EAPS DLS - Greg McLaskey (Cornell)

Earthquake initiation, fluid injection, rupture arrest, and the scaling of fracture energy: Insights from 3-meter laboratory rock experiments and dynamic rupture simulations.

Abstract: I describe experiments on a 3‐m rock sample where the slip nucleation process is imaged in detail and compare earthquakes initiated from externally applied shear stress to those triggered by direct fluid injection. Initiation properties are strongly affected by fault healing/loading rate, and fault strength heterogeneity. I also discuss why earthquakes ruptures stop. In the 3-m rock experiments, dynamic ruptures stop not because they reach a barrier of high strength or fracture energy, but because they propagate into a section of the fault with low initial shear stress (i.e. they run out of gas). We extend our lab results using dynamic rupture simulations that show how seismically observable breakdown energy can exhibit scaling with earthquake size, despite constant fault fracture energy. This is due to a scale invariant stress overshoot, which has been overlooked in recent studies of earthquake fracture energy. 

About this Series:

The Department Lecture Series at EAPS at MIT is a series of Weekly talks given by leading thinkers in the areas of geology, geophysics, geobiology, geochemistry, atmospheric science, oceanography, climatology, and planetary science. For more information and Zoom password please contact Madelyn Musick: mmusick@mit.edu