The Peculiarities of the Earth’s Outer-to-Inner Core Transition Zone from the Characteristics of PKIIKP and PKP c-dif Waves

Izvestiya, Physics of the Solid Earth - Abstract—The structure of seismic wavefield at distances close to antipodal is analyzed using two numerical methods—DSM and AXISEM—for...     

Weak velocity anomaly in the Earth’s outer core from seismic data

Experimental data on the differential travel time t _BC–t _DF of seismic waves PKP_DF and PKP_BC in the Earth’s core under Africa and Australia are analyzed. The differential travel-time residuals beneath Africa in a narrow range of angles from 21° to 25° between the direction of the seismic ray in the core and the Earth’s rotation axis exhibit a scoop-shaped peculiarity not accounted for by cylindrical anisotropy in the inner core. A model with a 0.2–0.8% P-wave velocity anomaly with a radius of 1375 km in the cylindrical region in the outer core is proposed, which closely fits the experimental data. We suggest that the velocity anomaly is generated by the dynamical processes occurring in the outer core, namely, the growth of the inner core and the convection in the outer core, both leading to the formation of a low-density anomaly in the outer core.     

Seismic Studies of the Earth’s Core

Izvestiya, Physics of the Solid Earth - Abstract—The paper presents the review of the conceptually most important results of seismological studies of the Earth’s core and their...     

Shear Wave Velocity in the Top of the Earth’s Inner Core

Doklady Earth Sciences - Analysis of PKIIKP waves reflected off the inner surface of the solid core boundary and recorded close to the antipode indicates that the shear wave velocity at its top can...     

Mechanical Q-Factor in the Earth’s Upper Inner Core Inferred from PKiKP Coda Waves

Izvestiya, Physics of the Solid Earth - Abstract—Based on the alpha-shape computer-graphics analysis of coda envelope of the waves from nuclear explosions reflected from the inner core...     

Comparative analysis of the characteristics of domestic and foreign broadband seismometers with capacitive transducers

A family of seismometers has been developed with capacitive transducers that convert the relative displacement between the inertial mass and the base of the device into an electric signal. The seismometers have high sensitivity and a unified electronic circuit, and they can be rather easily manufactured, installed, and calibrated. Mass production of these instruments looks promising. To assess the possibility of using these seismometers as substitutes for imported counterparts, a comparative analysis was carried out to study the performance of an SM-3E broadband sensor with a capacitive transducer and imported STS-2 and CMG-6T seismometers. Seismic recordings of these three instruments mounted on the same pedestal were statically analyzed in the time and frequency domains.     

The Density Jump at the Inner Core Boundary in the Eastern and Western Hemispheres

The results of analysis of more than 1300 new PKiKP/PcP amplitude ratios measured in Southeast Asia and South America at the epicentral distances of 3.2°–35.2° are presented. The density jump in the Eastern Hemisphere of the Earth’s inner core (IC) is 0.3 g/cm³, and it is 0.9 g/cm³ in the Western one. Taking the large discrepancy in the obtained estimates into consideration, maintenance of such large lateral variations in the mosaic properties of the IC reflecting surface requires considerable variations in the thermodynamic parameters (mostly temperature) of the inner–outer core transition. However, if the observed asymmetry in the density jump distribution is of a global character, the data presented support the translation model of the IC dynamics. This model implies IC crystallization in the Western Hemisphere and melting in the Eastern one, not vice versa, as suggested by another geodynamic model based on thermochemical convection in the outer core and the thermal balance of the core–mantle system.