Seminar - Peter Mora - The Lattice Solid DEM: advances in understanding the complex system dynamics of discontinuous solids and earthquakes

Wednesday 14 September 2011, 1.00 pm - 2.00 pm
Lecture Room 3, School of Civil Engineering

Prof. Peter Mora
The University of Queensland

Abstract:
One of the grand scientific challenges is that of earthquake forecasting. A long standing debate is centred around whether earthquake fault systems behave as a self-organised critical system, or whether they may behave like a critical point system in which there is a build up of correlations within the system prior to large earthquakes. If the former is true, then earthquakes cannot be forecast, whereas if the latter is true, then earthquake forecasting is an achievable goal. To address this goal, I have spent the last 20 years working towards building new numerical simulation models, research teams, multi-disciplinary international collaboration, and national research infrastructure via the Major National Research Facility Program to provide the means needed to achieve breakthroughs. This talk will be focussed on the Lattice Solid Model (LSM) developed by myself and my team, a parallelised particle-based model for studying the complex system behaviour of catastrophic rock failure and the multi-physics of earthquake and gouge dynamics.
LSM simulations of a discontinuous elastodynamic system provide evidence in support of the Critical Point Hypothesis for earthquakes, and hence for the possibility for earthquake forecasting. Another proposed earthquake forecasting method is based on the assumption that the fault system in a given region may become critically sensitive prior to a large event. If so, then the response under loading and unloading should be different. Numerical simulations using the LSM demonstrate that the so called Load-Unload Response Ratio spikes prior to catastrophic failure of model rock samples under uniaxial compression thus supporting the LURR hypothesis. The growth in stress correlation length prior to major events and LURR simulation results provide the first realistic elasto-dynamic simulation based evidence in support of a physical mechanism for earthquake forecasting.
The talk will also present other capabilities of the LSM model including its ability to simulate thermo-mechanical and thermo-porous coupling; and a finite deformation contact model where all rotational degrees of freedom are included: torsion, shear and bending moments. The full degrees of freedom allow rock fracture simulations to match closely with laboratory experiments. A number of examples of rock fracture and mining engineering applications are presented including collapse, hydraulic fracturing, and particles in fluids.

Biography:
Peter obtained a B.Sc. Hons First Class at Adelaide University in Geophysics, and subsequently worked with ESSO in Sydney and as a consultant writing seismic modelling software for Delhi Petroleum. He was awarded a PhD in Computational Geophysics at Stanford University in 1987. He believed future research breakthroughs would be driven by large scale numerical simulation, and as such, declined initial academic offers, and joined Thinking Machines Corporation in Boston where he pioneered the use of massively parallel supercomputers for nonlinear seismic wavefield inversion and 3D propagation of seismic waves through the whole earth. In 1989 he joined the Centre National de la Recherche Scientifique (CNRS) at the Institut de Physique du Globe in Paris where he was involved in a bid to establish a thematic parallel computational facility in the earth sciences. He subsequently was promoted to Professor of the IPGP and became the Director of the French National Centre for Parallel Computation in the Earth Sciences. In France he set up an industry-sponsored research consortium, the Seismic Simulation Project, and focussed his research on new simulation methodologies for complex solid earth phenomena. At this time, he commenced developing the Lattice Solid Model: a particle-based numerical model capable of simulating the nonlinear dynamics of earthquakes, fault gouge dynamics and catastrophic rock failure, with the aim of providing the means to study the complex system behaviour of earthquake fault systems and probe the underlying physical mechanisms that may enable earthquakes to be forecast.

He moved to Australia in 1994 to join The University of Queensland, where he established and directed the Queensland University Advanced Centre for Earthquake Studies (QUAKES). In 1997 he established a major international cooperation, the APEC Cooperation for Earthquake Simulation (ACES), involving over forty leading international research institutions and organisations to combine complementary research programs and miltidisciplinary research teams to build multi-scale multi-physics simulation models for earthquake processes from the microscopic to macroscopic scales. In 2002 he proposed and established the Australian Computational Earth Systems Simulator Major National Research Facility in collaboration with national simulation groups, and expanded QUAKES research to include research and development of simulation of solid earth processes at all scales. As such, QUAKES was renamed Earth Systems Science Computational Centre (ESSCC) with its research spanning: 1) natural hazards forecasting (earthquakes, tsunamis, landslides, catastrophic rock failure); 2) green energy resources such as hot fractured-rock geothermal energy; 3) mining innovations (granular flow, block caving, rock fracture); and 4) simulations for minerals exploration (mantle convection, geological formations such as basins and folding regimes, plume dynamics, volcanoes, collaboration on mineralisation).

Since returning to Australia in 1994, Professor Mora has won around $28M in competitive research grant funding to support his and his partners' research teams. He has over 200 publications in international journals and conference proceedings, and more than ten edited books.