By use of the dimensional analysis the following general relationship between the precursor time T,epicentral distance R and magnitude M of forthcoming earthquake with empirical coefficients m,C1,C2 which must be determined in the different concrete cases was obtained and discussedA Simple physical model of earthquake source development is studied for explaining the described three-stage development process of earthquake precursors.

Using the data of seismomagnetic phenomena observed in China, the relationship between geomagnetic precursor time, anomalous amplitude, epicentral distance and earthquake magnitude is comprehensively analyzed.

The linear empirical relationships between lg△T, lgL, lgS and earthquake magnitude M have been constructed approximately, where △T, L and S are the premonitory time (duration), maximum linear dimension and the area of epicenter distribution of the seismic cluster respectively.

研究了它们的时空特性。 近似建立了 lg△t,lgL,lgS 与震级 M 间的线性经验关系,此处△t,L,S 分别表示地震簇的前兆时间(持续时间)及其震中分布的最大线度与面积。

We also obtaindNthat precursor period and the variation of dt befor rupturing not only relation to strainharding and strain softing before and after the extremum stress but also environment conditoin (i. e. stiffness) and the mechanic property of rock.

In the light of the Weibull distribution theory,this paper makes a quantitative analysis of the frequency distribution of the precursory time and epicen-tral distance of the Haicheng (1975),Longling (1976),Tangshan (1976) and Songpan (1976) earthquakes,all of which occurred within the continental plate of china. Precursory temporal and spatial features are obtained respectively for the aforementioned 4 events as the following.

Generally speaking there is a tendency that seismomagnetic variation amplitudes，ranges in space and precursory times increase with earthquake magnitude.

The results show that the model indicates a stage of instable acceleration rupture progress, in which the time length (defined as precursory time) depends on greatly the medium and stress environments of earthquake preparation;

In this case the uplifted area had a radius of approximately 200 km, and the precursor time may have been about 30 years.

It is demonstrated that the precursor time interval (τ) vs.M relation approximately fits in that for the τ vs.

The precursor time observed 9±1.5 years is in fairly good agreement with current magnitude-precursor time relations.

Empirical relations are given between earthquake magnitude and the epicentral distance of the farthest groundwater anomaly, and between earthquake magnitude and the precursor time of groundwater.

It is obviously impossible to demonstrate in this study whether or not there is any relation between precursor time and earthquake magnitude.

Based on the analyses of abundent observational data of precursors before a series of strong and moderate earthquakes occurred in different regions of China,three basic stages of development process of the earthquake precursors have been discovered and studied.The α-stage may be characterized generally as a long stage in which the precursors develop from the focal region to the periphery.The β-stage indicates a very rapid propagation of the precursors,so they almost appear everywhere at the same time But during...

Based on the analyses of abundent observational data of precursors before a series of strong and moderate earthquakes occurred in different regions of China,three basic stages of development process of the earthquake precursors have been discovered and studied.The α-stage may be characterized generally as a long stage in which the precursors develop from the focal region to the periphery.The β-stage indicates a very rapid propagation of the precursors,so they almost appear everywhere at the same time But during the γ-stage the precursors develop and recover from the periphery to the focal region.Then comes the extremely short stage immediately prior to the main rupture,and at last the main shock occurs.By use of the dimensional analysis the following general relationship between the precursor time T,epicentral distance R and magnitude M of forthcoming earthquake with empirical coefficients m,C1,C2 which must be determined in the different concrete cases was obtained and discussedA Simple physical model of earthquake source development is studied for explaining the described three-stage development process of earthquake precursors.In this model the concepts of instability caused by fluid (water) diffusion and wave -like long-period deformation induced by premonitory aseismic-slip are presented and the three stages of the development of precursors may be related to three corresponding stages of the preparatory process of earthquakes.According to the results obtained in this paper,three stages of earthquake prediction can be discriminated on the physical basis.

In the light of the Weibull distribution theory,this paper makes a quantitative analysis of the frequency distribution of the precursory time and epicen-tral distance of the Haicheng (1975),Longling (1976),Tangshan (1976) and Songpan (1976) earthquakes,all of which occurred within the continental plate of china.Precursory temporal and spatial features are obtained respectively for the aforementioned 4 events as the following.Three kinds of precursors existed in the distribufion of precursory times during the...

