Origins and Mechanical Implications of Fault Geometry in the Sierra Nevada

The Pear Lake fault zone runs from where this picture was taken, across the lake, and through the notch on the opposite side.

Project Summary Faults are more than just narrow lines on a map -- they have a complex geometry and internal structure that can control their behavior. For example, bends or steps can act as barriers to rupture propagation or areas of stress concentration where ruptures can nucleate in the first place. Recent work in the seismological community has shown that structural heterogeneities on the order of tens of meters or less could play important roles in controlling fault behavior, but these studies often lack the resolution to fully illuminate all the subtleties of fault structure. In our project, we use field observations of exhumed faults to describe the detailed geometry of natural faults at a large range of scales from centimeters to tens of kilometers. We map the geometry of the Pear Lake fault zone and investigate the forces that gave rise to this complex geometry. We then use simple numerical models to determine how this geometry would affect the magnitude of fault slip. We map one end of another fault and discuss how pre-existing structures may have acted as a barrier that impeded fault growth, an observation that may be analogous to rupture termination in certain environments.

Tools Brunton Compass, Handheld GPS, Laser Range-Finder, Solar Panels, Hiking Boots, 2-D Boundary Element Modeling

Geographic Location Pear Lake, Sequoia National Park, California
Bear Creek Vicinity, John Muir Wilderness, California

Group Members Involved Matthew d'Alessio <Email> <Personal Web Site>
Stephen J. Martel (University of Hawaii)

Project Duration 1999 - 2002

More Information < Project Web Site >