GRAVITY ANALYSIS OF THE KATMAI VOLCANIC CLUSTER, SOUTHEASTERN ALASKA

The Katmai Volcanic Cluster (KVC) is located in southeastern Alaska on the Eastern Alaska Peninsula of the Aleutian volcanic arc. The KVC consist of eight andesitic to dacitic volcanic centers that are parallel to the Aleutian volcanic arc and cover an approximately 50 km length. The KVC is most primarily famous for the largest 20^th century eruption where in 1912 Novarupta erupted which resulted in the formation of a caldera at Mount Katmai. The only other 20^th century eruptions occurred between 1953 and 1974 where Southwest Trident erupted and produced 0.5 cubic kilometer of lavas. However, persistent seismic activity in the region suggests there is persistent subsurface fluid flow including magma degassing, hydrothermal fluid movement and magma intrusion. Three-dimensional inversion of P-wave velocity data obtained from local earthquakes suggest that low velocities beneath the axis between the Mageik-Katmai-Novarupta region is probable partially molten material. This area coincides with a prominent Bouguer gravity minimum which supplies further evidence of partially molten material. In this study, we analyze relatively new airborne gravity data that covers the Easter Alaska Peninsula in conjunction with the sparse ground gravity data to determine the subsurface structure of the KVC. The analysis will include the construction of residual gravity anomaly maps, derivative maps, 2D and 3D crustal models constrained by the above seismic inversions.