Quasi-static crustal deformations due to a surface load: Rheological structure of the earth's crust and upper mantle.

Abstract

In this paper, we treat quasi-static displacement fields due to an axially symmetric load applied on the surface of a composite medium which consists of elastic layers overlying a stratified viscoelastic half-space. Integral representations of the surface displacements are obtained from those in the associated elastic problem by applying the correspondence principle of linear viscoelasticity. General features of the viscoelastic displacements are examined from various aspects through the computation of numerical examples for a three-layered model composed of an elastic surface layer, an intervening low viscosity layer and a viscoelastic substratum with relatively high viscosity.Uplift phenomena in two tectonically different regions, Fennoscandia and Lake Bonneville (the Basin and Range province), are analyzed to investigate regional difference in rheological structure of the earth's crust and upper mantle. The uplift data in Fennoscandia are well interpreted by a three-layered model which consists of a 100km thick elastic surface layer (lithosphere) and a 100-200km thick low viscosity layer (asthenosphere) overlying a relatively high

Quasi-static deformation due to a dislocation source in a Maxwellian viscoelastic earth model.

“…According to analyses of postglacial uplift data; the average viscosity and thickness of the low viscosity layer are estimated as 10 20-10 21 poises and 100-200 km, respectively. The viscosity of the substratum is 10-100 times greater than that of the low viscosity layer (McCONELL, 1968;WALCOTT, 1973 ;CATHLES, 1975 ;IWASAKI and MATSU'URA, 1982).…”

“…From analyses of postglacial uplifts, the viscosity and thickness of the low viscosity layer have been determined to be 10 20-10 21 poises and 100-200 km, respectively (McCONELL, 1968;WALCOTT, 1973;CATHLES, 1975;IWASAKI and MATSU'URA, 1982). The viscosity of the substratum has been estimated as about 10 22 poises, which is greater than that of the asthenosphere by one or two orders.…”

Geometric evolution of a plate interface–branch fault system: Its effects on the tectonic development of the Himalayas

“…Here, the elastic surface layer and the viscoelastic substratum correspond to the lithosphere and the asthenosphere, respectively. Analyses of post-glacial uplift data show that the lithosphere and the asthenosphere behave like a perfectly elastic solid and a Maxwell fluid with the viscosity of 10 19 -10 20 Pa s on a time-scale shorter than 10 6 yr (Cathles, 1975;Iwasaki and Matsu'ura, 1982). In tectonically active regions such as the India-Eurasia collision zone, the viscosity of the asthenosphere has a somewhat smaller value (5·10 18 Pa s) than this global average.…”

Crustal and Lithosphere Dynamics: An Introduction and Overview

“…Iwasaki and Matsu'ura (1982) used uplift data from the shorelines of former Lake Bonneville and Fennoscandia to estimate both the elastic layer thickness, H (note that we use H in this paper to define the intermediate-term elastic layer thickness in order to distinguish it from the short-term elastic layer thickness, h, and the long-term elastic thickness, T e ), and upper-mantle viscosity, . He found that there were two spectral peaks in the Fennoscandia uplift data: a primary long-wavelength (l $ 800 km) peak that required very long relaxation times and hence a viscous mantle to explain it and a secondary short-wavelength (l $ 480 km) peak that required short times and a less-viscous mantle.…”