In the paper, we analyze 117 moderate-strong earthquakes occurred in Chinese mainland (M S≥5.5 in the east and M S≥6.0 in the west) since 1970, among them, 11 earthquakes (about 9%) have direct foreshocks and 63 earthquakes (about 51%) have generalized foreshocks. The predominant time interval between foreshock and main earthquake is no more than 30 days with a spatial distance less than 50 km and a magnitude difference over 1. From the digital seismic data in liaoning Province, we know that direct foreshock had an obvious shear-stress background before the M S=5.6 and M S=5.1 Xiuyan earthquakes occurred on Nov. 29, 1999 and Jan.15, 2000.

It has been analyzed the influence of the tectonic ambient shear stress value on response spectrum based on the previous theory. Based on the prediction equation BJF94 presented by the famous American researchers, CLB20, a new prediction formula is proposed by us, where it is introduced the influence of tectonic ambient shear stress value on response spectrum. BJF94 is the prediction equation, which mainly depends on strong ground motion data from western USA, while the prediction equation SEA99 is based on the strong ground motion data from extensional region all over the world. Comparing these two prediction equations in detail, it is found that after BJF94’s prediction value lg(Y) minus 0.16 logarithmic units, the value is very close to SEA99’s one. This case demonstrates that lg(Y) in extensional region is smaller; the differences of prediction equation are mainly owe to the differences of tectonic ambient shear stress value. If the factor of tectonic ambient shear stress value is included into the prediction equation, and the magnitude is used seismic moment magnitude to express, which is universal used around the world, and the distance is used the distance of fault project, which commonly used by many people, then regional differences of prediction equation will become much less, even vanish, and it can be constructed the universal prediction equation proper to all over the world. The error in the earthquake-resistant design in China will be small if we directly use the results of response spectrum of USA (e.g. BJF94 or SEA99).

Based on the analysis on the characteristics of spatial image variation of medium and small seismicity prior to M_S 6 earthquakes occurred in North China area since 1970, the space-time characteristics and the background for the occurrence of are studied. According to the characteristics of field-source relation, a strict selection and recognition is made for the earthquakes and the relevant prediction index for the signal shocks are obtained. Generally speaking, the signal shocks occur in 2 years prior to the strong earthquake and most of them occur within 15 months; the distance between the signal shock and the strong earthquakes is no larger than 200 km and most of them are within 100km; the magnitude of the signal shocks is usually about M_L4.0～5.3. The signal shocks generally occur in the M_L4.0 seismically quiet area of a certain region, which occur in or near the medium and small seismic stripes with the seismicity gap of medium and small earthquakes nearby. The testing results indicate that in 9 months after the signal shock, its predictive probability is 0.5 and its R value is 0.27; when the radius of the predicted region is within 100 km to the epicenter of signal shocks, the probability for the occurrence of the predicted earthquakes is 0.73 and the predicted magnitude is generally M_S 6.0. The study in the paper indicates that the environmental stress value τ_0 of the signal shock is obviously higher than that of other earthquakes, which shows the significant abnormal background of high stress. Its seismic waves might probably contain a great amount of essential information of the seismogenic zone for the coming strong earthquakes.

Two improvement measures pointed to the past error to calculate b ‐values have been proposed: (1) adopt seismic moment magnitude M W which is the uniform absolute magnitude scale; (2) discard the magnitude point in which some earthquakes are missing, then compute the b ‐value using least square method to fit the data. Therefore b ‐value is more accurate. The b ‐values all approach to 1.0 for three sets of various precision and sources. The earthquake occurrence periods of great earthquakes for coming 50~100 year (extend 1~2 magnitude) have been computed using 13 years recent earthquake observation data and fix b =0.85. The results demonstrate that the earthquake occurrence periods with magnitude greater and equal to 6 and 7 are well consistent with that which are calculated from the data of 100 years historical earthquakes. So, the extension is reliable.

Two improvements measurements pointed to the errors to calculating b values have been proposed: ( 1) to adopt the uniform absolute magnitude scale, seismic moment magnitude M-W, (2) to discard the magnitude points for which the earthquakes absent and lose, and then to compute the b value using least square method to fit the data. The b values obtained for three data sets of different precision and sources are close to 1.0. The occurrence periods of great earthquakes for coming 50 similar to 100 year (extend 1 similar to 2 magnitude) have been computed using 13 years recent earthquake observation data and fix b = 0.85. The results demonstrate that the earthquake occurrence periods with magnitude greater than and equal to 7 and 8 are well consistent with that calculated from the data of 100 years history earthquakes, implying the reliable extension.

