Measuring and Modeling Viscoelastic Relaxation of the Lithosphere with Application to the Northern Volcanic Zone, Iceland

• Main Author: DiCaprio, Christopher John
• Format: Thesis
• Language: English
• Published: California Institute of Technology 2010
• Subjects: geophysics; finite element modeling; Earthquake clustering; viscoelastic; Tides; Iceland; rifting; InSAR; Geophysics; FOS Earth and related environmental sciences
• Online Access: https://dx.doi.org/10.7907/5vwk-0t35; https://resolver.caltech.edu/CaltechTHESIS:01242010-103547444

Viscoelastic relaxation of the stress perturbation caused by an earthquake or diking event can produce measurable ground deformation over 100 km away from the source. We consider the role of viscoelastic relaxation in two different contexts. First, we explore the role that post-seismic relaxation may play in loading a fault over the entire seismic cycle. Viscous relaxation recycles the stress that is shed by the co-seismic fault, acting to reload the fault with stresses in a non-linear fashion. Under conditions of rapid post-seismic relaxation and slow tectonic loading, stress recycling via viscoelastic relaxation can lead to clustering of earthquakes in time. The second context in which we consider viscoelastic relaxation involves the lithospheric response to a mid-ocean ridge rifting episode in Northern Iceland. The diking and subsequent relaxation act as a natural rock mechanics experiment, and in measuring and modeling the post-rifting response we aim to constrain the rheological properties of the Icelandic lithosphere. In order to use post-seismic or post-rifting relaxation to probe properties of the lithosphere, we must be able to precisely measure surface deformation. To that end, we have developed a couple of new interferometric synthetic aperture radar (InSAR) processing approaches: (1) Automatically producing multiple interferograms in a common coordinate system and (2) removing displacements caused by ocean tidal loading from InSAR observations. Both of these developments are essential as we begin to consider the systematic use of tens to hundreds of interferograms.