Seismic velocity changes beneath Ebeko Volcano (Kuril Islands) based on observations in July-August 2021

Here we present seismic velocity changes in the northern part of Paramushir Island, where presently active Ebeko Volcano is located. We use the data of a seismic network that operated in this area in 2021–2022 during a continuous eruption activity of Ebeko. We selected the data from July 1 to August 15, when most stations of the network provided prompt recording of seismic signals. The velocity changes were derived from the ambient noise cross-correlation functions. To identify common features in the obtained velocity variation curves, we have performed the cluster analysis and separated all the curves in two groups having similar shapes within each group, but strongly different between the groups. Velocity changes in Cluster 1 corresponding to the station pairs covering the entire Northern Paramushir have some delayed correlation with the precipitation intensity, implying that these changes might be caused by meteoric fluid migration. In Cluster 2, which is more concentrated in the area of Ebeko Volcano, the velocity changes are apparently connected with both external factors (precipitation and atmospheric pressure) and internal indicators of volcano activity (phreatic explosions, seismicity, thermal anomalies and gas emission).