Magma plumbing system of Akutan volcano, Alaska inferred from InSAR images and numerical modeling

Akutan, one of the most active volcanoes in the Aleutian arc, has experienced over 27 eruptive episodes in the last two centuries. The most recent eruptive activity was a series of small steam and ash emissions from March to May 1992. Between 11 and 16 March 1996, more than 3000 earthquakes occurred in Akutan Island. This increase of seismicity was accompanied by significant surface deformation. We analyze interferograms from ERS-1/-2 and Envisat satellites which use C-band signal and an interferogram from JERS-1 satellite which uses L-band signal. The L-band signal, whose wavelength is about four times as long as the C-band signal, is less prone to vegetation-induced temporal decorrelation. Thus, the JERS-1 interferogram has better coherence and wider coverage. The ERS-1/2 interferograms consist of a number of isolated patches across which the relative offset cannot be determined. We explore the possibility of constraining the relative offsets using the JERS-1 interferogram. To explain the interferograms we model the surface deformation associated with the seismic swarm using a dike subject to a uniform pressure and a uniformly depressurized shallow dipping ellipsoidal spheroid. Combining interferograms before and after the 1996 seismic swarm, we produce a mechanical model to explain deformation observed from 1992 to 2006.