首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 828 毫秒
1.
ＩｎｖｅｓｔｉｇａｔｉｏｎｓｏｆｔｈｅｓｅｉｓｍｏｍａｇｎｅｔｉｃｅｆｆｅｃｔｉｎｔｈｅｇｅｏｍａｇｎｅｔｉｃｄｉｕｒｎａｌｖａｒｉａｔｉｏｎｓＰｏ－ＦａｎｇＣＨＥＮ（陈伯舫）（ＤｅｐａｒｔｍｅｎｔｏｆＰｈｙｓｉｃｓａｎｄＤｅｐａｒｔｍｅｎｔｏｆＧｅ...  相似文献   

2.
ＴｈｅｖａｒｉａｔｉｏｎｓｏｆｔｈｅｄｅｇｒｅｅｏｆｇｒｏｕｎｄｒｅｓｉｓｔｉｖｉｔｙａｎｉｓｏｔｒｏｐｙｄｕｒｉｎｇｔｈｅＴａｎｇｓｈａｎｅａｒｔｈｑｕａｋｅＴｏｎｇ－ＥｎＭＡＯ（毛桐恩）；Ｔｉｅ－ＣｈｅｎｇＷＡＮＧ（王铁成）；Ｊｉａ－ＬｉｕＹＡＯ...  相似文献   

3.
E. Keppler 《Annales Geophysicae》1998,16(12):1552-1556
The variation of the peak intensity of energetic ions accelerated at CIR related shocks in the interplanetary medium as observed by instruments on board of ULYSSES during its pass towards the south polar region and from the north polar region back to its aphelium is discussed. From ULYSSES measurements alone it cannot be decided whether the observed variation is a function of latitude or of radial distance, as its orbit changes distance and latitude at the same time. Therefore ULYSSES data is compared with earlier observations by the PIONEER and VOYAGER spacecraft and concluded that the major part of the observed variation of the peak intensity seems to be due to a radial distance change, on to which, however, at higher latitudes a latitude dependent feature is superimposed.  相似文献   

4.
Ｃｈａｒａｃｔｅｒｉｓｔｉｃｓ　ａｎｄ　ａｎａｌｙｓｉｓ　ｏｆ　ｔｈｅ　ｇｅｏｍａｇｎｅｔｉｃ　ｖａｒｉａｔｉｏｎｓ　ｉｎ　ｒｅｇｉｏｎｓ　ａｒｏｕｎｄ　ｔｈｅ　Ｑｉｏｎｇｚｈｏｕ　Ｓｔｒａｉｔ（范国华）（姚同起）（顾左文）（朱克佳）（陈伯舫）（冯戬...  相似文献   

5.
This article studies long-period variations in the Earth’s upper atmosphere density over several solar activity cycles, using long-term data on the evolution of motion of three artificial satellites (Intercosmos-19, Meteor-1-2, and Cosmos-1154) in orbits at heights of 400–1000 km. The time interval when the satellites were in the orbits covered three solar activity cycles (partly the 21st, completely the 22nd, and partly the 23rd). It is found that the variations in the average density of the upper atmosphere at heights of 400–600 km in the 1980–2000 period were governed by the changes in the solar activity level.  相似文献   

6.
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   

7.
We investigate the Tibet–Quinghai plateau and the Tarim basin in terms of spatial variations of the elastic thickness (Te) in the frame of the thin plate flexure model. The method of investigation makes use of a convolutive method, which allows high spatial resolution of the flexure properties and overcomes some of the problems tied to the spectral admittance/coherence methodologies. We study the relation between the topographic and subsurface loads and the observed crust–mantle interface (CMI) undulations, the latter having been obtained from gravity inversion. The gravity data used for the inversion are a unique set of high quality data available over the Chinese part of the plateau, and constitute the highest resolution grid today available in this impervious area. The gravity inversion is constrained by results from the study of the propagation of seismic waves. The two extensive sedimentary basins, the Tarim and the Qaidam basins, are modeled by forward gravity modeling. The oscillations of the CMI obtained from the gravity inversion agree well with those expected by loading the thin plate model of spatially variably elastic thickness with the surface and subsurface loads. It is found that the modeling of the sedimentary basins is essential in the flexure analysis. The spatial variations of elastic thickness correlate with the extensions of the different terrains that constitute the plateau. Most of the Tibet plateau has low Te, varying in the bounds 10–30 km, with lower values in the Qiangtang terrain, where the Te reaches 8 km. The Tarim and the Qaidam basins, Precambrian platforms overlain by sediments, are rigid and have a Te of up to 110 km and 70 km, respectively. The flexural analysis distinctly discerns the Tibet plateau, with thick crust, part of which is molten, from the cratonic areas, the Tarim and Qaidam basins, which though of thinner crust, act as undeformable rigid blocks.  相似文献   

