广州地磁台转换函数的长期变化和季节变化

本文全面系统地研究了1960——1987年广州地磁台转换函数的变化.结果表明:(1)季节变化的特点是夏季幅度大,冬季幅度小,具有12和6个月的主要周期成份;长期变化则表现以每年0.0025的速率下降.转换函数 B 的长期变化和季节变化不明显;(2)由转换函数 A,B 求出的帕金森矢量的方向明显地受海洋的影响,反映了海洋效应;(3)转换函数 A,B 的逐月值与地磁活动相关,而年均值与地磁活动无关.A 的年均值无明显的11年或22年周期.长期变化可能主要受地球内部电性结构的影响.      

The experimental study of acoustic emission during creep of rocks

Under normal temperature, the creep experiments with complete samples of Gabbro and Marble rocks are made under uniaxial compression. It is found that at the instantaneous creeping stage, AE activities increase with loading; at the steady creeping stage, large AE signals may appear at lower background of AE action, andm—value which shows the relationship between AE amplitude and frequency keeps stable on the low value or decreases; at the accelerate creeping stage, AE activities increase andm—value decreases quickly or decreases again after recovery. These experimental results are related to the quality of the samples. In this paper, AE activities during three stages of creeping process are connected with the seismic patterns (for exampleb—value, foreshocks). Finally, it is pointed out the possibility that the foreshock—mainshock—aftershock earthquake sequence has been formed by the mechanism of creep fracture of crustal rocks. The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,13, 104–112, 1991. This subject is sponsored by the Chinese Joint Seismological Science Foundation.     

标本非均匀性对岩石变形声发射时空分布的影响及其地震学意义

基于一组实验结果,讨论了岩石标本的非均匀性（预存微裂纹和宏观裂纹）对声发射 时空分布的影响. 对比分析表明,预存微裂纹的存在使得破裂成核前声发射率快速增加、 b值表现出一种短期异常现象,即在下降背景上出现起伏,从而增加了破裂时间的可预报 性. 宏观结构（节理、层面等）的存在对声发射率和b值的影响与微裂纹相同,而且宏 观结构对声发射的空间分布具有控制作用,声发射丛集的宏观构造通常控制着未来的主破裂 . 这意味着宏观构造的存在使得主破裂的时间和位置预报成为可能.      

The experimental research on b value of AE for the rock specimens with pre-existing crack or notch under uniaxial compression

A lot of researches onb value have been made in seismology. Since the 1960’s Mogi, Scholz and others have studied AE of rock specimens in laboratory and discovered that it is related to natural earthquakes. All former researchers used integral specimens to studyb value in the laboratory. However a major earthquake is usually related to a existing seismic-fault in that area. For this reason, a series of fracture experiments with rock and glass specimens having pre-existing crack or notch is performed in order to examine the effect of preexisting crack tob value. The experimental results show that theb value begins to decrease as soon as the initiation of the crack and finally drop to a very low value when the specimen breaks unstably. Based on these, a brief discussion on the possible mechanism ofb value change for natural earthquakes is given. The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,9, 393–400, 1987. Projects sponsored by the Chinese Joint Seismological Science Foundation.     

A model of nonuniform fracture system for Langcang-Gengma earthquake sequence and elasto-plastic computation method

Based on the observation data, it is found that the Lancang-Gengma earthquake sequence is resulting from the propagation of a nonuniform fracture system in which the lengths and strikes of fractures are different from each other, the stress field and medium condition around fractures are also heterogeneous. Therefore, a mechanical model simulating suitably the fracture processes of the Lancang-Gengma earthquake sequence is suggested in this paper. The fracture criterions and computation method for elastic fracture and elasto-plastic fracture are studied. The stress intensity factor, strain energy release rate and J-integral are evaluated respectively. The forward and inverse method jointing a variety of observation data to determine the earthquake fracture processes is also developed in this paper. The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,14, 463–471, 1992. This project was sponsored by the Chinese Jonit Seismological Science Foundation.     

The influence of stiffness of the true triaxial testing machine on the rupturing and acoustic emission of rocks and its correlation with seismic activities

This paper introduces how the ratioR of the characteristic stiffness of rock samplevs. the stiffness of testing machines would influence the rupturing process and the acoustic emission (AE) on the part of the tested rock samples. Result of the experiment shows: WhenR>0.20, the rock sample would rupture abruptly; whereas whenR<0.20, the rock samples would rupture slowly. When the samples rupture abruptly, the time-dependent variation of the AE rate takes such a pattern:peak value—stable low values—rises to the maximum value (concentration)—drops back to the minimum value (quiescence)—(rises again)—ruptures. Moreover, smallerR-value tends to be associated with longer quiescence and vice versa. WhenR>1.50, no pre-failure quiescence is detected. When the rock samples rupture slowly, the variation pattern of the AE rate (after the stress has increased to more than 50% of the rupturing stress) is as the following:stable low (or high) values—rises (or drops) to its maximum (or minimum) values and then continues for some time—ruptures. The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,13, 223–233, 1991. This study is supported by the Chinese Joint Seismological Science Foundation.     

The chemical anomalous behaviors of water-marble rock system under action of ultrasound

By the experiment, it is confirmed that water-marble rock system shows obviously chemical anomalous behaviors: the relevant minerals which formed marble rock are resolved fast, water becomes alkaline, meanwhile H₂ emission appears under action of ultrasound; based on rock identification by microscope and chemical analysis of water and rock, the mechanism of above chemical reaction is analyzed and discussed. The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,15 498–507, 1993. This study was supported by the Chinese Joint Seismological Science Foundation.     

Experimental study on the effect of the critical temperature of water on the preparing and occurring of large earthquakes

The features of fracturing and dissolving of Yunnan marble in distilled water near the critical temperature have been studied experimentally. The results indicate that the mechanical parameters of the samples (fracture strength, Young’s Modulus, shear fracture energy and fracture toughness) drop with the temperature of the environment water, near the critical temperature (380°C), these parameters have sudden changes (drop), then keep stable values roughly. The contents of some chemical materials in the water, PH value and conductivity at every experiment temperature have been analysed and measured. At 380°C, there all exist sudden changes. According to the results, it is pointed out that the sudden changes are related to strong stress corrosion of water near its critical temperature to the rock and the exist and its migration of the water solution near the critical temperature in the crust have important significance to the earthquake source process, the formation cause of the low-focal depth earthquakes in the crust. The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,14, 156–163, 1992. This work was sponsored by the Chinese Joint Seismological Science Foundation.     

The remote sensing observation in experiments of rock failure and the beginning of remote sensing rock mechanics

The remote sensing observational study for infrared radiation of rocks was proceeded during the loading on rocks until failure. The major instruments used in experiments were transient spectrum apparatus, intelligent spectrum apparatus, infrared radiation thermometer, infrared spectrum radiometer, and infrared thermal imaging system. The experiments for 26 kinds of rocks were made. The studies show that infrared radiation temperature of rocks increases along with increasing of stress. The amplitude of infrared radiation spectrum of rocks also increases along with increasing of stress. The observational results of infrared thermal imaging of rocks are consistent with infrared radiation temperature. Before formation of major faults for some rocks, the belt-shape thermal imaging of temperature anomaly displaies in position of future major faults. This study has led the new technology of remote sensing into rock mechanics and tend to establish a new field in rock mechanics — remote sensing rock mechanics (or remote sensing rock physics). The application of remote sensing rock mechanics in prediction of earthquake and rock burst, and in measurement of stress field in rock mass is expected. The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,14, Supp., 645–652, 1992. Jin-Shen HAO, Ji-Han LI, Xiao-Hong LIU, Yi-Qiao ZHI, Jin-Kai ZHANG, Yong-Hong Lü, Yi LIU, Yun-Shen YU, He ZHANG, Quan-Quan JI, Xiao-Fan ZHU and Ning CHEN took part in this work. This subject is supported by the Chinese Joint Seismological Science Foundation (91006). Work of Institute of Geophysics, SSB (93A0009).     

Geomagnetic daily variations around Huanghai earthquake

The geomagnetic daily variations of vertical component, which were recorded by geomagnetic array in Jiangsu Province, are investigated with the method of multichannel Wiener filtering. The results show that the daily standard errors between raw data and the actual output of the filter for the nearest stations away from epicenter are obviously higher than ordinary level before the Huanghai earthquake, especially three days before, then returned to normal after the earthquake. The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,13, 76–79, 1991. The project was supported by the Chinese Joint Seismological Science Foundation.     

Granite deformation and behavior of acoustic emission sequence under the temperature and pressure condition at different crust depths

IntroductionFocal depths of shallow strong intraplate earthquakes are mostly distributed in the highstrength range of lithosphere controlled by the rheology property of granite and diorite (Brace,Kohlstedt, 1980; Sibson, 1982; Meissner, Strehlau, 1982; CHEN, Molnap 1983). This is obviouslyrelated to the change of rock deformation characteriStics at different crust depths. So, for earthquake stUdy, both of the rock failure types (fractUre or rock flow) and its mechanical instabilityforms (…     

The features of multiple fractures associated with the great Haiyuan 8.5 magnitude earthquake of 1920

It is deduced on the basis of field investigation that the total length of the stratigraphic fault associated with the great Haiyuan 8.5 magnitude earthquake of 1920 was 225 km. This fault was formed by 6 secondary faults with different geometric parameters, which align regularly inen echelon arrangement. Each secondary fault can be divided into three segments with different characteristics of deformation where the middle segment was mainly of the horizontal strike—slip fault while another two segments the vertical deformation as shown by the features of reverse or normal faults. It is also shown by the data of vertical and horizontal displacements that the horizontal displacement approached a maximum at the middle segment for each secondary fault and gradually decreased toward and finally disappeared at both ends of each segment while in contrast the vertical displacement was minimum at the middle and became large at both ends of the segment. The feature of the multiple peaks appeared in the deformation as shown by the earthquake displacements along the whole fault. This feature indicates that the 6 secondary faults associated with the great Haiyuan earthquake were the horizontal interrupted planes (i.e., dislocation surface) which were independent on each other, and hence each dislocation surface may represent an independent secondary fracture event of the earthquake. We thus think that the 6 relatively independent secondary events which occurred successfully might result in the great 8.5 magnitude Haiyuan earthquake. The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,13, 21–31, 1991. This project is sponsored by the Chinese Joint Seismological Science Foundation.     

High-resolution Mechanics of a Microearthquake Sequence

—?Unique data from microseismic (MS) and acoustic emission (AE) systems monitoring a common rock volume have been analyzed from the Underground Research Laboratory in Canada. The two 16 sensor systems were installed to investigate stress-induced microcracking around clay and concrete bulkheads as part of the Tunnel Sealing Experiment. Single and double MS events are found to be spatially associated with clusters of between 19–86 higher frequency AE events. Each AE cluster is elongated with the longest axis between 15 and 50?cm. The AE events occurring before the associated MS event are termed foreshocks, and for two of the three analyzed AE clusters an acceleration in the AE frequency and cumulative magnitude occurs upto the time of the MS event, however with one AE cluster very few foreshocks are recorded, possibly indicating a more homogeneous failure plane. Time independent moment tensors were determined with the MS events showing significant deviatoric sources. The majority of the AE events have deviatoric mechanisms with a few crack opening and crack closure type events also determined. This study highlights the benefits of using small-scale seismic systems to investigate the temporal fracture mechanics of microcrack formation, and allows comparisons with larger more damaging seismicity.     

Study on the property of apparent resistivity changes of rock samples by in situ shear and friction test

In the strip limestone mine in Guiding county, Guizhou Province the shear and frictionin situ tests of rock body were made for the three typical inclined weak bands C ₃ ¹ /C ₃ ¹ , C ₃ ¹ /C ₂ ² and C ₂ ² /C ₂ ¹ . The tests were made according to the second scheme of cuneate sample of the standards on rock mechanics test of Water Conservancy and Electricity Ministry. The changes of the resistivity in the weak band and the acoustic speed across the weak band were measured in the same time. The apparent resistivity data, obtained for 8 samples on 27 measure lines in 38 cycle tests, show that the apparent resistivity changes have rather obvious characters as follows: 1. At shear and friction stage, the change of the apparent resistivity accelerates after the yield point, and reaches the maximum of change rate and change amplitude near fracture point (except the lines with resistivity invariant); 2. On the same sample, the resistivity changes are different on the various lines and related to the location settled the lines, there are some “sensitive” location; 3. At the stage of preloading normal stress before shearing, the resistivity decreases on most lines, but on a few lines the resistivity does not changes; 4. After unloading shear stress, the resistivity could not recover completely and the hysteresis of resistiviity takes place on a few lines. The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,15, 217–223, 1993. Support for this research was received from Guiding strip limestone mine, Guizhou Organic Chemistry Factory. This research is supported by the Chinese Joint Seismological Science Foundation.     

Response spectrum to strong aftershocks of the Lancang-Gengma earthquake

Near-field records of two strong aftershocks with magnitudeM _S=6.7 andM _S=6.3 in the Lancang-Gengma earthquakes sequence, Yunnan Province, November 1988, are used to calculate the response spectrum. The instruments, site conditions and the methods for computing are also illustrated in this paper. The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,13, 338–343, 1991. This project is supported by The Chinese Joint Seismological Science Foundation, SSB and the West Yunnan Earthquake Prediction Test Field, Yunnan Seismological Bureau.     

