Mechanical and Civil Engineering Seminar

Mechanical and Civil Engineering Seminar Series

Title: Mathematical and Computation Modeling of Injection-induced Seismicity

Abstract: It has long been recognized that pumping fluids into or out of the Earth has the potential to cause earthquakes. Some of the earliest field evidence dates to the 1960s, when earthquakes were turned on and off by water injection in Rangely, Colorado. More recently, induced seismicity has been reported worldwide in connection with many subsurface technologies, including wastewater disposal, natural gas storage, enhanced geothermal systems, and hydraulic fracturing. As a result, there has been a growing public concern around the world about the potential seismic hazard and environmental impact of subsurface energy technologies. Understanding the physical mechanisms that lead to induced seismicity is essential in efforts to mitigate the risk associated with subsurface operations. In the first part of the talk, I present a spring-poroslider model of frictional slip as an analogue for induced seismicity and analyze conditions for the emergence of stick-slip frictional instability—the mechanism for earthquakes—by carrying out a linear stability analysis and nonlinear simulations. We found that the likelihood of triggering earthquakes depends largely on the rate of increase in pore pressure rather than its magnitude. Thus, the model explains the common observation that abrupt increases in injection rate increase the seismic risk. Second, I present an energy analysis using the same spring-poroslider model to shed light into the partitioning of energy released into frictional and radiated energy—since the latter is associated with the overall size of the earthquake and its potential for damage to man-made structures. Two key elements of the analysis are: (1) incorporating seismic radiation within the model using a precisely defined viscous damper, and (2) partitioning the energy supplied by fluid injection into dissipated and stored energy in fluid and skeleton. The analysis shows how the rate of increase in pore pressure controls the radiated energy, stress drop, and total slip of the earthquake. Third, I present my current postdoc work on the two-dimensional modeling of laboratory experiments of injection-induced fault slip. This research, as a whole, enhances our understanding of the mechanics of fluid-injection-induced earthquakes and suggests strategies that mitigate or minimize the seismic risk associated with a wide range of subsurface operations, from hydraulic fracturing and geothermal energy extraction to wastewater injection and geologic CO2 sequestration.

Bio: Maryam is the Inaugural George Housner postdoctoral fellow in Earthquake Engineering. She obtained her PhD in Computational Science and Engineering from MIT, MS in Civil and Environmental engineering from UC Berkeley, and BS in Petroleum Engineering from Texas A&M University. She also worked as a reservoir engineer at Saudi Aramco for a few years. At Caltech, she is interested in studying the influence of fluids on friction and earthquakes.

NOTE: At this time, in-person Mechanical and Civil Engineering Lectures are open to all Caltech students/staff/faculty/visitors.