Ultrasonic Imaging to Reveal the Physics of Earthquake Precursors

Abstract
Earthquakes result from sudden frictional instabilities along tectonic faults. Death toll due to earthquakes can be enormous, especially in regions where proper infrastructure is lacking. Anthropogenic earthquakes near geothermal reservoirs or due to wastewater injection also threaten communities in regions of historically low seismicity. The objective of this research is to discover the mechanisms of precursory changes in rock and fault properties preceding laboratory earthquakes, to improve our understanding of earthquake precursors and ultimately better assess seismic risk. I will first begin this talk by providing an overview of the lab work conducted in this area and describe how it can be used to inform field observations. I will also describe the recent application of machine learning models to predict laboratory earthquakes. Finally, I will present more recent results from laboratory experiments where dense arrays of ultrasonic sensors are utilized (i) to characterize laboratory earthquakes and their foreshocks and (ii) to understand precursory changes to failure on heterogeneous faults. Our recent results show that, under similar conditions, some laboratory earthquakes exhibit simple ruptures while others reveal a rich seismic response, including ruptures of small asperities taking place concomitantly with the main rupture. Together, our laboratory experiments show that datasets with a seemingly simple configuration and simple mechanical response can exhibit both complex precursory changes to failure and complex seismic responses.

 

Biographical 

Jacques Rivière is an associate professor of Engineering Science and Mechanics, as well as Acoustics, at the Pennsylvania State University. Prior to his appointment at Penn State, he was a Marie-Curie postdoctoral fellow at the Université Grenoble Alpes, France (2016-2018), a postdoctoral scholar in the Department of Geosciences at the Pennsylvania State University (2015-2016), and a postdoctoral scholar at Los Alamos National Laboratory (2012-2015). He earns a Ph.D. from Université Pierre et Marie Curie in Paris, France and an M.S. in Mechanics and Acoustics from Université du Maine, Le Mans, France. He is a recipient of the U.S. Department of Energy Office of Science Early Career Award (2022). His research expertise spans across acoustics, ultrasonics and geophysics. It includes the use linear/nonlinear ultrasonics, ultrasonic imaging and acoustic emission for (i) the nondestructive evaluation (NDE) and/or structural health monitoring (SHM) of materials for industrial and civil applications, as well as (ii) the characterization and monitoring of rocks, granular media and fault friction in the context of earthquake physics and related geophysical applications.