Chemical composition of precipitation in the southern part of the Russian Far East

Distribution of macro-and microelements, found in precipitation in dissolved and suspended forms (solid material) is considered. Contribution of the main sources of substance input in the precipitation on the investigated area is assessed.     

Gravity indicator of rheological properties of the tectonosphere of the Russian Far East

Formal indicators of the existence of spatially isolated layers characterized by the absence of sources of intense gravity anomalies in them are revealed in the tectonosphere of the eastern Baikal region, the Amur region, the Sea of Okhotsk, Kamchatka, and northeastern Russia. A stable correlation of these layers with thermal, high electrical conductivity, and lower seismic velocity anomalies implies that they are related to rheologically weakened zones of the tectonosphere, i.e., layers of lower viscosity or higher plasticity or fluidity. Minimum vertical gradients of the surface density of spherical sources of gravity anomalies, equivalent to density inhomogeneities of the compaction class, are gravitational indicators of these zones.     

The Early Cretaceous coal‐forming plants of southern part of East Siberia and Russian Far East

For the first time the plants that gave rise to the Early Cretaceous coals of Transbaikalia (Khilok, Chita‐Ingoda, Bukachacha, and Turga‐Kharanor basins), Amur River region (Bureya Basin), and Primorye region (Razdolnaya River and Partizansk River basins) have been obtained. The plants that produced coals mainly belong to the ginkgoaleans (Pseudotorellia, Sphenobaiera, and Baierella), bennettites, and conifers having pinaceous, taxodiaceous, araucariaceous affinity, as well as extinct cheirolepidiaceous and miroviaceous plants. A parallel palynological study has identified a number of the same elements in addition to the cyatheaceous, gleicheniaceous, osmundaceous, and schizaeaceous ferns.     

Concept for developing a seismologic observation system for tsunami warning in the Russian Far East

The initial information and requirements for developing a seismologic observation system and data-processing and transfer tools for a tsunami warning system and its functions and tasks are considered. The structure of the seismologic observation system for the tsunami warning service (TWS) in the Russian Far East is proposed. A study of general technical and methodological problems is carried out to increase the efficiency for urgent tsunami prediction from continuous seismic monitoring data of territories of the Russian Far East and the world. Special attention is paid to the problem of tsunami prediction from seismologic data on strong earthquakes in near zone of a protected territory (up to 200 km).     

Crustal inhomogeneities and seismicity near the margins of the North Atlantic Ocean

Some very pronounced crustal inhomogeneities have been found in the North Sea and in Greenland, in regions which were adjacent to each other before the opening of the North Atlantic Ocean by sea-floor spreading. Some of these regions of inhomogeneities are zones of relatively high seismicity, while others are aseismic. In the North Sea, the Viking Graben has earthquakes, while its southern continuation, the Central Graben, is almost aseismic. In eastern Greenland, there are only few earthquakes near the Mesozoic graben, while there is a prominent earthquake zone at the coast line in north-eastern Greenland. It is concluded that, superposed on the apparent similarities in the two regions, some differences in stress conditions or crustal weakness patterns must exist.     

Gravity anomaly, lithospheric structure and seismicity of Western Himalayan Syntaxis

A compiled gravity anomaly map of the Western Himalayan Syntaxis is analysed to understand the tectonics of the region around the epicentre of Kashmir earthquake of October 8, 2005 (Mw = 7.6). Isostatic gravity anomalies and effective elastic thickness (EET) of lithosphere are assessed from coherence analysis between Bouguer anomaly and topography. The isostatic residual gravity high and gravity low correspond to the two main seismic zones in this region, viz. Indus–Kohistan Seismic Zone (IKSZ) and Hindu Kush Seismic Zones (HKSZ), respectively, suggesting a connection between siesmicity and gravity anomalies. The gravity high originates from the high-density thrusted rocks along the syntaxial bend of the Main Boundary Thrust and coincides with the region of the crustal thrust earthquakes, including the Kashmir earthquake of 2005. The gravity low of HKSZ coincides with the region of intermediate–deep-focus earthquakes, where crustal rocks are underthrusting with a higher speed to create low density cold mantle. Comparable EET (∼55 km) to the focal depth of crustal earthquakes suggests that whole crust is seismogenic and brittle. An integrated lithospheric model along a profile provides the crustal structure of the boundary zones with crustal thickness of about 60 km under the Karakoram–Pamir regions and suggests continental subduction from either sides (Indian and Eurasian) leading to a complex compressional environment for large earthquakes.     

