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81.
Tomotaka Iwata Takao Kagawa Anatoly Petukhin Yoshihiro Ohnishi 《Journal of Seismology》2008,12(2):223-234
We constructed a prototype of the basin and crustal structure model for the Kinki area, southwest of Japan, for the simulation
of strong ground motions of hypothetical crustal and subduction earthquakes. We collected results of the deep seismic velocity
profiles obtained by the reflection experiments and seismic imaging results, which were conducted in the Kinki area. The obtained
profiles give underground velocity structures of the crust, from the surface to the subducting slab. We also gather the basin
velocity structure information of the Osaka, Kyoto, Nara, and Ohmi basins. To examine the applicability of the constructed
velocity structure model to the ground motion simulation, we simulated waveforms of an intermediate size event occurred near
the source area of the hypothetical subduction earthquakes. Simulated ground motions using the basin and crustal velocity
structure model are fairly well reproducing the observations at most of stations, and the constructed basin and crustal velocity
structure model is applicable for the long-period ground motion simulations. 相似文献
82.
Anatoly Obzhirov 《世界地质(英文版)》2006,9(2)
The research works of methane concentration in water column of the Okhotsk Sea from 1984 to 2005 were reviewed. And some regularities of methane distribution in water column in the North-East Sakhalin slope of the Okhotsk Sea were concluded. 相似文献
83.
Nikiforov A. V. Ivanova A. A. Yarmolyuk V. V. Salnikova E. B. Kotov A. B. Kozlovsky A. M. Khertek A. K. Plotkina Yu. V. Kudryashova E. A. Galankina O. L. Polyakov N. A. 《Doklady Earth Sciences》2023,507(3):S382-S389
Doklady Earth Sciences - The temporal relations between alkaline rocks of the Aryskan rare metal (Y, REEs, Nb, Ta) deposit are determined using metamict zircon with high U and Th contents, which... 相似文献
84.
In 2013–2015 the Laboratory of spectroscopy and photometry of extragalactic objects (LS-PEO) of the Special Astrophysical Observatory together with Armenian specialists upgraded the 1-m Schmidt telescope of the Byurakan Astrophysical Observatory of the National Academy of Sciences of Armenia. We completely redesigned the control system of the telescope: we replaced the actuating mechanisms, developed telescope control software, and made the guiding system. We reworked and prepared a 4k × 4k Apogee (USA) liquid-cooled CCD with RON ~ 11.1 e?, a pixel size of 0.″868, and field of view of about 1□°, and in October 2015 mounted it in the focus of the telescope. The detector is equipped with a turret bearing 20 intermediate-band filters (FWHM = 250 Å) uniformly covering the 4000–9000 Å wavelength range, five broadband filters (u, g, r, i, z SDSS), and three narrow-band filters (5000 Å, 6560 Å and 6760 Å, FWHM = 100 Å). During the first year of test operation of the 1-m telescope we performed pilot observations within the framework of three programs: search for young stellar objects, AGNevolution, and stellar composition of galaxy disks.We confirmed the possibility of efficiently selecting of young objects using observations performed in narrow-band Hα and [SII] filters and the intermediate-band 7500 Å filter. Three-hours long exposures with SDSS g-, r-, and i-band filters allow us to reach the surface brightness level of 28m/□″ when investigating the stellar content of galaxy disks for a sample of nine galaxies. We used observations performed with the 1-m telescope in five broadband (SDSS u, g, r, i, and z) and 15 intermediate-band filters (4000–7500 Å) to construct a sample of quasar candidates with 0.5 < z < 5 (330 objects) in about one-sq. degree SA68 field complete down to RAB = 23m. Spectroscopic observations of 29 objects (19.m5 < R < 22m) carried out at the 6-m telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences confirmed the quasar nature of 28 objects. 相似文献
85.
Distribution and expression of gas seeps in a gas hydrate province of the northeastern Sakhalin continental slope, Sea of Okhotsk 总被引:1,自引:0,他引:1
Young Keun Jin Young-Gyun Kim Boris Baranov Hitoshi Shoji Anatoly Obzhirov 《Marine and Petroleum Geology》2011,28(10):1844-1855
Multidisciplinary surveys were conducted to investigate gas seepage and gas hydrate accumulation on the northeastern Sakhalin continental slope (NESS), Sea of Okhotsk, during joint Korean–Russian–Japanese expeditions conducted from 2003 to 2007 (CHAOS and SSGH projects). One hundred sixty-one gas seeps were detected in a 2000 km2 area of the NESS (between 53°45′N and 54°45′N). Active gas seeps in a gas hydrate province on the NESS were evident from features in the water column, on the seafloor, and in the subsurface: well-defined hydroacoustic anomalies (gas flares), side-scan sonar structures with high backscatter intensity (seepage structures), bathymetric structures (pockmarks and mounds), gas- and gas-hydrate-related seismic features (bottom-simulating reflectors, gas chimneys, high-amplitude reflectors, and acoustic blanking), high methane concentrations in seawater, and gas hydrates in sediment near the seafloor. These expressions were generally spatially related; a gas flare would be associated with a seepage structure (mound), below which a gas chimney was present. The spatial distribution of gas seeps on the NESS is controlled by four types of geological structures: faults, the shelf break, seafloor canyons, and submarine slides. Gas chimneys that produced enhanced reflection on high-resolution seismic profiles are interpreted as active pathways for upward gas migration to the seafloor. The chimneys and gas flares are good indicators of active seepage. 相似文献
86.
