Geophysical Site Characterization of Bay Area Seismic Monitoring Stations: Vs-depth Profiling, NEHRP Site Classifications, and Linear Shallow Seismic Amplification Functions

Dates

Publication Date: 2017
Start Date: 2016
End Date: 2017

Citation

Turner, Jamey, 2017, Geophysical Site Characterization of Bay Area Seismic Monitoring Stations: Vs-depth Profiling, NEHRP Site Classifications, and Linear Shallow Seismic Amplification Functions: Fugro USA Land, Inc, https://doi.org/10.5066/F78W3BJH.

Summary

New active-source shallow seismic (shear-wave and acoustic-wave) measurements were obtained at 18 prioritized seismic monitoring station locations in the north San Francisco Bay area to measure site-specific ground motion amplification effects, soil depth, depth to bedrock (Z1.0 Vs=1 km/s), calculate site specific velocity-depth profiles and Vs30, and develop NEHRP site classifications for each location. This study was led by Principal Investigators Jamey Turner, Cooper Brossy, and Daniel O’Connell and field data were acquired by Glendon Adams and Lincoln Steele. Seismic monitoring sites that recorded high PGA values during the M6.0 Napa earthquake, proximal to higher population densities, and sites recommended by ground motions practitioners [...]

Summary

New active-source shallow seismic (shear-wave and acoustic-wave) measurements were obtained at 18 prioritized seismic monitoring station locations in the north San Francisco Bay area to measure site-specific ground motion amplification effects, soil depth, depth to bedrock (Z1.0 Vs=1 km/s), calculate site specific velocity-depth profiles and Vs30, and develop NEHRP site classifications for each location. This study was led by Principal Investigators Jamey Turner, Cooper Brossy, and Daniel O’Connell and field data were acquired by Glendon Adams and Lincoln Steele. Seismic monitoring sites that recorded high PGA values during the M6.0 Napa earthquake, proximal to higher population densities, and sites recommended by ground motions practitioners were prioritized. The final site selections were ultimately controlled by property access during the field campaign. This report provides new data at earthquake seismic monitoring stations for updating ground motion prediction equations (GMPEs) to address a priority topic identified in 2015 NEHRP solicitation Section 6, Element 1 for Research in Northern California. A modified 2D Interferometric Multichannel Analysis of Surface Waves (IMASW) methodology, following on O’Connell and Turner (2011), was developed to obtain new site-specific active-source shear-wave velocity (Vs) structure 2D and 1D profiles. These shallow geophysical surveys were measured at seismic monitoring station sites ranked as “priority” sites by the USGS based on anomalous peak ground acceleration (PGA) and peak ground velocity (PGV) measurements at varying distances from the source 2014 M6.0 South Napa earthquake. The goal of obtaining these new data is to delineate shallow ground motion amplification site effects by providing new site-specific Vs-depth profiles and amplification-frequency plots, data which can be used to compare site-specific ground motion site effects based on shallow velocity structure, soil class, and bedrock depth for each seismic monitoring station with anomalous PGA. The 2014 South Napa earthquake was recorded by more than 400 local and regional strong-motion stations located within 100 km of the epicenter, including California Strong Motion Instrumentation Program (CSMIP) strong motion recordings at 40+ sites within 40 km of the epicenter (available at www.strongmotioncenter.org). The maximum horizontal peak accelerations observed at many of these sites generally follow the ground-motion attenuation relation of Boore and Atkinson (2008) (comparison of results with updated NGA-WEST 2 is forthcoming). However, several ground-motion values depart distinctly from this trend, indicating significantly greater spectral values that may reflect strong amplification at some of the sites. Measurements were obtained at “rock” reference sites ensure sufficient site-specific data are collected to make feasible the use of generalized inversion for site amplification following the method of Hartzell and Mendoza (2011). Additionally, a GIS-based study compares Vs-depth data to lithology using existing geologic mapping data to develop characteristic Vs-lithologic relationships between shear-wave velocity and lithology, adding additional data to the statewide California Vs-geologic unit database. The Vs-depth profiles are interpreted to estimate soil thickness and depth to bedrock at each site.

