The Nevada Seismological Laboratory has posted a public database of Refraction Microtremor (ReMi) survey results of shear-wave velocity (Vs) versus depth in the Reno-area basin, and additional locations. Most of the Vs profiles were published previously in peer-reviewed journal articles. The database collects values of Vs30, Z1.0, and Z2.5 measured at 170 sites throughout the basin. Vs30 is the time-averaged Vs between the surface and 30 m depth. Z1.0 is the depth to the first occurrence of Vs = 1.0 km/s or greater, and Z2.5 is the depth to Vs = 2.5 km/s. The database contains many more Reno-area sites with Vs30 measurements that did not also have a Z1.0 measurement; this report does not examine sites without Z1.0 values. All but a few sites have Vs30 between 260 m/s and 760 m/s, with a majority in NEHRP hazard class C. Sites that are geologically on bedrock have unexpectedly low Vs30, <760 m/s. Intensive surveying of bedrock sites shows extreme lateral variability of Vs30 as well as Z depths, with great variations over 20 m distances due to differential weathering of volcanic rocks. There appear to be no geological- or soil-mapping criteria able to predict Vs30 in Nevada, consistent with previous work. Neither Vs30 nor Z1.0 can distinguish basin from bedrock sites in Nevada. Basin sites may well have faster Vs30 measurements than nearby bedrock sites. Some bedrock sites have Z1.0 >0.1 km, and some basin sites have Z1.0 <0.05 km. In the Reno area, measured Z1.0 varies from 0.015 km to 0.45 km; Z2.5 varies from 0.1 km to 0.9 km. The ratio of Z2.5/Z1.0 is established with a minimum of 1.0, and with some sites exhibiting a ratio as high as 4.5. In 49 Las Vegas measurements along Las Vegas Blvd., Z1.0 varies from 0.05 to 0.68 km; Z2.5 measurements are not available. Z1.0 is typically between 0.05 km and 0.11 km. Variations are likely due to highly variable occurrence of Tertiary caliche cementation. Comparing the Vs30 and Z values to gravity-derived basin depths (Zg) correlates the depths and allows development of a practical approach for estimating Z1.0 and Z2.5 using ReMi or gravity data. Applying the models to gravity results for the Reno-area basin, Las Vegas Valley, and much of the Great Basin in Nevada and Eastern California produces maps of predicted Z1.0 in Reno only, and Z2.5 for wider areas, with reasonable results but large uncertainties. The Vs30 and Z values provide a basis for estimating basin effects on earthquake shaking throughout Nevada and Eastern California using current Ground Motion Models (GMMs), an important consideration for seismic design and performance assessment of major civil infrastructure and lifelines throughout the region. Data File Format Assembled measurements of Vs30, Z1.0, and Z2.5 in Reno are given in Table 1. Predicted Z1.0 and Z2.5 results are contained within three plain text data files in the .zip file accompanying this report. Within each text file, Z1.0 and Z2.5 have been estimated for each location listed in the corresponding gravity data set of Zg values: Abbott and Louie (2000) for Reno; Langenheim et al. (1998, 2001) for Las Vegas; and Saltus and Jachens (1995) for the entire Basin and Range. Each location’s estimate is one row in the text file. The columns of the text files, from left to right, are: latitude, degrees WGS84; longitude, degrees WGS84; Zg, km; Z1.0min, km; Z1.0, km; Z1.0max, km; Z2.5min, km; Z2.5, km; Z2.5max, km; Z1.0error, percent; and Z2.5error, percent. The latitude and longitude are converted directly from the published gravity databases, and the Zg values are taken directly from their published results. The Z values are determined as described above from the best-fit coefficients in Equations 1 and 2, estimated from the Zg values. Z values are not forced to any nearby measured Z values that appear in Table 1. The minimum Z values result from the application of the 95% confidence minimum coefficients in Equations 1 and 2; the maximum Z values result from the application of the 95% confidence maximum coefficients in Equations 1 and 2. The Z errors are the percentages resulting from subtracting the minimum Z from the best-fit Z, and then dividing by the best-fit Z. Users should bear in mind that the Z1.0 estimates are not thought to be valid outside the Reno-area basin. All Z1.0 predictions in the Langenheim and Saltus files, outside the Reno area, should be ignored. Geologically, Z2.5 is thought to coincide with the depth to the floor of Tertiary and Quaternary basins filled with either clastic or volcanic sediments having slower velocity and lesser density, atop denser and faster Mesozoic basement. Figures 12 through 15 present maps of Z1.0 and Z2.5 for Reno, and of Z2.5 for Las Vegas and all of Nevada and Eastern California, respectively. The accompanying .zip file has the map images, as well as a KML file allowing Google Earth to show the Z maps. Map data are supplied also as JRG Packs for plotting and spatial analysis with the free JRG/Viewmat software tools (Louie, 2020b).

This is a peer-reviewed publication of the Nevada Seismolgical Laboratory at the University of Nevada, Reno.