A Proposed Seismic Velocity Profile Database Model

Sean K. Ahdi, Shamsher Sadiq, Okan Ilhan, Yousef Bozorgnia, Youssef Hashash, Dong Youp Kwak, Duhee Park, Alan Yong, & Jonathan P. Stewart

Published August 10, 2018, SCEC Contribution #8386, 2018 SCEC Annual Meeting Poster #022

We describe the data model currently in use in a publicly available velocity profile database under development for the United States. The initial implementation of the database contains data primarily from California, but also currently includes various sites around the U.S. Our data model consists of JavaScript Object Notation (JSON) format files for storing metadata and data. For a site to be included in the database, the minimum metadata requirements are accurate geodetic coordinates, and the minimum data requirement is a shear-wave velocity profile. The JSON files are structured in a hierarchal manner to store metadata and data using a nested structure consisting of location, velocity profiles, dispersion curve data (for surface-wave methods), geotechnical data, and horizontal-to-vertical spectral ratios (HVSR). At the present stage of the project, we are populating the database using the schema described herein. However, the schema and JSON file structure are flexible, and as we continue to develop the data model and populate the database with various data sources, we have the ability to include other relevant data, as well as evaluate other file formats to increase the efficiency of data storage and querying. In the current data model, location information includes site geodetic values (latitude, longitude, and elevation) and various site descriptors related to surface geology, geomorphic terrain category, and topographic slope gradient, among other site-level metadata. Velocity data include the geophysical method(s) used to obtain the shear-wave velocity profile, modeled primary- and shear-wave velocity (VP and VS, respectively) and its uncertainty as a function of depth, modeled profile maximum depth, and the computed time-averaged VS to the maximum profile depth. VS30, the time-averaged VS to 30 m depth, is computed and included if the maximum profile depth reaches 30 m. In the case of surface-wave based data, dispersion curve data can be recorded in the data structure as phase velocity versus either wavelength or frequency. Geotechnical data includes boring logs, standard penetration resistance, cone penetration test sounding logs, and laboratory index test results. HVSR plots are given as a function of frequency. The database to date contains digitized velocity profiles at over 1000 sites, and we eventually anticipate to include an estimated 4500 total profiles in the U.S., with nearly 2000 profiles in California alone.

Key Words
Shear-wave velocity, database, seismic site characterization

Citation
Ahdi, S. K., Sadiq, S., Ilhan, O., Bozorgnia, Y., Hashash, Y., Kwak, D., Park, D., Yong, A., & Stewart, J. P. (2018, 08). A Proposed Seismic Velocity Profile Database Model. Poster Presentation at 2018 SCEC Annual Meeting.

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