Abstract:The features of Hydrochemical precursory field before the Gonghe M_S7.0 earthquake on April 20, 1990 are studied.The results show that proportion of hydrochemistry observation sites in which trend anomalies appear to all sites in focal region of the earthquake is higher than that far away from the focal region and the proportion reduces gradually as the epicentral distance increases. In the focal area the trend anomalies in which radon content in groundwater goes up gradually emerge earlier than far away from foci. The formation of hydrochemical precursory field has something to do with regional stress field, but has closer relation with focal stress field. Focal stress field may play a main role in the precursory process.

Abstract:Based on the recurrence data of large earthquakes(paleoearthquakes and historical earthquakes) in the mainland of China, the probability density function of the recurrence intervals of intraplate large earthquakes, which occur quasi-periodly in an active period, is defined by a reasonable method. The result shows that intraplate large earthquakes and interplate characteristic earthquakes have a similar probability distribution in their recurrence intervals. The main difference between them is that the COV of the recurrence intervals of intraplate large earthquakes is 0.26, while 0.215 for interplate characteristic earthquakes, that is, intraplate large earthquakes have a more irregular recurrence intervals.

Abstract:On the basis of experiences for earthquake prediction in recent years, in the light of the data of seismicity, starting with analysis of the law of great earthquake activity in global, adopting the method of reasoning from probability calculation, some important relative events and phenomena are deeply studied.
A series of medium term prediction indexes are developed which can be used to forecast the large earthquake (M_S≥7.0) in the mainland of China.

Abstract:Geometric pattern, distribution features and mechanics nature of surface rupture zone at Shangsi area are described. The mechanism of formation of the surface rupture zone is studied. It is proved that the Shangsi rupture zone is engendered during the Gulang earthquake,and is part of the rupture zone of the 1927 Gulang M_S8 earthquake.

Abstract:Short period digital seismic data of Lanzhou seismic station in Chinese digital seismic network are used to study variation of wave spectrum parameters of small earthquakes in Yongdeng area before and after the Yongdeng M_S5.8 earthquake in 1995.The results are the followings:
(1) About two years before the Yongdeng earthquake,corner frequence f_C of S_C wave spectrum of small earthquakes in Yongdeng area fall from 2.4 Hz to 1.8 Hz.
(2) Ratio of spectrum attenuation slope in high frequency between S_g wave and S_C wave increased since 1990, then decreased about 16 months before the Yongdeng earthquake. During the ratio decreasing,the earthquake occurred.After the shock,the ratio value recovered gradually. (3) Anomalies of Q value from spectrum parameters of S_g wave appeared before and after the Yongdeng earthquake.

Abstract:Based on the projection pursuit regression (PPR) principle, the PPR model has been set up with 15 independent variables such as b value, C_b value, A_b value etc., which are selected from seismometry parameters and one dependent variable representing maximum magnitude of earthquake that would occur in coming several months. By using the model,maximum magnitude of coming earthquake and probability of earthquake to occur in the future can be predicted.The PPR model of four mainly seismic regions in Xinjiang and their ridge functions are showed. The prediction effects of reservation test and practical test are satisfactory.

Abstract:As shown from calculation,the change of the earth's surface area and the crust's volume caused by the moon's maximum declination is 2.3 times as big as that caused by its minimum. This can well account for the gas release from the earth when the declination is at its maximum and for the corresponding droughts in China when at its minimum.This mechanism is also confirmed by both the periodical variation of the earth's rotation and the periodical occurrence of earthquakes.

Abstract:In order to locate the dangerous region for annual determination of seismic background, the relationship between the three parameters of future strong earthquakes and the moderate earthquake concentrating regions in the Tianshan seismic zone is analyzed. The results show that most strong quakes occur in the concentrating regions and their borders, especially the borders,and magnitude of strong earthquakes is related to the concentrating region size. The principle of determining the concentrating region is that length of the concentrating region is larger than 150 km and the number of earthquakes in the region is equal to or larger than 4.Further more,the relation among the source size, seismogenic zone size, concentrating region size and anomaly area size is discussed. It is considered that upper and lower limits of the concentrating region size are the anomaly area size and seismogenic zone size respectively.

Abstract:Method and data characteristics of high resolving shallow seismic prospecting for engineering surveying in different areas are introduced with examples. The results show that this method is very useful for layer division, determination of cavern and faults. It can afford reliable geological data for engineering design and construction.

Abstract:Observation network of ground fluid in northwestern China is comprehensively evaluated as three stages, that is, establishment, adjustment and development. The observation network of ground fluid has already tended to ripe and makes a certain effect in seismologic surveillance and earthquake prediction.But because it is restricted by some conditions, the network action is still limited. Efficacy of seismologic surveillance of the network is synthetically evaluated. The result shows that medium short term anomalies are observed at sensitive sites in distant field and short impending anomalies are observed at sensitive sites in close field.

