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1.
Promotingeffectsof1975HaichengforeshocksontheoccurrenceofthemainshockXing-CaiLI(李兴才)(InstituteofGeophysics,StateSetismologica...  相似文献   

2.
MechanicalanalysisofenechelonstructureanditssignificanceofcontrollingearthquakesXin-ShengXIE(谢新生)andXiao-PingRUAN(阮小平)(Instit...  相似文献   

3.
RandomfieldcharacteristicsofearthquakeoccurrenceandtestofearthquakeoccurrencerateMeng-TanGAO(高孟潭)(InstituteofGeophysics,State...  相似文献   

4.
Analysisofforeshocksequenceofthe1975HaichengearthquakeofMs7.3Zhao-RongZUO(左兆荣);Jian-PingWU(吴建平)andZhi-LingWU(巫志玲)(Instituteof...  相似文献   

5.
StaticsolutionofacrackdegeneratedfromdynamicsolutionofapropagatingcrackShi-YuLI(李世愚)andYun-TaiCHEN(陈运泰)(InstituteofGeophysics...  相似文献   

6.
ResearchofpatterndynamicsparametersofcrustaldeformationfieldinseismogenicprocessShuo-YuZHOU(周硕愚),YunWU(吴云),Ruo-BoWANG(王若柏)and...  相似文献   

7.
StochasticmodelofbedrockearthquakemotionanddeterminationofitsparametersDi-TaoNIU(牛荻涛)(Xi'anUniversityofArchitecturalSciencean...  相似文献   

8.
AstochasticmodeloftheFourierphaseofstron groundmotionZhen-PengLIAO;(廖振鹏)andXingJIN(金星)(InstituteofEngineeringMechanics,StateS...  相似文献   

9.
LyapunovexponentanddimensionofthestraneattractorofelasticfrictionalsystemZhi-RenNIU(牛志仁)andDang-MinCHEN(陈党民)(SeismologicalBur...  相似文献   

10.
Presentaddress:SouthCaliforniaUniversity,USA.ContributionNo.93A0032,InstituteofGeophysics,SSB,China.andstationareseparate,supposingarandomandhomogeneousdistributionofthescattersinathree-dimensionalinfiniteandperfectlyelasticmedium.TheenergydensityatadistanceofrisgivenasE(r,t|ω)=[W0(ω)g0(ω)]/(4πr2).K(vt/r).exp(-ωQc-1t)vt>r(2)WhereK(x)=(1/x)ln[(x+1)/(x-1)],andg0(ω)isthetotalscatteringcoefficientcharacterizingascatteringpowerperunitvolumeofthehomogeneousmedium.Comparisonofvariousobservationsincludingcodadecay  相似文献   

11.
The properties of rock resitivity were studied under pressure, particularly with “stress reversal”, a procedure in which the pressure applied was increased and decreased. It was observed that, 1) With pressure increasing, the main feature of resistivity change was increase-steady-decrease for high-saturation rock samples (saturation 70–100%). But the main feature for low-saturation samples was different. 2) In 10 out of 11 cases of “stress reversal” for high-saturation samples the resistivity droped (about 2%). Such drop could explain the anomalies in geoelectricity terms, which are commonly observed before earthquakes in China. 3) It was also observed shortly before rock failure that, a) the resistivity drops more dramatically (about 20%) during “stress reversal” period, which is much more than ordinary drops. b) these drops occurred not only during stress decrease but also during stress increase. c) Resistivity exhibits anisotropy: the resistivity along different directions may differ by 10%. These three features may indicate that the rock is nearing failure, while ordinary resistivity drops are only connected with “stress reversal” and may not mean the imminence of rock failure. 4) Resistivity increase was observed during the “stress reversal” period for low-saturation rock samples. The results mentioned above were explained with the effect of water flowing in and out of the cracks of rock. The temporary factors which yield a reduction of the maximum main stress, may enhence the possibility of earthquake occurrence.  相似文献   

12.
This paper aims to analyse the geoelectrical resistivityρ s data on the dipole electrode sounding, which were firstly accumulated from the earthquake prone region in China. The analyses on the one order difference value of the geoelectrical resistivity indicated that, firstly, more than 4 percent of theρ s data reveals the precursors by 3 to 76 days ahead the earthquakes occurring, with the magnitude range of 4 ≤M ≤ 6. 4, in a region of 100 km around the station, and secondly, the results revealed that the seasonal variation ofρ s data were slight. The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,14, 211–219, 1992.  相似文献   

13.
In this paper, the relations of the changes of earth resistivity (ρ) s recorded at 100 geoelectrical stations in 31 earthquakes occurred in the continent of China, to the active faults (active abyssal faults or badly active faults near the focal zone) and the causative stress fields are discussed and the following conclusions are obtained:
  1. On the condition that a station is near the active fault and in the direction of the causative stress (DCS) of an earthquake (EQ), the immediate variation ofρ s to the earthquake (called “immediate variation” for short) could be recorded generally at the station.
  2. The active fault which lies between a station and the epicenter of an earthquake seems to play a role in “obstructing” the recording of the imminent variation when the strike of the fault is close to the DCS of the earthquake. When that is parrallel with the DCS the “obstructing” function of the fault is strongest; when normal with the DCS, weakest.
The regularity seems to have the universality for moderate earthquakes and strong ones occurred in the continent of China.  相似文献   

14.
IntroductionSincethe1960′s,thedevelopmentofmodernscienceandtechnologyhasgradualymadeitposibletopredictearthquakesandhaspromot...  相似文献   

