[1] We measure P wave spectral amplitude ratios from deep-focus earthquakes recorded at broadband seismic stations of the Tanzania network to estimate regional variation of sublithospheric mantle attenuation beneath the Tanzania craton and the eastern branch of the East African Rift. One-dimensional profiles of QP adequately explain the systematic variation of P wave attenuation in the sublitho...

The thermal expansivity of oceanic lithosphere is a key mineral physics parameter that controls the rate of seafloor subsidence. Because of strongly temperature-dependent mantle rheology, effective expansivity for lithosphere as a whole could be substantially lower than indicated by mineral physics data. Viscoelastic modeling indicates that this reduction in expansivity could be as high as ∼15–...

[1] Recent evidence suggests that the Beta Regio equatorial highland, generally considered to be a plume-related structure, was emplaced over a relatively short period of time in the recent Venus history (100–400 m.y.). We perform numerical simulations which use this evidence as a new constraint on geodynamic models and find that it is difficult to satisfy simultaneously the constraint on the u...

[1] PS converted waves observed near Ancona on the Adriatic coast of central Italy, as revealed by teleseismic receiver functions (RFs), vary with earthquake backazimuth and epicentral distance in a manner consistent with a 1-D anisotropic seismic structure. Using reflectivity calculations, we develop a profile of anisotropic seismic velocity through the Adriatic lithosphere at this locality. W...

[1] Adakitic melts from Papua New Guinea (PNG) show adakitic geochemical characteristics, yet their geodynamic context is unclear. Modern adakites are associated with hot-slab melting and/or remelting of orogenic mafic underplate at convergent margins. Rift-propagation over collision-modified lithosphere may explain the PNG adakite enigma, as PNG was influenced by rapid creation and subduction ...

The Khoy Ophiolitic Complex (KOC) as a part of Tethyan, Izmir-Ankara- Erzincan and Bitlis-Zagros sutures of South East (SE) Turkey is broadly exposed around Khoy region (NW Iran). This complex comprises dismembered fragments of mantle lithosphere, obducted oceanic lithosphere and parts of volcanic arc remnants. The Khoy Ophiolitic Complex can be structurally divided into two major eastern and w...

The errors in plate motion azimuths inferred from shear wave splitting beneath any one tectonic plate are shown to be correlated with the errors of other azimuths from the same plate. To account for these correlations, we adopt a two-tier analysis: First, find the pole of rotation and confidence limits for each plate individually. Second, solve for the best fit to these poles while constraining...

S U M M A R Y Using both numerical experiments and approximate linear theory, we examine the stability of a 2-D, three-layered viscous system that represents crust over mantle lithosphere, overlying asthenosphere. If horizontal shortening of lithosphere occurs, as in mountain building, the development of gravitational instability may follow one of two distinct paths. Localized downwelling occur...

The. ce.c.c•ncl largest volcanic province on Mar• lies in the E!?ium region I•ike the larger Tharsis province, Elysium is marked by a topographic rise and a broad free air gravity anomaly and also exhibits a complex assortment of tectonic and volcanic features. We test the hypothesis that the tectonic features in the Elysium region are the product of stresses produced by loading of the Martian ...