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1.
For evaluating the deformations of the Earth’s crust in the Northern Tien Shan, we calculated the mode and intensity of the seismotectonic deformations (STD) for this region. The input for these calculations were the catalog data on the focal mechanisms of earthquakes, obtained by wave inversion of the signals recorded at the Kyrgyz seismic network (KNET) for the period 1994–2006. In the construction of STD maps, a modern approach to the classification of seismotectonic deformations was applied. This approach distinguishes eleven typical patterns of deformation. The areal distributions of the Lode-Nadai coefficient, as well as of the vertical component and the aspect angle of the deformed state were obtained. At the same time, based on the GPS measurements in the Northern Tien Shan during 1994–2006, the rates of dilatation and shear deformation of the Earth’s crust were estimated. A comparison between the directions of strain axes derived from the GPS data and from the earthquake focal data is carried out.  相似文献   

2.
The spatial-temporal dynamics of surface crustal movements revealed from GPS data is compared with seismicity in the Bishkek geodynamic test area documented in the regional KNET catalog. The geological information system (GIS) GeoTaim 2.0 is substantially improved, which allowed variations in seismicity and deformation fields to be analyzed in the 3D raster. It is shown that seismicity and surface deformations are correlative in the test area. The periods with extreme values of contraction and the extension rates of the Earth’s surface areas are accompanied by enhanced seismicity and strong earthquakes. The increase in the spatial gradient of surface crustal movements coincides with changes in the azimuths of compression axes indicated by mechanisms of earthquakes that occurred at depths of up to 25 km. For a better geological—geophysical interpretation of interactions between deformation and seismicity fields in the Bishkek geodynamic test area, the spatial system GPS stations and measurement frequency need substantial improvement.  相似文献   

3.
Orientations of the principal axes of the tectonic stress field reconstructed from seismological data on focal mechanisms of earthquakes and strain fields determined from GPS measurements in China are compared. The data of GPS measurements used in the paper were obtained by the Crustal Movement Observation Network of China (about 1000 stations) in the period of 1998–2004. On the basis of information on the recent horizontal crustal motions, the strain field is calculated for the study territory by the finite element method. Calculations of the strain tensor using GPS data were carried out with a step of 1° in latitude and longitude. A catalog of earthquake focal mechanisms was used for the reconstruction of tectonic stress field components. Focal mechanisms of earthquakes were calculated with the use of seismological data on signs of first arrivals from the bulletin of the International Seismological Center. To estimate characteristics of the regional stress field, an approach based on the kinematic method proposed by O.I. Gushchenko was applied. The tectonic stress field was reconstructed in depth intervals of 0 < H < 35 km and 35 km < H < 70 km from data on focal mechanisms of earthquakes over the periods of 1998–2004 and 1985–2004. Comparison of directions of the principal strain axes at the surface (according to GPS measurements) and directions of the principal stress axes (reconstructed from focal mechanisms of earthquakes) showed their good convergence. Seismotectonic strains and GPS measurements coincide within a larger part of the territory. The coincidence is best in a depth interval of 0 < H < 35 km. Maximum misfit values are confined to areas of high 3-D gradients of strain axis directions and are possibly related to the structural heterogeneity of the region, zones with strains of the same type along both horizontal axes (compression or extension along all directions), or areas of small absolute values of recent horizontal movements. Areas with invariable directions of the stress axes are recognizable regardless of the depth of initial data. Good reproducibility of results obtained by two different methods made it possible to check the method of stress field reconstruction using data on focal mechanisms of earthquakes.  相似文献   

4.
A new generation of global geopotential models (GGM) is being developed. These solutions offer a file with fully-normalized spherical harmonic coefficients of the Earth’s gravitational potential up to a degree greater than 2000 with very low commission errors. This paper analyses the recent Earth Gravitational Model EGM2008, developed up to degree and order 2159 with additional coefficients to degree 2190 and order 2159, which means recovering the gravitational field up to approximately 20 km wavelengths. 223 GPS/levelling points of the new Spanish High Precision Levelling Network in the Valencia region (Eastern Spain) are used as external tool for evaluation in that particular region. The same evaluation has been performed to other different global (EGM96 and EIGENCG03C), continental (EGG97), regional (IGG2005 and IBERGEO2006) and local (GCV07) geoid models for comparison purposes only. These comparisons show that EGM2008 is the geoid model that best fits to the GPS/levelling data in that region.  相似文献   

