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1.
Research on the Characteristics and Repeatability of Strong Earthquake Activity in Sichuan-Yunnan 总被引：1，自引：0，他引：1
According to the method for predicting strong earthquakes using seismicity patterns, this paper summarizes the seismicity anomalies, generally called anomalous seismicity patterns, as the basis for prediction based on some historical data in the Sichuan-Yunnan seismic zone. Using our results, it can be confirmed that these anomaly patterns, which reflect the features of the late stage of strong earthquake preparation process and stress release in the main shock rupture zone, did exist before many earthquake cases. This paper also introduced the characteristics of seismic repeatability and its validation result, and discussed the mechanism of repeatability, which will have an application value for strong earthquake tendency prediction. 相似文献
2.
By scanning modulated or un-modulated earthquakes spatio-temporally in the region of Sichuan-Yunnan,short-term non-stationary seismic precursory patterns were extracted with significant difference and the characteristic of non-stationary short-term seismic anomalies were analyzed as well as prediction efficiency of modulated small earthquakes before a strong earthquake. Besides,small earthquake modulation ratios near the region of the epicenter were calculated and sorted by time. The results indicated that there were significant effects using the modulated earthquake method to predict earthquakes greater than MS6. 0 in a short time. Before the MS8. 0 Wenchuan earthquake,there were obvious short-term precursory seismicity gap patterns of modulated small earthquakes. 相似文献
3.
A seismic gap on the Anninghe fault in western Sichuan, China 总被引：10，自引：0，他引：10
Through integrated analyses of time-varying patterns of regional seismicity, occurrence background of strong and large historical earthquakes along active faults, and temporal-spatial distribution of accu- rately relocated hypocenters of modern small earthquakes, this paper analyzes and discusses the im- plication of a 30-year-lasting seismic quiescence in the region along and surrounding the Anninghe and Zemuhe faults in western Sichuan, China. It suggests that the seismic quiescence for ML≥4.0 events has been lasting in the studied region since January, 1977, along with the formation and evaluation of a seismic gap of the second kind, the Anninghe seismic gap. The Anninghe seismic gap has the background of a seismic gap of the first kind along the Anninghe fault, and has resulted from evident fault-locking and strain-accumulating along the fault during the last 30 years. Now, two fault sections either without or with less small earthquakes exist along the Anninghe fault within the An- ninghe seismic gap. They indicate two linked and locked fault-sections, the northern Mianning section and the Mianning-Xichang section with lengths of 65 km and 75 km and elapsed time from the latest large earthquakes of 527 and 471 years, respectively. Along the Anninghe fault, characteristics of both the background of the first kind seismic gap and the seismicity patterns of the second seismic gap, as well as the hypocenter depth distribution of modern small earthquakes are comparable, respectively, to those appearing before the M=8.1 Hoh Xil earthquake of 2001 and to those emerging in the 20 years before the M=7.1 Loma Prieta, California, earthquake of 1989, suggesting that the Anninghe seismic gap is tending to become mature, and hence its mid- to long-term potential of large earthquakes should be noticeable. The probable maximum magnitudes of the potential earthquakes are estimated to be as large as 7.4 for both the two locked sections of the Anninghe fault. 相似文献
4.
This paper presents an overview of mining seismicity, gas outburst and their origin. The internal relation of mining seismicity and gas outburst in the dynamic process is studied on the basis of the fact that these disasters sometimes occur simultaneously. The examples show a close relationship between mining seismicity and gas outburst in high gassy coal mines. It is proposed that strong mine shocks plus the response of low value and delay time are early warning signals. The mechanism of the relationship between mining seismicity and gas outburst is analyzed by using the location of mining shocks, focus mechanism, cause of mining shocks and conditions of gas outburst. The trigger action of gas fluid on mining shocks, especially the effect of the anomalous property of supercritical fluid on the preparation and occurrence of mining shocks is discussed. According to the similarity between min-ing-induced earthquakes and tectonic earthquakes in terms of mechanism, the significance of the above results in the study of physics of earthquake source is also discussed. 相似文献
5.
Many uncertainty factors need be dealt with in the prediction of seismic hazard for a 10-year period.Restricted by these uncertainties,the result of prediction is also uncertain to a certain extent,so the probabilistic analysis method of seismic hazard should be adopted.In consideration of the inhomogeneity of the time,location,and magnitude of future earthquakes and the probabilistic combination of the background of long-term seismic hazard(geology,geophysical field,etc.)and the precursors of earthquake occurrence,a model of probabilistic prediction of seismic hazard in a period of 10 years s proposed.Considering the inhomogeneity of data and earthquake precursors for different regions in China,a simplified model is also proposed in order to satisfy the needs of different regions around the country.A trial in North China is used to discuss the application of the model.The method proposed in this paper can be used in the probabilistic prediction of seismic hazard in a period of 10 years.According to the 相似文献
6.