Abstract:The characteristics of four swarms from Dec. 1996 to July 1997 in Qinghai province are studied.The seismicity patterns are analysed. The results show that Xitieshan swarm and Dawu swarm are precursory swarms, and Longyangxia swarm and Mangya swarm are unprecursory swarms. Distribution of the swarms and two earthquakes constitutes a NW belt in the spacial distribution. Based on the total characteristics of swarms and seismic gap and so on,the seismic trend in recent time of Qinghai province is preliminarily discussed.

Abstract:Using the Gauss-type function, covariance matrix of displacement data of different monitoring nets which have a scattered distribution is imitated. Moreover, the method is applied in calculation of crustal strain field of Xinfengjiang area, Guangdong province. The results show that the method not only is simple, effective and stable, but also has a certain meaning in relating the scattered elements.

Abstract:Analysing characteristics of geomagnetic anomalies before M_S≥5 earthquakes in recent years in Gonghe basin and at middle east section of Qilian mountains and space time distribution of the anomalies, geomagnetic short term prediction indexes before strong earthquakes in northwestern China are studied. The results indicate that various degrees of anomalies of magnetic storm, geomagnetic low value displacement and correlation coefficients of geomagnetic vertical component between stations appeared before strong earthquakes. Interval from beginning of geomagnetic low value displacement anomalies to origin time is 10～40 days. Interval from magnetic storm to origin time is three days before and after the dates which are multiple of nine. Coming earthquakes are located at near line of demarcation of the low value displacement anomalies, or in the anomalous area. If duration of the correlation coefficient anomalies is over 5 months, it is possible that M_S≥5 earthquake occurs in anomalous area.

Abstract:Test observation data of the FSQ tiltmeter at Sunan station are analyzed, and it is found that the construction of a tilt station is feasible in Sunan. The data during several months after construction of the station are analyzed. The results show that the construction of the station is successful and precision of observations accords with the requirement of the present observation specification. The station will play an important role in earthquake monitoring at the mid Qilian Mountains in the western Gansu in the future.

Abstract:The sedimentation rate of Fen wei basin in recent 7 000～2 500 years has been studied from the buried depth data of 49 old cultural relics from the Yangshao to East Zhou dynasties.The results show that the average sedimentation rates in Weihe depression and Linfen depression are 0.46 mm/a and 0.36 mm/a respectively.In general,the sedimentation rate in upheavals is smaller than that in depression in the basin.Both the rate in Lintong upheavals and Xiangfen upheavals are 0.20 mm/a. The relative differences of sedimentation rate between every geological element are identical with distribution and movement characteristics of geological structures.It can also be discovered by analysis of sedimentation rate in various times that sedimentation rate in Weihe depression before the Yangshao (about 5 000 years ago) is smaller than after that. The sedimentation rate increased in depression and decreased in upheaval with time. Strong earthquakes in the Fen wei basin are mainly located in the geological units with relatively large sedimentation rate.

Abstract:The linear magnitude-frequency correlation advanced first by Gutenberg and Richter has played a great part in the study of earthquake and its prediction. The correlation itself has been improved and replenished constantly. In this paper it is pointed out that the important cause of generating the nonlinear behavior of earthquake is its fractal structure and its chaos principle. A new magnitude frequency correlation involving nonlinear terms is gained. It is proved that the correlation can be developed to the linear Gutenberg Richter relation through linear approximation. A further explanation in physics principle is also given.

Abstract:On the basis of further study on seismic zoning of Chinese sea area in recent years, the seismic zoning map of sea area of China and its vicinity compiled in 1987 is corrected. Scientific basises correcting the map are discussed. The map corrected is provided.

Abstract:Design earthquakes in earthquake hazard prediction are discussed in detail. The design earthquakes are divided into three kinds, that is, checking, prediction and recurrencing types. Principle and methods determining the design earthquakes are discussed. Application of the earthquakes in the different earthquake hazard predictions are further demonstrated.

Abstract:Based on data of strong earthquakes (M≥6) from 1500 to 1996 in Jiangsu Nanhuanghai region, the tracing prediction of M≥6earthquakes has been discussed by using the analysis of orderness,commensurability and cluster characters. The results show that the next M≥6 earthquake will probably occur during the period from 2002 to 2003.

Abstract:试样为取自中国北方黄土高原标准剖面^①中的马兰(Q₃)、离石(Q₂)、午城(Q₁)以及次生的洪积-冲积(Q₄)黄土.各方面成功的配合与多手段的综合性研究使我们能对黄土的微结构模型有了概念,能分析结构特征对黄土某些性质的影响,并可用来解释已提出的有关成因的一些看法.