The available experimental data and steady-state calculations make it difficult to explain the M discontinuity beneath both oceans and continents on the basis of the same phase change. The oceanic M discontinuity may be a chemical discontinuity between basalt and peridotite , and a similar chemical discontinuity ma,y thus be expected b�neath the conti­ nents. Since ayailable experimental data p...

By comparing records of the radial component of motion of teleseismic P waves to records of the vertical component, it is possible to identify S phases within the P wave form. These phases are generated by the mechanism of P to S conversion at discontinuities in velocity under the receiving station. Similar phases of the S to P converted type appear as precursors to the direct SV arrival. Model...

We perform ambient noise tomography of China using the data from the China National Seismic Network and surrounding global and PASSCAL stations. The results so far are summarized below. (1) Dispersion measurements and tomography. For most of the station pairs, we retrieve good Rayleigh waveforms from ambient noise correlations using 18-months of continuous data at all distance ranges across the...

Abstract Oceanic island basalts and related magmatic rocks from Hawaii are derived a compositionally heterogeneous mantle plume. Here we describe how this heterogeneity results the transport of filaments specific composition in plume, representing relatively small volume (~15 %) interbedded inside dry peridotite mantle. Four types considered: sub-primitive mantle, ultralow-velocity zone, fertil...

Mt. Cameroon is one of the most active volcanoes in Africa and poses a possible threat to about half a million people in the area, yet knowledge of the volcano's underlying magma supply system is sparse. To characterize Mt. Cameroon's magma plumbing system, we employed mineral-melt equilibrium thermobarometry on the products of the volcano's two most recent eruptions of 1999 and 2000. Our resul...

The crustal structure of the Nordland and Troms region, Norway, has received growing scientific attention because (a) region is one most seismically active areas mainland (b) there are differing interpretations but none proposed models simultaneously satisfy gravity, topography isostasy. At core puzzle Lofoten-Vesterålen archipelago, which exhibits considerable variations in thickness, seemingl...