Bulletin of Volcanology

, Volume 73, Issue 2, pp 143–153

Mechanism of the 1996–97 non-eruptive volcano-tectonic earthquake swarm at Iliamna Volcano, Alaska

Research Article

DOI: 10.1007/s00445-010-0439-7

Cite this article as:
Roman, D.C. & Power, J.A. Bull Volcanol (2011) 73: 143. doi:10.1007/s00445-010-0439-7


A significant number of volcano-tectonic (VT) earthquake swarms, some of which are accompanied by ground deformation and/or volcanic gas emissions, do not culminate in an eruption. These swarms are often thought to represent stalled intrusions of magma into the mid- or shallow-level crust. Real-time assessment of the likelihood that a VT swarm will culminate in an eruption is one of the key challenges of volcano monitoring, and retrospective analysis of non-eruptive swarms provides an important framework for future assessments. Here we explore models for a non-eruptive VT earthquake swarm located beneath Iliamna Volcano, Alaska, in May 1996–June 1997 through calculation and inversion of fault-plane solutions for swarm and background periods, and through Coulomb stress modeling of faulting types and hypocenter locations observed during the swarm. Through a comparison of models of deep and shallow intrusions to swarm observations, we aim to test the hypothesis that the 1996–97 swarm represented a shallow intrusion, or “failed” eruption. Observations of the 1996–97 swarm are found to be consistent with several scenarios including both shallow and deep intrusion, most likely involving a relatively small volume of intruded magma and/or a low degree of magma pressurization corresponding to a relatively low likelihood of eruption.


Iliamna VolcanoVT earthquakeEarthquake swarmsStress tensor inversionFault-plane solutions

Copyright information

© Springer-Verlag 2011

Authors and Affiliations

  1. 1.Department of GeologyUniversity of South FloridaTampaUSA
  2. 2.Alaska Volcano ObservatoryUnited States Geological SurveyAnchorageUSA