Inferring Viscous Properties of the Lithosphere

Figure 1. Viscosity of the lithosphere beneath the Mojave Desert immediately after the 1992 Mw=7.3 Landers earthquake. View shows a cross-section of a finite element model that incorporates the Landers and 1999 Mw=7.1 Hector Mine rupture surfaces. Viscosity calculations are based on a powerlaw rheology comprising of a diabase crust and an olivine mantle (the Moho is located at a depth of 30 km). Viscosities are lowest (blue) in regions where coseismic stresses are highest, and decrease with depth due to temperature increases. This rheologic structure will increase in viscosity postseismically as stresses diminish due to relaxation, then decrease again due to stress associated with Hector Mine rupture. The inset shows GPS observed postseismic deformation (yellow circles) at a particular station on the surface following the Hector Mine quake. The red line shows the calculated surface deformation based on the powerlaw model. The blue line shows the best fitting Newtonian (stress invariant) model. These results support the contention that the lithosphere is governed by a powerlaw rheology as inferred from laboratory experiments.

Project Summary ***summary***

Tools Finite Element Modeling, GPS Data

Geographic Location Mojave Desert, southern California

Group Members Involved Andy Freed <Email> <Personal Web Site>
Roland Bürgmann

Project Duration In Progress

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