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1.
Chen Xuezhong Yin XiangchuInstitute of Geophysics SSB Beijing ChinaCenter for Analysis Predicuon SSB Beijing China 《中国地震研究》1996,(2)
In this paper, the theory of the load/unload response ratio is applied to the prediction of the reservoir-induced earthquakes, and variation of the load/unload response ratio Y preceding the occurrence of main shocks of the reservoir-induced earthquakes in Xinfengjiang, Foziling, Danjiangkou, and Shenwo. The results show that the load/unload response ratio Y rises evidently prior to the main shocks. 相似文献
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Zhang Langping 《中国地震研究》2007,21(2):147-155
The variation of Load/Unload Response Ratio (LURR) against time for earthquakes in Kerman Province, Iran, on February 22, 2005, M6.4 and in Lorestan Province, Iran, on March 31, 2006, M6.1, has been calculated and analysed in this paper. The tempo-spatial scanning of LURR in the region of Iran during January 1, 2003 to March 31, 2006 has been conducted, with 1 year as a time-window, 1 month as a time-step, and the comparison of the LURR anomalous regions in 2004 with the actual earthquakes with M≥5.0 in the next year (2005) is also given, which shows that 11 earthquakes with M≥5.0 occurred in LURR anomalous regions while 12 earthquakes with M≥5.0 in LURR regions in 2005. Furthermore, the seismicity in this region is studied by investigating the evolvement of the anomalous LURR regions. 相似文献
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The changes of NH3-N, NO3-N, NO2-N and TN/TP were studied during growth and non-growth season in 33 subtropical shallow lakes in the middle and lower reaches of the Yangtze River. There were significant positive correlations among all nutrient concentrations, and the correlations were better in growth season than in non-growth season. When TP>0.1 mgL-1, NH3-N increased sharply in non-growth season with increasing TP, and NO3-N increased in growth season but decreased in non-growth season with TP. These might be attributed to lower dissolved oxygen and low temperature in non-growth season of the hypereutrophic lakes, since nitrification is more sensitive to dissolved oxygen and temperature than antinitrification. When 0.1 mgL-1>TP>0.035 mgL-1, TN and all kinds of inorganic nitrogen were lower in growth season than in non-growth season, and phytoplank-ton might be the vital regulating factor. When TP<0.035 mgL-1, inorganic nitrogen concentrations were relatively low and NH3-N, NO2-N had significant correlations with phytoplankton, indicating that NH3-N and NO2-N might be limiting factors to phytoplankton. In addition, TN/TP went down with decline in TP concentration, and TN and inorganic nitrogen concentrations were obviously lower in growth season than in non-growth season, suggesting that decreasing nitrogen (especially NH3-N and NO3-N) was an important reason for the decreasing TN/TP in growth season. The ranges of TN/TP were closely related to trophic level in both growth and non-growth seasons, and it is apparent that in the eutrophic and hypertrophic state the TN/TP ratio was obviously lower in growth season than in non-growth season. The changes of the TN/TP ratio were closely correlated with trophic levels, and both declines of TN in the water column and TP release from the sediment were important factors for the decline of the TN/TP ratio in growth season. 相似文献
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S. Boroughs J.A. Wolff B.S. Ellis B. Bonnichsen P.B. Larson 《Earth and Planetary Science Letters》2012
Two models have been proposed for the origin of the low-δ18O rhyolites of the Snake River Plain–Yellowstone hotspot trend. The first involves a single multicyclic caldera system, or multiple nested or overlapping systems, in which the early-erupted products become hydrothermally altered and are subsequently melted to form low-δ18O rhyolites (Bindeman and Valley, 2001; Watts et al., 2011). The second model appeals to a crustal magma source which was hydrothermally altered in a thermal event prior to the onset of Miocene magmatism (Boroughs et al., 2005). We critically evaluate the plausibility of each and provide thermal, temporal, and volume constraints which must be included in any model for the petrogenesis of low-δ18O rhyolites of the central Snake River Plain. Although the models are not mutually exclusive, we conclude that a component of pre-existing low-δ18O crust is required in the central Snake River Plain where the greatest volumes of strongly 18O-depleted rhyolite occur. This component could be provided by meteoric–hydrothermally altered granites of the Idaho batholith, which are cut by the central Snake River Plain. 相似文献
