Abstract

Assessing the hazard associated with naturally-occurring or induced earthquakes requires a prediction of the likelihood of occurrence and size if the largest earthquakes that might occur in a region. The size-frequency distribution of seismic events can be characterized by a fractal dimension or by a parameter that earthquake scientists call the b-value. Whether that dimension/parameter is a statistical result of the earth stress in a particular region, a function of the depth of the seismic event, characteristic of foreshocks or aftershock, or some other factor, is a matter that has been widely discussed in the literature without resulting in a general consensus. As induced seismicity has increased, so has our understanding of the importance of pre-existing faulting style on the size-frequency distribution of earthquakes. After thousands of smallish earthquakes routinely shook the Midwestern US from increased oil and gas related fluid injection, the occurrences of a few larger damaging earthquakes caused major concern about the risks related to induced seismicity. As a result, many more studies are underway to understand the subsurface structure prior to injection in order to mitigate that risk. In this talk I will present an overview of the basics of earthquake distributions, sizes, and hazards, what we know about earthquakes that are induced by human activities with examples from a number of different industries, and a geological explanation for the size-frequency distribution and how it can be used to enhance hazard assessment activities.

Download Flyer: http://isgs.illinois.edu/sites/isgs/files/seminar/ISGS_SeminarFlyer_20180910.pdf

About the speaker

Dr. Williams-Stroud is a Visiting Research Scientist, Structural Geologist, at the Illinois State Geological Survey/University of Illinois Urbana-Champaign. Her areas of expertise include structural and fracture analysis and modeling for oil and gas and geothermal energy production, with a specialization in microseismic data interpretation and induced seismicity. She is also President and CEO of Confractus, Inc., based in southern California. She received her MA and PhD from The Johns Hopkins University and her BA from Oberlin College and has over 25 years of experience in government and industry. In addition to teaching industry short courses, she has held adjunct positions at the University of Houston, California State U. Los Angeles and Northridge, and has been a full-time faculty member at Whittier College. She is an active member of several professional organizations, has been an AAPG Visiting Geoscientist since 2014, and is a member of the NASEM Committee on Seismology and Geodynamics.