8.
The modeling results are presented on the annual dynamics of seismicity in the northeastern segment of the Amur plate, which are obtained from statistical studies of the number of earthquakes with magnitudes 2 ≤ М ≤ 6 in different phases of variations in the Earth’s rotation rate. We have calculated a degree of relationship between the observed seismicity variations and phases of decrease and increase in the Earth’s rotation rate for the magnitude ranges between 2 ≤ М < 4 and 4 ≤ М < 5 using rank correlation methods. It has been established that epicenters of earthquakes with magnitudes 5 ≤ М ≤ 6 are spatially grouped into a sequence of homogeneous equally spaced, 3.5°–4°, on average, east-westerly oriented clusters.  相似文献   

9.
For more than a decade, the global network of GPS stations whose measurements are part of the International GPS Service (IGS) have been recording cyclic variations in the radius vector of the geodetic ellipsoid with a period of one year and amplitude of ~10 mm. The analysis of the figure of the Earth carried out by us shows that the observed variations in the vertical component of the Earth’s surface displacements can induce small changes in the flattening of the Earth’s figure which are, in turn, caused by the instability of the Earth’s rotation. The variations in the angular velocity and flattening of the Earth change the kinetic energy of the Earth’s rotation. The additional energy is ~1021 J. The emerging variations in the flattening of the Earth’s ellipsoid lead to changes in the surface area of the Earth’s figure, cause the development of deformations in rocks, accumulation of damage, activation of seismotectonic processes, and preparation of earthquakes. It is shown that earthquakes can be caused by the instability of the Earth’s rotation which induces pulsations in the shape of the Earth and leads to the development of alternating-sign deformations in the Earth’s solid shell.  相似文献   

10.
Spatiotemporal variations of P species and adsorption behavior in water column, interstitial water, and sediments were investigated in the large shallow eutrophic Lake Chaohu. Ortho-phosphate (Ortho-P) and total phosphorus (TP) concentrations were significantly higher in the western part than in the eastern part of the lake, due to different nutrient inputs from the surrounding rivers. Moreover, paniculate phosphorus (PP) concentration was in a similar spatial pattern to Ortho-P and TP concentrations, and also showed significantly positive correlation with the biomass of Microcystis, indicating more uptake and store of phosphorus by Microcystis than by other algae. Increase of pH and intensive utilization of P by phytoplankton were the main factors promoting P (especially Fe-P) release from the sediment to interstitial water during the cyanobacterial blooms in Lake Chaohu. Spatial dynamics in TP concentration, P species and adsorption behavior of the sediment, coupled with the statistical analyses, suggested that the spatial heterogeneity of P contents in the sediment was influenced by various factors, e.g. human activities, soil geochemistry and mineral composition. In spite of similar TP contents in the sediments, increase in proportion of Fe-P concentration in the sediment may result in a high risk of P release.  相似文献   

11.
Extraterrestrial forcing of natural environmental processes by gravitational interaction between the Sun, the Moon, and the Earth is considered. Based on the instrumental data, the main periodical components and cycles are identified in the time variations of some geophysical fields at the boundary between the Earth’s crust and the atmosphere. Correlation analysis shows that the lunar-solar tides are the key factor responsible for diurnal and quasi-biweekly variations in the ground electric field, radon emanation, water level in wells, and microseismic vibrations. The tidal influence on the various-scale movements of the blocks of the Earth’s crust is analyzed. In the context of the vertical, lateral, and rotational motion of crustal blocks, which is very important for the platforms, a new, precession-like type of displacements is revealed. These movements develop as a result of the nonsynchronous tidal responses of the block and the adjacent interblock gaps or tectonic structures whose strength and strain properties are different in different directions.  相似文献   