Intergranular trace elements in mantle xenoliths from Russian Far East: Example for mantle metasomatism by hydrous melt

Based on both major and trace element chemistry, the occurrence of the intergranular component in mantle-derived xenoliths from far eastern Russia has been constrained. Whole-rock trace element measurements of one xenolith show apparent negative anomalies in Ce, Th, and high field strength elements on normalized trace element patterns. The trace element pattern of the whole rock differs from those of constituent minerals, indicating that the anomalies in the whole rock are attributable to the presence of an intergranular component. That assumption was confirmed using in situ analysis of trace elements in the intergranular substance and melt inclusion using laser ablation inductively coupled plasma–mass spectrometry. Both the intergranular component and the melt inclusions have identical trace element patterns, which mean that these materials are a cognate metasomatizing agent. The anomalies are regarded as mantle metasomatism related to an aqueous fluid. Hydrous minerals were observed on the wall of the melt inclusions using micro-Raman spectroscopy, indicating that the melt inclusions contained a large amount of water. Thus, this study reveals a trace element composition of a hydrous metasomatizing agent in the mantle.     

Structural variations along the Kuril-Kamchatka trench and a possible relation to seismicity

This paper considers the results from seismic investigations of the Kuril-Kamchatka trench (KKT) using continuous seismic profiling (CSP), the common-depth point (CDP), and deep seismic sounding (DSS). The outcome is an approximate 2D seismic model that reflects the overall structure of the landward trench slope for most of the KKT, with the greatest departure of the data from the model being for the middle Kuril Islands area. A deep-seated fault has been identified in the upper part of the slope 60–80 km from the trench axis, with the fault being traceable throughout the depth interval between the seafloor and the bottom of the crust. In the portion between the fault and the trench axis the seismic velocities are lower, the gradient higher, and the crust thins rapidly seaward. The sediment thickness on the landward slope varies along the trench, reaching the maximum off the southern Kuril Islands. The structural variations along the KKT show a broad correlation with the behavior of geophysical fields and seismicity, which seems to be an expression of global tectonic processes.     

On the cold wave of January 1954 in the Far East

Summary A synoptic study is made based primarily on 10-day and 5-day mean maps on an unusually cold spell which appeared all over the Far East in the end of January, 1954, following an abnormal warmth. It is found that while it is warm in Japan, cold air is accumulated in Siberia to the north of the climatological jet stream and is confined in the northern latitudes by the latter as long as the high index pattern prevails. But once the index drops, with the southward displacement of the jet stream, the permanent trough of the Far East deepens and the cold air so far accumulated is allowed to penetrate into southern latitudes. Some characteristic features of contour pattern and frontal activity preceding and following the cold air outbreak are described. Further, it is shown that the blocking wave directly related to the cold air outbreak in the Far East can be traced from as far east as North America or possibly the eastern Atlantic.     

地磁低点位移异常类型特征与地震活动

通过对大量的地磁低点位移异常震例研究,结果表明: ① 地磁低点位移异常的形态、空间展布有明显的地区特征。异常大致可分为: 大范围异常和区域性异常二大类, 还可细分为 5个类型 ; ② 地磁低点位移异常与我国的地质活动构造有较密切的联系。 异常范围的大小、形态与异常所在地区的活动构造的规模、展布形态特征,以及这一地区即将发生的地震强度有关。     

The development of the system of integrated instrumental monitoring of volcanoes in the Far East Region

This work presents the project of the first stage of implementation of the integrated instrumental system of volcanic activity monitoring in Kamchatka and the Kuril Islands. The system of monitoring was designed for the purpose of ensuring public safety, aviation safety, and reducing economic losses caused by volcanic eruptions. The most active and dangerous volcanoes in Kamchatka (North and Avacha groups of volcanoes) and the Kuril Islands (volcanoes on the islands of Kunashir and Paramushir) are of first priority for monitoring. For this purpose, special observation points are planned to be installed on the volcanoes. The system of monitoring will include a complex of observations (broadband seismic station with a large dynamic range, tiltmeter, devices for gas, acoustic, and electromagnetic observations, and video camera). All the data will be passed to information processing centers in real time. New methods and algorithms of automatic and automated identification of the volcanic activity level and the probabilistic volcano hazard assessment have been developed.     

