Using linear inverse methods and finite element models to characterize fissure opening indicated by deformation measured using InSAR from the 2000 eruption of Hekla volcano, Iceland

Interferometric synthetic aperture radar (InSAR) is an invaluable tool for characterizing magmatic migration and storage within active volcanoes, based on surface deformation. With 18 eruptions over the past 11 centuries, Hekla is one of Iceland's most active volcanoes and began a 10-year eruption cycle with an eruption in 1970. The most recent eruption occurred in 2000, and Hekla is showing signs of renewed unrest. InSAR for Hekla, spanning October 1999 to June 2000, captured deformation of the 2000 eruption and is indicative of shallow dike intrusion that intersects the summit. For an elastic system, the observed deformation is a linear function of the dike opening. We use linear inverse methods to estimate the magnitude of opening, based on elastic half-space models and the following assumed geometric parameters for the dike: 6.6 km long, 5.8 km wide (down-dip), azimuth 65 degrees and dip of 72 degrees. Preliminary results suggest the dike opened by several tens of centimeters. We construct finite element models of Hekla to simulate an opening dike in an elastic domain having the irregular free surface of topography (image) and a distribution of material properties determined from seismic tomography models. We will reanalyze the InSAR data for Hekla's 2000 eruption by inverting for the distribution of dike opening, as well as for possible shearing, using finite element models to calculate the Green's Functions for displacement due to dike opening. This analysis will allow us to assess the importance of problem domain complexities for Hekla in an effort to better understand the behavior of this dynamic volcano.