Slow earthquakes are one of the forms of earthquake energy releases. The study of the dynamics of slow earthquakes has become a frontier of contemporary research with great impact. This paper reviews the status of the international and domestic research of slow earthquakes，including the definition and main features of slow earthquakes, their characters in kinematics and dynamics，its identification and location，generation of slow earthquakes and their relations to geological settings，their physical mechanism of occurrence，numerical simulation of the complete process of slow earthquake occurrences，and so on. The paper alms reviews the relations between long period precursors and slow earthquakes，as well as the relations between slow earthquakes and stress triggering and seismicity. The observation and investigation of slow earthquakes are not only important for theoretical studies on instability of the faults，but also provide a new approach in exploring the short and imminent earthquakes prediction. In China，the study of slow earthquakes is in a preliminary stage. It is believed that the immediate task is to show solid evidence to identify and locate some continental slow earthquakes and study their mechanism. For this purpose，it is critical to strengthen the netwark density and deploy seisrmmeters,strainmeters，GPS and INSAR to cover entire frequencies of the crust deformation. At the same time，the comprehensive ability to analyze various data and simulate slow earthquakes should be reinforced.
The cxperimental results of rheological properties of rocks and minerals were reviewed in this paper. The physical and chemical factors that influence creep behavior of olivine aggregates were discussed in detail. Rocks and minerals have two major micro mechanisms when defomed under high temperature and high pressure. One is diffusion creep and the other is dislocation creep. In the diffusion creep rcgime, the stress-strain relation is linear and in dislocation creep regime, the stress strain relation is power law for olivine aggregates. 100MPa is the trarxsition stress between diffusion creep regime and dislocation creep regime. When the temperature or melt-fraction increases, strain rate will increase under the sane stress level. Water can strongly weaken the strength of olivine. Grain size is a complicat,d factor. Observations suggest that the defamation mechanis in the grain size insensitive regune is dislocation creep, while that in the grain size sensitive regime is diffusion creep.
The ratio of radiated energy over seismic moment, or the so called reduced energy, is studied for global deep-focus earthquakes deeper than 70km using the scalar seismic moment in the Harvard CMT catalogue and the radiated energy estimated by NEIL from January 1987 to December 2001. The scaling of reduced energy versus seismic moment is obtained for different depth ranges, respectively. It is olxerved that for earthquakes with depths between 70km and 400km, reduced energy decreases with seismic moment,while for earthquakes with depths beyond 400km, reduced energy increases with seismic moment. This characteristic is apparently different from that of shallow earthquakes.
Considering different spatial and temporal ranges for the same earthquake，we investigate the objectivity and generality of the phenomenon of accelerating strain release before stmng earthquakes. A systematic analysis of all the earthquakes which occurred in China with Ms≥7.0 from 1990 to 2003 is conducted. It is found that the real seismic activity seems much more complex than the simple pattern as described by the accelerating strain release model.Therefore，the potentials of application of accelerating strain release model to the estimation of seismic hazard are in need of future investigation.
GPS (global positioning system) velocity can be used to calculate the horiwntal strain rate，but it should be done with great care because digital differentiation is involved，which brings about a prominent problem in minimizing the error. In this paper,a general strain rosette method(GSRM) is proposed，in which the plane strain rosette method in engineering is widened to include spherical earth surface. Then the GSRM is compared with the least squares collocation method (LSCM) in specific case by a digital experiment in which displacements and the strain field are known. The result shows that the accuracy of strain rate computed by GSRM is higher than that of L SRM.Finally，with Chinese Sichuan-Yunnan area as an example,the strain rate is calculated by GPS data and some discussions of computation methods and results are made.
