CAREER: Response of fault systems to shifts in tectonic regime: Implications for the evolution of and present-day activity of fault systems in Southern California How do faults in the EarthÕs crust evolve?

In the 100 years since the 1906 San Francisco earthquake, which instigated the study of earthquake science, geologists have learned much about how faults accumulate stress and interact with one another. However, we still cannot predict the behavior of faults. The next revolution in understanding active faulting will consider not just individual faults but entire systems of three-dimensional faults. Dr. Cooke is developing innovative computer tools that will enhance our understanding of fault system evolution and she is also incorporating deaf high school students into her research program.

Dr. CookeÕs study investigates the systemic evolution of faults by assuming that faults evolve to minimize the energy in the system; in other words, fault systems grow along paths of least resistance. By assessing the work associated with active faulting, the evolution of fault systems are simulated in three-dimensional computer models. In particular, Dr. Cooke is interested in how fault systems adapt when their tectonic setting changes. For example, faults that developed in an extensional tectonic setting might deform inefficiently under later contraction. The computer models show that upon such tectonic shifts, some faults reactivate, some link up and some new, more efficient fault surfaces develop. Many parts of the world have undergone tectonic shifts. Of particular interest to Dr. Cooke is how the present-day fault systems in Southern California, evolved over the last 6 Mya. The combination of dense population and active faulting makes understanding fault evolution in Southern California quite important for estimating potential damage from future earthquakes.

Computer models are only useful if we have some way to validate the results. An important component of this project is the validation of model predictions of fault evolution with table-top experiments. Faults are put into a thick layer of clay that is then stretched to simulate deformation of the Earth. The experiments are being performed by UMass researchers as well as deaf teachers and students at three high schools around the country. Dr. Cooke anticipates that incorporating deaf students into the project may: 1) motivate life-long interest in geoscience, 2) inspire deaf students to pursue science in college, 3) improve the technical communication skills of the students 4) empower students by utilizing their spatial visualization skills and 5) dispel views of geoscience as an able-bodied (or male) occupation. Like Cooke, the deaf students use American Sign Language, an inherently spatial language. The use of spatial language is expected to foster spatial cognitive skills critical for analyzing interacting, three-dimensional fault surfaces. In fact, geoscientists may learn from the deaf community innovative approaches for the presentation of 3D data.

In summary, CookeÕs work will advance our understanding of fault system evolution and provide deaf students with invaluable scientific skills and appreciation for geoscience.