Comparison of High Temporal Resolution Gas Composition and Seismic Data from Three Persistently Degassing and Seismically Active Alaskan Volcanoes

Abstract:

Fluid movement in the subsurface of active volcanoes is frequently thought to produce elevated seismicity; however the actual type of fluid (i.e. magma, volatiles, or hydrothermal waters) cannot be uniquely distinguished using seismic data alone. The chemical composition of emitted volcanic gases can be used to distinguish magmatic from hydrothermal degassing, as well as to identify magma recharge from depth. In this project we aim to use complementary geochemical and seismic datasets to identify possible correlations between volcanic gas composition and seismicity, in an effort to constrain seismic signatures of subsurface fluid movement. We present new datasets collected in July and August 2013 from three very seismically active and persistently degassing volcanoes within the Katmai Volcanic Cluster (KVC), Alaska: Mount Martin, Mount Mageik, and Trident Volcanoes. During the field deployment, high temporal resolution (~1 Hz) major-species (e.g. H₂O, CO₂, SO₂, H₂S) gas composition measurements were collected over four ~30 minute sample periods each day from the target volcanoes using campaign MultiGas instruments located adjacent to the primary degassing sources. These instruments were complemented with two co-located 6TD broadband seismometers on the crater rims of Mount Martin and Mount Magiek, as well as by the Alaska Volcano Observatory Katmai seismic network, which consists of nine short-period and two broad-band seismometers located within 30 km of the target volcanoes. Here we present a comparison of coincident timeseries gas geochemistry and seismic datasets from the three target volcanoes in an effort to provide insight into the types of fluids that may be triggering volcano-seismicity at these actively degassing volcanoes.