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L. P. Imaeva B. M. Koz’min V. S . Imaev N. N. Grib S. V. Ashurkov 《Journal of Seismology》2017,21(2):385-410
The paper presents the modern structural-tectonic pattern and a tectonodynamic model of the zone of interaction of the most seismically active northeastern side of the Baikal rift zone (BRZ) and the conjugate system of seismogenic structures of the Aldan-Stanovoy block, where disastrous events with M ≥ 6.0 have been reported. Regularities in the structural formation of active faults and their kinematics are discussed. The faults form block structures accumulating significant tectonic strain. Motions between large tectonic blocks cause sudden release of the strain, which results in catastrophic events (M ≥ 6.0) with focal mechanisms of definite kinematic type. 相似文献
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On the basis of distribution of active fault and regional rheological structure, a three-dimensional finite element model of Sichuan-Yunnan region, China, is constructed to simulate contemporary crustal motion and stress distri- bution and discuss the dynamic mechanism of crustal motion and deformation in the Sichuan-Yunnan region. Lin- ear Maxwell visco-elastic model is applied, which includes the active fault zones, the elastic upper crust and vis- cous lower crust and upper mantle. Four different models with different boundary conditions and deep structure are calculated. Some conclusions are drawn through comparison. Firstly, the crustal rotation about the eastern syntaxis of the Himalaya in the Sicuan-Yunnan region may be controlled by the special dynamic boundary condition. The drag force of the lower-crust on the upper crust is not negligible. At the same time, the main active fault zones play an important role in the contemporary crustal motion and deformation in Sichuan-Yunnan region. 相似文献
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V. V. Adushkin A. A. Spivak V. A. Kharlamov 《Izvestiya Physics of the Solid Earth》2018,54(6):859-871
The results of processing and analyzing the instrumental observations of the Earth’s magnetic field at the Geophysical Observatory Mikhnevo of the Institute of Geosphere Dynamics of the Russian Academy of Sciences (IGD RAS) for 2010–2015 are presented. Quasi-harmonic components with the periods close to the lunar–solar tidal waves are revealed in the spectra of geomagnetic variations over a period of 0.4 to 30 days. The elliptical S1 tidal wave which is detected in the geomagnetic variations has modulations with periods of 1/3, 1/2, and 1 year. The spectra of the geomagnetic variations contain peaks corresponding to the free oscillations of the Earth. The analysis of the time series of the magnetic field for the period of the strong earthquakes in the absence of geomagnetic disturbances revealed the fine structure of the Earth’s fundamental spheroidal mode 0S2, which splits into five singlets. The established features of the spectrum of geomagnetic variations are helping the development of the new method for studying the deep structure of the Earth and the properties of the inner geospheres for estimating the viscosity of the Earth’s outer core and dynamics of the current systems in the outer (liquid) core, as well as for exploring, with the use of empirical data, the general regularities governing the regimes of energy exchange processes in the geospheres. 相似文献
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ＫｉｎｅｍａｔｉｃｆｅａｔｕｒｅｓｏｆｔｈｅｓｅｉｓｍｏｇｅｎｉｃｆａｕｌｔｏｆｔｈｅＴａｎｇｓｈａｎｅａｒｔｈｑｕａｋｅａｎｄｔｈｅｒｅｃｕｒｒｅｎｃｅｐｅｒｉｏｄｏｆｌａｒｇｅｅａｒｔｈｑｕａｋｅｓＪＩＥＬＩＵ１）（刘洁）ＨＵＩ－ＺＨＥＮＳＯＮ... 相似文献
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LIU Yongsheng GAO Shan WANG Xuance HU Shenghong & WANG Jianqi . State Key Laboratory of Geological Processes Mineral Resources China University of Geosciences Wuhan China . Key Laboratory of Continental Dynamics Department of Geology Northwest University Xi’an China 《中国科学D辑(英文版)》2005,48(8):1106-1119
Hofmann[1] found that the depleted mantle (DM) and bulk continental crust (BCC) are simply compen-satory in terms of many elements and elemental ratios. High-field-strength elements (HFSE) (e.g., Zr, Hf, Nb, Ta and Ti) are immobile and thus useful to track the primary features of the ancient mafic volcanics. It has been long considered that Nb-Ta behave as identical twins during magmatic processes, based on their matching atomic radii and valence state and hence coherent geochemical affi… 相似文献
