Analysis of injection-induced failure for DuPont test 1#, Dongying, Shandong Province     

李行船 郭飚曲国胜  刘启元李顺成陈九辉  李岩峰谢晓峰 《地震学报(英文版)》2007,20(3):290-301

From December 3, 2005 to May 18, 2006, a water injection-induced seismicity test was conducted on DuPont test well 1# for about six months by China Earthquake Administration. To the vertical injected well, 11 water injection processes were conducted on four depth intervals, including middle Shahejie3, the top of the upper Shahejie3, the bottom of the upper Shahejie3 and Shahejie2, with the vertical span from 1 464 m to 3 034 m. Monitoring stations has been run throughout the procedure. From the recorded data, there were 5 090 events being picked out manually, 274 events located. It indicates that the energy of seismic signal is very small, and the largest magnitude is no more than ML0.5. And also, the major energy is centered on the vertical component, while amplitude of the other hori-zontal components is very small. From the start of water injection, the number of seismic events varied with time. And the event was most frequent in the period of upper Shahejie3 injection. The distribution of events extended from the injected well to the outside with time, and the direction of events distribution rotated in different injected interval. Of which, in the low permeability interval, events trend close to the direction of principal compressive stress direction; while in higher permeability interval, they trend close to the predominant seepage direction.  相似文献   

Mining seismicity, gas outburst and the significance of their relationship in the study of physics of earthquake source     

和雪松李世愚  潘科张天中  王林瑛许忠淮蒋秀琴  宋绪友陆其鹄 何淑韻 《地震学报(英文版)》2007,20(3):332-347

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   

A local-magnitude scale for Mt. Vesuvius from synthetic Wood-Anderson seismograms     

Edoardo Del Pezzo  Simona Petrosino 《Journal of Seismology》2001,5(2):207-215

The Local-Magnitude scale actually in use at Vesuvius Observatory is basedon the measure of seismogram coda duration, and calibrated with data fromIrpinia aftershocks. A recent study on local seismic attenuation at Mt.Vesuvius reveals coda shapes highly different from those from Irpiniaaftershocks, and a very low quality factor, if compared to the average Qof the region, indicating the necessity of the revision of the Magnitudescale, in order to better compare the seismic energy associated to the localseismicity of Mt. Vesuvius to that of other active volcanoes. Being theseismic attenuation parameters known in the area, we could correct theseismic amplitudes for the path effect to obtain precise estimates of theamplitude level of the displacement spectrum. Hence we estimated theMoment-Magnitude, M _W, for a set of well recorded micro-earthquakes.To use the Richter formulaM _L =log₁₀ A _max –log A₀(R)we estimated the log Amplitude-Distance correction curve, - log A₀(R),numerically synthesizing an S-wave-packet and letting it propagate in aearth medium with the same attenuation properties of those measured at Mt.Vesuvius. Then we synthesized the Wood-Anderson equivalent seismogram forthe same data set and used the distance correction in order to calculate theWood-Anderson Magnitude.This Magnitude scale was normalized in order to fit the Richter formulavalid for Southern California at a distance of 10 km, and resultsto be M _WA =log A + 1.34log(R) –1.10. The comparison of the Wood-Anderson scale with the Duration-Magnitude scalein routine use at Vesuvius Observatory indicates that care must be takenwhen the estimate of the Duration-Magnitude is carried out for smallearthquakes recorded at a site characterized by a high level of seismicnoise.  相似文献   

Seismicity and present-day tectonics of the Svalbard region     

B. J. Mitchell  H. Bungum  W. W. Chan  P. B. Mitchell 《Geophysical Journal International》1990,102(1):139-149

  相似文献   

An application of the time- and magnitude-predictable model to long-term earthquake prediction in eastern Anatolia     