2004年印尼苏门答腊MW9.0地震前地震活动增强现象及其与地球自转的关系

选取2004年12月26日印尼苏门答腊M_W9.0地震的余震分布空间范围为研究区域,该区域位于缅甸小板块中部,纬度范围为2°N~15°N.根据USGS地震目录,研究了2004年印尼苏门答腊M_W9.0地震前地震频次的时空变化,并分析了地震活动与地球自转的关系.结果显示:1)在余震区域范围内,地震频次自2000年开始出现了明显的上升趋势变化,反映了地震活动的增强过程,临近地震发生前,地震频次有一定幅度的回落;2)通过地震频次空间扫描,发现震前在震中附近区域地震活动增强显著;3)在1990~2004年的15年中,单位时间内发生的地震数在地球自转季节性变化减速时段与加速时段之比值r_da在震前出现明显的上升过程:1998年~2002年r_da缓慢上升,2002年底r_da快速上升达最高值,之后,r_da呈现下降趋势,直至苏门答腊M_W9.0地震发生;4)2000年1月~2004年11月间,在纬度1°N~7°N的空间范围内的震中附近地区, 5.5级以上地震都发生在地球自转季节性变化减速时段内;5)地震活动累积年频次相对于其长期平均值的变化量ΔN与地球自转"十年起伏"变化关系表现为地球自转减速时ΔN上升,地震活动增强,加速时ΔN下降,地震活动减弱.这些现象并非偶然,可能预示着地球自转减速与苏门答腊M_W9.0地震之间存在着某种联系,这些结果对地震孕育过程的认识和地震预测研究具有一定的价值.     

Kema terrane: A fragment of a back-arc basin of the early Cretaceous Moneron–Samarga island-arc system, East Sikhote–Alin range, Russian Far East

Abstract The Kema terrane is a suite of Barremian(?)–Aptian to Albian volcano-sedimentary rocks of Sikhote–Alin that are interpreted as deposits of the back-arc basin of the Moneron–Samarga island-arc system. Compositional features of the different-type deposits indicate a near-slope depositional environment influenced by volcanic processes. Studies of slump fold orientation testify to the accumulation of material from southeast to northwest by gravitational sliding. Compositional characteristics of terrigenous rocks suggest the major provenance for detrital material was an ensialic volcanic island arc. Petrochemical characteristics of basaltic rocks indicate that the formations studied were confined to the back part of the arc.     

Station corrections for the Kaapvaal seismic network: Statistical properties and relation to lithospheric structure

Station corrections for body wave travel times are required to compensate for lateral variations in the crust and uppermost mantle in the analysis of seismic travel times that are used to determine deep Earth structure by various methods, including tomography. Station corrections to be applied to P wave arrival times from teleseismic earthquakes recorded by the Kaapvaal seismic network were estimated by five different methods: (1) averaging, (2) computing the median, and (3) weighted averaging of residuals; (4) least-squares regression, and (5) weighted least-squares regression. The corrections display variations that are related to the tectonic features of southern Africa inferred from surface geology, clearly delineating the southern and central areas of both the Kaapvaal and Zimbabwe cratons as regions of early arrivals, and the area around the Bushveld complex by later arrivals. Use of a simple ray method for generating synthetic station corrections suggests that lateral variations in the top 230 km of the Earth can explain the observed pattern of variations in station corrections. A satisfactory way of compensating for the biasing effects of outliers in the individual estimates of station corrections is through adaptation of a method originally developed by Jeffreys, which involves ascribing weights to the observations that reduce the standard deviation on a single estimate of a station correction from 0.123 to 0.096 s. Methods (2), (3) and (5) avoid serious bias by outliers, although methods (3) and (5) are preferred, because they also provide information on the causes of outliers. The presence of some outliers cannot be explained by errors in the measurement process, but must be caused by timing errors at the stations during recording, and/or errors introduced during the process of constructing the archived data files from the field data.     

