Progress in development of thermodynamically based models of straint on the thermal state of the Earth’s upper mantle (e.g. Klein & Langmuir, 1987; McKenzie & Bickle, 1988; silicate equilibria with explicit entropy budgets has motivated a reexamination of the conclusion of McKenzie that isentropic upwelAsimow et al., 2001). Meaningful interpretation of these data, however, requires a thorough u...

Isosta.tica,lly compensated crusta,1 thickness variations and associated topographic contrasts a,t the surface of a planet result in lateral pressure gradients, which may cause the lower crust to flow and reduce the relief. Areas of thicker crust are genera, lly associated with more rapid relaxation of topography. On Mars, topographic features such as impa, ct basins a, nd the hemispheric dicho...

Reducing scatter in measurements of regional-phase amplitude ratios is desirable for seismic discrimination applications and also provides insight into crustal structure controls on energy partitioning of regional seismic waves. Our previous analysis (Fan and Lay, 1998) of the regional seismic discriminant, Pg/Lg, indicated that variations in crustal structure cause path-specific fluctuations o...

[1] We estimate crustal structure and thickness of South America north of roughly 40°S. To this end, we analyzed receiver functions from 20 relatively new temporary broadband seismic stations deployed across eastern Brazil. In the analysis we include teleseismic and some regional events, particularly for stations that recorded few suitable earthquakes. We first estimate crustal thickness and av...

We evaluate the parameters that control the thickness of ductile shear zones that are generated by viscous heating. We employ two-dimensional thermomechanical numerical models to simulate shear zone development under compression. Results show that the shear zone thickness is essentially independent on the numerical resolution and the initial size of a weak inclusion that triggers shear localiza...

in this study we use the p receiver function technique to determine the moho depth and vp/vs ratio for 8 short period stations of qochan and mashhad seismic networks and map the variations of moho depth under kope dagh region. it is shown that a receiver function can provide a relatively good point measurement of moho depth under a short period station. the crustal thickness estimated from the ...

[1] Two of the most popular mechanisms for thickening the crust beneath the Tibetan Plateau are (1) pure shear with faulting and folding in the upper crust and horizontal shortening below and (2) flow of lower or middle crust without significant shortening of the upper crust. To help discriminate between the relative contributions of these two mechanisms, well-constrained estimates of upper cru...

The viscosity of lavas erupted at volcanic arcs varies over orders of magnitude. A comparison of the relative abundance of viscous lava dome eruptions indicates that the average viscosity of arc lavas also varies considerably between arcs. It is shown that for continental or transitional arcs with little within-arc crustal deformation and without underlying slab windows or tears, average lava v...