Shao Huicheng 《中国地震研究》2007,21(2):189-195
The gestation and occurrence of strong earthquakes are closely related to fault activity, which is not only revealed by abundant experimentation and seismism but also proved by modern seismology. On the Chinese mainland, the relation between earthquake activity and active faults is one of the bases for partitioning potential seismic sources, analyzing the seismotectonics and estimating location of strong earthquakes.Due to the nonuniformity of earth media, instability of observation systems and disturbance of the environment, etc, the variety of observational data is complicated, that is, there is no absolutely "normal" or "abnormal", and seismic anomalies can be divided into many mutually exclusive "abnormal states". In different conditions of combined time-space-strength, determining seismic anomalies by different monomial forecast methods and its efficiency could be different due to the uncertainty of a precursor itself or complexity of the relationship between a precursor and earthquake gestation. It is very difficult to discover and dispose of this difference in actual application in a "two-state" model. But in a "multi-state" model, the difference can be easily reflected and the optimal combination of forecasting parameters for a forecast method can also be determined easily.Based on the "multi-state" precursory model and the optimization method for parameters of earthquake forecast model under the condition of optimal forecast efficiency, the relationship of the spatial location of earthquake with M≥6.0 and active faults in three seismic belts are analyzed. The results demonstrate that in the Hetao Seismic Belt, seismicity is mostly concentrated in the range of 20 km along the fault, the optimization model can forecast the location of potential earthquakes of M≥6.0 near the faults with a relatively high accuracy and the reliability is 0.5; while in the Qilian Mt. Seismic Belt, the reliability only reaches 0.14 when we use the model to estimate earthquakes within 30 km range along the faults. The "multi-state" precursory model, the efficiency-evaluating model and the parameter selection of individual earthquake forecast model based on optimal efficiency are of certain revelatory and practicable meanings for developing knowledge about precursors, investigating the laws of earthquake preparation and searching for optimal forecasting methods. 相似文献
7.
Zhang Guomin Li Li and Shi YaolinCenter for Analysis Prediction CSB Beijing China Graduate School of Chinese Academy of Sciences Beijing China 《中国地震研究》1999,(4)
The relationship between the strain cumulative rate (i.e., the crustal strain rate, or CSR in short) and seismic activity is analyzed to develop a new method to determine risky regions for strong shocks within recent years by the recorded crustal strain field. Seismic activity, especially the recurrence period, is different in different areas. Ding Guoyu (1984) pointed out that, for different seismic regions, the difference in the recurrence period of strong earthquakes is mainly controlled by their difference in the rate of the tectonic movement, which is controlled by the seismogenic environment and the tectonic conditions. The method of determining the risky regions for strong shocks from the gradient of vertical strain rates observed in a geodetic survey is preliminarily tested with the earthquakes in recent years; the results show that this method is effective and useful for earthquake prediction. The relationship between CSR and seismicity in a specific region is studied with strain theories, obse 相似文献
8.
Zhang Guomin Li Li and Jiao MingruoCenter for Analysis Prediction CSB Beijing China 《中国地震研究》1999,(2)
Seismological approaches used in earthquake prediction involve many subjects. To predict large earthquakes from small to moderate foreshocks has a clear meaning in physics. Some of the main methods of earthquake prediction used in China are outlined in this paper. According to the anomalies used for earthquake prediction, seismological approaches can be divided into two groups: those that use the anomalies in seismic patterns, including the increase and decrease in regional seismicity, the appearance of seismic gaps, seismic belts, seismic swarms, and foreshocks and those that use anomalies in special values and in seismic waves, such as the anomalies in b values and f values, in the Vp/VS ratio, Q values, stress drop, and shear stress. 相似文献
9.
On the basis of our predecessors' research,we study the distribution and the space-time evolution characteristics of the seismic apparent strain field in Yunnan since the 1970's using the seismic data of Yunnan and its surrounding areas.The result shows that there is a rather strong corresponding relationship between the anomaly region of seismic apparent strain and strong earthquakes.In the nine earthquakes studied,anomaly areas of seismic apparent strain had appeared before eight earthquakes,including five occurring in the anomaly region and three on the edge.Finally,the investigative result is demonstrated primarily. 相似文献
10.
Group Strong Earthquakes and Triggering by Tidal Stress 总被引：4，自引：1，他引：4
The results obtained using the group model of earthquakes generated in tectonic blocks are fur ther used in this paper to analyze the relationship between the Ms ≥ 7.0 events in Chinese ma inland and the modulation and triggering from the earth tides. The research shows that the Ms 7.0 events in Chinese mainland have been significantly triggered by the tidal stress, especially within the active period with group strong earthquakes. In the quiescence period of strong earthquakes, no Ms7.0 events were triggered, while within the active period, over 82.4% of strong earthquakes took place within a special moon phase, which is 36.4 % higher than the average. Therefore, the modulation and triggering of tidal stress can be used to distinguish the active periods and to forecast the time of the strong earthquakes within the active period. The relationship between the tidal triggering and the tectonic dynamic condition is investigated and the mechanism of the modulation is simulated with the group model of earthquakes generated in tectonic blocks. 相似文献
11.
