From the Atomic to the Tectonic: Friction, Fracture and Earthquake Physics

Coordinators: James H. Dieterich, Michael L. Falk, Mark Owen Robbins

Understanding the physics of sliding, cracking, and deformation is critical for understanding seismic activity in the earth. Each of these phenomena involve complex physical processes over a range of length scales from atoms to tectonic plates. These topics have received considerable study in the context of engineered systems. However recent advances by researchers in physics, mechanics, materials science, seismology and geophysics are not often communicated across disciplines. The program will bring together a diverse interdisciplinary group to explore the physical processes that control deformation, rupture and slip at all scales. It will promote the interchange of ideas and approaches, and seek to develop new interdisciplinary research directions that link our understanding of physical phenomena from atomic scale processes to seismic events.

The program will be organized around five themes described below. When describing your interest please reference these themes. The dates in parentheses denote the weeks we expect to focus on each theme. Participants are encouraged to come for the entire program or extended stays that span multiple themes. If you are considering only staying for part of the program please consider this when suggesting your proposed dates of participation. The initial weeks in August will be devoted to cross-disciplinary tutorials and a week-long conference. The final weeks in December will be devoted to identifying and synthesizing themes that have emerged during the program.

A. Localization - Deformation often begins homogeneously over extended regions and then localizes along cracks, fault lines or shear bands. While localization is observed at all scales, the microscopic mechanisms that produce it are unclear.(29 Aug-16 Sept and 21 Nov-2 Dec)

B. Propagation - Oustanding problems exist regarding the relation between the constitutive behavior of the interface or continuum and the rate of advance of the moving fronts associated with cracks, slip pulses and shear bands.(29 Aug-7 Oct)

C. Complexity - Controversy exists regarding the origins of complexity in earthquakes. Faults form geometrically complex systems, and similar structures are seen in branched cracks and multiply intersecting shear bands. This complexity takes several forms and may arise from purely dynamical processes during earthquake slip, or it may be controlled by geometry.(19 Sept - 28 Oct)

D. Nucleation - Inadequate understanding of initiation of cracks or cavities, sliding along faults, plastic deformation, and slip pulses on interfaces limits our ability to predict failure events. In each case, nucleation involves rare events due to thermal activation or quenched disorder.(10 Oct - 18 Nov)

E. Friction - The physics of sliding interfaces in intimate contact is an area of active physics, geophysics and engineering research. Fault gouge, a product of wear and chemical alteration, may involve issues similar to those that arise due to organic third bodies between frictional sliding interfaces and mechanically worked regions that form near tribological surfaces in engineering applications.(31 Oct - 2 Dec)