IS THERE A LINK BETWEEN THE MIGRATION OF THE MENDOCINO TRIPLE JUNCTION AND THE DEVELOPMENT OF THE WALKER LANE – EASTERN CALIFORNIA SHEAR ZONE?

Although it is clear that the San Andreas component of the Pacific – North America plate boundary forms in response to the migration of the Mendocino triple junction (MTJ), it is less clear how MTJ migration may lead to the development of this second major component – the Walker Lane/Eastern California Shear Zone (WL-ECSZ) – of the plate boundary system. Although there are hints that the WL-ECSZ system may be actively lengthening to the north in sync with the MTJ, its position far from the edge of the Pacific plate complicates any simple explanations of the possible links. Here we explore the kinematics of the plate interactions, the 3-D lithospheric evolution in the wake of the MTJ, and the implications of the formation and evolution of the San Andreas system for localizing additional strain in the WL-ECSZ. In order to better constrain any geodynamic links between the MTJ and development of the plate boundary system to the east, we need to better constrain the following: 1) patterns of strain at the northern limits of the Walker Lane and the transition into eastern Oregon; 2) displacement rates (both current and geologic) along the WL-ECSZ and their variation in time and space; and 3) improved resolution of the patterns of crustal deformation in the corridor between the MTJ and the northern Walker Lane. With this additional information we can perhaps rigorously test the oft-repeated concept that the WL-ECSZ will eventually mature to become the primary plate boundary structure.