2008 Alum


Miriam Garcia

Miriam Garcia


Years participated in RESESS:
2006 →
2007 →
2008


An Overview

Mogi model application on Grímsvötn Volcano, Iceland: continuous GPS data (2004-2008)

Academic Affiliation: Graduate Student, New Mexico Institute of Mining and Technology, Geophysics
Science Research Mentors: Rick Bennett – University of Arizona; Charles Meertens – UNAVCO
Writing and Communication Mentor:Frederick Blume – UNAVCO


Abstract

Grímsvötn is a subglacial volcano in Iceland with the highest eruption frequency of any of Iceland’s 30 volcanic systems during the past 800 years. It is located below the Vatnajökull ice cap and above the Iceland mantle plume. This study focused on the analysis of Grímsvötn’s recent deformation that will allow a better understanding of its behavior. This insight might also be applicable to the assessment of the risk of volcanic hazards, such as glacial floods (jökulhlaups), that affect the local population. The 2004-2008 time series data from the continuous GPS station (GFUM) was divided into five events. A Mogi model for each event was used to find characteristics of an equivalent point source that results in the same 3-D displacements displayed by GFUM. The Mogi code consists of four parameters: source geometry, observation point, and the Poisson’s ratio and shear modulus of the surrounding crust. Three values are output by the code: displacements, strains, and stresses in the east, north, and up directions. All five recent volcanic events at Grímsvötn were fitted to a volume change at a specific depth using the displacement output. The November 2004 eruption (event 2) resulted in a volume decrease of 23.5E-3 km3 at a depth of 2.55 km. All events had similar model results with the exception of event 4, which had a deep source,15.2 km. There were several aspects of the modeling process that contributed to errors in the results: 1) a non-spherical magma source, 2) an inhomogeneous crust, 3) lack of continuous GPS data at GFUM.