许多学者对软土在动力作用下的变形特性进行了大量的研究,并提出了相应的经验公式,但其经验公式参数较多且试验复杂,不易被一般工程技术人员掌握运用。本文采用天津滨海地区软土为研究对象,进行钻探取样、波速测试、室内静力学和动三轴试验,获取该地区软土的静、动力学参数,并利用相对简单的模型对残余应变和软化指数随振次的变化规律采用最小二乘法进行拟合,取得很好的效果。成果表明,利用简单的模型对软土的动力特性进行区域性研究是可行的。该成果可为今后软土动力特性和软土震陷计算方法研究提供参考和基础性资料。 相似文献
12.
基于动三轴试验的压实黄土动强度特性研究 总被引：5，自引：2，他引：3
选取吕梁地区黄土,通过静压压实制备三轴试样,在GDS振动三轴仪上研究含水率、干密度和加载频率对压实黄土动强度的影响规律。结果表明:压实黄土的动强度及动强度参数均随振次的增加而减小,随含水率的增大而减小,随干密度和加载频率的增大而增大,动强度与振次之间的关系可用对数方程进行拟合。研究对黄土地区填方区基础建设具有重要意义。 相似文献
13.
Based on the dynamic triaxial test system and using the fitted wave of the Wenchuan earthquake and 1 Hz constant amplitude sinusoid,the paper compares the results of tests on undisturbed loess samples under different loads and vibration modes but under same saturated conditions.Results of the comparative experiment show:The stress-strain curves have a similar trend under random seismic loading and constant amplitude sinusoidal loading,but the random seismic loading is more sensitive to failure strength of the undisturbed loess samples under the same stress. 相似文献
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基于相似性导出基础的动力刚度矩阵 总被引：2，自引：0，他引：2
详细论述了基于相似性导出基础动力刚度矩阵的思想，包括克隆算法、无限元方法、一致无穷小有限元法和标度有限元法。这些方法，仅对地基－基础界面进行有限元离散，使问题的空间维数减少一维；但是，它们不需要基本解就可以满足无穷远辐射条件，从而避免了奇异积分的计算，减少了计算工作量。 相似文献
16.
通过在三轴试样的轴向和径向同时施加循环荷载,并以试样45°面上的应力来模拟地震拉压动荷载和剪切动荷载的作用,分析双向循环荷载耦合下黄土的动剪切模量和动变形特性。试验结果表明:相位差对黄土的动剪切模量有一定影响,其动剪切模量随相位差的增大以φ=180°为转折点呈现先减小后增大的趋势,在φ=180°时达到最低水平。φ180°时相位差的增大加速了黄土动剪应变的发展,φ180°时黄土的动剪切变形的发展速度随相位差的增大而减缓。同时径向动荷载幅值的增大明显降低黄土的初始动剪切模量。通过计算转化,分析拉压动荷载和剪切动荷载变化对黄土动剪切变形发展的影响规律,发现拉压动荷载的施加能加快黄土动剪切变形的发展,而当拉压和剪切动荷载同时变化时,剪切动荷载变化对黄土动剪切变形发展的影响更明显,作用更显著。 相似文献
17.
A critical evaluation is made of the dynamic pressures and the associated forces induced by ground shaking on an upright, circular, rigid vault that is embedded in a uniform viscoelastic stratum of constant thickness and infinite extent in the horizontal plane. Both the vault and the stratum are presumed to be supported on a non-deformable base undergoing a space-invariant, uniform horizontal motion. The effects of both harmonic and earthquake-induced excitations are examined. Simple approximate expressions for the responses of the system are formulated, and comprehensive numerical data are presented which elucidate the underlying response mechanisms and the effects and relative importance of the various parameters involved. The parameters investigated include the height to radius ratio for the vault, the conditions at the vault-medium interface, and the material properties of the stratum. In addition to valuable insights into the response of the particular system being examined, the results presented provide a conceptual framework for the analysis and interpretation of solutions for more involved systems as well. 相似文献
18.
A critical evaluation is made of dynamic pressures and the associated forces induced by ground shaking on a rigid, straight, vertical wall retaining a semi-infinite, uniform viscoelastic layer of constant thickness. The effects of both harmonic and earthquake-induced excitations are examined. Simple approximate expressions for the responses of the system are developed, and comprehensive numerical data are presented which elucidate the effects and relative importance of the various parameters involved. These solutions are then compared with those obtained by the use of a simple model previously proposed by Scott, and the accuracy of this model is assessed. Finally, two versions of an alternative model are proposed which approximate better the action of the system. In the first, the properties of the model are defined by frequency-dependent parameters, whereas in the second, which is particularly helpful in analyses of transient response, they are represented by frequency-independent, constant parameters. 相似文献
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面板堆石坝的动力离心模型试验研究 总被引：1，自引：0，他引：1
为研究面板堆石坝的地震响应规律,采用Parkfield波作为地震动输入,在清华大学50g-t土工离心机上进行了动力离心模型试验.试验在50倍重力加速度条件下采用电液伺服离心机振动台系统完成,采用加速度传感器测量了模型不同位置动力响应的加速度时程并且测量了面板的变形.结果表明,地震最大响应发生于坝顶,该处地震动放大系数接... 相似文献