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1.
Improving Seismic Resolution Through Array Processing Techniques 总被引:4,自引:0,他引:4
Seismic arrays, first introduced in the late 1950s to detect underground nuclear explosions, have helped to improve our knowledge about the structure of the Earth for the last 40 years. During these years, numerous array processing methods have been developed that use the high signal coherence and accurate timing of array data to generate high-resolution images of Earth structure. Here, we present an overview of resolution issues related to seismic array studies of Earth structure by first introducing basic array processing techniques and then discussing more advanced techniques applied to array data recently. The increase of seismic stations deployed in experiments or permanently in many regions of the globe allows a much denser sampling of the seismic wavefield. This dense sampling enables the adaptation of controlled source analysis techniques for the study of Earth structure using earthquakes with higher resolution than previously possible. Here we will discuss different migration methods of teleseismic data that use the incidence angle information of scattered arrivals to obtain images of Earth structure. Finally, we show data examples how these methods can be used to increase our knowledge of the structure of the Earth’s deep interior. 相似文献
2.
利用地震学方法估算爆破当量,一直以来都是地震学研究的难点之一。影响当量估算的因素很多,如震源特征、事件埋深、传播路径、能量衰减、地壳结构的不均匀性,等等。想要精确估算特定事件的当量,除了要克服以上各种困难外,还需选择合适的当量经验公式。当量与事件所释放的能量直接相关,震级在一定程度上可以反映能量的大小。目前使用的当量估算公式主要是震级-当量关系公式,其中,有利用体波震级、面波震级以及尾波估算当量的,各有利弊。本文的主要目的是总结目前存在的当量估算公式,并对其影响因素做简单分析。重点描述地下核试验当量估算,汇总了历次朝鲜核试验的信息。 相似文献
3.
利用布设在长白山地区临时地震台站接收到的朝鲜核爆的波形资料,对2009年5月25日和2013年2月12日两次朝鲜核试验的地震学特征进行比较.震中距范围从145km到420km.采用P/S型谱比值方法识别朝鲜核爆,通过与2009年3月20日长春地震和2013年1月23日沈阳地震事件的比较,表明在频率大于3 Hz时P/S型谱比值能够有效识别发生在中朝边境地区的地下核试验.选定参考台站,利用区域震相Pg波的振幅谱比值计算朝鲜核爆至各台站路径上的相对衰减.结合介质速度模型,在一定程度上反映了长白山地区衰减情况,为进一步研究长白山地区衰减层析成像提供初始模型. 相似文献
4.
J. R. Murphy I. O. Kitov B. W. Barker D. D. Sultanov 《Pure and Applied Geophysics》2001,158(11):2077-2101
—?During the period 1965 to 1988, the former Soviet Union (FSU) conducted over 120 peaceful nuclear explosions (PNE) at locations widely dispersed throughout the territories of the FSU. These explosions sample a much wider range of source conditions than do the historical explosions at the known nuclear test sites and, therefore, seismic data recorded from these PNE tests provide a unique resource for use in deriving improved quantitative bounds on the ranges of seismic signal characteristics which may require consideration in global monitoring of the Comprehensive Test-Ban Treaty (CTBT). In this paper we summarize the results of a detailed statistical analysis of broadband seismic data recorded at the Borovoye Geophysical Observatory from 21 of these PNE tests at regional distances extending from about 7 to 19 degrees, as well as the results of theoretical waveform simulation analyses of near-regional (Δ?25?km) seismic data observed from a selected sample of nine of these PNE tests. The results of these analyses have been found to be consistent with those of previous teleseismic investigations in that they indicate that the seismic source coupling efficiencies are very similar for explosions in a wide variety of hardrock and water-saturated media, while explosions in water-saturated clay are observed to have significantly higher coupling efficiencies. Moreover, the scaling of the seismic source function with explosion yield and depth of burial inferred from these analyses of the Soviet PNE data are shown to be generally consistent with the predictions of the Mueller/Murphy source model. These results suggest that the Mueller/Murphy source model can provide a reasonable basis for estimating the expected variation in regional phase spectral composition over a wide range of nuclear source conditions of potential interest in CTBT monitoring. 相似文献
5.
