A 3-dimensional, fully nonlinear numerical geodynamo model is used to study the core-mantle coupling arising from a non-hydrostatic pressure field acting on an aspherical core-mantle boundary (CMB) based on a seismological model. The simulation results demonstrate that the topographic coupling torque is close to being proportional to the square of the amplitude of the CMB topography. We conclud...

A lower mantle S-wave triplication is detected using shortand long-period SH seismograms in the distance range 70 ø to 95 ø . Modeling of the observations with synthetic seismograms indicates that the tripliGation is produced by a 2.75 • 0.25% shear velocity increase about 280 km above the core-mantle boundary. The SH data from intermediate and deep focus events for three distinct source ragion...

Various phase transitions occur in the Earth's interior. They cause discontinuities seismic velocity and density profiles. The 410 km 660 are explained by olivine–wadsleyite transformation decomposition of ringwoodite into ferropericlase bridgmanite, respectively. major lower mantle spin transition minerals containing ferric ferrous irons, post-perovskite i.e., bridgmanite a with CaIrO3 structu...

Seismicity along continental transform faults is usually confined to the upper half of the crust, but the Newport-Inglewood fault (NIF), a major fault traversing the Los Angeles basin, is seismically active down to the upper mantle. We use seismic array analysis to illuminate the seismogenic root of the NIF beneath Long Beach, California, and identify seismicity in an actively deforming localiz...

[1] We used the Yellowknife seismic array (YKA) to measure the slowness of 1,371 P and Pdiff waves from earthquakes occurring in the circum-Pacific region. The corresponding anomalies in P-velocity show a sharp reduction of up to 6% across a patch of the lowermost mantle beneath the Northwest Pacific with lateral dimensions of several hundred kilometers. The location of this ultra low velocity ...

The internal structure of the core-mantle boundary (CMB) region of the Earth plays a crucial role in controlling the dynamics and evolution of our planet. We have developed a comprehensive model based on the radial variations of shear velocity in the D'' layer (the base of the lower mantle) and the high-P,T elastic properties of major candidate minerals, including the effects of post-perovskite...

Several seismic phases that scattered within a few hundred kilometers of the base of the mantle are observed in a very dense seismic section. The Los Angeles Region Seismic Experiment passive phase array was composed of 88 seismometers placed along a 175 km profile. Records from two deep earthquakes in Tonga and one earthquake near Honshu, Japan show a secondary arrival between clear P and PcP ...

[1] We calculated the elasticity of (Mg,Fe)SiO3-perovskite, using the plane-wave pseudopotential method for a pressure range that encompasses the earth’s lower mantle. Adding 25 mol% FeSiO3 to the Mg endmember decreases the shear modulus by 6% at zero pressure and by 8% at core mantle boundary pressures. The bulk modulus is less affected by iron, increasing by 2% at zero pressure and by 1% at t...

[1] Tharsis province is a major center of Martian volcanic activity characterized by large gravity and topography anomalies. The origin of Tharsis is debated. One hypothesis is that the province was produced by melting associated with a mantle plume from the coremantle boundary. An alternative hypothesis is that Tharsis formed by a plume associated with an impact. Recent studies have shown that...