The ADSS-3 broadband stand-alone digital seismic station

The SSD-3 three-channel seismic recorder and the ADSS-3 three-component broadband standalone digital seismic station based on the SSD-3 together with SM-3E seismic sensors were developed. The main advantage of this equipment in comparison with foreign and domestic analogs is simplicity and convenience while maintaining high technical characteristics. The structure and operation of the seismic sensor and seismic recorder are considered, and their main technical characteristics are given. Laboratory, bench, and comparative tests of the seismic recorder and station demonstrated their working capacity and compliance with the development goal. Based on the test results, the ADSS-3 seismic station was commissioned as a three-component broadband observation point of the Mikhnevo small-aperture seismic array. The data obtained using the ADSS-3 made is possible to study the structure of the crust and upper mantle of this region using the receiver function method.     

The Japan Earthquake: Problems of Forecast

The results of registration of the catastrophic earthquake of March 11, 2011, that occurred near Honshu Island (Japan) with the broadband bottom seismograph of the Oceanology Institute, Russian Academy of Sciences on a test bed of the Experimental Design Bureau of Oceanologic Equipment (EDBOE), Russian Academy of Sciences (Moscow) are considered. The specification of the equipment and conditions of the experiment are presented. The records of the earthquake made in EDBOE and those made with a seismograph at the University of Portland (Oregon, United States) are compared, since these registration points are located at identical distances from the epicenter, but the distributions of seismic waves are essentially different. The possible directions of the development of methods and equipment for forecasting strong sea earthquakes and tsunami are examined.     

Long-term seismological sea-bottom monitoring using autonomous bottom stations

Merits and demerits of recording of seismic signals at the bottom of water areas are considered. It is shown that long-term seismological monitoring systems should be placed in the regions of industrial development of the shelf and continental slope and in the areas of high seismic and tsunami hazard of oceans and seas. The results obtained during expeditions of the Shirshov Institute of Oceanology of the Russian Academy of Sciences with the use of broadband bottom seismographs are reported. Autonomous bottom seismographs with long-term operation at the bottom and operative communication via satellite and radio channels are proposed for the formation of a marine seismological network.     

地震传感器的新技术与发展

宽频带、大动态、低噪声、低功耗、便携式、高度智能化是地球物理观测技术的发展趋势.本文简要回顾了地震传感器的发展,详细介绍了几种设计先进、性能优越、基于不同换能机理的新型地震传感器.这些传感器有些已经有原理样机,有些还处于概念设计中,它们将是未来宽频带地震仪技术发展的主要方向.     

Monitoring of the Arctic region: contribution of the Arkhangelsk seismic network

We evaluate the contribution of the Arkhangelsk seismic network to the recording of seismic events of the Arctic region. The evaluation is performed by means of the general analysis of the network seismic catalog, evaluation of the magnitude sensitivity, and comparative analysis of the Arkhangelsk network catalogs with NORSAR seismological data services and the Geophysical Service of the Russian Academy of Sciences. It is established that the Arkhangelsk network has a rather high sensitivity and records the intra-plate and inter-plate seismic activity in the Arctic Region. Due to the start of the seismic station operation on the Franz Josef Land Archipelago, there is a capability to record earthquakes, data on which are missing in the catalogs of well-known seismological data services.     

Time variations in the mechanical characteristics of local crustal segments according to seismic observations

The results of the seismic observations made with two different experimental setups are presented. In the first case, the signals produced by underground nuclear explosions at the Semipalatinsk Test Site were measured on a linear profile, which allowed one to definitely outline the areas where the mechanical properties of rocks experienced considerable time variations. In the second case, the waves excited by the open-pit mine blasts recorded at a small-aperture seismic array at the Mikhnevo Geophysical Station (Institute of Geosphere Dynamics, Russian Academy of Sciences) on the East European Platform favored the estimation of variations in the integral characteristics of the seismic path. Measurements in aseismic regions characterized by diverse geological structure and different tectonic conditions revealed similar effects of the strong dependency of seismic parameters on the time of explosions. Here, the variations experienced by the maximum amplitudes of oscillations and irrelevant to seasonal changes or local conditions reached a factor of two. The generic periods of these variations including the distinct annual rhythm are probably the fragments of a lower-frequency process. The obtained results suggest that these variations are due to changes in the stressstrain state of active fault zones, which, in turn, can be associated with the macroscale motion of large blocks triggered by tidal strains, tectonic forces and, possibly, variations in the rate of the Earth’s rotation.     