12.
The spatial-temporal variations in localization of the sources of earthquakes with H ≥ 14 km are reviewed for the Garm region. The uneven distribution of such earthquakes is related to the block structure: their amount is higher in the weakened zones rather than in blocks. Three weakened zones are characterized by higher activity of deepened seismicity, which varies in time and increases before the earthquakes with K ≥ 12.5. The temporal variations in distribution of earthquake sources with depth allow a suggestion of the relation of the velocity of the Earth’s rotation and activity of deepened seismicity.  相似文献   

13.
  相似文献   

14.
ＴｈｅｐａｔｔｅｒｎｃｈａｒａｃｔｅｒｉｓｔｉｃｓｏｆｔｈｅｔｅｎｄｅｎｃｙｖａｒｉａｔｉｏｎｓｏｆｅａｒｔｈｒｅｓｉｓｔｉｖｉｔｙａｎｄｉｔｓｒｅｌａｔｉｏｎｔｏｅａｒｔｈｑｕａｋｅｓＨｅ－ＹｕｎＺＨＡＯ（赵和云）（ＥａｒｔｈｑｕａｋｅＲｅｓｅａｒ...  相似文献   

15.
The refinement of the accuracy and resolution of the monthly global gravity field models from the GRACE satellite mission, together with the accumulation of more than a decade-long series of these models, enabled us to reveal the processes that occur in the regions of large (Mw≥8) earthquakes that have not been studied previously. The previous research into the time variations of the gravity field in the regions of the giant earthquakes, such as the seismic catastrophes in Sumatra (2004) and Chile (2010), and the Tohoku mega earthquake in Japan (2011), covered the coseismic gravity jump followed by the long postseismic changes reaching almost the same amplitude. The coseismic gravity jumps resulting from the lower-magnitude events are almost unnoticeable. However, we have established a long steady growth of gravity anomalies after a number of such earthquakes. For instance, in the regions of the subduction earthquakes, the growth of the positive gravity anomaly above the oceanic trench was revealed after two events with magnitudes Mw=8.5 in the Sumatra region (the Nias earthquake of March 2005 and the Bengkulu event of September 2007 near the southern termination of Sumatra Island), after the earthquake with Mw=8.5 on Hokkaido in September 2007, a doublet Simushir earthquake with the magnitudes Mw = 8.3 and 8.1 in the Kuriles in November 2006 and January 2007, and after the earthquake off the Samoa Island in September 2009 (Mw=8.1). The steady changes in the gravity field have also been recorded after the earthquake in the Sichuan region (May 2008, Mw = 8.0) and after the doublet event with magnitudes 8.6 and 8.2, which occurred in the Wharton Basin of the Indian Ocean on April 11, 2012. The detailed analysis of the growth of the positive anomaly in gravity after the Simushir earthquake of November 2006 is presented. The growth started a few months after the event synchronously with the seismic activation on the downdip extension of the coseismically ruptured fault plane zone. The data demonstrating the increasing depth of the aftershocks since March 2007 and the approximately simultaneous change in the direction and average velocity of the horizontal surface displacements at the sites of the regional GPS network indicate that this earthquake induced postseismic displacements in a huge area extending to depths below 100 km. The total displacement since the beginning of the growth of the gravity anomaly up to July 2012 is estimated at 3.0 m in the upper part of the plate’s contact and 1.5 m in the lower part up to a depth of 100 km. With allowance for the size of the region captured by the deformations, the released total energy is equivalent to the earthquake with the magnitude Mw = 8.5. In our opinion, the growth of the gravity anomaly in these regions indicates a large-scale aseismic creep over the areas much more extensive than the source zone of the earthquake. These processes have not been previously revealed by the ground-based techniques. Hence, the time series of the GRACE gravity models are an important source of the new data about the locations and evolution of the locked segments of the subduction zones and their seismic potential.  相似文献   

