Temporal analysis of the magma supply system beneath the Okmok caldera by Interferometric Synthetic Aperture Radar and statistical seismology

Abstract

The temporal characteristics of the magma supply system beneath the Okmok caldera is examined using Interferometric Synthetic Aperture Radar (InSAR) and statistical seismology. Surface deformation produced by a shallow magma chamber is studied through time series analysis of InSAR imagery acquired between 1995 and 2008 by the ERS-1/2 satellites. A spherical source model (Mogi Source) is utilized to simulate the deformation pattern produced by the shallow magma chamber's fluctuating geometry. Statistical seismology provides an independent estimate of the magma chamber's depth to reduce the non-uniqueness of the Mogi source model solutions. Seismic results show that a shallow magma chamber is located approximately 4.0 km below the caldera floor. InSAR imagery indicates the chamber has expanded continuously between 1997 and 2008. Modeling results suggest that magma replenishment has occurred at an average rate of approximately 7.0 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> km <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> /year and that the volume within the chamber returned to its pre-1997 eruption state by June 2008.