS30 compilation originated from publications directly reporting the work of field investigators. A subset consisting of 20 percent of VS30 values was previously compiled by the USGS and other research institutions. VS30 originating from these earlier compilations were crosschecked against published reports when clarification was needed. Both downhole and surface-based VS30 estimates are represented in our VS30 compilation. Most of the VS30 data are for sites in the western contiguous United States (3,128 sites); 682 VS30 values are for sites in the Central United States; 267 VS30 values are for sites in the Eastern United States and Puerto Rico; 15 VS30 values are for sites in Alaska; 30 VS30 values are for sites in Hawaii. The remaining 247 sites are in the vicinity of Vancouver, Canada.