A five component land seismic sensor for measuring lateral gradients of the wavefield

We built a five-component (5C) land seismic sensor that measures both the three-component (3C) particle acceleration and two vertical gradients of the horizontal wavefield through a pair of 3C microelectromechanical accelerometers. The sensor is a small cylindrical device planted vertically just below the earth's surface. We show that seismic acquisition and processing 5C sensor data has the potential to replace conventional seismic acquisition with analogue geophone groups by single 5C sensors placed at the same station interval when combined with a suitable aliased ground roll attenuation algorithm. The 5C sensor, therefore, allows for sparser, more efficient, data acquisition. The accuracy of the 5C sensor wavefield gradients depends on the 3C accelerometers, their sensitivity, self-noise and their separation. These sensor component specifications are derived from various modelling studies. The design principles of the 5C sensor are validated using test data from purpose-built prototypes. The final prototype was constructed with a pair of 3C accelerometers separated by 20 cm and with a self-noise of 35 ng Hz^−1/2. Results from a two-dimensional seismic line show that the seismic image of 5C sensor data with ground roll attenuated using 5C sensor gradient data was comparable to simulated analogue group data as is the standard in the industry. This field example shows that up to three times aliased ground roll was attenuated. The 5C sensor also allows for correcting vertical component accelerometer data for sensor tilt. It is shown that a vertical component sensor that is misaligned with the vertical direction by 10° introduces an error in the seismic data of around –20 dB with respect to the seismic signal, which can be fully corrected. Advances in sensor specifications and processing algorithms are expected to lead to even more effective ground roll attenuation, enabling a reduction in the receiver density resulting in a smaller number of sensors that must be deployed and, therefore, improving the operational efficiency while maintaining image quality.     

2009年4月19日新疆阿合奇5.4级地震

利用俄罗斯科学院比什凯克科学站地震台网中3个台站资料和新疆地震台网12个台站资料,分别用不同地震定位方法,对2009年4月19日中国新疆阿合奇5.4级地震和其3个余震震源参数进行重新定位。并且将其结果与新疆地震目录、中国地震台网统一地震目录进行了比较,对其宏观震中、发震构造、震源机制及地震类型等进行了分析与讨论。     

宽频带流动地震台站中地震计浅井式安装研究

在井下地震观测中,各种地表背景噪声具有显著衰减作用,针对中国地震科学台阵现有大量非专用浅井式设计的Guralp CMG系列地震计,以及目前多个新获批项目在高背景噪声区域的观测需求,设计一种野外实用浅井观测方式,在北京国家地球观象台进行不同深度、不同井壁材质的观测对比实验,分析研究观测数据的背景噪声功率谱密度,结果表明,随着浅井深度的增加,地震背景噪声在垂直、水平向得到改善,改善程度随频率变化有所不同。分析认为,在华北现有地质环境下,6 m浅井是较为经济的观测方式,性价比高、占地小、施工简便,可用于后续多个项目的宽频带流动地震台阵观测。     

Neutron generation and geomagnetic disturbances in connection with the Chilean earthquake of February 27, 2010 and a volcanic eruption in Iceland in March–April 2010

The relationship between solar and geomagnetic activities in connection with seismicity and volcanic eruptions on the globe during the period 1680–2010 is studied. The centennial cycles of terrestrial endogenous activity, related to solar and geomagnetic activity, are revealed; at the beginning of these cycles, solar cycles with small Wolf numbers were detected, while intensive seismic and volcanic activity was observed for several decades. A stable negative correlation between seismicity and volcanism, on the one hand, and solar and geomagnetic activity, on the other hand, were found. Experiments, which were simultaneously carried out at the Pushkov Institute of Geomagnetism, Ionosphere, and Radiowave Propagation, Russian Academy of Sciences (IZMIRAN), Troitsk, Moscow oblast, and the Karymshina Complex Geophysical Observatory, Kamchatka Branch, Geophysical Survey, Russian Academy of Sciences, have verified the suggestion that disturbances in the geomagnetic field and neutron generation occur during the early stages of strong earthquakes. It is supposed that the mechanism of primary generation of terrestrial neutrons is related to nuclear reactions in the Earth’s interior.     

Adaptation of the hardware/software system for seismic monitoring in the Elbrus region and some observation results

The changes in the hardware/software system for seismic monitoring as applied to the conditions of the adit of the Institute of Nuclear Research, Russian Academy of Sciences, in the Elbrus region are described. A three-component computer recording within the frequency range of 10–120 Hz was carried out with the averaging of vibration amplitudes on an interval of 5 s. The results of data processing for the first six months of monitoring carried out starting from March 2008 in the adit are considered. The seismic field in the observation site has three main components: local earthquakes related to the two main magmatic fluid sources located nearby; a slowly changing wave field, possibly related to the same sources; and technogenic noise, in particular, vibration caused by the trolleys in motion, and a weak stationary background.     

