Abstract:Three typical stages in the resistivity anomalies were observed in the neighbourhood of the epicentres before a number of great and medium ear-thquakes in China.Those anomalies of different stages were remarkedly different from each other in their forms and laus.This paper systematically deals with the resistivity observations of the short-term and imminent-term before earthquakes,and presents their characteristics at this stage.
The relationship between resistivity anomalies and the preparation pro-cess of earthquakes is also discussed preliminarily in this paper.Some con-ditions on which the short-term and imminent term anomalies might be observed more outstandingly and validly are presented.Those conditions are as follows:the structure of underground medium of an observatory,of possible,should be adapted to ρ₂/ρ₁ << 1,and the smaller the amplitude of so-called "annual change" in the resistivity observation is,the better it will be.

Abstract:By applying the conception of image force acted on dislocation by free surface in solid physics,in this paper the following topics have been dis-cussed.the effects of adjustmentary elements on the creep fracture of the fault in earthquake source,the propagation of creep slip just before earth-quake in the locked fault and unsteady propagation of crack when earth-quake occurs.The formulas of the image force acted on screw and edge dislocations by sevral different shape free-boundaries have been derived.As an example,the additional stress field on the fault due to the image force of free surface when the relative displacement of a section of the fault in earthquake source occurs bas been calculated.The order of this additional stress field has been estimated under the actual condition.We come to the conclusion that the effects of image force can not be ignored in earthquake source process,particularly,in studying the trigger effects on large earthquake.Based on the point of image force,some phenomena following when the earthquake occurs have been interpreted.Studying the dynamic effects of image force would be helpful for catching some short-term and immediate precursors imformation.

Abstract:In this paper,the theoretical model for the developing earthquake media has been proposed and the mechanics relations and motion equation intwo-phase media have been established.The properties of two-kind p-waves in the developing earthquake media have been demonstrated.The authors have studied also the reflective and refractive coefficients for propagation of seismic waves in the layered multi-phase media.The methods for selecting parameteres have been discussed and The displacement field in the developing earthquake media calculated.Specifically,for instance,the authors have analysed the temporal and spatial characteristics of the amplitude ratio,including those of the imminent shock anomaly before and after the Haicheng earthquake of February 4.1975 Finally,the amplitude ratio anomaly is interpreted preliminarily from the point of view of physical implication.
Theoretical and practical results show that (1) The seismic velocities,amplitudes and waveforms may variate when they travel through the developing earthquake media,especially,the variations of the p-amplitude are bigger.The variations of amplitude ratio depend mainly on the variations of p-amplitude.In the two-phase media with gas saturation,the p-amplitude is bigger than in the solid-phase,oppositely,in the two-phase media with liquid-saturation the p-amplitude is less than in the solid-phase.(2) The forms of the temporal variation before and after the Haicheng earthquake appeared as follows:lower value and then revalue-higher and stable value-occurence of shock-falling.The spatial variation was that the amplitude ratio in the periphery was lower,in the middle higher,the fringe on the high-value region was a dangerous region of major shcok.(3) The amplitude retio increased sharply before imminent shock and earthquak occured when the amplitude peak was falling.The time for appearing peak depended on the epicentral distance and azimuth Generally,it appeared in periphery and in some position at first and then in epicentral area.Based on the preceding coclusions the possibility that the amplitude ratio as a pre cursor may be applied to earthpuakes prediction has increased.

Abstract:Two fundamental concepts-detective depth and detective range mostly used in apparent resistivity method have been studied theoretically.Some problems including deficiencits about these two concepts in electrical pro-specting have been discussed in this pager.In order to compare the under-ground condition of stations and study detective capability of stations,a sort of new definition of detective depth has been proposed,based on the theoritical formula of apparent resistivity in layered-medium.The detective depths in different structures and arrangements of current electr-ods have been quantitatively calculated under a unified standard.Besides,the relations between the theoritical positions of upper and lower in-terface of detective range in media and the parameters such as the mag-nitude of variation of resistivity in the top-Layer or deep-Layer,the distance of current electrods and the precision of instruments bave been discussed.The calculation indicates that the maximun detective depth of the lower interface in media can be about 1.5 times as much as the dis-tance between electrods AB in homogeneous media,using Symmetrical-Four-Pole-arrangement and instruments whose precision is 1.0.The approach of increasing detective range have been suggested theoretically.
This paper also discusses the difference and the relation between these two concepts as well the method of calulating detective depth in inhomo-geneous media in principle.

