2024 T. H. Wu Distinguished Lecture: Brady R. Cox

Non-Invasive Subsurface Site Characterizatrion: Opportunities, Challenges, Emerging Technologies and Advanced Analysis

Presented on Friday, February 16, 2024, Dept of Civil, Environmental and Geodetic Engineering at The Ohio State University

Non-invasive site characterization methods based on seismic stress wave propagation have become fully entrenched as powerful tools for use in geotechnical engineering projects over the past several decades. The expanding use of these methods is driven by the desire to “reach” within the earth and retrieve accurate and meaningful engineering parameters in materials that are difficult to sample and/or at larger spatial scales and greater depths than possible with traditional invasive approaches like geotechnical borings or cone pentration soundings. In particular, the use of stress waves allows for retrieval of small-strain compression and shear moduli of soils and rock in situ, which are key input parameters in many engineering analyses.

This talk will discuss the use of noninvasive site characterization methods, such as multi-channel analysis of surface waves (MASW), microtremor array measurements (MAM), horizontal-to-vertical spectral ratios (HVSR), and full waveform inversion (FWI), for developing 1D, 2D and 3D models of the subsurface. Open-source software for applying these methods will be discussed and case history examples will be provided that illustrate their application over depths and lateral extents ranging from 10’s of meters to kilometers. Future opportunites in the field based on emerging technolgies such as distributed fiberoptic sensing and advanced anlyses based on machine learning will also be discussed. An overarching theme throughout the lecture will be the need to acknowlege and quantify uncertainty and non-uniqueness when utilizing non-invasive methods for site characterization, as the failure to do so is the most common challenge faced by practitioners today.