Mechanisms of deformation at Erebus volcano, Antarctica using 20 years of GPS Observations

Mount Erebus, Ross Island, Antarctica is a 1.3 Myr old active stratovolcano with a unique convecting highly alkaline phonolite lava lake. Seismic data (body wave seismic interferometry and seismic tomography) show the lava lake forms the top of a shallow magma system which is connected to deeper magma reservoirs. Low and high velocity features characterize the shape and structure of the summit magma reservoir and conduit. Gas slugs frequently ascend to the surface, causing Strombolian eruptions that sometimes eject lava bombs up to 250 m from the lava lake. Since the late 1990's 8 continuous and 7 campaign GPS stations have been distributed over Erebus. Elsewhere on Ross Island there are 2 continuous stations and 3 campaign sites. The Transantarctic Mountains Deformation network (TamDEF) and Mount Erebus Volcano Observatory (MEVO) were the primary drivers for these installations. Most of the continuous GPS stations now record GPS signal phase and range at 1 sample per second, all archived at UNAVCO.

To measure deformation across the island, we generate consistent position time series with JPL's GIPSYx for the entire archive and explore processes affecting these stations through time series analysis, and analytical and numerical modeling. Processes impacting the position time series include: plate motion, rifting, glacial isostatic adjustment (GIA) and other surface loading processes including seasonal processes, deformation due to magmatic processes, and strombolian eruptions. To constrain magmatic and eruptive processes through formal inversions, we remove a combination of forward modeled known processes (e.g., GIA) and fitted functions to isolate the volcanic signals. Our preliminary results suggest that most stations are dominated by tectonic and more subtle seasonal processes. Stations closer to the summit plateau show occasional deviations from long term trend that appear to be related to dynamics of the shallow magmatic system.