Strain and tilt measurements are thought to be important methods to find precursors in the earthquakePrediction. It is cnrcial to distinguish the noise from tectonic signals. The temperature variation of earth surfazeechanges the temperature of the subsurface. Hence the stress field is affected and the deformation of the ground isproduced. In present work, finite element techniques are employed to study the effect of annual temperaturevariation, when czunplex landfonn exists. The depth concerned and the magnitude of stress and tilt are evaluated.The results show that; thermal convergence and dispersion caused by topography, which is similar to light, mayproduce the non-uniformity of temperature distribution.The temperature anisotropy affects the stress field and tilt.The depth concerned is larger than that of temperature.Attention should be paid to the annual temperature variationand other noise effects when measurement sites are chosen.
Based on the analysis of GPS data and the results of a 3D viscoelastic modeling，it is proposed that themacro movement form of Ordos block is composed of two parts. One is anti-clockwise rotation of Ordos block itself，and the other is the movement of the whole continent of China. This opinion can explain the contradiction of therotation directions of south，north rupture belts and east，west rupture belts. Furthertmore，a new model describingthe interaction of Ordos block and adjacent blocks，“Extrusive，Impellent and Impeditive Mod(E11
In this paper, the global topography, the depth of the Moho(the cxustalmodel CRUST2.0)，th a depths ofupper mantle discontinuities were analyzed using the spherical harmonics. Based on these data, the spatial large scaledistribution information has been obtained by sacking the first 4 degree modes, and the main energy distributionshave been understood by synthesizing the four items with the maxunal squares of amplitudes. The results show thatthere exiss a large scale asynrrnetry on the scale of semisphere in the topographies of the Moho and the‘410'discontinuities, and the asynrrnetry character of the nor-tl}rsouth semispheres is more obvious than that of the westeast semispheres; However, there exiss a scale asymmetry on the small side in the topographies of‘520' and‘660'discontinu ides, instead of such a large sphere scale asynrrnetry.
The numerical test shows that the ill effect will be brought in the inversion result of velocity structure with receiver functions when the parameterized models in the forwarding and inversing procedures are not matched. Some information will be lost in the real data processing when the observed and synthetic receiver functions are normalized respectively.Accordingly, the inversion program of Neighborhood Algorithm with receiver functions is improved and then the crust velocity structure under station HLR is obtained in this paper.
3-D velocity structure of crust and upper mantle beneath the East Asia and West Pacific marginal seas (60bE~ 150bE, 10bS~ 60bN) down to the depth of 300km has been studied by using a total of 170550 P-wave first arrival times from the ISC bulletin, which are selected from 12500 events and 928 seismic stations within the studying areas. The result is given with the resolution of grid spacing of 2b@ 2b. The preliminary results show: (1) The P-wave velocity structure is so different between the eastern part and western part of the East Asia and West Pacific marginal seas by the boundary of 108bE. The western part isthe thickening convergent lithosphere caused by Indian subcontinent colliding with the Eurasian continent, and the eastern part is a disassembly causing the lithosphere thinning and extension arising from intrusion of asthenospheric material. (2) The crust and lithosphere of the Tibet is very thick, and the LVZ is not obvious. The Indian subcontinent dived to the beneath of the Tibet. (3) There are the high-velocity anomalies beneath the Japan Sea and the Philippines Sea. It could be the evidence that the Pacific slab dived to this area.
The geologic deformation generally is predigested as a tiny distortion problem in studies.However,some actual geologic progress,i.e.,the rise and subsidence of Xisha Trough in margin crust splitting of the South China Sea do not accord with the condition of tiny distortion, whereas, the geologic progress belongs to the finite deformation problem.According to the theory of finite distortion,this paper calculated the field of tectonic stress and deformation components of Xisha Trough.The result shows that the moving direction of tectonic deformation depends on the size of structure resistance.The resistance is the smallest in the vertical direction in central Xisha.The largest vertical deformation appears here.Presently, there is a rising move with a velocity of 7 ×10-3cm a in the center of Xisha Trough.The strain component exx of finite distortion is compression at the center of Xisha Trough,but is tension at south and north sides.On the other hand,the strain component ezz of finite distortion is tension at the center of Xisha Trough,but is compression at south and north sides.
