Superionic hcp-Fe alloys and their seismic velocities in Earth’s inner core

Earth’s inner core (IC) is less dense than pure iron, indicating the existence of light elements within it1. Si, S, C, O, and H have been suggested to be the candidates2,3, and the properties of Fe-light-element alloys were studied to constrain the IC composition4-19. Light elements have a significant influence on seismic velocities4-13, melting temperatures15-17, and thermal conductivities of Fe-alloys18,19. However, the state of the light elements in the IC is rarely considered. Using ab initio molecular dynamics (AIMD) simulations, we found that H, O, and C in hexagonal close-packed (hcp) Fe transform to a superionic state under IC conditions, showing high diffusion coefficients like liquid. It suggests the IC can be in superionic state rather than normal solid state. The liquid-like light elements lead to a significant reduction in the seismic velocities approaching the seismological observation of the IC20,21. The significant decrease in shear wave velocity (VS) gives an explanation on the soft IC21. In adddtion, the light-element convection in the IC has potential influence on the IC seismological structure and magnetic field.

Where is seismic anisotropy located beneath the Alps and the Apennines?

<p>A general review on measurements of upper mantle seismic anisotropy in the Alpine and Apennines region is now encouraged by the large amount of data produced by several projects (i.e AlpArray, Cifalps1). Geodynamic studies need to have a sketch of mantle flows that drives the evolution of a<br>tectonically active region. This is particularly important for the Italian peninsula, where several slabs have been involved in the Alps and Apennines building and where they are still interacts with the Adriatic plate. Draw mantle flows starting from seismic anisotropy requires to locate the source of what SKS phases detect. The answer, often undetermined, it is frequently hypothesized cross-checking different seismological observation. Overlapping SKS data with tomographic models in this region gives little help, because of the large differences in the shape, depth and dimension of fast bodies identified by different tomographic studies. Mapping and comparing SKSs data with other types of anisotropy measurements (Pn anisotropy, azimuthal anisotropy from surface waves tomography, crustal anisotropy) allow to discretise where fast anisotropy direction is much more probably astenospheric or where it pervades also regions at shallower depths.</p>

GNSS Data Processing and Analysis for Earthquake Disaster Prevention Monitoring

This article describes how an earthquake with highest magnitude 5.8 on the Richter scale occurred in the Gyeongju area on Sep. 12, 2016 since the first seismological observation. In addition, continuous aftershocks have occurred. There is a pressing need for proper earthquake monitoring and prevention systems. This article is intended to apprehend the dislocation and location change of Continuously Operating Reference Station (CORS) caused by earthquake by means of data on CORS of the National Geographic Information Institute (NGII) and suggest effective seismic monitoring methods. Through Precise Point Positioning (PPP) over earthquake occurrence locations, it was possible to determine the dislocation aspects of CORS for TEGN and CHSG near the seismic epicenter. The nationwide Relative Positioning processing of data for 58 CORS from Sep. 1 to Sep. 30 suggested that CORS had not transitioned coordinates due to the earthquake. For the sake of more efficient earthquake observation and monitoring, it is believed that highly frequent GNSS data acquisition and the additional installation of observation devices such as seismometers is required.

THE EXPERIENCE AND THE RESULTS OF ENGINEERSEISMOMETRIC MONITORING OF ARMENIAN HYDRAULIC STRUCTURES

В работе приводятся результаты мониторинга системы инженерно-сейсмологического наблюдения, разработанных ИГИС НАН РА, для грунтовых плотин. The results of the monitoring system of the engineering seismological observation of NAS RA IGIS for ground dams