V. V. Adushkin 《Pure and Applied Geophysics》2001,158(11):2217-2226
—?A statistical procedure is described for estimating the yields of underground nuclear tests at the former Soviet Semipalatinsk test site using the peak amplitudes of short-period surface waves observed at near-regional distances (Δ < 150 km) from these explosions. This methodology is then applied to data recorded from a large sample of the Semipalatinsk explosions, including the Soviet JVE explosion of September 14, 1988, and it is demonstrated that it provides seismic estimates of explosion yield which are typically within 20% of the yields determined for these same explosions using more accurate, non-seismic techniques based on near-source observations. 相似文献
6.
Generally the decomposition of a seismic moment tensor is not unique. However, to favorably view the characteristics of a certain seismic source, one must decompose a seismic moment tensor into parts according to assumptions about the properties of the seismic source. Different from natural earthquakes in which the shear dislocation component plays a predominant role in the source process, and the seismic moment tensor can be separated into an isotropic component, a double couple, and a compensated linear vector dipole (CLVD), underground nuclear explosions have three major components in their source process, i.e., the explosion, the tensional spalling, and the tectonic strain release associated with the explosion. In such a situation the conventional moment tensor decomposition for earthquakes is not convenient to estimate the yield of the explosion and to characterize the tectonic strain release. In this paper, an alternative decomposition scheme is proposed to deal with the moment tensor of underground nuclear explosions, which might benefit the approach to study the tectonic strain release induced by underground nuclear detonations. 相似文献
7.
自2006年至2017年,朝鲜民主主义人民共和国在中朝边界地区的试验场进行了6次地下核试验.本文综合报道根据东北亚地区的宽频带数字地震资料利用地震学方法对这六次地下核爆炸的研究.结果表明,朝鲜地下核试验在区域台网产生的地震记录具有典型浅源爆炸的特征.针对上述资料发展了处理核爆数据的方法并据此得出各次朝鲜核爆的地震学参数,包括事件识别、当量测定、以及震中相对定位等.对6次核爆和4次天然地震P/S类型谱振幅比的统计分析表明,2 Hz以上台网平均谱振幅比可以正确地将朝鲜核爆从天然地震中识别出来,从而有效监测在朝鲜半岛进行的当量大于0.5 kt的地下核试验.同时也发现,建立在体波-面波震级比之上的识别方法不适用于朝鲜核试验场.通过建立中朝边界地区基于Lg波的体波震级系统,计算了各次朝鲜核试验的体波震级mb(Lg),并由此估计了它们的地震学当量,其值介于0.5 kt至60 kt之间.由于缺少爆炸埋藏深度的数据,上述当量有可能被低估,因而有必要对深度影响做进一步研究.以第一次爆炸的位置为参考震中,利用Pn波相对走时数据和高精度相对定位方法获得了各次核爆在试验场中的精确定位. 相似文献
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The Comprehensive Nuclear-Test-Ban Treaty prescribes the use of seismic stations and arrays as the main measure for verification of Treaty compliance. Since the inception of the Treaty, a vast amount of open source earth observation satellite data has become available. This paper investigates the potential for combining seismic and satellite data for more effective monitoring and response. With data acquired before, during and after the alleged North Korean underground nuclear test on October 9, 2006, wide area change detection techniques using medium resolution optical/infrared satellite sensors are combined with localized high-resolution imagery to attempt to pinpoint the test location within the area identified by the seismic measurements. Problems associated with the timeliness, degree of coverage and ambiguity of the remote sensing data are pointed out, however it is generally concluded that their integration into the CTBT regime would valuably complement the existing seismic observation network. 相似文献
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The problems of initiation of earthquakes by other strong earthquakes and by underground nuclear explosions are considered. For this purpose, special software was designed that made it possible to process all of the world catalog data on earthquakes of 1950–2005. A more effective and reliable method was applied to the analysis of seismic activity, taking into account its background state. As a result, it is unambiguously established that the effect of strong earthquakes or explosions is negligibly small. In any case, their effect cannot be recognized from catalog data that served as a basis for many studies of induced seismicity problems. This conclusion is of great significance for assessment of the possibility of real-time prediction of earthquakes. If this effect were to exist, such prediction would become impossible due to unpredictability of the triggering action. 相似文献
12.
