Wave disturbances induced by crustal earthquakes: Case study of two strong earthquakes in the Caucasian-Anatolian sector of the Alpine Mediterranean mobile belt

The display conditions of strong earthquakes in the Caucasian-Anatolian sector of the Mediterranean mobile belt are analyzed with allowance for the instrumental observations by titlmeters and magnetic variometers at the North Caucasian geophysical observatory of Schmidt Institute of Physics of the Earth of the Russian Academy of Sciences (NCGO IPE RAS) (Elbrus volcanic region) and at the magnetic stations operated by the Institute of Terrestrial Magnetism, Ionosphere, and Radio Wave Propagation (IZMIRAN). It is demonstrated that the geophysical information obtained during the preparatory stages of the earthquakes on March 8, 2010 and January 19, 2011 in Turkey and the North Caucasus, respectively, reflect the fine structure of the anomalous wave processes of the preparation and evolution of the crustal earthquakes. The results provide a general idea of the geomagnetic activity and some characteristic features of the induced anomalous disturbances in the Caucasian-Anatolian sector of the Alpine Mediterranean mobile belt, which precede and accompany strong seismic events.     

Klimovskaya: A new geomagnetic observatory

In 2011 Geophysical Center RAS (GC RAS) began to deploy the Klimovskaya geomagnetic observatory in the south of Arkhangelsk region on the territory of the Institute of Physiology of Natural Adaptations, Ural Branch, Russian Academy of Sciences (IPNA UB RAS). The construction works followed the complex of preparatory measures taken in order to confirm that the observatory can be constructed on this territory and to select the optimal configuration of observatory structures. The observatory equipping stages are described in detail, the technological and design solutions are described, and the first results of the registered data quality control are presented. It has been concluded that Klimovskaya observatory can be included in INTERMAGNET network. The observatory can be used to monitor and estimate geomagnetic activity, because it is located at high latitudes and provides data in a timely manner to the scientific community via the web-site of the Russian–Ukrainian Geomagnetic Data Center. The role of ground observatories such as Klimovskaya remains critical for long-term observations of secular variation and for complex monitoring of the geomagnetic field in combination with low-orbiting satellite data.     

Instrumental observations of geomagnetic disturbances prior to seismic events in several regions of China

The paper presents results of instrumental observations of seismic processes and variations in the Earth’s magnetic field at the stages of nucleation and development of earthquakes in the Chinese provinces of Qinghai, Sichuan and Yunnan. Data on manifestations of all these strong seismic events are indicated. Monitoring of the changes in the magnetic field is based on data obtained at the Northern Caucasus Geophysical Observatory, IPE RAS and integrated observation points of the Institute of Terrestrial Magnetism, the Ionosphere and Radio Wave Propagation, RAS (IZMIRAN). The experimental results have allowed us to represent the structure of induced anomalous geomagnetic disturbances, which can be associated with the development of related geodynamic processes in the geological medium of the seismic source zone.     

The catalogue of Quaternary volcanoes of the Greater Caucasus based on geochronological,volcanological and isotope-geochemical data

A catalogue of Quaternary volcanoes of the Greater Caucasus has been compiled based on recent geological, petrological-geochemical and isotope-geochronological data obtained in the last decades. This catalogue provides insight into the evolution of the youngest magmatism in this part of the Alpine-Himalayan fold belt at the modern level of knowledge. The catalogue is given as a set of tabular data on 74 volcanic edifices that have been found and described in literature in varying detail, including their coordinates, absolute height, type of edifice and the predominant type of eruption, age, as well as main petrographic, isotope-geochemical characteristics, and the chemical composition of the products of magmatic activity. For the sake of convenience, the volcanoes of the Kazbek and Elbrus neovolcanic areas representing two main areals of young magmatism at the Greater Caucasus are described separately. In addition, data on the Kazbek area are grouped by traditionally distinguished volcanic centers. Text presents general information on the Quaternary volcanic activity within the Greater Caucasus, its geochronology, spatiotemporal distribution, and petrogenesis of the youngest volcanic rocks.     

Geodynamic models and their application in the combined interpretation of geological and geophysical data (a review)

The paper presents a review of investigations in the field of the theory and practice of the interpretation of geological and geophysical data with geodynamic models that were carried out mainly by researchers of the Institute of Physics of the Earth, Russian Academy of Sciences. Evolutionary models of platform structures, passive continental margins, rift zones, and orogens are examined. The review presents formulations of inverse problems and results of interpretation for various regions, including sedimentary basins of the East European Platform, Atlantic Ocean margins, the Caucasus, the South Urals, and others.     

