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Format: Virtual Webinar. 45 min. presentation followed by 15 min. Q&A

An optional post-lecture workshop will immediately follow each lecture for expanded Q&A and networking

Session 1, Wednesday, Feb 2, 2022, 4 pm to 5 pm Central European Time

Session 2, Thursday, April 7, 2022, 3 pm to 4 pm British Summer Time

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Two live sessions are completed. Please scroll down to watch the videos from the recordings below. SEG members, view the course for free!

Abstract

The shallow subsurface contains soil, glacial, and alluvial deposits as well as weathered and/or fractured bedrock. It is from these thin surficial layers that we draw our drinking water and produce our food, and it is also where we ultimately discharge much of our waste. Recent history has taught us that overuse, let alone abuse, of our environment, may lead to the long-term detriment to our livelihood. In densely populated and highly industrialized regions, the protection and sustainable use of this fragile surficial environment have therefore become a societal and political issue of critical importance. Near-surface geophysics has an essential role to play in this endeavor and has seen correspondingly dramatic growth and evolution during the recent past. While state-of-the-art near-surface geophysical techniques have a proven capacity to provide realistic structural images and characterizations of the surficial environment, there also is an emerging trend towards using this information to infer estimates of soil and rock physical properties. This is a focus of our research group. Specifically, we are interested in relating relatively easy-to-measure geophysical data and their associated proxy parameters to more elusive rock and soil physical properties, such as permeability or fracture compliance, which tend to be difficult to infer through direct techniques. To achieve this objective, we pursue two fundamentally different, yet highly complementary, approaches, which will be introduced and discussed in this lecture through selected case studies. Our first approach is based on the idea of using geostatistical techniques for integrating spatially sparse, point-type measurements of soil or rock physical target properties with spatially extensive geophysical images of corresponding proxy parameters. A distinct advantage of this approach is that it naturally closes the notoriously large gaps in terms of spatial resolution and coverage associated with such datasets and, additionally, provides some measure of the uncertainty of the inferred distributions of the target properties. Conversely, our second approach is more direct in that it seeks to directly relate specific attributes of ground-penetrating radar and seismic data to the underlying soil or rock physical target properties.

Figure 1. Estimating the detailed porosity distribution in a heterogeneous surficial aquifer from surface-based ground-penetrating radar (GPR) data. a) 3D surface-based GPR data from the Boise Hydrogeophysical Research Site (BHRS). The data were acquired in a bi-static common-offset manner at a nominal center frequency of 100 MHz. b) Porosity distribution inferred from the stochastic simulation of the GPR data conditional to information provided by neutron-neutron borehole logs. c) Comparison of observed (top row) and synthetic (bottom row) GPR data along selected inline profiles. The latter is consistent with the inferred porosity distribution. This is a work in progress courtesy of Zhiwei Xu (formerly the University of Lausanne, now the China University of Geosciences). See also Xu et al., GEOPHYSICS, 86, WB147-WB157, 2021.