Contacts

Point of Contact :: Jamey Turner
Originator :: Turner, Jamey
Metadata Contact :: GHSC Data Steward
Publisher :: Fugro USA Land, Inc
Distributor :: Robert Williams

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Geophysical_Characterization_Bay_Area.xml Original FGDC Metadata	View	9.78 KB	application/fgdc+xml
Seismic_Stations_2015_2016.csv		1.01 KB	text/csv
Vs_depth/NEHRP_1765_final_line_S4_velocity_depth_model.csv		768 Bytes	text/csv
Vs_depth/NEHRP_1765_Line_S5_final_velocity_model.csv		752 Bytes	text/csv
Vs_depth/NEHRP_CE.68150_1D_from_2D_ln_mean_sigma_Vs-depth.csv		10.41 KB	text/csv
Vs_depth/NEHRP_NC.C032_1D_from_2D_ln_mean_sigma_Vs-depth.csv		10.41 KB	text/csv
Vs_depth/NEHRP_NC.GDXB_1D_from_2D_ln_mean_sigma_Vs-depth.csv		9.89 KB	text/csv
Vs_depth/NEHRP_NC.N019B_1D_from_2D_ln_mean_sigma_Vs-depth.csv		12.98 KB	text/csv
Vs_depth/NEHRP_NC.NAPC_1D_from_2D_ln_mean_sigma_Vs-depth.csv		10.41 KB	text/csv
Vs_depth/NEHRP_NC.NLH_1D_from_2D_ln_mean_sigma_Vs-depth.csv		10.41 KB	text/csv
Vs_depth/NEHRP_NC.NMC_1D_from_2D_ln_mean_sigma_Vs-depth.csv		10.41 KB	text/csv
Vs_depth/NEHRP_NC.NMI_1D_from_2D_ln_mean_sigma_Vs-depth.csv		10.41 KB	text/csv
Vs_depth/NEHRP_NC.NMW_1D_from_2D_ln_mean_sigma_Vs-depth.csv		10.41 KB	text/csv
Vs_depth/NEHRP_NC.NSM_1D_from_2D_ln_mean_sigma_Vs-depth.csv		10.41 KB	text/csv
Vs_depth/NEHRP_NC.NSP_1D_from_2D_ln_mean_sigma_Vs-depth.csv		12.98 KB	text/csv
Vs_depth/NEHRP_NC.NTO_1D_from_2D_ln_mean_sigma_Vs-depth.csv		10.41 KB	text/csv
Vs_depth/NEHRP_NC.NTYB_1D_from_2D_ln_mean_sigma_Vs-depth.csv		12.98 KB	text/csv
Vs_depth/NEHRP_NGVB_Line_S3_final_velocity_mode.csv		672 Bytes	text/csv
Vs_depth/NEHRP_NGVB_merged_lines_S1-S2_final_model.csv		884 Bytes	text/csv
Vs_depth/NEHRP_NP.1759_1D_from_2D_ln_mean_sigma_Vs-depth.csv		11.7 KB	text/csv
Vs_depth/NEHRP_NP.1760_1D_from_2D_ln_mean_sigma_Vs-depth.csv		12.98 KB	text/csv
FinalTechnicalReport.pdf “Final Technical Report”		8.44 MB	application/pdf
		1.41 GB	application/zip
SEGY_p2.zip		940.25 MB	application/zip

Shapefile: Survey_Lines_WGS84UTM.zip
Survey_Lines_WGS84UTM.cpg		5 Bytes
Survey_Lines_WGS84UTM.dbf		1.3 KB
Survey_Lines_WGS84UTM.prj		403 Bytes
Survey_Lines_WGS84UTM.sbn		308 Bytes
Survey_Lines_WGS84UTM.sbx		124 Bytes
Survey_Lines_WGS84UTM.shp		16.05 KB
Survey_Lines_WGS84UTM.shx		260 Bytes

Purpose

The goal of obtaining these new data is to delineate shallow ground motion amplification site effects by providing new site-specific Vs-depth profiles and amplification-frequency plots, data which can be used to compare site-specific ground motion site effects based on shallow velocity structure, soil class, and bedrock depth for each seismic monitoring station with anomalous PGA. The data were collected as part of USGS Grant ?Award Number G16AP00009.

Geophysical Site Characterization of Bay Area Seismic Monitoring Stations: Vs-depth Profiling, NEHRP Site Classifications, and Linear Shallow Seismic Amplification Functions

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