HR: 1330h
AN: S22A-0408    [PDF]
TI: Convergence in a Model Viscous Lower Crust and its Surface Topographic Expression
AU: * Bendick, R
EM: bendick@esc.cam.ac.uk
AF: Department of Earth Sciences, Bullard Laboratories Madingley Road, Cambridge, CB3 0EZ United Kingdom
AU: McKenzie, D
EM: mckenzie@madingley.org
AF: Department of Earth Sciences, Bullard Laboratories Madingley Road, Cambridge, CB3 0EZ United Kingdom
AU: Jackson, J
EM: jackson@esc.cam.ac.uk
AF: Department of Earth Sciences, Bullard Laboratories Madingley Road, Cambridge, CB3 0EZ United Kingdom
AB: A 2-D analytic solution for the displacement of the upper surface of a viscous layer moving past a rigid body illustrates that such a system can produce measurable signals at the Earth's surface. This problem is best-known in the case of a rigid indenter intruding into a viscous fluid, often used to describe the case of rigid Indian lithosphere intruding into a fluid layer beneath Tibet. Similar geometry and distribution of mechanical properties may exist in other regions of convergent tectonics. In these cases, the indenter excites vertical velocity in the fluid, which drives displacement of the upper boundary at amplitudes and wavelengths related to the length scales of the fluid layer and the indenter. These displacements decay over time, but persist sufficiently to be expressed in real landscapes, such that observations of characteristic topography may serve as direct tests for the presence of flow in the lower crust. In particular, this model may be applied in cases such as Tibet where additional independent evidence for a channel of low viscosity exists in the distribution of seismic moment release or in observations of rheology from seismic wave velocities.
DE: 5460 Physical properties of materials
DE: 7205 Continental crust (1242)
DE: 7218 Lithosphere and upper mantle
DE: 8120 Dynamics of lithosphere and mantle--general
DE: 8159 Rheology--crust and lithosphere
SC: Seismology [S]
MN: 2003 Fall Meeting