Phase velocities of rayleigh waves in the MELT experiment on the east pacific rise   总被引：2，自引：0，他引：2  

DW Forsyth  SC Webb  LM Dorman  Y Shen 《Science (New York, N.Y.)》1998,280(5367):1235-1238

The phase velocities of Rayleigh waves increase more rapidly with distance from the East Pacific Rise (EPR) axis than is predicted by models of conductive cooling of the lithosphere. Low velocities near the axis are probably caused by partial melt at depths of 20 to 70 kilometers in a zone several hundred kilometers wide. The lowest velocities are offset to the west of the EPR. Wave propagation is anisotropic; the fast direction is approximately perpendicular to the ridge, parallel to the spreading direction. Anisotropy increases from a minimum near the axis to 3 percent or more on the flanks.  相似文献   

Predatory dinosaur remains from madagascar: implications for the cretaceous biogeography of gondwana   总被引：1，自引：0，他引：1  

SD Sampson  LM Witmer  CA Forster  DW Krause  PM O'Connor  P Dodson  F Ravoavy 《Science (New York, N.Y.)》1998,280(5366):1048-1051

Recent discoveries of fossil vertebrates from the Late Cretaceous of Madagascar include several specimens of a large theropod dinosaur. One specimen includes a nearly complete and exquisitely preserved skull with thickened pneumatic nasals, a median frontal horn, and a dorsal projection on the parietals. The new materials are assigned to the enigmatic theropod group Abelisauridae on the basis of a number of unique features. Fossil remains attributable to abelisaurids are restricted to three Gondwanan landmasses: South America, Madagascar, and the Indian subcontinent. This distribution is consistent with a revised paleogeographic reconstruction that posits prolonged links between these landmasses (via Antarctica), perhaps until late in the Late Cretaceous.  相似文献