2009 Annual Meeting: Dynamic Weakening Mechanisms Workshop
Dates: September 12-13, 2009
Organizers: Eric Dunham, Judi Chester
Location: Plaza Ballroom, Hilton Palm Springs Resort, Palm Springs, CA
Over the past several years there has been a surge of research on dynamic weakening mechanisms, i.e., processes by which fault strength is dramatically reduced during coseismic slip. Dynamic weakening offers a possible resolution of a number of outstanding issues in fault and rupture mechanics, including the heat flow paradox, the low stresses inferred to be acting on major faults, and why ruptures take the form of narrow slip pulses. A variety of weakening mechanisms have been proposed, including flash heating of asperity contacts, thermal pressurization of pore fluid, macroscopic melting, and thermal decomposition weakening. At this workshop, speakers will provide an overview of 1) the latest high velocity friction experiments; 2) theoretical predictions of fault strength as a function of slip rate, normal stress, and other variables; 3) consequences of dynamic weakening in spontaneous rupture models; and 4) field constraints. The objective of the workshop is to foster discussion between experimentalists, modelers, and geologists in order to determine which weakening mechanisms are active in natural earthquakes and how they influence rupture behavior.
| SATURDAY, SEPTEMBER 12th | ||
| Introduction and Overview | ||
| 10:00-10:10 | Introduction | Eric Dunham, Judi Chester |
| 10:10-10:40 | Overview of Dynamic Weakening Mechanisms | Jim Rice |
| Session I: High Velocity Experiments and Understanding Weakening Mechanisms | ||
| 10:40-11:10 | Experimental constraints on coseismic slip | David Goldsby |
| 11:10-11:40 | Laboratory experiments to understand slip weakening due to flash heating at seismic slip rates | Vikas Prakash |
| 11:40-12:10 | Fault plasticity at seismic slip rates: Experiments and theory | Kevin Brown |
| 12:15-13:45 | Lunch | |
| 13:45-14:15 | Dynamic weakening by gouge lubrication: Experimental observations of granite friction at velocity range of 0.001-1.0 m/s | Ze'ev Reches |
| 14:15-14:45 | High-speed friction of Punchbowl Fault ultracataclasite in rotary shear: Characterization of frictional heating, mechanical behavior, and microstructure evolution | Hiroko Kitajima |
| 14:45-15:30 | Session I Discussion | Terry Tullis |
| 15:30-15:45 | Break | |
| Session II: Interpreting Observations and Integrating Dynamic Weakening into Rupture Models | ||
| 15:45-16:15 | Flash weakening and the onset of melting | Alan Rempel |
| 16:15-16:45 | 3D earthquake-sequence simulations with thermal pressurization of pore fluids: Effect of heterogeneous fault properties on slip complexity and interseismic stress | Nadia Lapusta |
| 16:45-17:00 | Wrap-Up Discussion | |
| 18:30-20:00 | Dinner | |
| SUNDAY, SEPTEMBER 13th | ||
| Session II: Continued | ||
| 08:30-09:00 | 3D earthquake-sequence simulations with thermal pressurization of pore fluids: Effect of heterogeneous fault properties on slip complexity and interseismic stress | Giulio Di Toro |
| 09:00-09:30 | Semi-empirical constitutive relations for dynamic weakening based on high speed friction experiments | Nick Beeler |
| 09:30-09:45 | Break | |
| 09:45-10:15 | What can ground motion in the Chi-chi earthquake tell us about dynamic weakening? | Joe Andrews |
| 10:15-11:30 | Session II Discussion | Nadia Lapusta |
| Moving Forward - What earthquake physics science priorities should SCEC4 pursue? | ||
| 11:30-11:59 | Open Discussion and Wrap-Up of Day 2 | Eric Dunham, Judi Chester |
PARTICIPANTS:
