Abstract:According to the seismic data from 1911 to 1994, division of seismic periods, seismicity features and the trend of strong earthquake in Tibet have been discussed in detail. Time distribution of strong earthquakes and the probability of occurrence have also been analysed by using statistical method. The results show that the region has gone through three strong-earthquake cycles since this century,and now it is between the end of the quiet episode and the beginning of the active episode in the 4th cycle. There will be several swarms here in the future. During 1995 and 1996, the occurrence probability of M_S ≥ 6.0 earthquake is 80%-87%, and that of M_S ≥ 6.5 earthquake is 60%-76%in Tibet region.

Abstract:It is considered that the shost-period variations of electro telluric field at Daishan middle school station belong to the geodetic potential through the analyses of parallel direction correlation, the pure anomaly vector ratio, P_C electrotelluric pulsation, geoelectric bay, etc. The station is highly sensitive to geodetic potential change. In addition, the characters of geodetic potential anomaly before the strong earthquakes occurring in Lancang, Batang, etc. are analyzed. These anomaly variations affected by the ultra-low frequency electromagnetic radiation occurred within 8.8 -32.5 hours before earthquakes and lasted the time from 20 min to 75 min.

Abstract:On the basis of microearthquake data recorded by the Datong telemetry network, the temporal and spatial evolution regularity of small earthquake swarms in the region is analyzed by using the combination pattern theory. The results show that the predicted epicenter is consistent with the real epicenter of the Datong-Yanggao M_S 5.8 earthquake occurring on Oct. 18, 1989. In addition, through the analysis on relation of earthquake swarms to external causes, the origin time is predicted better.

Abstract:Based on reference[1] and the dislocation theory and corresponding gravity change in the layered media offered by previous papers, authors modified two equations presented by reference[1] and studied the relation between dislocating gravity variations and the rectangular planes with different sizes, buried depths, dislocating directions and dislocating magnitudes by numerical simulating method. The dislocating conditions and gravitational anomaly of the Tangshan (M 7.8) and Gonghe (M 7.0) earthquakes were also simulated for several points in this paper to probe the complexity of the space and intensity distributions of the earthquake precursor field. The results show that the gravity change caused by dislocating is very complicated in space and intensity distributions, which is the combined result of deformation and stress variation due to dislocating effect, both negative and positive gravity variations can appear in earthquake effect area. The dislocating plane conditions above mentioned have strong influence on gravitational space and intensity distributions.The simulating results suggest that if one wants to analyze the gravity anomaly caused by an earthquake, one should consider the concrete mechanism of the event. An enlightenment for understanding the complexity of other geophysical precursors of earthquakes is provided in this paper.

Abstract:The magnetotelluric sounding results show that electrical structure inside Ordos massif is simple and clearly layered, the top of the first high conductivity layer of upper mantle is about 109 km deep and there is no crustal high conductivity layer. Near Daluoshan, there exist a few electrical layers within crust. These layers are not linked between the MT sites because crust is broken by fault zones. In this place, the first high conductivity layer of upper mantle is uplifted and its top is about 92 km deep. Through analysis, it is considered that on the east side of Mt. Daluoshan there is a deep-seated fault zone which is the west boundary of Ordos block.

Abstract:Earthquake and mud-rock folw are all the common natural disasters. This paper preliminarily discusses the effects of earthquake on formation of debris folw and some features of induced earthquake debris flows. It is considered that the regions where seismicity is strong or neotectonic movement is active are usually the regions where debris flows frequently occur; earthquakes affect the formation and development of debris flow by nourishing loose solid material, water source, dynamic and triggering condition; debris flows induced by seismic activities often have overdue, periodic and regional characters.

Abstract:By using 228 acceleration records of 73 events such as Songpan-Pingwu, Sunan, Gonghe earthquakes, shear stress values are calculated according to the theoretical formulas derived by Mr. Chen Peishan and influence of environmental shear stress field on peak acceleration is studied based on earthquake-triggering tectonic environment.