Nilgün?SayilEmail author 《Journal of Seismology》2005,9(3):367-379

In order to estimate the recurrence intervals for large earthquakes occurring in eastern Anatolia, this region enclosed within the coordinates of 36^∘–42^∘N, 35^∘–45^∘E has been separated into nine seismogenic sources on the basis of certain seismological and geomorphological criteria, and a regional time- and magnitude-predictable model has been applied for these sources. This model implies that the magnitude of the preceding main shock which is the largest earthquake during a seismic excitation in a seismogenic source governs the time of occurrence and the magnitude of the expected main shock in this source. The data belonging to both the instrumental period (M_S≥ 5.5) until 2003 and the historical period (I₀≥ 9.0 corresponding to M_S≥ 7.0) before 1900 have been used in the analysis. The interevent time between successive main shocks with magnitude equal to or larger than a certain minimum magnitude threshold were considered in each of the nine source regions within the study area. These interevent times as well as the magnitudes of the main shocks have been used to determine the following relations: fwawhere T_t is the interevent time measured in years, M_min is the surface wave magnitude of the smallest main shock considered, M_p is the magnitude of the preceding main shock, M_f is magnitude of the following main shock, and M₀ is the released seismic moment per year in each source. Multiple correlation coefficient and standard deviation have been computed as 0.50 and 0.28, respectively for the first relation. The corresponding values for the second relation are 0.64 and 0.32, respectively. It was found that the magnitude of the following main shock M_f does not depend on the preceding interevent time T_t. This case is an interesting property for earthquake prediction since it provides the ability to predict the time of occurrence of the next strong earthquake. On the other hand, a strong negative dependence of M_f on M_p was found. This result indicates that a large main shock is followed by a smaller magnitude one and vice versa. On the basis of the first one of the relations above and taking into account the occurrence time and magnitude of the last main shock, the probabilities of occurrence P(Δ t) of main shocks in each seismogenic source of the east Anatolia during the next 10, 20, 30, 40 and 50 years for earthquakes with magnitudes equal 6.0 and 7.0 were determined. The second of these relations has been used to estimate the magnitude of the expected main shock. According to the time- and magnitude-predictable model, it is expected that a strong and a large earthquake can occur in seismogenic Source 2 (Erzincan) with the highest probabilities of P₁₀ = 66% (M_f = 6.9 and T_t = 12 years) and P₁₀ = 44% (M_f = 7.3 and T_t = 24 years) during the future decade, respectively.  相似文献   

Undead earthquakes   总被引：1，自引：0，他引：1  

R.?M.?W.?MussonEmail author 《Journal of Seismology》2005,9(1):111-114

This short communication deals with the problem of fake earthquakes that keep returning into circulation. The particular events discussed are some very early earthquakes supposed to have occurred in the U.K., which all originate from a single enigmatic 18th century source.  相似文献   

A Relative Moment Tensor Inversion Technique Applied to Seismicity Induced by Mining   总被引：1，自引：0，他引：1  

