Detection of plumes at Redoubt and Etna volcanoes using the GPS SNR method

Abstract

Detection and characterization of volcanic eruptions is important both for public health and aircraft safety. A variety of ground sensors are used tomonitor volcanic eruptions. Data fromthese ground sensors are subsequently incorporated into models that predict the movement of ash. Here amethod to detect volcanic plumes using GPS signals is described. Rather than carrier phase data used by geodesists, the method takes advantage of attenuations in signal to noise ratio (SNR) data. Two datasets are evaluated: the 2009 Redoubt Volcano eruptions and the 2013/2015 eruptions at Mt. Etna. SNR-based eruption durations are compared with previously published seismic, infrasonic, and radar studies at Redoubt Volcano. SNR-based plume detections from Mt. Etna are compared with L-band radar and tremor observations. To place these SNR observations from Redoubt and Etna in context, amodel of the propagation of GPS signals through bothwater/water vapor and tephra is developed. Neitherwater nor fine ash particles will produce the observed attenuation of GPS signals, while scattering caused by particles N1 cm in diameter potentially could.