Systematic search for background seismicity rate changes and correlation at Alaskan volcanoes

Abstract

Recent studies have noted a correlation between large earthquakes and localized seismicity rate changes, particularly those associated with volcanic systems. Few studies have been performed to determine if the background seismicity contains meaningful rate changes in the absence of large earthquakes. The Alaska Volcano Observatory (AVO) seismicity catalog is analyzed for background seismicity rate changes at the monitored volcanoes throughout the Aleutian Arc. The primary analysis was to identify statistically significant seismicity rate changes at the eighteen individual volcanic regions. Eleven volcanic regions had statistically significant background seismicity rate changes. Of particular interest are time periods when several volcanic regions have activity rate changes close in time. Once the groups are established using several criteria, they are probabilistically analyzed. If they have a low probability of being random and independent, it is inferred that the activity changes are related to one another. Ten groups of volcanoes with activity changes are found and may be evidence of regional stress changes in the Aleutian Arc. Seven groups are composed of statistically independent activity rate changes; of which, three groups are robustly independent. Speculations as to the cause of some of the regional stress changes include regional earthquakes and slow slip events.