Abstract:In this paper, a crack is thought to be a physical model in which two semi-infinite uniform media were connected by spring s. The crack is of continuous stress and discontinuous strain. Based on propagation theory of plane wave, it is suggested that coherence in a crack could be indicated by the amplitude ratio or the coupling dynamic stiffness (CDS). The relation between CDS and the ratio has been deduced. The research is used to check the effect of grouting crevices in the Dunhuang Caves.

Abstract:Based on the anisotropic elastic theory of rock mass, the X-ray method is adopted to measure the 3-D macro-residual principal stresses as well as distribution of the maximum horizontal and vertical shear stresses with depth in rock mass from 9 measuring boreholes in Anninghe fault zone. The regularities of the distributions are analysed and the vertical gradient values are obtained.

Abstract:In this paper, on the basis of division and comparison of the micro-geomorphy along the Mao-maoshan fault zone, the distribution of displacements is analysed in detail. The results indicate that the distributions of horizontal and vertical displacements along the fault zone have obvious grouping and compensation characters. From east to west of the fault, the horizontal displacements are characterized by cumulative slip deficit, on the contrary, vertical displacements are characterized by compensation. These reflect difference and inhomogeneity of the manners and intensity of faulting. Cumulative slip deficit of displacements directly reflects the behavior of faulting in some period and is an important segmentation scale.

Abstract:This paper introduces an application software system. By using this system, the seismological data which are exchanged with other areas can be automatically selected from the data base, and their errors can be checked up. Then this software makes the operator's work become easier and more efficient, it also makes the data more reliable.

Abstract:Seismic situation in North China after the Datong M 6.1 earthquake is analysed by using several kinds of methods. It is considered that probability for M_s ≥ 5. 5 event to occur in the region during 1995 and 1996 is from 7/11 to 8/11 and probability to occur in southeast Shanxi Province is from 7/8 to 1.

Abstract:Studies the relation between M_L ≥ 4 earthquakes in recent years in southern Shandong Province and location of deep well observing the resistivity. Proves further that effect of active fault-stress field exists.

Abstract:1994年1月3日至10月12日,在青海共和境内连续发生6次地震。

Abstract:最近,美国哥伦比亚大学的宋晓东和理查兹首次利用地震波测量了地球固态内核,发现它的旋转速率比地壳和地幔的旋转速率快,每年大约快1.1°^[1]。

Abstract:根据有关资料,将澜沧-天祝地震序列的震中位置(纬度x,经度y)、震源深度(z)、震级(M_S,简用M)及发震日期(T)摘录于表1。

Abstract:On the basis of previous research on three earthquake source preparation and occurrence models, the comprehensive model about earthquake forming mechanism,earthquake prediction indexes and prediction methodology have been suggested in the present paper. Comprehensive model consists of 7 major units:the earthquake source, two adjustment elements at ends of source region, two weak medium layers above and below the source body,which are located in upper lithosphere, and two deep shear creep faults in lower lithosphere, in which one is perpendicularly stereoscopically crossed with the seismogenic fault and another parallel to it in the same plane. The 7 basic units compose a structure having strong earthquakes.
According to this model, the differentiation between the source region and the other units and the differentiation among the adjustment elemonts, adjustment layers and deep shear creep faults can lead to temporal and spatial evolution of earthquake source and the boundary of various seismic precursory anomalies regions will pass through the source region. The intersection region of several boundaries of various seismic precursory anomalies regions in various time interval is epicenter of future strong earthquake.
During latter preparation period, the interaction between some units of the model intensifies and forms positive feedback, and the fluctuation intensification anomalies of precursor change with time. According to our study, the main shock occurs generally just at the third peak of fluctuation intensification of precursor or after it,and fluctuation intensification displays certain periodicity. Therefore we can estimate roughly the third peak time and get formula
M=4.29 +0.11t
t indicates anomalous time interval of fluctuation intensification, in month. According to above mentioned indexes, the moderate and short term prediction of strong earthquake may be made. At the end of this paper, we take the 1976 Tangshan earthquake as an example to show the application of the comprehensive model in the earthquake prediction.