Abstract The crust beneath transform faults at slow-spreading ridges has been considered to be thin, comprising a thin mafic layer overlying serpentinized peridotite. Using wide-angle seismic data, we report the presence of Moho ?6 km depth and low-velocity anomaly extending down 9 20-km-wide Romanche valley floor in equatorial Atlantic Ocean. low crustal velocities above could due either highl...

[1] Mars Orbiter Laser Altimeter (MOLA) topography and gravity models from 5 years of Mars Global Surveyor (MGS) spacecraft tracking provide a window into the structure of the Martian crust and upper mantle. We apply a finite-amplitude terrain correction assuming uniform crustal density and additional corrections for the anomalous densities of the polar caps, the major volcanos, and the hydrost...

We discuss the use of a genetic algorithm (GA) to invert data for many acceptable solutions, in contrast to inversion for a single, "optimum" solution. The GA is a directed search method which does not need linearization of the forward problem or a starting model, and it can be applied with a very large mode!-space. Consequently, fewer assumptions are required and a greater ange of solutions is...

study crust and upper mantle structure below the surface of earth is one of the important objectives of geophysics. teleseismic body waveforms have been used to infer crust and upper mantel structure. the iranian plateau is part of the alpine-himalayan orogenic belt. the zagros mountain belt in southwestern iran has resulted from the collision of arabian plate with the continental crust of cent...

earthquakes travel times inversion for determination of velocity structure of crust is one of the most important objectives in seismology. in the simultaneous inversion method, the parameters of earthquakes and velocity model are determined initially and are improved during inversion steps. in this study, we have used more than 22000 calculated travel times for first arrivals of 6000 earthquake...

The fate of the colliding Indian and Asian tectonic plates below the Tibetan high plateau may be visualized by, in addition to seismic tomography, mapping the deep seismic discontinuities, like the crust-mantle boundary (Moho), the lithosphere-asthenosphere boundary (LAB), or the discontinuities at 410 and 660 km depth. We herein present observations of seismic discontinuities with the P and S ...

Rare ultrahigh-temperature–(near)ultrahigh-pressure (UHT–near-UHP) crustal xenoliths erupted at 11 Ma in the Pamir Mountains, southeastern Tajikistan, preserve a compositional and thermal record at mantle depths of crustal material subducted beneath the largest collisional orogen on Earth. A combination of oxygen-isotope thermometry, major-element thermobarometry and pseudosection analysis reve...

The appearance of the earliest felsic crust can be estimated by dating zircons and rocks tonalite-trondhjemite-granodiorite (TTG) composition. However, necessary geodynamic processes that form basis for metamorphism differentiation as well role emerging TTG on evolving crustal dynamics is still poorly understood. To investigate formation with composition, we conduct a detailed analysis series p...

We find that in young and warm subducting plates, earthquakes occur just below the Moho. In older plates, earthquakes occur throughout the subducting oceanic crust, as well as the subducting mantle. We document this behavior in several subduction zones where there are independent constraints on earthquake locations and slab structure, specifically for northern and southern Japan, Alaska, and te...

The spatial and temporal variability of chemical signals in lavas, residues and melt inclusions provides important constraints on source heterogeneity, the efficiency of convection, and melt transport processes in the mantle. The past decade has seen an impressive increase in the number, precision and spatial resolution of chemical analyses. However, as resolution has increased, the picture of ...