87.
V. A. Kotov 《Astronomy Reports》2008,52(5):419-428
Measurements of the mean magnetic field of the Sun as a star (the line-of-sight component of the magnetic field of the visible hemisphere for a given day) carried out at six observatories are used to compile a catalog of the mean magnetic field for 1968–2006 (containing about 18 000 daily values). The cataloged data are compared with direct daily measurements of the absolute line-of-sight field made at the Kitt Peak Observatory in 2003–2006 (original data with a resolution of 1″ averaged over the solar disk). The true absolute mean field strength averaged over the visible solar hemisphere is determined for 1968–2006 to be B 0 = 7.7 ± 0.2 G. This figure exceeds previous estimates by almost a factor of four. B 0 exhibits no appreciable slow trend over the entire 39-year interval, but varies substantially with the cycle. The period of this variation is 10.5 ± 0.7 yr, and its harmonic amplitude is 1.7 G. The magnetic flux of spots and active regions makes B 0 almost twice the field strength in the “normal” photosphere at the solar minimum, i.e., for the “quiet” Sun. 相似文献
88.
V. V. Yarmolyuk V. I. Kovalenko A. M. Kozlovsky V. P. Kovach E. B. Sal’nikova D. V. Kovalenko A. B. Kotov E. A. Kudryashova V. I. Lebedev G. Eenzhin 《Petrology》2008,16(7):679-709
The paper reports data on the evolutionary history of magmatism, its conditions, and sources in the process of the development
of the Southern Mongolian Hercynides during the pre-accretion, continental-margin, and rifting stages within the time span
from the Silurian to Early Permian. The Hercynian continental crust in the southern Mongolian segment of the Central Asian
Foldbelt (CAFB) was determined to have grown in the environment of ensimatic island arcs, backarc basins, spreading centers,
and oceanic islands or plateaus, with material coming from the depleted and, perhaps, also enriched mantle sources in the
open ocean that surrounded the Siberian paleocontinent on the side of the Caledonian margin. This made it possible to recognize
the Early-Middle Paleozoic epoch of juvenile crustal growth in CAFB and the corresponding isotopic crustal province with a
total area of more than 200 thousand km2. The principal differences between the composition and structure of the blocks surrounding the Hercynian regions (Caledonides
in the Gobi Altai and Grenwillides in the South Gobi microcontinent) testify that the southern margin of the Caledonian Siberian
continent and the Grenvillides of the South Gobi microcontinent had different geological histories and were spatially separated.
The structural complex of the Paleoasian ocean, including the terranes of the South Gobi microcontinent, were transformed
into a continental block in the latest Devonian-earliest Carboniferous, in relation with accretion processes, folding, metamorphism,
and tectonic delamination along the boundaries of structurally heterogeneous domains. The subsequent recycling of the crust
by magmatic processes was related to the development of an active continental margin (ACM). The development of an ACM in the
Hercynides resulted from and was a continuation of the motions of the continental and oceanic lithospheric plates, i.e., processes
that brought about the Hercynian accretion. The evolution history of the ACM was subdivided into two stages: early (a continental-margin
stage proper) and late (rifting stage). The rocks of the early stage were produced at 350–330 Ma and compose a differentiated
basalt-andesite-rhyodacite complex and related massifs of the granodiorite-plagiogranite and banatite (diorite-monzonite-granodiorite)
associations. During the rifting stage at 320–290 Ma, a bimodal basalt-comendite-trachyrhyolite association was formed, along
with accompanying alkali granite massifs. In the southern Mongolian segment of the Hercynides, the rocks of the rifting stage
compose two subparallel rift zones: Gobi-Tien Shan, which extends along the boundaries of the South Gobi microcontinent, and
the Main Mongolian lineament, which marks the boundaries between the Hercynides and Caledonides in the CAFB. The rift structures
are made up of alkali granitoids and normal-alkalinity granitoids, which are atypical of rift zones. Their genesis is thought
to have been related to crustal anatexis, a process that was triggered by rift-related magmas at an unusual combination of
rifting and ACM tectonic setting. The basic rocks of the rift associations have geochemical signatures atypical of continental
rifting. They show Ta and Nb minima and K and Pb maxima, as is typical of rocks generated at convergent plate boundaries.
