IS LONG VALLEY CALDERA PART OF THE EASTERN CALIFORNIA SHEAR ZONE? SOME ANSWERS FROM HYPERSPECTRAL IMAGING

Long Valley Caldera sits on the western edge of Basin and Range extensional deformation and the eastern edge of the Sierra Nevada. We suggest that Long Valley is accumulating strain imposed on it from the Eastern California Shear Zone (ECSZ). Recent hyperspectral-based mineral mapping in the caldera confirms the presence of a set of contentious NE-trending faults in the western caldera; Suemnicht and Varga's Discovery Fault Zone. The presence of these faults is consistent with right-lateral shear imposed by the Eastern California Shear Zone of Dokka and Travis, 1990a. Resurgent dome normal faults may also be accommodating some of this right lateral shear. Conflict between geologic and gps/strain determined slip rates in the region could be resolved by allowing the crust of Long Valley to accumulate some of the regional 11 + 1 mm/yr measured slip. Northward propagation of the ECSZ into this latitude roughly coincides with the inception of widespread volcanic activity in this region (~3 Ma). We suggest that ECSZ strain localizes along northwest trending normal faults (Hilton Creek Fault, Hartley Springs Fault, Resurgent Dome Faults). Such faults now experience right lateral offset in addition to normal movement from Basin and Range imposed deformation. In addition, several reactivated NE-trending faults act as zones of strain transfer across the caldera from east to west. These mapped fault patterns are consistent with those seen farther south along the ECSZ, and help to explain the origin of this massive caldera.