Microtremor Data Collected in Sacramento-San Joaquin Delta Region of California

The Sacramento-San Joaquin Delta is located in California’s Central Valley, roughly 50 km east of the San Francisco Bay area, and much of it is underlain by peaty-organic soils. These soft-soils affect seismic demand as a result of site amplification of ground motions (i.e., site response). Geotechnical site characterization data is needed in order to facilitate empirical site response analysis. The University of California, Los Angeles (UCLA) has partnered with the California Department of Water Resources (CDWR) to collect ambient microtremor data to aid in the characterization of organic soft-soil sites in the Delta. Ambient microtremor data were collected using temporary broadband seismometers provided by the United States Geologic Survey (USGS) over continuous time intervals ranging between 2 and 2.8 hours at 33 seismic recording stations between August 18 and September 1, 2019. These data may be used to produce Horizontal-to-Vertical Spectral Ratio (HVSR) curves which can provide additional information regarding site characteristics such as fundamental site frequency. The HVSR curves developed using this dataset may be accessed in the United States Community Shear-Wave Velocity (VS) Profile Database (PDB) (https://uclageo.com/VPDB/). We acknowledge CDWR Precision Electronics Specialist Andrew Cowell for assistance with performing field measurements at CDWR seismic stations.