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Group 1 – EFP | Poster Abstracts
Earthquake Forecasting and Predictability (EFP)
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MEDIUM-TERM EARTHQUAKE FORECASTING WITH NUMERICAL
EARTHQUAKE SIMULATORS Van Aalsburg JD, Rundle PB, Morein G, Rundle JB, Turcotte
DL, Grant Ludwig LB, Donnellan A, and Tiampo KF
Topologically realistic earthquake simulations are now possible using numerical codes such as
Virtual California (VC). Currently, VC is written in modern object-oriented C++ code, and runs
under MPI-II protocols on parallel HPC machines such as the NASA Columbia supercomputer. In
VC, an earthquake fault system is modeled by a large number of Boundary Elements interacting by
means of linear elasticity. A friction law is prescribed for each boundary element, and the faults are
driven at a stressing rate that is consistent with their observed long-term average offset rate. We
note that the parameters that enter into the model are set using the long term average properties of
the fault system -- earthquake and plate rate variability are not used at this stage of the simulation.
We have carried out simulations for earthquakes on models of California’s fault system for
simulation runs over time intervals from tens of thousands of years to millions of years. Using
these simulations, we have now developed techniques to assimilate observed earthquake
variability into the simulations. Our technique is based on mining the simulation data to identify
time intervals that look most like the recent past history of earthquakes on the California fault
system. We then use these optimal time intervals to “look into the future” and forecast the likely
locations of future major earthquakes. Here we describe this method and develop fault-based
probabilities that are comparable with recent results from the Working Group on California
Earthquake Probabilities.
1-086
A VIRTUAL CALIFORNIA EARTHQUAKE SIMULATION TEST Yikilmaz MB, Turcotte
DL, Yakovlev G, Rundle JB, and Kellogg LH
Virtual California (VC) is a geometrically realistic numerical model which is specifically designed
to simulate earthquake occurrences along the San Andreas and adjacent faults. It is a stochastic,
cellular automata (CA) simulation of an earthquake backslip model. The term backslip specifies
that the loading of each fault segment occurs due to the accumulation of a slip deficit at the
prescribed slip rate of the segment. Recurrence intervals are also specified. VC includes the major
strike-slip faults in California and is composed of more than 650 vertical fault segments, each
having a width of ~ 10 km and a depth of 15 km. The fault segments are treated as dislocations and
interact with each other elastically, utilizing dislocation theory. In this paper we present the initial
results of a simple fault geometry model from a recently updated VC code. The model consists of a
linear and vertical fault divided into two equal segments each having 23, 10 x 10 km, elements. The
interaction of the two segments is studied by gradually making one segment stronger by
prescribing higher recurrence intervals for this segment. In all cases a limit cycle is obtained. We
observe that the number of periods in the system increases with increasing recurrence interval.
1-087
MULTISCALE EARTHQUAKE SIMULATOR FOR PARKFIELD, CALIFORNIA,
USING RATE AND STATE FRICTION AND FAST MULTIPOLES Tullis TE, and Beeler N
We have developed a multiscale grid and corresponding distribution of constitutive parameters to
simulate earthquake sequences over a wide range of scales at Parkfield, CA. The geometry of grid
elements and the distribution of constitutive parameters have been designed based on the
distribution of microseismicity at Parkfield, including earthquakes ranging from magnitude 1 to
magnitude 6. The intent of this work is to understand the interplay between earthquakes of a wide
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