Abstract
Mt. Spurr is the largest active volcano in Alaska of high explosive potential. The most recent activity, including two recent magmatic eruptions in 1953 and 1992, has occurred via the flanking Crater Peak. From 2004 to 2006, strong seismicity, gas flux, and heating were observed in the summit area, which had remained inactive for more than 5 Ka. To understand the cause of this reactivation, we performed repeated tomography inversions that clearly imaged the magma reservoir beneath Mt. Spurr and showed temporal changes in its shape and intensity. During the two years preceding the unrest, we observed ascension of the upper limit of the reservoir-related anomaly from a depth of 5 to 3 km below the surface, accompanied by strong seismicity. During the following years, the shape of the anomaly remained unchanged, but its intensity weakened. These observations may indicate the release of fluids from the ductile reservoir and fast upward ascent through the brittle cover that caused intensive seismicity and gas flux during the unrest from 2004 to 2006. The origin of this zone will possibly cause a resumption of explosive eruptions in the summit area of Mt. Spurr.
Highlights
Active volcanoes are dynamic geological structures in which considerable changes in physical properties may occur very quickly[1,2]
The ratio reaches a value of 2, whereas in the surrounding areas, the Vp/Vs is generally low. Another common feature observed during all periods is an inclined anomaly connecting the reservoir-related anomaly to Crater Peak, where most of the recent magmatic eruptions have occurred
We can conclude that in the case of the selection of datasets of similar configurations, repeated local earthquake seismic tomography is able to show temporal variations in underground seismic velocities. These variations are clear beneath volcanoes in which active processes in the plumbing system may change the structure very rapidly compared to that of other geological structures
Summary
Active volcanoes are dynamic geological structures in which considerable changes in physical properties may occur very quickly[1,2]. Among the main causes of such changes is the migration of fluids, phase transitions, and degassing within the volcanic plumbing system that are the main reasons for explosive eruptions[3,4]. Based on interferometric synthetic aperture radar (InSAR) observations, Lu and Dzurisin[15] calculated a total inflation of ~5 cm in the Mt Spurr area during the unrest period of 2004–2006. They estimated that the source of this deformation was an expansion in volume of 0.05–0.06 km[3] at 10–14 km depth. All of these observations resulted in a high hazard level until early
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