华北克拉通中东部基底构造单元的重磁特征

系统收集并重新处理了华北克拉通中东部的重磁资料,利用处理结果,结合近年来华北克拉通前寒武纪结晶基底构造研究的进展,重新将华北克拉通中东部划分为2个一级重磁异常单元和7个二级重磁异常单元;重点描述了7条分划性断裂的重磁特征,特别指出中国东部重力梯度带正是华北克拉通中部带的集中表现,而郯庐断裂带和兰考～聊城～盐山～台安-大洼断裂带是燕山期陆内不同刚性块体调整的重要边界,所以也是重磁特征的变异带．据此,对华北克拉通断裂与构造单元的重磁异常特征赋予了新的地质意义．研究表明,华北克拉通现今的地球物理特征能够反映结晶基底构造,其原因是华北克拉通现今构造格局是中新生代构造继承结晶基底构造的结果．     

Common oscillatory modes in geomagnetic activity, NAO index and surface air temperature records

Detection and extraction of quasi-oscillatory dynamical modes from instrumental records of geophysical data became a useful tool in analyzing variability of observed phenomena reflected in complex, multivariate geophysical signals. Using the extension of the Monte Carlo singular system analysis (MC SSA), based on evaluating and testing regularity of dynamics of the SSA modes against the colored noise null hypothesis, we demonstrate detection of oscillatory modes with period of about 96 months in the long-term records of aa index as well as in the records of surface air temperature from several mid-latitude European locations and in the North Atlantic Oscillation index.     

Studying the Deep Structure of Elbrus Volcano by Microseismic Sounding

This paper presents results from a study of the deep structure of the Elbrus edifice and adjacent areas using geophysical techniques. We confirmed the existence of a shallow magma chamber, derived a more accurate location of the chamber in the host rocks and its characteristic dimensions, and compared new results with known studies. More accurate estimates have been obtained for the temperature at the top of the magma chamber and new evidence is adduced concerning the deep structure of the fluid magmatic systems in the Elbrus volcanic area.     

Influence of meteorological and wave processes on the lower ionosphere during solar minimum conditions according to the data on midlatitude VLF-LF propagation

The statistical characteristics of the intensity of VLF-LF radio signals transmitted from the midlatitude radio stations and recorded by the receiver at the Mikhnevo geophysical observatory (54.94°N, 37.73°E; Institute of Geosphere Dynamics, Russian Academy of Sciences) in 2007–2010 are analyzed. The experiments revealed strong variations in the intensity of radio signals during the deep solar minimum conditions, when the medium does not experience impacts from above associated with solar and geomagnetic activity. We relate the observed variations to the disturbances from below, which are caused by the meteorological and wave processes occurring in the lower atmosphere.     

Assessment of earthquake hazard for the northwestern Vietnam from geological and geophysical data using an original program package

The highest seismic activity in Vietnam is observed in the northwest of the country, hence the practical significance of more accurate assessment of the earthquake hazard for the area. The worldwide experience of seismicity, in particular, the recent Tohoku mega-earthquake (March 11, 2011, M _w = 9.0, Japan) shows that instrumental and historical data alone are insufficient to reliably estimate earthquake hazard. This is all the more relevant in relation to Vietnam where the period of instrumental observation is short and historical evidence is nearly lacking. In this connection we made an attempt to construct maps of earthquake hazard based on known seismicity data using the available geological and geophysical data and the method of G.I. Reisner and his associates for classification of areas by seismic potential. Since the question of what geological and geophysical parameters are to be used and with what weights remains unresolved, we developed a program package to estimate Mmax based on different options in the use of geological and geophysical data. In this paper we discuss the first results and the promise held by this program package.     

江苏新沂地震台短水准新场地映震能力分析

介绍了江苏新沂地震台短水准新场地的基本情况 ,运用滑动分析和自回归分析法对该台1995年至 1999年的资料进行了分析 ,得出江苏新沂地震台短水准新场地有一定映震能力的结论     

Observations of crustal tide strains in the Elbrus area

Results of observations of tidal strains of the crust in the tectonically active Elbrus area of the Northern Caucasus carried out with the use of the Baksan SSAI laser interferometer strainmeter over the period from 2003 through 2006 are presented. Harmonic analysis is performed with the help of the ETERNA software package. Statistically significant time variations in the amplitudes of the main tidal waves M ₂ and O ₁ are revealed. The influence of the topography on tidal strains in the Baksan gorge is estimated at 22% (an increase in the measured strain values). The reduced amplitude factors of the main diurnal (O ₁) and semidiurnal (M ₂) waves are underestimated. Numerical modeling of tidal anomalies produced by regional heterogeneous inclusions is performed in a 2-D approximation. The observed anomaly of the M ₂ wave (12%) is shown to be due to the influence of the main magma-controlling fault associated with the deep magma source of the Elbrus dormant volcano.     

Geomagnetic variation peculiarities at middle latitudes of the East European Platform

The results of instrumental observations of geomagnetic variations at the Mikhnevo midlatitudinal observatory of Institute of Geosphere Dynamics of the Russian Academy of Sciences (54.9595° N; 37.7664° E) are presented and discussed. The main periodicities of the local background variations of geomagnetic field are determined. Variations of ~ 27 days have been registered, as well as periodicities with periods of ~6–9, 12–14, 60 days, and a semiannual periodicity. It has been shown that the background geomagnetic variation periodicities have a sporadic and scaling character. An alternating effect of increasing and degradation periods in geomagnetic variation intensity (the intermittency effect) is found.     