Comprehensive study on stability of deep crust and unstable behavior of earthquake source by both failure mechanism and frictional sliding mechanism

In this paper the relation between fault movement and stress state in deep crust is discussed, based on synthetic analysis of the crustal stresses measured over the world and the concerned data of focal mechanism. Using Coulomb criterion for shear failure and frictional slip, analytical expressions for estimating stabilities of intact rock and existing fault in the crust and for identifying the type of faulting (normal, strike-slip or thrust fault) are derived. By defining the Failure FunctionF _m and the Fraction FunctionF _f, which may describe steadiness of crustal rock and existing fault, respectively, a synthetic model is set up to consider both fracturing mechanism and the sliding mechanism. By this model, a method to study stability and unstable behavior of crustal rock and fault at different depths is given. According to the above model, quantitative study on the crustal stability in the North China plain is made in terms of the measured data of hydraulic fracturing stress, pore-fluid pressure, terrestrical heat flow in this region. The functionsF _m andF _f and the shear stresses on faults with different strike angle and dip angle at various depths in this region are calculated. In the calculation the constraint condition of fault movement obeys Byerlee’s Law, and the depth-dependent nonlinear change in the vertical stress due to inhomogeneity of crustal density and the high anomalous pore-fluid pressure in deep crust of this region are considered. The conclusions are: the unstable behavior of the crust in the North China plain is not failure of crustal rock but slip on existing fault; the depth range where stick-slip of fault may happen is about from 8 to 20 km or more; stability of steep fault is lower than that of gentle sloping fault; the shear stresses in the range where may occur stick-slip are nearly horizontal; the steep faults trending from NNE to NE in this region are liable to produce strong earthquakes, whose co-seismic faultings are, for the most part, right lateral slip; the change in pore-fluid pressure in depth remarkably affects the stability of the crust and the increase in pore-fluid pressure, therefore, would be an important factor exciting strong earthquake in this region. The above theoretical inferences are consistent with the data measured in this region. The Chinese version of this paper appeared in the Chinese edition ofActa Seismologia Sinica,13, 450–461, 1991. This work is supported by Chinese Joint Seismological Science Foundation.     

岩石蠕变过程中声发射活动的实验研究

在常温下、单轴加压下对两种岩石完整样品进行蠕变破坏过程中声发射活动实验.根据实验获得的数据讨论了蠕变三个阶段中声发射活动特征.在瞬态蠕变阶段,随着加载,声发射活动逐渐增强;在稳态蠕变阶段,在较低的声发射活动背景上,可能出现较强的信号,声发射幅值-频度关系的 m 值可能稳定于某一低值,也可能下降;进入加速蠕变阶段,声发射活动水平增强,m 值下降加快,也可能表现为明显回升后再下降,并与岩石样品的性质有关.将蠕变破坏三个阶段中声发射活动与地震孕育过程中某些地震活动图象变化(如 b 值、前震活动)进行了联系,提出地壳岩石蠕变破坏机制形成前震——主震——(余震)型地震序列类型的可能性.      

Trial results of YRY-2 shallow borehole strainmeter at eight observation sites in North China

The analysis results of observations data indicate that this shallow-borehole (21 m – 52 m) strainmeter can record accurate crustal movements. Its records of earthquake and solid tide can be analysed. To use long period frequency data, null drift must be considered. To extend its application, the technique of installation and anti-lightning stroke should be improved. The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,15, 224–231, 1993. This project is supported by the Earth-quake Monitoring Department of the State Seismological Bureau.     

Analytical comparison of geomagnetic total field between Sino-US stations

Using observational data of geomagnetic total intensity from 13 stations in the Beijing-Tianjin region, 3 stations in the western Yunnan region of China, and 6 stations in California of U. S. A., the daily variations and their spectra of geomagnetic total intensity were analyzed and compared. The results show that the morphology, the range and spectrum of daily variations in geomagnetic total intensity are basically the same within the local extent of 100–200 km and are different in the large extent of 500 km. The latitude factor of the daily variation range of geomagnetic total intensity is about 1–2 nT/degree within the latitude extent of 25°–40°. The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,14, 83–89, 1992. This work is supported by the State Seismological Bureau and the Chinese Joint Seismological Science Foundation, and U.S. Geological Survey.     

The application of the method of reconstruction a phase space with higher dimensions to the study of seismic processes and earthquake prediction

The method of reconstructing a phase space with higher dimensions can be applied to analysing the observaiton data for studying the dynamic behavior of seismic processes and earthquake prediction. It is found that seismic processes are chaotic. So earthquakes could be determinately predicted only within the predictable period. Here, some related problems (e.g. several primary parameters and the relations among them, the relation between the quality of used data and analytical results, the relation between a reductive process of the fractal dimensions and earthquake prediction and so on) are discussed. The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,15, 470–476, 1993. This study was sponsored by the Chinese Joint Seismological Science Foundation under Contract NO. 9000007.