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41.
The paper deals with interpretation of global digital maps of gravity anomalies and surface topography for the northwestern Pacific and Kamchatka regions. A transformation procedure is suggested to reveal subtle features of surface topography against high elevation contrasts. Gravity data (free-air and Bouguer anomalies) have important implications for the evolution of the circum-Pacific region and the problems of volcanism and geodynamics in subduction zones. The patterns of gravity anomalies and transformed topography interpreted jointly with onshore and offshore geological data can make a basis for tectonic paleoreconstructions of upper crust and lithospheric mantle structures. 相似文献
42.
Based on the example of the strong earthquake of November 24, 1971, with the earthquake source near the Petropavlovsk-Kamchatskii, the new modeling technique of the strong ground motions within the broadband is tested. In this technique, the seismologically-substantiated models of the radiation source and elastic medium are used. The source is represented by an array of point radiation sources-dislocations with the random seismic moments (amplitudes) and with the random time functions. The new method of calculation of the Green functions is developed to describe the propagation of waves and residual displacements of a layered medium. The method is used for the simulation of the horizontal ground motion, recorded by a S5S-ISO instrument for the strong earthquake that took place on November 24, 1971 with the source near the Petropavlovsk-Kamchatskii (with a depth of 105 km). The position of the hypocenter, the sizes and the position of the fault, and “fault mechanism” were considered to be known a priori. By a trial and error method of the duration of the source process and only two spectral parameters, it was possible to simulate successfully the fundamental characteristics of the ground vibrations: the amplitude of acceleration, the velocity and displacement of the ground, their Fourier spectrum, the duration of the vibrations, and the response spectrum. The surprisingly high level of high-frequency radiation, probably connected with the intraplate position of the source, is a specific feature of the source. 相似文献
43.
44.
T. V. Oreshkina 《Stratigraphy and Geological Correlation》2009,17(3):331-345
Diatom assemblages from the marine Paleogene of Western Kamchatka (the Kovachina, Viventek, and Kuluven formations) are studied. The shallow-water neritic assemblage from the Kovachina Formation of the Pyatibratskii Cape section is tentatively attributed to the middle Eocene, as it is lacking zonal index species. A high abundance and great taxonomic diversity are characteristic of diatoms from the upper part of the Viventek Formation in the Kovran River section. The zonal index species Cavitatus rectus identified here among the diatoms suggests that the respective assemblage is macerated from the synonymous diatom zone of the middle Oligocene (29.6?28.2 Ma). According to its taxonomic composition and structure, this assemblage is indicative of transgression environments and the presumable influence of the middle Oligocene climatic optimum. The Rocella gelida (upper part) and Thalassiosira praefraga diatom zones of the Oligocene-Miocene transition are established in the Kuluven Formation sediments of the Mt. Uvuch section in Kovachina Bay. 相似文献
45.
Insights into Li and Li isotope cycling and sub-arc metasomatism from veined mantle xenoliths,Kamchatka 总被引：3，自引：2，他引：1
Ralf Halama Ivan P. Savov Roberta L. Rudnick William F. McDonough 《Contributions to Mineralogy and Petrology》2009,158(2):197-222
Harzburgitic xenoliths cut by pyroxenite veins from Avachinsky volcano, Kamchatka, are derived from the sub-arc mantle and
record element transfer from the slab to the arc. Olivine and orthopyroxene in the harzburgites have Li isotopic compositions
(δ7Li = +2.8 to +5.6) comparable to estimates of the upper mantle (δ7Li ~ +4 ± 2). The pyroxenite veins, which represent modal metasomatism and may therefore provide information about the metasomatic
agent, have mantle-normalized trace element characteristics that suggest overprinting of their mantle source by an aqueous,
slab-derived fluid. These include relative enrichments of Pb over Ce, U over Th and Sr over Nd. Li is enriched relative to
the HREE, and ortho- and clinopyroxene from the veins are in Li elemental and isotopic equilibrium with each other and the
surrounding harzburgite. Vein samples (δ7Li = +3.0 to +5.0) do not record a significant slab-derived δ7Li signature. These observations can be reconciled if slab Li diffusively re-equilibrates in the mantle wedge. Modeling demonstrates
that Li equilibration of small (1–2 cm width) veins or melt conduits is achieved at mantle wedge temperatures within 101–105 years. We conclude that strongly fractionated Li isotopic signatures cannot be sustained for long periods in the sub-arc
mantle, at least at shallow (<70 km) depths.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
46.