15.
IntroductionShort-to-imminentprecursorsstillarethemainbasisforearthquakepredictioninthepresenttime.Strongquakes,especiallythosewithnoforeshocks,canbeforecastedtosomeextentbasedonabundantshoat-to-imminentprecursorsandcombiningwiththemid-to-longtermvar...  相似文献   

16.
IntroductionMany anomalies due to earthquake have been recorded in observation of earth-resistivity for30 years and over, which showed that there objectively existed the anomalies of each-resistivity.The crustal strUcture and medium conditions are quite complex, so the complexity of the temporal,spatial and intensive development of the anomalies is inevitable. Both of time and amplitUde ofanomalies among some stations near an epicenter are different (even among different observational directi…  相似文献   

17.
Using the natural limestone samples taken from the field with dimension of 500 mm×500 mm×1 000 mm, the D-D (dilatancy-diffusion) seismogeny pattern was modeled under the condition of water injection, which observes the time-space evolutionary features about the relative physics fields of the loaded samples from deformation, formation of microcracks to the occurrence of main rupture. The results of observed apparent resistivity show: 1 The process of the deformation from microcrack to main rupture on the loaded rock sample could be characterized by the precursory spatial-temporal changes in the observation of apparent resistivity; 2 The precursory temporal changes of observation in apparent resistivity could be divided into several stages, and its spatial distribution shows the difference in different parts of the rock sample; 3 Before the main rupture of the rock sample the obvious “tendency anomaly” and “short-term anomaly” were observed, and some of them could be likely considered as the “impending earthquake” anomaly precursor of apparent resistivity. The changes and distribution features of apparent resistivity show that they are intrinsically related to the dilatancy phenomenon of the loaded rock sample. Finally, this paper discusses the mechanism of resistivity change of loaded rock sample theoretically. This subject is supported by the key project during the 8-th “Five Year Plan” from the State Science and Technology Commission of China (85-04-04).  相似文献   

18.
The wave velocity for two types of granitoids was measured using the analytic method of full-wave vibration at high pressure and high temperature. The laws of velocity changes for them differ with the pressure boost and temperature rise, and the velocity change of S-type is more violent than that of I-type. The “softening point” of compressional wave velocity (V μ) is also revealed during the measurement for two types of granitoids imitating the pressure and temperature at a certain depth. But the depth of “softening”, Vp after “softening” and the percentage of Vp’s drop around the “sofrening point” for two types of granitoids are obviously different. The depth of “softening” is 15 km approximately and Vp after “softening” is 5.62 km/s for S-type granitoid. But for I-type granitoid the depth of “softening” is 26 km approximately and Vp after “softening” is 6. 08 km/s. Through careful analysis of rock slices after the experiment, it was found that the “softening” of elastic-wave velocity is caused by the partial melting of granite. Combined with the results of geophysical prospecting, these results suggest that the low-velocity layers developing in the interior of Earth crust are related to thc partial melting of different types of granitoids. The formation of the low-velocity layer in the upper-middle Earth crust is closely related to the development of S-type granitoid, but that in the lower Earth crust is closely related to the development of I-type granitoid.  相似文献   

19.
On the basis of S wave information from Tai’an-Xinzhou DSS profile and with reference to the results from P-wave interpretation, the 2-D structures, including S-wave velocity V s, ratio γ between V p and V s; and Poisson’ s ratio σ, are calculated; the structural configuration of the profile is presented and the relevant inferences are drawn from the above results. Upwarping mantle districts (V s≈4.30 km/s) and sloping mantle districts (V s≈4.50 km/s) of the profile with velocity difference about −4% at the top of upper mantle are divided according to the differences of V s, γ and σ in different media and structures, also with reference to the information of their neighbouring regions; the existence of Niujiaqiao-Dongwang high-angle ultra-crustal fault zone is reaffirmed; the properties of low and high velocity blocks (zones) including the crust-mantle transitionalzone and the boudary indicators of North China rift valley are discussed. A comprehensive study is conducted on the relation of the interpretation results with earthquakes. It is concluded that the mantle upwarps, thermal material upwells through the high-angle fault, the primary hypocenter was located at the crust-mantle juncture 30.0∼33.0 km deep, and additional stress excited the M S=6.8 and M S=7.2 earthquakes at specific locations around 9.0 km below Niujiaqiao-Dongwang, the earthquakes took place around the high-angle ultra-crustal fault and centered in the brittle media and rock strata with low γ and low σ values. This subject is part of the 85-907-02 key project during the “8th Five-Year Plan” from the State Science and Technology Commission.  相似文献   

20.
Broadband P and S waves source spectra of 12 MS5.0 earthquakes of the 1997 Jiashi, Xinjiang, China, earthquake swarm recorded at 13 GDSN stations have been analyzed. Rupture size and static stress drop of these earthquakes have been estimated through measuring the corner frequency of the source spectra. Direction of rupture propagation of the earthquake faulting has also been inferred from the azimuthal variation of the corner frequency. The main results are as follows: ①The rupture size of MS6.0 strong earthquakes is in the range of 10~20 km, while that of MS=5.0~5.5 earthquakes is 6~10 km.② The static stress drop of the swarm earthquakes is rather low, being of the order of 0.1 MPa. This implies that the deformation release rate in the source region may be low. ③ Stress drop of the earthquakes appears to be proportional to their seismic moment, and also to be dependent on their focal mechanism. The stress drop of normal faulting earthquakes is usually lower than that of strike-slip type earthquakes. ④ For each MS6.0 earthquake there exists an apparent azimuthal variation of the corner frequencies. Azimuthally variation pattern of corner frequencies of different earthquakes shows that the source rupture pattern of the Jiashi earthquake swarm is complex and no uniform rupture expanding direction exists.  相似文献   

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