张永荣 《地震地磁观测与研究》1992,13(1):24-30
核爆炸与地震相比,围绕爆炸源的初动具有更多的向上记录和更高的振幅周期比,初动可以作为核爆与地震的一个识别标志。某些核爆炸的向下记录。或许是由于低信噪比的原因,记录到的是初至波的第二个半周;其余的也许是由于近P波走时曲线的反射波造成。 相似文献
13.
HE Yongfeng & CHEN Xiaofei . Department of Geophysics School of Earth & Space Sciences Peking University Beijing China . North-West Institute of Nuclear Technology Xi’an China 《中国科学D辑(英文版)》2005,48(12):2118-2122
Since the sign up of CTBT (Comprehensive Test Ban Treaty), the nuclear monitoring and distinguishing has gained great attention by the treaty countries. Seismology is one of the primary technical means available for monitoring compliance to a CTBT. However, there does not exist a single criterion, so far, that can effectively distinguish explorations from earthquakes. It has been known that source time function (abbreviated to STF) of an underground nuclear explosion contains important p… 相似文献
14.
V. V. Svettsov 《Izvestiya Physics of the Solid Earth》2007,43(7):583-591
The results of the numerical modeling of experimental concentrated atmospheric explosions, both nuclear and chemical, are presented. The surface pressure spectra are calculated and constraints are gained on their relation to the energy of surface seismic waves and to earthquake magnitudes. For a more accurate determination of the source parameters of the Tunguska event (June 30, 1908), atmospheric explosions at various altitudes and vertical falls of meteoroids are modeled numerically and their seismic effect is estimated. 相似文献
15.
A. Ya. Sidorin 《Seismic Instruments》2007,43(1):43-55
Detailed analysis of the information contained in the earthquake catalogue of the Kyrgyz digital broadband seismic network over the period from 1994 to 2005 is performed. The graphs of earthquake recurrence were plotted and analyzed. The energy threshold of representativeness of the catalogue was determined. Stroboscopic and Fourier spectra of time series of earthquakes in the range of periods T ≤ 48 h are presented. A similarity between the obtained graph of diurnal course of seismicity with similar graphs for other regions was found. Peculiarities of diurnal course of earthquakes of different energy were studied. Earthquake sampling of the southwestern part of the territory presented in the catalogue was studied separately. Erroneous information in the catalogue caused by explosions is identified. A conclusion is made about a need for special measures to identify the explosions contained in the catalogue. Special algorithms for processing digital seismograms should be used in addition to collecting information about the time of explosions. 相似文献
16.