L. M. Linzer 《Rock Mechanics and Rock Engineering》2005,38(2):81-104

Summary. Studies of source mechanisms of mining-induced seismic events play an important role in understanding the various modes of failure observed around underground excavations and enable the geometry of likely planes of failure to be determined. These planes can be mapped using conventional techniques, for example, geological fracture mapping. However, such an approach is often problematical due to limited access to the site and/or poor exposures (if any) of the failure plane. An added difficulty is that planes of failure often do not follow faults of geological origin, but are related to the geometry of the advancing stope face. For example, the development of face-parallel shear zones ahead of deep-level stope faces. In such cases, the stresses induced by mining dominate over the geological structure in the critical region close to the stope face. Seismic methods therefore have the potential of being a practical method of studying the development of seismic shear zones underground.Slip on such a failure plane generates a three dimensional elastic wave that propagates through the rockmass, carrying a wealth of information regarding the source rupture process. The ground motions caused by the passage of the wave can be recorded by arrays of sensitive instruments called seismometers. These sets of recordings (seismograms) provide the basic data that seismologists use to study these elastic waves as they propagate through the Earth. Conventional seismic analyses provide scalar measurements of the rupture size and intensity. However, through a process known as moment tensor inversion (MTI), the seismograms recorded from a seismic event can be used to calculate a moment tensor that describes the three dimensional nature of the source mechanism. Interpretation of the moment tensor gives insight into whether the rockmass failed in tension, compression or shear and indicates the direction of movement and the failure plane.Moment tensor solutions computed using conventional MTI methods are sensitive to noise and may be biased due to systematic errors in the measurements. The primary objective of this study was to develop a robust MTI method to estimate the moment tensors of clusters of seismic events recorded in the underground environment. To achieve this, three hybrid MTI methods were developed by the author. These methods involve different iterative weighting schemes designed to enhance the accuracy of the computed moment tensors by decreasing the effect of outliers (data points whose residuals lie far from the mean or median error). The additional information required for hybrid methods is obtained by considering a spatial cluster of seismic events and assuming that the waves generated by each event in the cluster follow a similar path through the rockmass and allowing a common ray-path to be assumed. Hence the unknown effect of the heterogeneous rockmass on the waveform is similar for all the events in the cluster.The final objective was to determine whether the techniques developed could be successfully applied to real data. The hybrid MTI methods using the median and the weighted mean correction were applied to a cluster of 10 events, having remarkably similar waveforms, recorded at Oryx Gold Mine. For comparative purposes, the more conventional absolute method was also applied. The solutions computed using the hybrid MTI with a median correction displayed a distinct improvement after the iterative residual correction procedure was applied, in contrast to the solutions obtained from the absolute method. The radiation patterns and fault-plane solutions from the hybrid method showed a high degree of similarity, and were probably more accurate reflections of reality. These observations are very encouraging and point towards the potential for using the hybrid MTI method with a median correction as a standard processing tool for mine seismicity.The implications of this work are that a robust method for calculating the focal mechanisms of clusters of seismic events induced by mining activities has been developed. Regular application will lead to a better understanding of rock fracture processes and to improved safety underground.  相似文献   

地震临界丛集的判定及其应用     

孟国杰  罗灼礼  牛安福  翟璐媛 《大地测量与地球动力学》2004,24(1):68-71

介绍了地震临界时间丛集的判定方法——时间结构变异诊断方法。把时间结构变异诊断方法运用于1999年岫岩地震序列及中国大陆强震活动特性研究，并按此方法预测了中国大陆未来大震可能发生的时间点。研究认为，时间结构变异诊断法不仅可以用作前震序列和余震序列以及正常震群活动的判断，同时也适用于区域地震活动状态的描述。震例研究表明，时间结构变异诊断法在地震预测中具有实际意义。  相似文献   

非地震因素引起水氡异常一例     

邹昌明  王雪芳 《地震地磁观测与研究》1995,16(4):68-74

从分析观测资料入手，合理地剔除与异常时段观测环境条件不同的部分，科学地判定了王１井水氡正常动态和异常界限，并进行现场试验，排除对该异常真实性的各种疑虑，确认了异常的可靠性。在此基础上进一步开展水文地质调查，探讨异常产生的机理。  相似文献   

井水混浊度监测及其与地震活动的相关性研究     

葛林林  俞飞鹏  詹碧燕  陈子林  田钧  白汝兴  唐振兴 《大地测量与地球动力学》1995,(2)

报道了云南玉溪市杯湖机井使用地下水动态光纤监测系统样机对井水混浊度微观定量自动监测情况，并对其结果与高精度水温、地电等地震前兆以及气温、气压、降雨等气象因素和地震活动性进行了相关分析。结果表明：混浊度异常与邻近井及本身的水温异常有良好的相关性，与地电等有关地震前兆和地震活动性有一定程度的相关，而与气象因素没有明显的关系。  相似文献