16.
The variations of the Earth’s geometry (ETP) pre-dominate climate changes such as monsoon on the Earth[1], serving as its external forcing. The loess/ paleosol sequence in Central China provides a good record of terrestrial deposition to study the evolution of the east Asian monsoon[2―4]. However, the deep sea deposition, due to its high resolution dating and abun-dant climate proxies, should be able to provide more climatic information in the geological time, such as the forcing mechanis…  相似文献   

17.
The accuracy limitations of critical frequency predictions in the ionospheric F2 layer are considered, which arise due to random variations in the Sun’s extreme UV radiation during the month. An analysis of δf (relative values of monthly rms scatters of the F2-layer critical frequencies) and the appropriate δu values (monthly rms scatters of extreme UV radiation) has shown their dependence on the solar activity level. A conclusion is drawn that when prognostic models of monthly medians are used for forecasting foF2 for a particular date, the error can hardly be less than ～7% at low solar activity and ～15% at a higher solar activity level.  相似文献   

18.
ＴｈｅＱｖａｌｕｅｖａｒｉａｔｉｏｎｓｉｎｔｈｅｐｒｅｐａｒｉｎｇｐｒｏ┐ｃｅｓｏｆｒｏｃｋｒｕｐｔｕｒｅＢＩＮＷＡＮＧ１）（王彬），ＺＨＡＯ－ＹＯＮＧＸＵ１）（许昭永），ＪＩＮ－ＭＩＮＧＺＨＡＯ１）（赵晋明）ＹＩ－ＬＩＨＵ２）（胡毅力）１）Ｓｅｉ...  相似文献   

19.
Bakker M 《Ground water》2006,44(3):478-482
A rule of thumb is presented to determine where variations in the discharge of a pumping well have a significant influence on the flow in an aquifer. The rule of thumb relates the period of the variation of the discharge to the distance from the well beyond which the transient effect on the flow in the aquifer is insignificant. For example, when an irrigation well pumps intermittently during the growing season, the rule may be applied to determine the distance from the well beyond which flow in the aquifer can be simulated with an average discharge during the growing season; the distance from the well beyond which flow can be simulated with a steady, yearly averaged discharge can also be computed.  相似文献   

20.
Aerosol can induce visibility reduction, affect radiation balance and modify cloud property on the environmental effect, and show the harmful effects on human health. Insight of aerosol becomes an integral task in the process of control measures for environmental pollution. The present study provided an analysis of temporal–spatial variations of aerosol optical depth (AOD) using the MOD04 level-2 in collection 6 (C6) with the deep blue retrieval algorithm from January 2005 to December 2015 over Yangtze River Delta (YRD) in China. The AOD validations between MODIS and Aerosol Robotic Network (AERONET) were estimated by the methods of regression, correlation. Then, the periodic features and trends of AOD and angstrom exponent (AE) were explored with the wavelet transformation (WT) procedure. Further, the variations of AOD and AE spatial distribution on multi-time scales (annual, monthly and season) were demonstrated. Meantime, the sources of AOD are discussed. It was found that the daily AOD from MODIS has a strong correlation relationship (slope?=?0.9838, r?=?0.84) with AERONET over YRD. The variations of both AOD and AE on time series have been distinct temporal periodic (12, 6 and 4 months) characteristics, and show the decreasing trends on annual and semi-annual periods. On annual, the AOD on spatial distribution is slowly declining from the northwest towards the southeast, and the AE on spatial distribution is gradually decreasing from the northwest to the southeast and from the land to the coast. The variations both inter-annual AOD and AE on spatial distribution show the inverse trends, respectively. On monthly, the means of AOD range from minimum 0.46 in January to maximum 0.90 in July, and the variations of spatial distribution mainly occur in the north parts of Yangtze River and some scattered areas with high terrain and south coast. The means of AE range from minimum 1.13 in October to maximum 1.58 in April, and the variations of spatial distribution are mainly found in the south of Henan, the north of Jiangsu, the coast belt and the riverside of Yangtze River and the high terrain regions. On seasonality, the means of AOD reaches its maximum 0.68 in summer and minimum 0.50 in winter, and the variations of spatial distribution mainly occur in the coast belt, the north parts of Hongze Lake and the south parts with high terrain. The means of AE reaches its maximum 1.48 in spring and minimum 1.25 in autumn, and the variations of spatial distribution were shown the similarity with that of monthly.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号