Abstract:This Paper is based on data of surveys of the strong earthquakes occur-ring in China in the Last ten years or more and some observational results.We analysed and discussed ordinal characteristics of common animal unu-sual behavior prior to earthquakes.
The results are as follows:
1.Although amount of events of animal abnormal behavior before ear-thquakes reaches their dimax within the day,the precursory time (△T_c⁰) from distinct emerging animal unusual behavior to occurring of earth-quakes is distinctly diffierent;According to it,we found ordinal charac-teristics of them:△T⁰CⅠ→△T⁰CⅡ→△T⁰CⅢ→occurring of earthquakes,there △T⁰CⅠ,△T⁰CⅡ and △T⁰CⅢ are the mean precursory time of snakes,mou-ses and fishes,birds and dogs,and domestic animals respectively.
2.Ordinal characteristics of animal unusual behavior before earthquakes are in close relationship with their ecoenvironment and sensibility which sense some geophysical chimecal predictiye stimulus in the environment of their living.
3.Ordinal characteristics of animal unusual behavior before earthqua-kes are important marks to judge relation between events of animal abnormal behavior and earthquakes.

Abstract:In this paper,we have computed the correlation between the seasonal velocity variations of earth rotation and the seasonal frequent curves of strong earthquakes.The correlative coefficient is related to the earthqua-ke magnitude.And we found that the latitude distribution of strong ear-thquakes relates to centrifugal force,hence we have found some evidence about earth rotation inducing earthquakes.We have also analysed the relation between short cycle of earth rotation and earthquakes,according to the anomaly of underground water and the forerunner of earthquakes measured by laser lock-paper strain instruments.

Abstract:In this paper,the mechanism and characteristics of the two models of "the anomalous stress field" and the difference between them are discussed.The first is the model of "concentrated action of the external stress";and the second,of "locked-up segment" Some extension of them are also considered.
The primary distinction between the two models is as follows:In the first model,the anomalous field is caused by the external stress system,which is concentrated over some specific segments of the fault.And the second is caused by the existence of the "locked-up segment" on the fault which is acted upon by a homogeneous fiels of the external stresses.
The mathematical formulae related to the two models are given in dif-ferent cases in this paper.
The analytical results show that due to the difference among the ac-ting modes and the acted sections of the external stresses (in the first model),or to the difference among the orientations of the related faults and the locations of the locked-up segments (in the second model),the characteristics and the distributions of those anomalous fields will also be different to some extent.But in any case,there is no essential distinction between these two models in the most pasts of their anomalous fie-ids with the exception of a few parts,such as those parts which are very near to the acted segment of external stress,the locked-up segment and the end of the faults.

Abstract:The basic characteristics of Tangshan earthquake sequences have been analysed in this paper according to the seismic data by the end of 1979.The authors suggest that the Tangshan earthquake sequences are characte-rized by many macroquakes,slow attenuation of energy,great fluctuation,large size extension and so on in the general and it is of obvious regional features showing the different seismicities in various areas.From this,the authors have discussed the type of the Tangshan earthquake sequences.The authors emphasise that the magnitudes of the three strongest earthquakes (M=7.8 in Tangshan、M=7.1 in Luanxian and M=6.9 in Ninghe) were almost similar to each other but different in seismotectonics and the existence of three sub-sequences headed by the three earthquakes.It is reasonable to name it as a sequence of multi-main shock type.

