University of Texas at Austin

Seismic Hazard and Risk Assessment - Shear Wave Velocity Characterization

Synopsis: Acquisition and analysis of shear wave velocity throughout Texas and development of Vs30 maps for input into ground shaking models

Project Status: Active

Funding Source: 100% CISR IA

Research Leaders: Brady Cox, Ellen Rathje

Project Start: 3Q2016

Project Interface: Project interfaces closely with Seismic Hazard and Risk Assessment - Shaking Intensity, and Seismic Hazard and Risk Assessment - Building Infrastructure

Expected research outcomes:

  • Vs30 site characterization
  • Database of Vs30 for Texas Vs30 map

This research involves the measurement of shear wave velocity (Vs) profiles across Texas and development of a shear wave velocity map of Texas. The Vs measurements will be performed at TexNet recording stations, as well as other targeted locations within various geologic units within areas of interest in Texas. The shear wave velocity profiles will be measured using non-intrusive, active and passive surface wave techniques. The depth of the profiles will be at least 50 m at all locations and will be extended as deep as possible (500-plus m) depending on site access constraints (i.e., ability to deploy large-aperture 2D arrays of seismometers). Deep Vs profiles will be helpful to constrain the regional velocity profile used in locating earthquakes. For each testing location, the average shear wave velocity over the top 30 m (Vs30) will be computed.

There are various methods that can be used to develop a Vs30 map of Texas. The measured Vs data and geologic unit information can be used to assign Vs to each geologic unit, or proxy methods can be used that relate Vs30 to ground slope or terrain. Each of these methods will be assessed using the Vs30 velocity data collected in Texas and one approach will be selected to develop the final map for Texas. The Vs30 map will be important for properly accounting for site characteristics in estimates of earthquake ground shaking within Texas.