IGPP is pleased to invite you to join its Winter 2023 Seminar Series presentation featuring Caltech's Tom Heaton. Dr. Heaton's talk, "Slip Pulses and the Strength of the Crust" will occur April 4, 2023 in the Munk conference room and over Zoom: https://ucsd.zoom.us/j/91217290430?pwd=V25Mb1JZcC8yRzd2Nk1xQUYrbTNNUT09 Password: igpp
Time: 12:00 pm, Pacific Time
Location: Revelle conference room, and Zoom
Abstract: I discuss the difference between crack-like and pulse-like earthquake ruptures. The observation that average stress drops (3 MPa) are scale independent over an enormous range of earthquake sizes has been the primary motivation for modeling earthquakes as expanding cracks. However, constant stress drop expanding cracks can only be arrested by introducing a zone of high fracture energy at the crack tip. Furthermore, the fracture energy increases linearly with the scale of the rupture. In that sense, crack models are not independent of scale. Slip pulses have fundamentally different physics; a propagating slip pulse knows nothing about the ultimate dimension of the rupture. How can slip pulses match the observation of scale-free stress drops? I show that slip pulses are inherently unstable and that they are dynamically chaotic. I show a simple spring-block slider model that has a prestress that evolves into a complex state that results in events that have scale independent stress drop; heterogeneous prestress from self organization is the mechanism of rupture arrest. Furthermore, the mechanical strength of this system decreases as a power law of the length of the rupture.