5.
The long-term variations in the second degree sectorial Stokes parameters of the geopotential have been determined from TOPEX-POSEIDON (T/P) satellite altimeter data, covering the period of January 1, 1993 to January 3, 2001 (T/P cycles 11-305). It is the first attempt to determine the variations in the second sectorial harmonics in the Earth’s inertia tensor due to the ocean dynamics. The variations amount to about 1 × 10−10 (J 2 (2) ≈ 1.6 × 10−6 and S 2 (2) ≈ −0.9 × 10−6). The variations are about 5% of the tidal effect. This corresponds to variations in the directions of the equatorial axes of the Earth’s inertia ellipsoid of up to 10 arc-seconds. Consequently, the annual and semi-annual variations of the Earth’s equatorial flattening is about 10−9; i.e. it corresponds to a change of 8 units of its denominator of 91 030. (The equatorial flattening ≈ 1/91 030). Since the coverage of the Earth’s ocean surface is not worldwide, and the inclination of T/P is i = 66°, it is only 58.2% (min. depth of the ocean 2 000 m) of the Earth’s surface which is processed, the torque, resulting from the seasonal transfer of masses within a sea surface layer, is not zero. It amounts up to 1016 kg m2s−2, which is comparable to the total indirect tidal torque due to the Moon and the Sun, ∼ 3.9 × 1016 kg m2s−2. However, the above estimate strongly depends on the adopted thickness of the sea surface layer, ΔR = 50 m. For a larger thickness of ΔR = 100 m, the seasonal torque amounts to about ∼ 2.3 × 1016 kg m2s−2.  相似文献   

6.
Earth’s free wobble is often referred to as the Euler wobble (for the rigid case) or the Chandler wobble for the real case. In this study, we investigate the theory of the free wobble of the triaxial Earth and demonstrate that: (1) the Euler period should actually be expressed by the complete elliptic integral of first kind, and (2) the trace of the free polar motion is elliptic, with the orientations of its semi-minor and major axes being approximately parallel to the Earth’s principal axes A and B, respectively. Numerical calculations show that, due to the triaxiality of the Earth, the spin rate ω 3 fluctuates with the semi-Euler/Chandler period, although its amplitude (about 10−19 rad/s) is rather small and beyond the present measurement accuracy; the tilt of the instantaneous spin axis (or the amplitude of the free wobble), θ, has a fluctuation whose amplitude is around 0.34 milli-arcsecond (mas), which could be detected by present observations. Thus, we conclude that the Earth’s triaxial nature has little impact on ω 3, but has an influence on the polar motion which should not be ignored. On the other hand, our study shows that there is a mechanism of frequency–amplitude modulation in the Chandler wobble which might be a candidate to explain the correlation between the amplitude and period of the Chandler wobble. We compare the theoretical polar parameters (m 1, m 2) with the observed values for the Chandler components obtained from the data EOP (IERS) C 04, and find that they coincide with each other quite well, especially for recent years. In addition, a polar wander towards 76.7°W, which is in agreement with previous results given by other scientists, is also obtained.  相似文献   

7.
Extreme high precipitation amounts are among environmental events with the most disastrous consequences for human society. This paper deals with the identification of ‘homogeneous regions’ according to statistical characteristics of precipitation extremes in the Czech Republic, i.e. the basic and most important step toward the regional frequency analysis. Precipitation totals measured at 78 stations over 1961–2000 are used as an input dataset. Preliminary candidate regions are formed by the cluster analysis of site characteristics, using the average-linkage clustering and Ward’s method. Several statistical tests for regional homogeneity are utilized, based on the 10-yr event and the variation of L-moment statistics. In compliance with results of the tests, the area of the Czech Republic has been divided into four homogeneous regions. The findings are supported by simulation experiments proposed to evaluate stability of the test results. Since the regions formed reflect also climatological differences in precipitation regimes and synoptic patterns causing high precipitation amounts, their future application may not be limited to the frequency analysis of extremes.  相似文献   

8.
    