Abstract:Based on the analysis of characteristics of major structural systems in the Northwestern region of China,the author has studies the formative process,the phase of type evolution,the compound relationship,and the trend of development of major structural systems.The characteristies of active structural systems are further studied.Finally,several view-poins have been put forward.The purpose of this paper is to offer geological background of regional crustal motion for studying the laws of seismic activities.

Abstract:The Tonghai-Shiping area is located in South Yunnan province.Many large historical earthquakes occurred in the area.It is important to study seismotectonics here.
In this paper,the method of geomorphological analyses,the sur-face vertical tectonic deformation since pleistocene in the area is obtaine,and right iateral displacement 5KM and average movement velocity 5mm/yr are calculated from the vertical deformation by elastic dislocation the-ory.The results show that present and quaternary tectonic stress fields are same,their principle compression axes are NNW-SSE direction.
The average interval of earthquakes as large as magnitude 7 along the Qujiang fault is about 400 years.The data of earthquakes in this area show that there had been a gap of the large earthquake along the fault during 400 years before the large Tonghai earthquake.

Abstract:Laboratory experiments of volume changes of Jinan gabbro and Chang-ping granite in various stress paths are performed.Firstly,we loaded the rock sample to a given stress state,and the further loadings were ap-plied according to the following three modes:Case A,the maximum prin-cipal stress was increased until the rock sample failed;Case B,the minimum principal stress was decreased until the sample failed;Case C,the minimum principal stress was increased,but no rupture occurred.In experiments we measured axial and lateral strains by means of strain gages so that the volumetric strains could be calculated.It has been found that the dilatancy effects of the same rock are quite different in various stress paths.The experimental results suggest that there exist the super-dense state in case B,and the ultra-dilatant state in case C.In case B,just before rupture the state of rocks changes,from the super-dense to the ul-tra-dilatant.The studies of other authors on acoustic emission,wave velo-city and microcraeks have confirmed the existence of the super-dense state and the ultra-dilatant state.The magnitude of the super-dense and ultra-dilatant effects of gabbro was calculated.As we have known,the rock under cyclic hydrostatic pressure has hysteresis effects,and in fact,both the super-dense state and the ultra-dilatant state are also hysteresis effe-cts.Because the microfracturing occurred in these states,these hysteresis in magnitude are about one order greater than that in hydrostatic pres-sure experiments and influence greatly on the properties of rocks.
The conditions of the super-dense appeared in case B has been stu-died.The super-dense state exists only in those experiments of case B,in whi-ch the minimum stress is decreased from the stress state about 80% of rock strength.The results of more complex stress paths are reported.Finally,the possible application of the experimental results to earthquake predic-tion has been discussed.

Abstract:1979年3月2日15点20分,在固镇(φ_N:33°11'λ_z:117°25')发生M_s=5.0级地震震源深度11公里,震源机制解为。

Abstract:郊城-庐江断裂带中南段,不仅是贯穿苏鲁皖三省的一条著名的北北东向断裂带,同时-也是中国东部强震活动的主要区段之一。

Abstract:峡东地区,指长江西陵峡段、巴东至宜昌的范畴(见图1)。

Abstract:1979年8月25日,内蒙古五原县发生了6.0级地震。震前测震学指标和某些地球物理场存在着不同程度的异常反应。

Abstract:1979-1981年我们完成了河西走廊东部张掖-武威一带的大地电磁测深野外探测。经过室内资料处理,发现走廊盆地下部地壳内普遍存在一异常低阻层。

Abstract:当前,在对地震信息还没有一个清晰地识别判定的情况下,地震预报是一件难事,一般传统数学计算方法都将感到困难。本文就利用模糊方法识别地震前兆问题作一些初步讨论。

Abstract:就目前的预报水平而言,由于地震发生的许多地球物理背景尚未认清,所以许多预报规则在某种程度上常有"经验"的性质。正因为是"经验"的,所以不是十分确切的,带有"模糊"的性质。