In the light of the Weibull distribution theory,this paper makes a quantitative analysis of the frequency distribution of the precursory time and epicen-tral distance of the Haicheng (1975),Longling (1976),Tangshan (1976) and Songpan (1976) earthquakes,all of which occurred within the continental plate of china.Precursory temporal and spatial features are obtained respectively for the aforementioned 4 events as the following.Three kinds of precursors existed in the distribufion of precursory times during the Haicheng earthquake.The mean time value of them were respectively 418,4.2 days and 2.8 hours; 2 kinds of precursors emerged prior to the occurrence of theTangshan earthquake,the mean time value of which were 497 and 21 days respectively.Kind 3 precursors seemed to be predominant before the Longlingand Songpan earthquakes,the mean time value of which were 50 and 25 daysrespectively.The frequency distribution of focal distance of the precursor-emerging localities was basically similar but for different mean values for each of the shockswhich were.Haicheng.139 km,Longling.228 km,Tangshan.123 km,Songpan.179 km.The above-listed result shows the temporal and spatial features of the events are not the same.This might have something to do with the types of intra-plate earthquakes in continental China,and essentially,they might also be related to the medium conditions of the earthquake sites,e.g.homogeneity,degree of fracturing,etc.Result of the analysis also show that earthquake precursors do not emerge randomly at any locality or any time.On the contrary,they have stage predominance in time and regional predominance in space.Time sequence analysis of earthquake precursors helps people to understand the proccess of earthquake preparation and to make prediction of the occurrence time of future shocks.Analysis of the temporal and spatial sequences of earthquake precursors,on the other hand,helps people to emplace with a scientific point of view the observation stations for collecting more precursory data so as to predict the locality liable to future shocks.

A method of fuzzy mathematics has been applied to the recognition of seismic clusters from earthquake catalogues in a given region. A seismic cluster consists of a series of earthquakes related to each other in time and space. Every strong earthquake may be preceded by its seismic cluster. The fuzzy relative degree between two earthquakes has been determined as a function of time interval△t and distance △s by the formula:After calculating the degrees of relatedness of all earthquakes with M≥M0 in some region...

A method of fuzzy mathematics has been applied to the recognition of seismic clusters from earthquake catalogues in a given region. A seismic cluster consists of a series of earthquakes related to each other in time and space. Every strong earthquake may be preceded by its seismic cluster. The fuzzy relative degree between two earthquakes has been determined as a function of time interval△t and distance △s by the formula:After calculating the degrees of relatedness of all earthquakes with M≥M0 in some region and taking an empirical parameter A, the seismic clusters can be recognized according to the principle of fuzzy netting.By use of seismic clusters the seismicity patterns of strong earthquakes can be recognized and studied more clearly, simply and quantitatively.This method have been applied to the recognition of seismic clusters and the study of seismicity pattern of earthquakes in North China and Southwest China. The seismic clusters of 13 large earthquakes (M≥6.5) have been recognized clearly, and their temporal and spatial distributions studied. The linear empirical relationships between lg△T, lgL, lgS and earthquake magnitude M have been constructed approximately, where △T, L and S are the premonitory time (duration), maximum linear dimension and the area of epicenter distribution of the seismic cluster respectively. Obviously, these relationships may be useful to earthquake prediction researches.

本文应用模糊数学方法从给定地区的地震目录中识别出地震簇。这些地震簇由一系列时空相关的地震组成,每一次强震前都可能有其地震簇出现。两次地震的函数由以下公式来确定:(?)计算出某一地区所有 M≥M_0地震相互之间的联系强度,并取一个经验参数λ之后,就可以根据编网原则识别出地震簇。利用地震簇,可以把强震的地震活动性图象识别得更清楚,简单和定量化。此方法曾用于我国大华北及西南地区的地震簇识别与地震活动图象研究。清楚地识别出了13次大震(M≥6.5)的地震簇。研究了它们的时空特性。近似建立了 lg△t,lgL,lgS 与震级 M 间的线性经验关系,此处△t,L,S 分别表示地震簇的前兆时间(持续时间)及其震中分布的最大线度与面积。显然,这些关系式对地震预报研究可能有一定用途。