HR: 15:10h
AN: S22C-07    [PDF]
TI: The Influence of Loads Without Topographic Expression and Edge Effects on Estimates of the Elastic Thickness of Continents
AU: * McKenzie, D
EM: mckenzie@esc.cam.ac.uk
AF: Cambridge University, Bullard Labs Madingley Rd., Cambridge, CB3 0EZ United Kingdom
AB: The elastic thickness $T_e$ of continental lithosphere is of great importance because it controls the mechanical behaviour of continents. In tectonically active regions there is general agreement that it is small, but estimates for shields still differ by as much as a factor of five. Estimates from Bouguer coherence often exceed 100 km, whereas those from the shape of the flexural gravity anomalies are often less than 20 km. The reason why the Bouguer coherence gives such large values of $T_e$ is because erosion produces loads with no topographic expression, which are therefore incoherent with the topography. However, they do have a coherence of 1 between their surface and internal components. Though such loads are assumed to be absent when estimates of $T_e$ are obtained by the standard methods, they dominate the gravity field over most shields. Though in-plane stresses have an important effect on the stress state of the continental lithosphere, they produce negligible changes in the estimates of $T_e$. Gravity anomalies due to edge effects at the margins of plateaus also have a minor influence on such estimates when their value exceeds 15-20 km.
DE: 7218 Lithosphere and upper mantle
DE: 8120 Dynamics of lithosphere and mantle--general
SC: Seismology [S]
MN: 2003 Fall Meeting