远东地区近期强震系列及其相关性研究

远东地区的强震系列可以分为板间强震系列与板内强震系列。研究了它们的分类、特征及其适用的公式，得出远东地区板间强震系列与板内强震系列的相关性十分明显、板内强震系列常发生在板间强震系列之后的结论。     

日本海沟大震与华东地区地震的相关性

应用模糊相关方法,研究了日本海沟与我国华东地区地震活动的相关性.计算结果表明:日本海沟地区(35～45°N,140～150°E)MS6.8级以上地震和华东地区(29～34°N,119～124°E)MS4.8级以上地震有较好的相关对应关系;用相关分析方法对华东地区尤其是上海附近地区未来发震的可能性进行了分析,并估算了两地区延迟相关的平均概率.     

Electromagnetic study of lithospheric structure in the marginal zone of East European Craton in NW Poland

The marginal zone of the East European Platform, an area of key importance for our understanding of the geotectonic history of Europe, has been a challenge for geophysicists for many years. The basic research method is seismic survey, but many important data on physical properties and structure of the lithosphere may also be provided by the electromagnetic methods. In this paper, results of deep basement study by electromagnetic methods performed in Poland since the mid-1960s are presented. Over this time, several hundred long-period soundings have been executed providing an assessment of the electric conductivity distribution in the crust and upper mantle. Numerous 1D, 2D, and pseudo-3D electric conductivity models were constructed, and a new interpretation method based on Horizontal Magnetic Tensor analysis has been applied recently. The results show that the contact zone is of lithospheric discontinuity character and there are distinct differences in geoelectric structures between the Precambrian Platform, transitional zone (TESZ), and the Paleozoic Platform. The wide-spread conducting complexes in the crust with integral conductivity values reaching 10 000 S at 20–30 km depths are most spectacular. They are most likely consequences of geological processes related to Caledonian and Variscan orogenesis. The upper mantle conductivity is also variable, the thickness of high-resistive lithospheric plates ranging from 120–140 km under the Paleozoic Platform to 220–240 km under the East European Platform.     

Nonlinear magnitude frequency relation and two types of seismicity systems

A nonlinear magnitude frequency equation has been derived in this paper on the assumption that all seismicity systems hold fractal characteristics, and according to the differences of relevant coefficients in the equation, seismicity systems are classified into two types: type I, the whole earthquake activity is controlled by only one great unified system; type II, the whole earthquake activity is controlled by more than one great system. One type of seismicity system may convert to the other type, generally. For example, a type I system will change to a type II system prior to the occurrence of a strong earthquake in North China. This change can be regarded as an index for earthquake trend estimation. In addition, the difference between b value in nonlinear magnitude frequency equation and that in linear equation and the term dΔM related to the coefficients of nonlinear terms obtained in this paper are proved to be a pair of available parameters for medium short term earthquake prediction.     

Stress in the lithosphere generated by terrain topography and density inhomogeneities in the earth's crust

Summary The methods are described and results presented of computing the two-dimensional stress field in a particular section of International Geotraverse I. The present effects of loads, caused by terrain topography and density inhomogeneities in the Earth's crust, were considered to be the sources of the stress. The corresponding values of the deviatoric stresses in the area considered are of the order of 5 MPa.

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Space-time variations of the frequency-energy relation for mining-induced seismicity in the Ostrava-Karviná mining district

The values of parameters of the relation logN=a–b logE characterize in general the level of seismicity of individual regions. In the present paper, a detailed analysis ofb values of the frequency-energy distributions was carried out with the aid of a database of seismic events recorded by the seismological networks in the Ostrava-Karviná Coal Mine District (Czech Republic), using the least squares regression and maximum likelihood method, as well. The determination ofb value was performed for a relatively large number of regions investigated and for different time series of observations. Special attention has been paid to induced seismic events statistics for the vicinity of one of the coalfaces in the Lazy Mine. It could be generally stated that lowerb values correspond to a higher level of induced seismic activity, while the higher ones correspond to a low and a moderate seismic activity.