Deformation near the Long Valley Caldera, eastern California, 1982–1986

Abstract

Annual surveys of trilateration and leveling networks in and around Long Valley caldera in the 1982–1985 interval indicate that the principal sources of deformation are inflation of a magma chamber beneath the resurgent dome and right‐lateral strike slip on a vertical fault in the south moat of the caldera. The rate of inflation of the magma chamber seems to have been roughly constant (0.02 km3/yr) in the 1982–1985 interval, but the slip rate on the south moat fault has decreased substantially. In addition, there is evidence for a shallow source of dilatation (possibly dike intrusion) beneath the south moat of the caldera in 1983 and less certain evidence for a deep source (possibly magma chamber inflation beneath Mammoth Mountain) in the western caldera in 1983–1985. Deformation in the 1985–1986 interval as inferred from trilateration alone seems to be similar to that observed in 1984–1985.