The Solid Earth Response to Earthquake Cycle Processes and Glacial Fluctuations in the Eastern Aleutians of Alaska

We are processing and analyzing broad-scale gravimetric change from GRACE-GFO and ongoing crustal deformation with Sentinel-1 InSAR data integrated with continuous GPS data to unravel and model the temporal and spatial sources of gravimetric change and surface deformation in the Kodiak-Katmai region of the eastern Aleutians of Alaska.   As background, the Kodiak-Katmai segment of the eastern Alaska-Aleutian subduction zone experienced large coseismic slip during the great 1964 earthquake (M=9.2).  Furthermore, the largest volcanic eruption of the twentieth century (VEI = 6) occurred in 1912 at the Novarupta volcano, 10 km to the west of Mount Katmai on the Alaska Peninsula.  Here, we report the simulated coseismic and postseismic gravimetric change associated with the 2021 Chignik earthquake (M=8.2) that occurred southwest of our study area.   Earlier, we estimated the predicted ongoing rate of gravimetric change due to the post-seismic response to the 1964 great earthquake; however, more recent sources of gravimetric change make it difficult to detect this signal.    Some of the individual volcanoes monitored now with InSAR in the Katmai complex have undergone volcanic surface deformation in the last decade.    We hypothesize that some of the observed vertical land motion across the Kodiak-Katmai region includes a discernible component of surface uplift due to ongoing regional deglaciation of the Katmai area glaciers based on our initial examination of continuous GPS data from this area, as well as earlier seismic cycle, glacier retreat, and volcanic models of the predicted surface deformation. We anticipate our study results will enable better characterization of geohazards associated with the subduction main thrust zone, upper crustal faults, ongoing volcanic processes, and post-glacial rebound.    We will discuss the implications of our current work on constraining earthquake source parameters and Earth rheology that can be derived from gravimetric and surface deformation change data in the context of our broader study of earthquakes with GRACE-GFO data over the last two decades.