Russian studies of Antarctic auroras: A review

The studies of auroras at Russian Antarctic observatories in the Southern Hemisphere began in 1957 during the second Complex Antarctic expedition and performed almost continuously up to 1993 during more than 30 years. Many observers of auroras and scientists that analyzed obtained results participated in these studies. Members of the Arctic and Antarctic Research Institute (AANII), Russian Committee on Hydrometeorology (Rosgidromet); Pushkov Institute of Terrestrial Magnetism, Ionosphere, and Radiowave Propagation, Russian Academy of Sciences (IZMIRAN); Vernov Institute of Nuclear Physics, Moscow State University (NIIYaF MGU); Polar Geophysical Institute, Russian Academy of Sciences (PGI); St. Petersburg State University (SPbGU); Schmidt Institute of Physics of the Earth (IFZ); Shafer Institute of Cosmophysical Research and Aeronomy, Siberian Branch, Russian Academy of Sciences (IKFIA SB RAN); and other institutions made an enormous contribution to the studies of Antarctic auroras. The main results of the studies of Antarctic auroras, obtained by Russian scientists, are reviewed in this work.     

Regional variation of spectral parameters for seismic design from broadband probabilistic seismic hazard analysis

The characterisation of the seismic hazard input is a critical element of any seismic design code, not only in terms of the absolute levels of ground motion considered but also of the shape of the design spectrum. In the case of Europe, future revisions of the seismic design provisions, both at a national and a pan‐European level, may implement considerable modifications to the existing provisions in light of recent seismic hazard models, such as the 2013 European Seismic Hazard Model. Constraint of the shape of the long‐period design spectrum from seismic hazard estimates on such a scale has not been possible, however, owing to the limited spectral period range of existing ground motion models. Building upon recent developments in ground motion modelling, the 2013 European Seismic Hazard Model is adapted here with a new ground motion logic tree to provide a broadband Probabilistic Seismic Hazard Analysis for rock sites across a spectral period range from 0.05 seconds to 10.0 seconds. The resulting uniform hazard spectra (UHS) are compared against existing results for European and broadband Probabilistic Seismic Hazard Analysis and against a proposed formulation of a generalised design spectrum in which controlling parameters can be optimised to best fit the uniform hazard spectra in order to demonstrate their variability on a European scale. Significant variations in the controlling parameters of the design spectrum are seen both across and within stable and active regions. These trends can help guide recalibrations of the code spectra in future revisions to seismic design codes, particularly for the longer‐period displacement spectrum.     

A parametric representation of Kamchatka seismicity over time

This paper presents a set of seismicity parameters that are estimated at the Kamchatka Branch of the Geophysical Service, Russian Academy of Sciences based on the regional catalog data with the purpose of routine monitoring of the current seismic situation in the region. The focus is on the identification of changes in the seismic regime (seismic quiescences and seismicity increases) in earth volumes adjacent to the maturing rupture zone of a large earthquake. The techniques we use include estimation of the seismicity level for the region using the SOUS’09 scale; calculation of the variations in the slope of the recurrence relation, identification of statistically significant anomalies in the slope using the Z test, and calculation of the seismic activity A ₁₀; monitoring the RTL parameter and variations in the area of seismogenic ruptures; using the Z test to detect areas of statistically significant decreases in the rate of seismicity; and identification of earthquake clusters. We furnish examples of such anomalies in these seismicity parameters prior to large earthquakes in Kamchatka.     

Variations in the Parameters of Background Seismic Noise during the Preparation Stages of Strong Earthquakes in the Kamchatka Region

The results of the long (2011–2016) investigation of background seismic noise (BSN) in Kamchatka by the method suggested by Doct. Sci. (Phys.-Math.) A.A. Lyubushin with the use of the data from the network of broadband seismic stations of the Geophysical Survey of the Russian Academy of Sciences are presented. For characterizing the BSN field and its variability, continuous time series of the statistical parameters of the multifractal singularity spectra and wavelet expansion calculated from the records at each station are used. These parameters include the generalized Hurst exponent α*, singularity spectrum support width Δα, wavelet spectral exponent β, minimal normalized entropy of wavelet coefficients En, and spectral measure of their coherent behavior. The peculiarities in the spatiotemporal distribution of the BSN parameters as a probable response to the earthquakes with М_w = 6.8–8.3 that occurred in Kamchatka in 2013 and 2016 are considered. It is established that these seismic events were preceded by regular variations in the BSN parameters, which lasted for a few months and consisted in the reduction of the median and mean α*, Δα, and β values estimated over all the stations and in the increase of the En values. Based on the increase in the spectral measure of the coherent behavior of the four-variate time series of the median and mean values of the considered statistics, the effect of the enhancement of the synchronism in the joint (collective) behavior of these parameters during a certain period prior to the mantle earthquake in the Sea of Okhotsk (May 24, 2013, M_w = 8.3) is diagnosed. The procedures for revealing the precursory effects in the variations of the BSN parameters are described and the examples of these effects are presented.     

