Structure of the Mina Deflection in Mono Lake, CA: Inferences from Paleoseismology
Sangani, Radhika Chandrakant
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Walker Lane, a zone of transcurrent faulting along the Sierran range front, is dominated by NNW trending normal faults. Within the Walker Lane, the Mina Deflection is a region of structural anomaly, where a significant component of regional displacement and seismicity is transferred from NNW-trending faults to ENE-trending faults of the Excelsior-Coledale domain. Geographically, the western boundary of the Mina Deflection lies along the western margin of Mono Basin. This is kinematically implied by the distributed tensional and shear stress in the NNW- and ENE- trending faults of the region. Transfer of strain from the NNW-trending, right-lateral oblique slip faults to the ENE-trending, primarily left-lateral faults is poorly understood. The nature of this transfer is complicated by the presence of the young volcanics of Mono Lake at the stepover bend. I undertook detailed study of the sub-km scale geometry and kinematics of the stepover bend, and its relation to nearby recent magmatic fluid flow within the Mono Lake. Fault orientations, slip rates and ages of most recent events allow for understanding strain transfer between faulting and volcanism. The results suggest that strain is transferred from the outer arc to the inner arc of the stepover bend. Within the inner arc, the magmatism on Paoha Island seems to have arisen from a sill-like intrusion. Furthermore, strain transfer is accomplished through sets of faults and fissures that variously act as large-scale Reidel shears and tension gashes allowing the migration of magmatic fluids from depth.