提出了一种估计一个地区平均构造剪应力值的方法.用这种方法,选取哈佛大学公布的1977～1999年共15 993次地震的矩张量数据,估计了美国西部19个地区、中国和邻区43个地区(每个地区为10(×10(范围)的平均环境剪应力值.结果表明,美国西部南加州西部海域和南加州应力最高,达13.7和12.0 MPa,然后向北、向南和向东逐渐递减,但最小也达8.7 MPa,是最高值的63%.中国新疆西北部地区和西藏察隅地区应力水平最高,达17.2和12.9 MPa,比美国高.中国的华北、云南、四川、台湾和美国南加州的应力水平差不多.中国南北地震带的应力水平为13 MPa左右,比南加州略高.两个重要地区的平均剪应力值分布图,提供了地学的基本数据.这些结果可为研究地震活动的大背景提供依据,对研究强地面运动参数(如峰值加速度及反应谱等)的衰减关系也是有用的.

借鉴断裂力学的研究成果和位错模式,提出了断裂力学地震破裂模式.根据此模式可以通过测定震源参数(位错量D与断层长度L;或地震矩M0与断层面积S;或地震矩M0与体波震级mb)直接估计构造环境剪应力场,同时还解释了应力降模式所存在的矛盾.用美国哈佛大学给出的1990-1999年分布在全球的7660个地震的M0和mb值,计算了这些地震的构造剪应力场τ0值.结果表明,绝大部分地震的τ0值在5-20MPa之间,平均值为10MPa.利用Geller收集的1923-1968年全球41个大地震的震源参数D和L;M0和S,估计了这些地震的构造剪应力场τ0值.结果表明,板间地震τ0的值为7MPa左右,板内地震为15MPa左右,全部平均值约为10MPa.我们还同时计算了地震时释放的应变能和地震辐射效率值,效率大约为5%,且与地震大小无关.

On the basis of fracture mechanics earthquake rupture model, the relations between source parameters and τ 0, the value of tectonic ambient shear stress in the place where the earthquake occurs, have been derived. Thus, we can calculate a large number of values of tectonic ambient shear stress or values of background stress in the place where the earthquake occurs. If nuclear explosions are treated as earthquakes in the calculation, we find that τ 0 values of nuclear explosions have about 20 MPa, which is obviously higher than average τ 0 values of earthquakes with the same magnitude. This result can be used to discriminate nuclear explosions from earthquakes.

介绍了计算理论地震图的F-K方法在不同深度,不同震中距,不同震源类型的情况,表明这种方法在高频区和多层水平层状模型计算效果较好,适用于研究中小地震的震源机制.采用F-K方法得到了发生在腾冲火山区的3个地震的震源机制,结果表明地震1和地震2是走滑断裂,地震3是逆断层.3个地震的主压应力轴基本呈北西向,与云南地区主压应力轴方向基本吻合,因此,推断这3个地震是构造地震.

在研究构造环境应力场特征的过程中，发现构造环境剪应力场量值、对峰值地震动速度PGV有很大影响.用公式定量地把、值引入到PGV的预测方程中，得到了新的预测方程CLB97V；并用观测资料证明了所得方程在震中距＝5──250km范围内，对美国大地震和中国大地震均适用．本文还考虑了大、中、小地震的速度具有不同的优势频率：大震较低，小震较高，因此，小震的PGV衰减较快．这样，CLB97V不仅适用于大震，也适用于中、小地震．如果考虑了世界各地不同的构造区域具有不同的构造环境应力场以后，预测方程可以适用于世界各地．

We have found from the fracture mechanics rupture model of earthquakes that the peak ground acceleration PGA and velocity PGV and displacement PGD strongly depend on the tectonic ambient shear stress value τ0．τ0 value is introduced into the predictive equation of PGD by us, at the same time the dependence of predominant frequency of PGD fd on magnitude is considered. Based on both improvements, the predictive equation of PGD (CLB98d) has been derived from theoretical analysis. It has been tested by observahon data that this predichve equahonit is sintable for epicentral distance range △=10-250km and magnitude range Mw = 4-7.2. There are different To values in different regions all over the world, but the influence of τ0 value on PGD is not large.

火山能产生多种灾害.火山喷发能够产生破坏性的岩浆流、火山碎屑和气体的高速崩塌流;大量的火山灰云可漂浮至几百千米远,严重影响喷气式飞机的飞行,危害人体健康并造成财产损失.即使火山不喷发,在火山区也可能产生巨大的、毁灭性的火山泥流、危害性气体及酸雨.但是火山灾害是可以预测的,其主要的监测预报手段是地震学和地形变.世界上已有不少火山预测成功的例子,本文列举了其中8个实例.

According to the fracture mechanics rupture model of earthquakes put forward by us, several equations to compute tectonic ambient shear stress value τ0 have been derived [equations (1), (2), (3), (5)]. τ0 values for intermediate and small earthquakes occurred in Chinese mainland and Southern California have been calculated by use of these equations. The results demonstrate that the level and distribution of τ0 are closely related to the location where large earthquakes will occur, i.e. the region with higher level of τ0 will be prone to occur large earthquakes and the region with lower level will usually occur small earthquakes. According to the spatial distribution of τ0, the seismic hazard regions or the potential earthquake source regions can in some degree be determined. According to the variation of τ0 with time, the large earthquake occurrence time can be roughly estimated. According to the distribution of τ0 in Southern California and variation with time, three high stress level regions are determined, one (Goldfield area) of them is the present seismic hazard region.