The interpolation is an usual method to represent the continuous geophysical fields. The Natural Neighbor Interpolation (NNI) is a new method based on the Voronoi Diagram. We use the NNI method and some common interpolation methods to interpolate the thermal flow data of Chinese Mainland and the gravity data of Taiwan province. Comparing the NNI method with the others, we consider that the NNI method is more fit for irregularly distributed geophysical data.
The ISC, SCSN and CRN seismic catalogue data are first transformed to the local time system and the sequence statistics are made, the time-occurring number of earthquakes are set up on the system of local time, and then the frequency spectrum analysis on the earthquake sequence is done to pick up information related to the characteristic period.The results indicate :(1)time-occurring number of earthquake is up to the maximum value at local time 0:00 AM and 1:00 PM while down to the minimum at local time 9:00AM and 7:00 PM ;(2)there are two typical periods of 12h and 24h;(3)The small earthquakes and large earthquakes are different in spatial and temporal distributions.The results of frequency spectrum analyses show that there are not only periods of 12h and 24h connectedwith the diurnal tide and the semidiurnal tide, respectively, but also the periods of 11.7a, 1a, and 17.5a connected with 11-year sunspot cycle, earth revolution, and nearly to ascending node tropical year of the moon, respectively.
In seismic exploration, the random noise is an interference wave that has broad band and deteriorates effective wave. LOG operator derives from edge extracting thought in Marr vision theory, which can effectively extract image detail edge, has optimal smoothness for original image and restrains the noise the farthest. In order to enhance the signalΠnoise ratio and resolution of seismic profile, LOGoperator and the modified coherence algorithm are introduced and compared with other methods. The processing results of a theoretical record and an actual field data show that the method has an obvious effect on separation of signal from noise and can effectively improve resolution of seismic data.
The article develops a conception named hinterland service potential (HSP) and a spatial economic model from HSP. The model combines spatial analysis and economic analysis more effectively and closely. With a gradual analysis pattern, which consists of general hinterland evaluation, directive economic analysis, precise hinterland evaluation, and finally, evaluation of HSP, the model can deal with huge-scale data in analysis. The article employs Dalian Port as an instance to illuminate the high-availability strategy of decision-making of port scale derived from spatial economic model in the article.
The approach of shif-t share analysis is used to decompose the regional and industrial structure and its competitiveness inNortheast China. Some conclusions may be obtained. First, the regional development should utilize the comparative advantage, that is, to find a suitable developing way. Secondly, improving institution to construct a modern enterprise system and a modern social security system mainly through sel-f reliance. And last, to win more FDI should also be taken as a very important development strategy.
A simplified thermal inertia model is proposed. In the model, the surface sensible and latent fluxes are introduced into the boundary condition of thermal conductivity equation in order to extend the area of using the thermal inertia method. Furthermore,a two-layer model is applied to regions with better covered vegetation, which extends the scope of the thermal inertia method. Compared with field measured inertia, the result shows that the improved thermal model is feasible.
The energy balance closure and standard deviations for vertical wind velocity and scalar quantities were applied to test the liability of measurement results of eddy covariance system at two heights, which provided the foundation for decision of the measurement height. The results showed that 23mwas better than 39m in measurement using the standard deviations for vertical velocity and scalar quantities; however, energy balance closure analysis showed that 23m was better than 39m in winter, while 39m better than 23m in spring. Totally, 23m is better than 39m in flux measurements of scalar gases and heat.
Observation data show large interannual variability of atmospheric CO2.By analyzing yearly mean observation data of global precipitation and atmospheric CO2mixing ratio at Mauna Loa Observatory, we have found a significant positive correlation between the interannual variability of CO2growth rate and the year-to-year changes in global land precipitation.We suggest that this positive correlation results mainly from the influence of clouds in Monsoon areas on terrestrial net ecosystem production (NEP).Here a set of monthly mean data of temperature, precipitation and atmospheric CO2 is used to reanalyze their relationships.In addition, we use satellite-based monthly grid cloud data over the period of 1984～ 1993 to study its relationship with atmospheric CO2 and find that the interannual variability of atmospheric CO2matches cloud cover growth rate.