Horizontal-to-vertical spectral ratios (HVSR) of three-component ambient noise measurements are commonly used to estimate a site’s resonant frequency (f0). The importance of understanding the spatial variability of f0 across a site cannot be overstated in regards to earthquake engineering hazard studies. However, the random nature of ambient noise (both in time and space), in conjunction with variable subsurface conditions and sensor coupling issues, can lead to uncertainty in f0,HVSR estimates. Hence, it is important to report f0,HVSR in a statistical manner (e.g., as a median value with standard deviation).
In this webinar, we will discuss new statistical approaches to estimate f0,HVSR and its uncertainty as a function of time, azimuth, and space. Furthermore, we will demonstrate recently-developed open-source tools (hvsrpy and HVSRweb) that can easily be used to perform the statistical calculations. The HVSR theory and tools will be illustrated within the context of several case studies ranging from fault detection, to seismic site classification, to constructing large-scale 3D subsurface models for use in site response.
Dr. Brady R. Cox, Ph.D., P.E.: Dr. Cox is a Professor in the Civil and Environmental Engineering Department at Utah State University (USU). Prior to joining USU, he served on the faculty of The University of Texas for eight years and The University of Arkansas for six years. Dr. Cox specializes in geotechnical engineering, with emphasis on issues related to seismic design and in-situ site characterization for major construction projects. His research efforts combine experimental field testing with computational analyses and high-performance computing for subsurface imaging purposes.
He has led teams deployed to collect seismic site characterization data at ground motion recording stations, soil liquefaction sites, and structural failures following significant earthquakes in the U.S. and around the world (e.g., Ecuador, Haiti, Japan, New Zealand, Peru, Turkey). He has also participated in numerous dynamic site characterization projects for the seismic design of critical facilities (e.g., nuclear power plants, U.S. DOE laboratory sites, bridges, tunnels) in the U.S. and abroad. Dr. Cox has authored over 100 peer-reviewed publications and is a recipient of the Presidential Early Career Award for Scientist and Engineers (PECASE), which he received in a ceremony at the White House from President Barack Obama.
Joseph P. Vantassel: Joseph P. Vantassel is currently a Ph.D. candidate and Research Associate in the Data Intensive Computing Group at the Texas Advanced Computing Center at The University of Texas at Austin. His research is in the area of non-invasive seismic imaging using stress-wave methods. Through his research he seeks to advance non-invasive seismic imaging toward more robust and uncertainty-aware solutions through the intersection of field experiments, numerical simulation, and computing with an emphasis on applications in site characterization, infrastructure monitoring, and natural hazards.
In the past four years, Joseph has authored seven peer-review journal publications, five peer-review conference proceedings, six technical reports for projects located in the U.S. and abroad, and four open-source Python packages. One of these packages named hvsrpy, which will be discussed as part of the course, has gained widespread popularity in the short time since its release in February of 2020 with over 18,000 downloads and an active community of users located around the world.
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