Harvey Mudd College Student's Research Contributes to Understanding of the Physics of Earthquakes
Study of California quakes also has possible applications for brain research

CLAREMONT, Calif.-A student at Harvey Mudd College, Paul Rundle, has studied the history and physics of earthquake faults in Southern California using sophisticated new computer simulations, to uncover distinct patterns in the way in which quakes cluster and interact with each other. This research has enabled Rundle, along with six other scientists, to develop a new statistical method of analyzing earthquake faults that examines not just individual fault lines, but how they relate to each other in a network of such earthquake faults. The method also holds promise of being applied to other kinds of physical and biological systems in which energy is slowly built up, then suddenly released.

Map of the major faults in southern California, together with historic earthquakes larger than magnitude 6 (circles) occurring since 1812. (Click on the map to download a larger TIF file).

Rundle's work appears in the article he co-authored, "Nonlinear Network Dynamics on Earthquake Fault Systems." The article was published in the October 1 issue of Physical Review Letters (volume 87, issue 14). It is already available on the journal's website. Click here to download a PDF file of Rundle's article and accompanying illustrations.

"Our research suggests that earthquake faults must be studied in a network, not in isolation," says the paper. "Even so, there has been little work to date focused on understanding how networks of faults behave."

The scientists developed computer simulations based on the known network of earthquake faults in Southern California, as well as the physics of the friction and stress found on the fault lines. These simulations showed that when an earthquake occurs, it both releases elastic strain in one area, and can either increase or decrease the strain on other faults within the network.

Major strike-slip faults in southern California used in the model. The difference in frictional coefficients are shown superposed above each fault. Fault key: SA, San Andreas; SJ, San Jacinto; E, Elsinore; IV, Imperial Valley; LS, Laguna Salada; G, Garlock; PV, Palos Verdes; S, Santa Cruz Island; PG, Pisgah; B, Brawley; SM, Santa Monica; L, Landers. (Click on the map to download a larger TIF file).

This in turn leads to more earthquakes on other fault lines by means of slow, chain reaction effects. The results of these simulations strikingly resemble the historic record of actual earthquakes in Southern California, with similar quake clusters and magnitudes.

Rundle and his collaborators also believe that the mathematical simulation developed can be used for other areas of research. "Though the simulations were applied to earthquake research, the principles involved can be applied to other systems, such as the neural network of our brain. Just as with a network of faults, neurons in the brain fire off signals that are transmitted to other neurons, and that triggers more brain activity."

Plot of Coulomb failure functions plotted as a function of time vs spatial location for 2000 simulation years for a set of values obtained by approximately matching the ratio of aseismic creep to seismic slip on various fault segments (Click on the map to download a larger TIF file).

Rundle, who is now a sophomore at Harvey Mudd College, began his research two years ago while he was a high school student. He then continued his research while working as a summer intern of the Southern California Earthquake Center for the last two summers. SCEC is headquartered at the University of Southern California and is funded by the National Science Foundation and the U.S. Geological Survey.

One of the co-authors with Paul Rundle is his father, Dr. John Rundle, a member of the Colorado Center for Chaos & Complexity (CIRES); a professor in the Department of Physics, University of Colorado, Boulder; and a distinguished visiting scientist at the Jet Propulsion Laboratory. The other co-authors are Kristy F. Tiampo, Jorge de sa Martins, and Seth McGinnis, graduates students at the Colorado Center for Chaos & Complexity; and Dr. William Klein, of the Los Alamos National Laboratory.

Harvey Mudd College is a coeducational institution of engineering, science, and mathematics that also places strong emphasis on humanities and the social sciences. The college's aim is to graduate engineers and scientists sensitive to the impact of their work on society. HMC ranks among the nation's leading schools in percentage of graduates who earn Ph.D. degrees. It is the pioneer of the internationally known Clinic Program, established in 1963.

Harvey Mudd College is a member of The Claremont Colleges Consortium, the first consortium of colleges in the United States, which offers students the expansive physical facilities and wide selection of courses, faculty, student services and extracurricular activities of a university, and the small classes and personalized education of a small private college. The Consortium includes Pomona College (established in 1887), Claremont Graduate University (1925), Scripps College (1926), Claremont McKenna College (1946), Harvey Mudd College (1955), Pitzer College (1963), and the Keck Graduate Institute of Applied Life Science (1997).

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