Based on the time series of observational variations of the length of day (LOD) and seismic data in the world, the relations of the decadal fluctuation and seasonal variation in the Earth’s rotation with global seismic activity are studied in this paper. The results suggest that there are overall correlations on temporal scale and regional discrepancy on spatial scale between global seismic activity and the Earth’s variable rotation, especially the seismic activity in the Eurasian seismic zone (not including southeast Asia) and the Lower California-Eastern Alaska seismic zone correlating well with the Earth’s variable rotation. According to the relations mentioned above, the observational data of the Earth’s rotation might provide a referential basis for monitoring global seismic activity. This project is sponsored by the National Key Basic Research Project and the National Natural Science Foundation of China. The English version is improved by Prof. Xin-Ling QIN, Institute of Geophysics, SSB, China.  相似文献   

9.
Climatic trends in the middle and high latitudes of the Northern Hemisphere   总被引：1，自引：0，他引：1  
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10.
The Vladikavkaz Fault Zone is a regional boundary between the Alpine folded-block system of the Greater Caucasus and Pre-Caucasus foredeep (Ossetian Depression). A complex of geological and geomorphological techniques was used for its study. The data of recent activity of discontinuous and folded dislocations were obtained as a result. Additional application of the microseismic sounding method allowed us to trace the behavior at depth and along the direction of the Vladikavkaz Fault Zone’s branches known on the Earth’s surface from geological and geophysical surveys. An idea of the three-dimensional structure of this system of tectonic faults was made up. It was shown that the structure of the upper section of the fault zone has a form of listric foldthrust, and in the deep layers of the Earth’s crust it is represented by a well-formed contrast zone with subvertical plunging. Expressive deformations of young sediments and a clear manifestation of the fault zone at a depth make it possible to consider the Vladikavkaz Fault as a major seismogenerating structure.  相似文献   

11.
The Earth’s crossings of the magnetic sector boundaries are accompanied by changes in the magnetosphere, ionosphere, and troposphere. We considered the baric field’s response to the crossing of the inter-planetary magnetic field (IMF) sector boundaries during a geomagnetically quiet period. The IMF sign is shown to affect atmospheric pressure in high-latitude regions. The efficiency and sign of the relationship vary during the year. The baric field response to the Earth’s crossing of the IMF sector boundaries is most distinct during equinoxes. It is shown that, during a geomagnetically quiet period, the circulation processes in the atmosphere drive the changes in the atmospheric pressure when the Earth passes from one IMF sector into another.  相似文献   

12.
The global stress field appearing in the Earth’s lithosphere under the action of forces caused by the difference of gravitational potential is calculated. An original algorithm is proposed and the operational Earth Stresses program code is developed. The data on the topography, thickness, and density of the Earth’s crust and the upper mantle, as well as the gravitational anomalies and thermal conditions in the lithosphere were taken into account in the calculations. A comparison of the calculation results and the observed data makes it possible to conclude that the action of the forces of the difference of the gravitational potential alone is sufficient to explain the features of the first order of the stress field in the Earth’s lithosphere.  相似文献   

13.
The studies on the structure and physical properties of the Earth‘s interior done by Chinese geophysicists from 1999 to 2002 were reviewed in this paper. It includes several research areas: the structure of the Earth‘s interiors using seismic tomography, anisotropy of the upper mantle in China and its adjacent areas, quality factor Qβ for S waves, subduction zone, mantle discontinuities, physical properties of Earth‘s materials and others. The review concerns mainly the contents, the methods and the results of the studies. It can be seen that new progress in the study on the structure and physical properties of the Earth‘s interior has been made in the last 4 years in China. It is shown on three aspects: advancement made on some preexistent areas; pioneering on some new fields and new methods adopted.  相似文献   

14.
The elasto-gravitational deformation response of the Earth’s solid parts to the perturbations of the pressure and gravity on the core-mantle boundary (CMB) and the solid inner core boundary (ICB), due to the dynamical behaviors of the fluid outer core (FOC), is discussed. The internal load Love numbers, which are formulized in a general form in this study, are employed to describe the Earth’s deformation. The preliminary reference Earth model (PREM) is used as an example to calculate the internal load Love numbers on the Earth’s surface, CMB and ICB, respectively. The characteristics of the Earth’s deformation variation with the depth and the perturbation periods on the boundaries of the FOC are also investigated. The numerical results indicate that the internal load Love numbers decrease quickly with the increasing degree of the spherical harmonics of the displacement and depend strongly on the perturbation frequencies, especially on the high frequencies. The results, obtained in this work, can be used to construct the boundary conditions for the core dynamics of the long-period oscillations of the Earth’s fluid outer core. Foundation item: State Natural Science Foundation of China (40174022 and 49925411) and the Projects from Chinese Academy of Sciences (KZCX2-106 and KZ952-J1-411).  相似文献   

15.
The Mohorovičić discontinuity is the boundary between the Earth’s crust and mantle. Several isostatic hypotheses exist for estimating the crustal thickness and density variation of the Earth’s crust from gravity anomalies.  相似文献   