Recent Efforts Toward the Establishment of the Lonjsko Polje Geomagnetic Observatory

More than ten years ago, the Geophysical Institute initiated the installation of a geomagnetic observatory in Croatia. Over the past decade, extensive surveys and studies have been conducted in order to determine the proper location for the observatory. Finally, in 2012, the observatory was established in Lonjsko Polje. This paper presents the first data recorded in the period 2012.5-2015.0. Also presented are the technical aspects and data processing techniques of this remotely operated observatory. Analysis of data quality and comparison with data from the surrounding INTERMAGNET observatories is discussed in detail. Although remote observatories cannot provide the ideal environment for magnetometers, the obtained results accentuate the potential of the new observatory to provide high-quality data. The establishment of this observatory paves the way for scientific and professional development of geomagnetism in Croatia.     

Estimating the influence of seismic and meteorological factors on the accuracy of measurements by relative gravimeters

Continuous high-precision long-term gravity measurements are carried out at the geophysical observatory located in the experimental base of Vladimir State University. The long time series of gravity acceleration and its standard deviation are obtained. The factors responsible for the increases in the studied deviations are analyzed. The recommendations for improving the accuracy of relative gravity measurements are formulated.     

Induction Sounding of the Earth’s Mantle at a New Russian Geophysical Observatory

Deep magnetotelluric (MT) sounding data were collected and processed in the western part of the East European Craton (EEC). The MT sounding results correspond well with impedances obtained by magnetovariation (MV) sounding on the new geophysical observatory situated not far from the western border of Russia. Inversion based on combined data of both induction soundings let us evaluate geoelectrical structure of the Earth’s crust and upper and mid-mantle at depths up to 2000 km, taking into account the harmonics of 11-year variations. Results obtained by different authors and methods are compared with similar investigations on the EEC such as international projects CEMES in Central Europe and BEAR in Fennoscandia.     

Not just computers and companions

Mary Brück's historical survey is the second RAS Series publication, and one that gives an insight into the different roles taken by women astronomers: original thinkers, computers, educators, and entrepreneurs. In this extract from the chapter "The Labyrinths of Heaven", we find out how Maria Short (c1788–1869) came to own and operate an observatory open to the public in the mid-19th century.     

Earthquake precursory research in western Himalaya based on the multi-parametric geophysical observatory data

The opening of cracks and influx of fluids in the dilatancy zone of impending earthquake is expected to induce short-term changes in physical/chemical/hydrological properties during earthquake build-up cycle, which should be reflected in time-varying geophysical fields. With this rationale, eleven geophysical parameters are being recorded in continuous mode at the Multi-Parametric Geophysical Observatory (MPGO), in Ghuttu, Garhwal Himalaya, for earthquake precursory research. The critical analysis of various geophysical time series indicates anomalous behavior at few occasions; however, the data is also influenced by many external forces. These external influences are the major deterrent for the isolation of precursory signals. The recent work is focused on the data adoptive techniques to estimate and eliminate effects of solar-terrestrial and hydrological/environmental factors for delimiting the data to identify short-term precursors. Although any significant earthquake is not reported close to the observatory, some weak precursory signals and coseismic changes have been identified in few parameters related to the occurrence of moderate and strong earthquakes.     

兰州卫星热红外与短临地震预报(Ⅰ)

甘肃省地震局在兰州观象台建成了专门用于地震预报的极轨气象卫星云图接收站 ,为利用卫星资料进行短临地震预报新方法的探索提供了得天独厚的资料条件。本文主要阐述地面热红外数据反演的基本方法和步骤。     

Synchronization system of stations records for Mikhnevo small aperture array

The small-aperture seismic array (SSA) operating in the seismic observatory of the Institute of Geosphere Dynamics, Russian Academy of Sciences (IGD RAS) in Mikhnevo allows establishment of spatial and timing distribution of seismic events with a magnitude of M = 1.5 and higher. In the course of its exploitation, we revealed the disadvantages of the synchronization system of seismic stations, which led to mismatches of seismic records both with astronomic time and between the channels of different analog-to-digital converters (ADCs). The complex of hardware-software tools was worked out in order to enlarge the reliability of the system and to provide its correspondence to the requirements of the SSA modernization. By the signals of the GPS receiver, the minute marker driver generates the pulses whose rising edges precisely coincide with the beginning of every minute of astronomic time. In addition to the main functions, the RS-485/RS-232 transmitter-receiver transforms these pulses into a serial code and passes it to the remote seismic station via the digital communication line. A specially designed COM-port switch receives the data from seismic stations and directs them to the computer in a single stream. Each data fragment from different channels is recorded in the common file as it proceeds to the switch inputs, which completely excludes the time mismatch between the records.