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Applicability of regional P/S amplitude ratios for the discrimination of low-magnitude seismic events was tested and proved using earthquakes and explosions in Central Asia. Results obtained show that regional P/S amplitude ratios which may discriminate medium or large magnitude events well, are also applicable to low magnitude events. Their performances for low magnitude events are almost as good as that for medium or large events. Statistical comparisons based on 25 P/S discriminate from the four seismic stations WMQ, BLK, MUL and MAK showed that the average misclassification rate for low-magnitude seismic events averagely was only 2 percent higher than that for medium and large magnitude seismic events. 相似文献
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Dynamical diagnosis of the breakup of the stratospheric polar vortex in the Northern Hemisphere 总被引：3，自引：0，他引：3
The research on climate change in polar regions, especially on the role of polar in the global climate system, has gain unprecedented level of interest. It has been the key scientific issue of the International Polar Year program (IPY, 2007―2008). In this paper, we dealt with the debate upon the breakup time of the stratospheric polar vortex in boreal spring. An observational study of the relation between strato- spheric polar vortex breakup and the extra-tropical circulation was performed. The mean breakup date―when the winter westerly at the core of polar jet turns to summer easterly―is about April 10. The breakup time has large interannual variation with a time span of about 2 months. It also has a long-term trend with the 1990s and 2000s witnessing more and more late breakups of polar vortex. Composite of wind speed at the core of polar jet for the extremely early and late breakup years shows that late years have two periods of westerly weakening while early breakup years have only one. The first weakening in the late years happens in middle January with wind speed dropping sharply from more than 40 m s?1 to about 15 m s?1. This is accompanied with anomalous activities of planetary waves in both strato- sphere and troposphere; while the second weakening in the late breaking years is mainly the results of diabatic heating with very weak wave activities. In early breakup years, the transition from westerly to easterly is rapid with wind speed dropping from more than 30 m s?1 to less than ?10 m s?1 within a month. This evolution is associated with a strong bidirectional dynamical coupling of the stratosphere and troposphere. The circulation anomalies at low troposphere are also analyzed in the extremely early and late breakup years. It shows that there are significant differences between the two kinds of extreme years in the geopotential height and temperature composite analysis, indicating the dynamical cou- pling of stratosphere and troposphere with the evolution of stratospheric polar vortex. 相似文献
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Analysis of fault outcrops and trench sections indicates fault displacements of 0.2m - 6.0 m on the bottom paleosol layer of the Epipleistocene with the maximum rate of 0.047 mm/a and an average displacement of 1.1 meters. The activity appears as fissures on the fault surface in the late Epipleistocene and there is no obvious displacement. The fault activity is weak and the most active segment is the Bailuyuan segment. 相似文献
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The profile crossing the west Kunlun region cov-ers the area between the Tarim Basin and the Kara-korum Fault, which is the highest (~5000 m a.s.l.) andthe most narrow part (400—500 km from north tosouth) of the Tibetan Plateau, thus attracting great at-tention of the geological community because of itsunique tectonic features. The Geological Bureau of Xinjiang Uygur Auton-omous Region and Chinese Academy of Sciences(CAS) carried out mineral exploration and geologicalmapping in th… 相似文献
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Sediment samples were collected from sandy beaches at a variety of sites in the southern Galápagos Archipelago to assess levels of hydrocarbon contamination following the wreck of the oil tanker Jessica. Hydrocarbon levels in sediments were generally very low by international standards ranging between 0.4 and 48.9 ppm, with contamination attributable to the Jessica only detected at three sites Santa Fe, Playa Estación (Puerto Ayora, Santa Cruz) and Long Beach (Isabela). There was evidence of residual hydrocarbon contamination from sources other than the wreck of the Jessica. 相似文献
18.