Yu. F. Kopnichev I. N. Sokolova K. N. Sokolov 《Izvestiya Physics of the Solid Earth》2013,49(6):786-795
The characteristics of the attenuation field of short-period shear waves in the region of Nevada nuclear test site (NNTS) are studied. The seismograms of underground nuclear explosions (UNEs) and earthquakes recorded by three seismic stations in 1975–2012 at the epicentral distances of up to 1000 km are processed by the methods based on the analysis of the amplitude ratios of Sn to Pn and Lg to Pg waves, as well as the S-coda envelopes for close events. It is shown that the structure of the attenuation field in the Earth’s crust and upper mantle in the NNTS region experienced significant temporal variations during the interval of nuclear operations. The strongest variations were associated with UNEs conducted in the Pahute Mesa area, which held about two-thirds of the most intense explosions. Our data indicate that temporal variations in the structure of the attenuation field are related to the migration of deep fluids. A comparison of the general characteristics of the attenuation field in the regions of the three large nuclear test sites is presented. 相似文献
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O. K. Kedrov E. O. Kedrov N. A. Sergeyeva L. P. Zabarinskaya V. R. Gordon A. B. Chulkov 《Izvestiya Physics of the Solid Earth》2010,46(11):974-999
The Method of Dynamic Calibration (MDC) of stations of the International Monitoring System (IMS) was developed for calibrating
regions where no underground nuclear explosions were carried out, with the purpose of providing conditions for implementation
of the Comprehensive Nuclear-Test-Ban Treaty (CTBT) in nontrivial cases. Initially, the MDC had been presented in [Kedrov,
2001; Kedrov et al., 2001; Kedrov O.K. and Kedrov E.O., 2003] and then considered in detail in [Kedrov et al., 2008]. The
core of MDC relates to adapting diagnostic parameters for the identification of underground nuclear explosions (UNE) and earthquakes
elaborated for the region of Eurasia, taken as a basic region (BR), for other researched regions that differ from BR in the
character of the attenuation of seismic waves. The unique characteristic of this method lies in the fact that calibration
of diagnostic parameters with the help of attenuation coefficients b
Δ at varied source-station traces is implemented using only natural seismicity data within the limits of an explored region
and does not require special underground chemical explosions. The MDC algorithm is implemented in the research program ”Kalibr”,
which was tested by using the experimental data from Eurasia region. It is shown in this work that MDC can be used for calibration
of regions where a very low level of natural seismicity is observed. According to the results of the calibration of diagnostic
parameters at IMS stations in several regions of North America, Africa, and Asia, the approximate classification of propagation
conditions for seismic signals at source-station traces in platform and tectonically active regions is made. The results for
the development of two research programs, “Spektr” and “Signal”, are presented; this software is intended for automation of
calculation procedures for spectral diagnostic parameters of UNEs’ and earthquakes’ identification by amplitude spectra of
P waves and by the maximal amplitudes of P, S, and LR signals. The application of these programs allowed us to accelerate the whole calibration procedure for a particular source-station
trace using the ”Kalibr” program. 相似文献
19.
The government of Ghana in a bilateral agreement with the Preparatory Commission for the Comprehensive Nuclear Test-Ban Treaty Organization (CTBTO) has established a National Data Center in Ghana with the aim of monitoring the testing of nuclear explosions. Seismic, hydroacoustic, radionuclide and infrasound methods are used for the monitoring. The data center was commissioned on 3 February, 2010 at the Ghana Atomic Energy Commission. At present Ghana does not have any operational, centralised data (seismic, hydroacoustic, radionuclide and infrasound) acquisition system with the capability of accessing data from other international stations. Hence, the need of setting up the National Data Center which would enable us constantly monitor, manage and coordinate both natural and man-made seismic activities in the country and around the globe, upload data to the International Data Center (IDC) as well as receive and use International Monitoring System (IMS) data and IDC products for treaty verification and compliance. Apart from these, the center also accesses and analyzes seismic waveforms relevant to its needs from the International Data Center; makes data available to its stakeholder institutions for earthquake disaster mitigation; reports on all aspects of disasters related to earthquake to the relevant government agencies that deal with disasters; makes recommendations to the government of Ghana on earthquake safety measures; provides information to assist government institutions to develop appropriate land and building policies. The center in collaboration with stakeholder agencies periodically organises public lectures on earthquake disaster risk mitigation. 相似文献
20.
Shen Ping Zheng ZhizhenInstitute of Geophysics SSB Beijing ChinaCenter for Seismic Data Informadon SSB Beijing China 《中国地震研究》1996,(3)
In this paper,the nonstationary theory of Wigner Distribution is used to discriminate between underground nuclear explosions and natural earthquakes.Five underground explosions in Kazakhstan region and seven regional earthquakes in its adjacent areas have been analyzed.The result shows that the transient spectra of underground nuclear explosions are concentrated in the frequency range of 5-10 Hz,while the transient spectra of natural earthquakes are distributed widely from lower frequency to higher frequency.The transient frequency of nuclear explosions shows linearity in the first stage(0相似文献