16.
We investigate the roughness of and the correlation with topography of the observed, topographically corrected (T), and bathymetrically and topographically corrected (BT) gravity disturbances. The numerical investigation is carried out for the gravity disturbances at the Earth’s surface and for the upward continued gravity disturbances at different altitudes. The area of study comprises a rough part of the Canadian Rockies surrounded by flat regions. The smoothest at the Earth’s surface are the BT gravity disturbances. The evolution of roughness with altitude shows an interesting phenomenon, diverse for the three types of gravity disturbances. The correlation with topography over the study area of the observed gravity disturbances is bellow 0.6, and of the BT gravity disturbances approximately −0.6. The largest absolute value, of about −0.75, is found between the topography and the T gravity disturbances. This large negative correlation indicates a presence of the isostatic compensation in mountainous regions of the Canadian west coast.  相似文献   

17.
Besides generating seismic waves, which eventually dissipate, an earthquake also generates a static displacement field everywhere within the Earth. This global displacement field rearranges the Earth’s mass thereby causing the Earth’s rotation and gravitational field to change. The size of this change depends upon the magnitude, focal mechanism, and location of the earthquake. The Sumatran earthquake of December 26, 2004 is the largest earthquake to have occurred since the 1960 Chilean earthquake. Using a spherical, layered Earth model, the coseismic effect of the Sumatran earthquake upon the Earth’s length-of-day, polar motion, and low-degree harmonic coefficients of the gravitational field are computed. Using a model of the earthquake source that is composed of five subevents having a total moment-magnitude M w of 9.3, it is found that this earthquake should have caused the length-of-day to decrease by 6.8 microseconds, the position of the Earth’s generalized figure axis to shift 2.32 milliarcseconds towards 127° E longitude, the Earth’s oblateness J 2 to decrease by 2.37 × 10−11 and the Earth’s pear-shapedness J 3 to decrease by 0.63 × 10−11. The predicted change in the length-of-day, position of the generalized figure axis, and J 3 are probably not detectable by current measurement systems. But the predicted change in oblateness is perhaps detectable if other effects, such as those of the atmosphere, oceans, and continental water storage, can be adequately removed from the observations.  相似文献   

18.
The present-day models of the Earth’s upper atmosphere make it possible to construct the spatial-temporal pattern of variations in the atmospheric parameters on the planetary scale in essence in the averaged form. The set of data on the satellite deceleration in the atmosphere, probe measurements aboard geophysical rockets, and radiowave incoherent scatter measurements in the Earth’s atmosphere are used to construct these standard models. The current level of the space studies makes it possible to use a new method to study the Earth’s upper atmosphere: to study the upper atmosphere by measuring the absorption of the solar XUV radiation by the Earth’s atmosphere during the solar disk observations.  相似文献   

19.
The work is dedicated to investigation of Hot Flow Anomaly (HFA), formed at the front of Earth’s bows hock. Using Interball-Tail data we estimated orientation of the current sheet that was a cause of the anomaly. From the ion energy-time spectrogram we divided the anomaly into several regions. The motional electric fields near the HFA were estimated with 3D model of Earth’s bow shock. In accordance with previous investigations of HFA’s formation conditions these fields were directed towards the current sheet on both sides of it. We also provided the picture of HFA’s motion along the bow shock and calculated its speed. Analyzing ions’ bulk velocities within the HFA we found that the anomaly is expanding. This conclusion was supported by estimation of thermal and magnetic pressure balance. Ion energy-time spectrogram shows that anomaly is a complicated structure consisting of two parts—leading and trailing. Comparison of ion velocity distributions, magnetic field data and ion energy-time spectrogram provides better understanding of the phenomena and indicated the region that is the source of thermal and convective energy inside HFA.  相似文献   

20.
A mathematical modeling method and the global numerical model of the Earth’s upper atmosphere were used to study nighttime enhanced electron density regions (EEDRs) in the ionospheric F2 layer and their possible manifestations at altitudes of the Earth’s plasmasphere. It has been established that EEDRs are formed owing to latitudinally nonuniform longitudinal (along the magnetic field) plasma flows from the plasmasphere into the nighttime ionosphere and the wind transport of ions along geomagnetic field lines. The specific features of the effect of ionospheric-plasmaspheric plasma transport processes, related to their three-dimensional character, on EEDRs have been revealed.  相似文献   

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