Session Overview: Mike Blanpied (USGS) and Peter Mora (QUAKES) (15 minutes)

Earthquakes result from the formation and/or rapid sliding of faults.
Decades of laboratory, field, and theoretical work has shown fault
slip to be enormously complicated, due to the wide variety of rock
types, physical and chemical environments, deformation rates, and
deformation mechanisms at play. The objective of Session 1.2 is to
identify what micro-scale elements of the faulting and fault slip
processes are the critical ones in determining macroscopic faulting
behavior, and to discuss conceptual strategies for incorporating
these key processes into tractable models. (This session will discuss
model philosophy and leave the nuts and bolts of numerical design to
Session 1.1.)  We will explore three main topics during this session:

1. Identifying the key deformation processes
2. Scaling issues and constitutive laws
3. Model-building strategies

1. Identifying the key deformation processes:

• What are the key deformation processes and conditions that much be taken into account when constructing a reasonably representative micro-scale fault model?

2. Scaling issues and constitutive laws:

• How has the complexity of nature been boiled down into useful mathematical laws?
• Are these laws useful building-blocks for micro-scale model development, or useful benchmarks to judge their success?
• How is it possible using simulations to go from laboratory to fault zone scale to access fault zone behavior?

3. Model-building strategies:

• How best can key issues of scaling and process be incorporated into numerical models?
• Do such models need to simulate the full earthquake cycle or only a portion of it (e.g., just the quasi-static or just the fully dynamic portions)?
• Can a single type of model hope to cover conditions from near-surface to sub-seismogenic zone?
• What trade-offs of realism for tractability are permissible?

Session Plenary: (1 Hour)

Mike Blanpied (20 minutes)
Laboratory and field observations of fault zone meso- and
micro-structure, deformation processes, roles of fluids.

Miti Ohnaka (20 minutes)
Laboratory and theoretical aspects of dynamic fault slip.
The shear rupture nucleation: Horizons broadened by high-resolution 
laboratory experiments

Peter Mora (20 minutes)
Model development - where things stand and where things may be heading.

Detailed Session: (2.5 Hours)

1. Identifying the key deformation processes

James H. Dieterich (15 mins)
Observations of micro-mechanical processes during frictional slip

Discussion and comments (30 minutes)

2. Scaling issues and constitutive laws

Hideo Aochi and Mitsuhiro Matsu'ura (15 mins)
Evolution of contacting rock surfaces and a slip- and time-dependent
fault constitutive law

Chris Marone (15 mins)
Static Friction, Healing, and Constitutive Laws for Time- and
Slip-Dependent Friction

Mengfen Xia, Jie Bai, Fujiu Ke and Yilong Bai (15 mins)
(Joint with 2.3 and 5.1)
Sample-Specificity and Predictability of Material Failure

Discussion and comments (30 minutes)

3. Model-building strategies

Peter Mora, David Place, Steffen Abe, Dion Weatherley and Therese Keane
(to be presented in the plenary)
The Lattice Solid Model: towards a realistic simulation model for earthquake
micro-physics and the development of a virtual laboratory for the earthquake
cycle

Discussion and comments (30 minutes)