Collaborative Research: How is Strain of the Eastern California Shear Zone Transferred Across the Garlock Fault?

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The interaction of intersecting fault systems can be complex and can lead to complicated deformation and overprinting on structures at all scales. An area of particular interest in this regard is in eastern California where the Eastern California shear zone (ECSZ) and the Garlock fault intersect. The ECSZ is a 100 km wide belt of north-northwest trending strike-slip faults of similar type and orientation as the San Andreas fault; the Garlock fault a roughly east trending strike-slip fault of opposite sense of motion. The Garlock is through going whereas faults of the ECSZ seem to end as they approach the Garlock. Although the Garlock appears to be the more continuous structure, GPS and satellite information seem to show that deformation related to the ECSZ passes continuously across it. The project is investigating how these two systems interact at mesoscopic and macroscopic scales. In particular, mapping in the field of faults and folds related to both structural systems is aimed at assessing whether faults of the ECSZ do indeed end (and if so how) before reaching the Garlock. Mapping is also showing if the Garlock is as continuous as previously thought. Samples are also being collected to determine the ages of various offset landforms and surface features. This provides the rate at which each fault is moving. This information complements the mapping showing how the faults end in that the loss of motion can be correlated with the rates of motion. In some locations, Ground Penetrating Radar is used to image how faults are oriented in the subsurface. This information is also critical to assess the rates of motion. By the collection of all these different types of information, the project is attempting to understand in detail the interaction of the ECSZ and Garlock and thus determine how the crust of the earth deforms in areas of complicated faulting. This is critical to understanding the overall deformation of the crust in the western part of North America.