俄罗斯勘察加半岛热泉的地球化学和微生物学 总被引：3，自引：0，他引：3
勘察加半岛位于欧洲板块、北美板块和太平洋板块交汇的过渡带上,是世界火山活动最活跃的地区之一.其众多的热液系统不断的向地表释放地热气体和流体.以N2和CO2为主的地热气体也经常含有高浓度的H2,CH4和H2S.大气水和熔岩水构成了勘察加热泉水的主要源,水体温度从20
℃到＞90 ℃不等.水化学性质变化同样显著,pH范围从3.1到9.8.热泉水溶解盐以氯化钠为主,同时包括K+,H3BO3,H4SiO4,Ca2+和SO42-等其他多种溶解组分.此区域也有以直链烷烃为主的石油形成.从勘察加的热泉系统中已分离出至少24种嗜热微生物.尽管其中大多数是异养微生物,但根据其生存环境的特点,自养微生物在热泉系统中可能同样很多.这些微生物对碳、硫和铁在热液系统中的生物地球化学循环有着非常重要的作用.目前,非培养的方法和生物定量的手段已用来研究勘察加热泉中微生物生态及其所具有的生物地球化学功能. 相似文献
47.
N. I. Zaporozhets V. N. Sinel’nikova M. A. Akhmet’ev 《Stratigraphy and Geological Correlation》2006,14(6):668-689
Organic-walled phytoplankton assemblages from Eocene and Oligocene reference sections of western Kamchatka are analyzed. They are close in taxonomic composition to coeval assemblages of northern Japan and Sakhalin that is a good opportunity to correlate regional units and verify their age. The euryhaline species Trinovantedinium boreale that is associated with Paralecaniella indentata and Micrhystridium preferring shallow low-salinity waters, on the one hand, and taxa dwelling in normal-salinity open sea environments, on the other, are dominant in most assemblages, which are examined. The suggested variant of bed succession with dinocyst assemblages may be valid for Japan, Sakhalin, Kamchatka, and the Bering Sea. 相似文献
48.
Jens Hartmann 《International Journal of Earth Sciences》2006,95(4):649-664
The analysis of earthquake-related signals in hydrochemical time series is still a challenging task. Mostly it is unclear how the geometrical and energetic distribution of earthquakes is influencing variation in the hydrochemical composition of monitoring sites, e.g. located close to volcanoes. Past research showed that linear stress-release models alone are not capable to explain sufficiently observed variation in hydrochemical time series due to earthquake activity. A spring located at the base of Koryaksky Volcano, which has shown hydrochemical variation close to 5, major earthquakes, was chosen to analyse relation patterns between hydrochemical variation and seismicity. A possible mechanism, explaining observed hydrochemical variation, that seismic waves trigger an underground water pumping caused by nucleation of gas bubbles in magma was proposed. Consequences are an increase of discharge, gas content in water and changes in the mixing ratios of waters of different genesis. Based on functions of aggregated earthquake information (E) it is herein shown that seismotectonic-triggered processes have a significant influence on the variation of the hydrochemistry of the spring, lasting longer than two decades. At least seven categories of relation patterns between hydrochemical variation and seismotectonic activity E can be identified. A conducted spectral analysis shows that earthquake activity and hydrochemistry share spikes in frequencies. Results prove that the use of functions of transformed aggregated seismic observations is useful to represent the seismotectonic activity for analysing earthquake-related signals in hydrochemical time series. 相似文献
49.
Paleomagnetic characteristics of several Paleogene sections in Kamchatka (Il’pinskii Peninsula, Bering Island, Chemurnaut Bay, Mametcha Bay) are considered. The sections are correlated with due account for biostratigraphic data, and possible correlation of magnetic polarity zones distinguished in the sections with the international magnetostratigraphic scale is presented. 相似文献
50.
An explosive eruption occurred at the summit of Bezymianny volcano (Kamchatka Peninsula, Russia) on 11 January 2005 which
was initially detected from seismic observations by the Kamchatka Volcanic Eruption Response Team (KVERT). This prompted the
acquisition of 17 Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) satellite images of the volcano over
the following 10 months. Visible and infrared data from ASTER revealed significant changes to the morphology of the summit
lava dome, later seen with field based thermal infrared (TIR) camera surveys in August 2005. The morphology of the summit
lava dome was observed to have changed from previous year’s observations and historical accounts. In August 2005 the dome
contained a new crater and two small lava lobes. Stepped scarps within the new summit crater suggest a partial collapse mechanism
of formation, rather than a purely explosive origin. Hot pyroclastic deposits were also observed to have pooled in the moat
between the current lava dome and the 1956 crater wall. The visual and thermal data revealed a complex eruption sequence of
explosion(s), viscous lava extrusion, and finally the formation of the collapse crater. Based on this sequence, the conduit
could have become blocked/pressurized, which could signify the start of a new behavioural phase for the volcano and lead to
the potential of larger eruptions in the future. 相似文献