Seismic and infrasonic monitoring on the Spitsbergen archipelago

In late 2010, the Geophysical Survey, Kola Branch, Russian Academy of Sciences installed a system of constant seismic and infrasonic monitoring on the Spitsbergen archipelago. To date, this system is the only tool to implement joint monitoring of seismic and infrasonic events in this part of the Arctic. The hardware and software structure of subsystems of monitoring and data transmission are considered. The automatic detection of infrasonic events is described. Widespread commercially available hardware components have been used. Preliminary results of the seismic and infrasonic monitoring on the Spitsbergen archipelago in 2011 are given. A hypothesis is developed about the relationship between infrasonic and seismic emissions with the processes occurring in the cryosphere of the archipelago.     

Operating principles and technical characteristics of a small-sized molecular-electronic seismic sensor with negative feedback

The results of analysis of the output parameters of small-sized seismic motion sensors based on molecular electronics are presented. These devices feature a molecular-electronic transducer with negative feedback the introduction of which makes it possible to improve the sensor performance (specifically, to broaden the frequency range, reduce the amplitude-frequency characteristic (AFC) unevenness, and reduce the nonlinear distortion factor (NDF) value). The operating principle of these devices is outlined. The basic characteristics such as AFC, NDF, and the inherent noise level are determined experimentally, and the methods of their determination are described. The obtained data are analyzed and compared to the data on similar foreign devices. Principal lines of further research aimed not only at improving the technical characteristics but also at establishing a serial production process are specified.     

Some results of microseismic monitoring in the Elbrus Region

The results of microseismic monitoring in the adit of the neutrino laboratory (Institute of Nuclear Research, Russian Academy of Sciences) in the Elbrus Region are presented. Three-component computer recording was carried out in the frequency band 10–120 Hz with 5-second averaging of the amplitudes of vibrations. We consider the results of processing the data yielded by the monitoring in the adit during nine months since March 2008. The seismic field at the observation point is composed of three main contributions: the local earthquakes associated with two main fluid-magmatic sources, which are located nearby the adit; a slowly varying wave field, which is probably related to the same sources; and the industrial noise, namely, the vibrations caused by the traffic of carriages and a weak stationary background noise.     

On the application of fiber optic gyroscopes for detection of seismic rotations

In recent years, the measurement of rotational components of earthquake-induced ground motion became a reality due to high-resolution ring laser gyroscopes. As a consequence of the fact that they exploit the Sagnac effect, these devices are entirely insensitive to translational motion and are able to measure the rotation rate with high linearity and accuracy over a wide frequency band. During the last decade, a substantial number of earthquakes were recorded by the large ring lasers located in Germany, New Zealand, and USA, and the subsequent data analysis demonstrated reliability and consistency of the results with respect to theoretical models. However, most of the observations recorded teleseismic events in the far-field. The substantial mass and the size of these active interferometers make their near-field application difficult. Therefore, the passive counterparts of ring lasers, the fiber optic gyros can be used for seismic applications where the mobility is more important than extreme precision. These sensors provide reasonable accuracy and are small in size, which makes them perfect candidates for strong motion applications. The other advantage of fiber optic gyroscopes is that if the earthquake is local and shallow (like one occurred early this year at Canterbury, New Zealand), the large ring lasers simply do not have the dynamic range??the effect is far too large for these instruments. In this paper, we analyze a typical commercially available tactical grade fiber optic gyroscope (VG-951) with respect to the seismic rotation measurement requirements. The initial test results including translation and upper bounds of seismic rotation sensitivity are presented. The advantages and limitations of tactical grade fiber optic gyroscope as seismic rotation sensor are discussed.     

On applicability of the RTL prognostic algorithms and energy estimation to Sakhalin seismicity

Premonitory phases (seismic quiescence and foreshock activity) have been retrospectively identified before the Neftegorsk and Uglegorsk earthquakes using the RTL technique. The probabilities that these phases were accidental are less than 1 and 2%, respectively. This allows an optimistic assessment of the possibility of applying this technique to seismicity at Sakhalin. The estimates of the time and energy class for the two earthquakes, using a model of self-organized seismic criticality, proved to be unconvincing because obvious acceleration of the seismic process prior to these seismic events did not occur. The applicability of this approach to the seismicity at Sakhalin should be tested for future large earthquakes. The regional Sakhalin catalog for 1980–2000, with a lowest completely reported energy class of K = 8 (lent by the Geophysical Service, Russian Academy of Sciences) was used as the database for this study.