Huangfu Gang 《中国地震研究》2006,20(4):449-459
INTRODUCTIONYunnanis located in the east margin of the collision zone between the India Plate and theEurasian Plate on the Chinese Continent , where crustal movement is violent and moderate-strongearthquakes are frequent withlarge magnitudes and wide distributions .It is also a place of particularinterest to geo-science researchers both at home and abroad. Since 1970 , 8 earthquakes withmagnitude 7·0 have occurred here .It is a perfect site to study seismicity.Whether or not seismicit… 相似文献
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Analyzing the spatial distribution characteristics of earthquake-induced secondary disasters based on advanced techniques is significantly important, especially in understanding the process of strong earthquakes in the Loess Pateau. Using ArcGIS, this study interprets multi-temporal high-resolution satellite images, field investigation data, and historical seismic records. Major conclusions are obtained as follows:① Landslides induced by the Haiyuan earthquake are mainly distributed in the intersection area of the end of the Haiyuan fault and Liupanshan fault, as indicated by multiple dense distribution centers; ② The landslide distribution of the Haiyuan Earthquake is determined by the distance to the fault, topographic relief, slope, lithology, and other factors. In detail, the closer the distance to the fault, the greater the density of the landslide. The greater the slope and relief of the terrain, the greater the density and the smaller the average area of a landslide. Compared with tertiary strata, Quaternary strata has a larger average area, and the density of the landslides is smaller; ③ The density curve of the death toll in the Haiyuan earthquake can be used as a reference for the distribution of co-seismic landslides. Several Haiyuan co-seismic landslides are distributed in the Tongwei landslide area; however, the major landslides here are induced by the 1718 Tongwei earthquake rather than the 1920 Haiyuan earthquake; ④ The co-seismic landslides of the Haiyuan earthquake exhibits the "slope effect" in the south-west plate of Haiyuan fault, presenting the dominant sliding direction towards the fault and epicenter; however, the "slope effect" is not evident in the northeast plate of the fault. 相似文献
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V. V. Adushkin N. G. Gamburtseva M. A. Nesterkina I. A. Sanina D. D. Sultanov O. A. Usol’tseva 《Izvestiya Physics of the Solid Earth》2010,46(3):244-256
The results of long-term sounding of the lithosphere by seismic waves from the deep-focus Hindu Kush earthquakes are presented.
The travel time series of the first longitudinal wave on a fixed base are constructed for six seismic observation stations
(SS) located on the Russian Platform (the Obninsk SS), on the Siberian Platform (the Eltsovka SS), on the Cis-Ural Trough
(the Arti SS), in the Central-Ural Megazone (the Sverdlovsk SS), in the Transbaikalia (the Bodaibo SS), and in the Northern
Tien Shan (the Przhevalsk SS). The time series duration in years for these stations ranged from 1964–1970 to 2007. The travel
time series of seismic waves for the stations indicated are characterized by multi-slope negative linear trends caused by
changes in the stress-strain state of rocks. From the comparison of the trend slopes at different stations it follows that
the changes in the stress conditions within the lithosphere are relatively weak in the aseismic regions of the Russian and
Siberian Platforms and in the Ural Megazone, whereas in the seismically active regions of Tien Shan, Transbaikalia and the
Cis-Ural Trough they are more pronounced. The correlation has been observed between the time series trends of the average
annual travel times of seismic waves and the time series of the Earth’s rotation speed. The strongest correlation between
the series can be seen for the stations, located on the platforms with weak manifestations of both seismicity and active geodynamic
processes. Within the long-term periods of deceleration and acceleration of the Earth’s rotation, travel times of seismic
waves are decreased and increased, respectively. 相似文献