Nevertheless, the broad variations in the concentrations and ratios of some major and incompatible trace elements and in the
Sr, Nd, and O isotopic composition of the rift basaltoids allowed us to distinguish their high-and low-Ti varieties, which
were produced with the participation of three mantle sources: depleted mantle similar to the source of basalts in midoceanic
ridges, enriched mantle like the source of basalts in oceanic islands, and the mantle material of the metasomatized mantle
wedge. The origin of andesites in the rift zones is explained by the contamination of mantle basaltoid melts with sialic (predominantly
sedimentary) material of the continental crust or the assimilation of anatectic partial granite melts. 相似文献
89.
Y. V. Amelin Anatoly M. Larin Robert D. Tucker 《Contributions to Mineralogy and Petrology》1997,127(4):353-368
The U-Pb dating of 18 samples, representing the principal rock types of the 4000 km2 Salmi anorthosite-rapakivi granite complex and its satellite Uljalegi pluton, southeastern Baltic (Fennoscandian) Shield,
reveals that six temporally distinct episodes of igneous activity occurred in a timespan of 17 million years. From oldest
to youngest they are: (1) gabbronorite and monzonite at 1546.7 Ma; (2) syenogranite at 1543.4 Ma; (3) early wiborgite and
pyterlite at 1540.6–1537.9 Ma; (4) biotite granite and more evolved granite at 1538.4–1535 Ma; (5) late pyterlite at 1535.2
Ma; (6) olivine gabbro and biotite-amphibole granite at 1530 Ma. The resolvable intervals between magmatic episodes are 3.5–5.0
million years. Early wiborgite and pyterlite (3, above) and biotite granite (4, above) probably crystallized from multiple
magma intrusions. Age differences of 3.4±1.5 million years between zircon and baddeleyite in olivine gabbro (6, above) are
probably a result of xenocrystic origin of baddeleyite extracted from an earlier mafic phase of the Salmi complex. The ages
and chemical features of early and late zircon populations, together with our modeling of magma crystallization and zircon
growth, show that the duration of magma crystallization and Pb-diffusion in zircon was short lived and insignificant compared
to the precision of dating of about ±1–2 million years. Hence, the range of U-Pb ages for each of the major rock types may
approximate the emplacement intervals of their respective magmas. Average rate of magma emplacement was about 0.01 km3/year for the most voluminous phase of early biotite-amphibole rapakivi granite, and about 0.0024 km3/year for the Salmi complex as a whole. Compositional changes of the Salmi magmas over time are in agreement with the model
of magmatism related to lithospheric extension.
Received: 2 August 1996 / Accepted 19 December 1996 相似文献
90.
K. E. Degtyarev T. Yu. Tolmacheva A. A. Tretyakov A. B. Kotov K. N. Shatagin 《Geotectonics》2016,50(1):71-142
A comprehensive study of the Lower Palaeozoic complexes of the Kokchetav Massif and its fringing has been carried out. It has allowed for the first time to discover and investigate in detail the stratified and intrusive complexes of the Cambrian–Early Ordovician. Fossil findings and isotope geochronology permitted the determination of their ages. The tectonic position and internal structures of those complexes have also been defined and their chemical features have been analyzed as well. The obtained data allowed us to put forward a model of the geodynamic evolution of Northern Kazakhstan in the Late Ediacaran–Earliest Ordovician. The accumulation of the oldest Ediacaran to Earliest Cambrian siliciclastics and carbonates confined to the Kokchetav Massif and its fringing occurred in a shallow shelf environment prior to its collision with the Neoproterozoic Daut island arc: complexes of the latter have been found in the northeast of the studied area. The Early Cambrian subduction of the Kokchetav Massif under the Daut island arc, their following collision and exhumation of HP complexes led to the formation of rugged ground topography, promoting deposition of siliceous–clastic and coarse clastic units during the Middle to early Late Cambrian. Those sediments were mainly sourced from eroded metamorphic complexes of the Kokchetav Massif basement. At the end of the Late Cambrian to the Early Ordovician within the boundaries of the massif with the Precambrian crust, volcanogenic and volcano-sedimentary units along with gabbros and granites with intraplate affinities were formed. Simultaneously in the surrounding zones, which represent relics of basins with oceanic crust, N-MORB- and E-MORB-type ophiolites were developed. These complexes originated under extensional settings occurred in the majority of the Caledonides of Kazakhstan and Northern Tian Shan. In the Early Floian Stage (Early Ordovician) older heterogeneous complexes were overlain by relatively monotonous siliceous–clastic units, that were being deposited until the Middle Darrivilian Stage (Middle Ordovician). 相似文献