根据我们提出的断裂力学破裂模式,推导出了几个计算构造环境应力值τ0的公式(见文中公式(1)、(2)、(3)、(5)).根据这些公式,计算了中国大陆地区中小地震及美国南加州的中小地震的构造环境剪应力值.结果表明,τ0值的大小和分布与大震发生的地点有密切的关系,即剪应力水平较高的地区将容易发生大地震,而剪应力水平较低的地区通常只发生小地震.震级大小与lg(τ0)统计上呈线性相关.依据τ0值的空间分布,可以一定程度上确定地震危险区或潜在震源区;依据τ0值随时间的变化,可以粗略地估计大震发生的时间.根据τ0值在南加州的分布和随时间的变化,有3个地区应力值较高.其中,Goldfield地区是现今的地震危险区.

The parameter τ 0 of tectonic ambient shear stress field has been introduced into the prediction equation of peak acceleration. Authors have found that peak ground acceleration (PGA) strongly depends on τ 0, and also depends on frequency. Because predominent frequency f a for large earthquake is lower than that for small earthquake, the attenuation coefficient of PGA for large earthquake is smaller than that for small one, and PGA attenuation for large earthquake is slower. Based on above two improvements, a new prediction equation of PGA (equation (16) in text) has been put forward, which can be used not only for large earthquakes (M w = 6.0-7.8) but for small earthquakes (M w = 4.0- 6.0), and which can be used for larger range of epicenter With consideration of the different level of τ 0 of each region around the world, the new prediction equation can be used for various regions all over the world (e.g. California in USA, North China and South-West China). Proved by observation data, the effect of prediction is encouraging.

Earth media are incomplete media. There exist many cracks in it. The achievements of fracture mechanics show that the strength of the incomplete materials will be much lower than that of the complete materials. We consider that earthquake occurrence is the result of unstable propagation of a crack in crust media in proper condition and the earthquake rupture is the phenomenon of a failure by fast fracture under applied low shear stress. It has already been explained by fracture mechanics.

The environment shear stress of Tangshan main earthquake and 38 great aftershocks have been calculated by the acceleration data of Tangshan earthquake sequence. The environment shear stress for 52 smaller aftershocks from July of 1982 to July of 1984 have also been calculated by use of the digital data of the Sino-American cooperation recorded by the instrumental arrays in Tangshan. The results represent that the environment shear stress τ0 values have a weak dependence on the seismic moment, only the small and moderate earthquakes will be able to occur in the region with smaller τ0 value and the large earthquakes are only in the region with greater τ0 value. The peak acceleration, velocity and displacement will be larger for the earthquakes occurred in the region with greater τ0 value, Therefore, the measurement of environment shear stress τ0 value for the significant region will play an important role in earthquake prediction and engineering shock-proof. The environment shear stress values for the great aftershocks occurred in the two ends of the main fault are often higher than that for the main shock. This case may represent the stress concentration in the two ends of the fault. This phenomenon provides the references for the place where the great aftershock will occur.

The theoretical acceleration spectrum of observation site has been obtained from source acceleration spectrum derived from scaling law, using attenuation modelQ=Q ν f η . A comparison of a set of theoretical acceleration spectra with observation spectra has been made, and we have obtained the attenuation model for observation site and seismic moment magnitude. We obtain thatQ o=300,η=0.25 for Wuqia area, Xinjing Zizhizhou, and seismic moment magnitudes of 18 greater aftershocks of Wuqia earthquake occurred in 1985. In order to obtain seismic moment magnitued conveniently, three functional tables of acceleration spectra at 1Hz as the distances for variousQ value have been made. The seismic moment magnitude can be quickly measured from acceleration spectrum at 1Hz according to these tables (epicenter has to be known).

The various useful source-parameter relations between seismic moment and common use magnitude lg(M 0) andM s,M L,m b; between magnitudesMs andM L,M s andm b,M L andm b; and between magnitudeM s and lg(L) (fault length), lg (W) (fault width), lg(S) (fault area), lg(D) (average dislocation);M L and lg(f c) (corner frequency) have been derived from the scaling law which is based on an “average” two-dimensional faulting model of a rectangular fault. A set of source-parameters can be estimated from only one magnitude by using these relations. The average rupture velocity of the faultV r=2.65 km/s, the total time of ruptureT(s)=0.35L (km) and the average dislocation slip rateD=11.4 m/s are also obtained.

本文利用1960.0—1965.0全球157个地磁台站的X、Y、Z三分量年均值资料,进行了地磁场长期变化的球谐分析。我们采用5种加权方案（从主要考虑法矩阵条件数的方案S过渡到仅考虑资料误差的方案D）,并选择5种截断水平（球谐函数的截取级次从n=4到n=8）,共作了25次分析,从获得的法矩阵条件数和拟合残差两者的分析中发现,对这一组资料球谐级数的截取级次取为n=6,而加权方案采用S 3/4 D 1/4可能是最有效的,其结果即为地磁场长期变化球谐模型SVSHM 1960—1965。