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宽频带地震仪可以连续不断地记录地面振动信号,进而探索地壳振动的变化与地震前兆之间的物理关联性。选取2019年6月17日四川长宁Ms6.0地震前后的震中500km范围内15个宽频带地震仪的连续波形数据,通过傅里叶变换计算分析地震前后的地壳振动低频信号(8× 10~(-5)～2×10~(-4)Hz)的振幅谱变化,并对低频信号源进行定位,探讨地震前后地壳振动异常演变规律和物理特征。结果表明,长宁Ms6.0地震前10天,震源区500km范围内多个地震台的低频信号(8×10~(-5)～2×10~(-4)Hz)出现显著的增强现象,地震前2天出现异常源的集中区域,来源在震源区100km范围内,异常的时间尺度和空间区域与长宁地震基本一致。利用连续波形记录进行地壳振动研究可能对地震短期至短临预报具有重要的参考价值。 相似文献
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钻井过程中钻头对井底的冲击振动为钻头前方地层的探测提供了震源，可用来消除钻井过程中的地质不确定性和降低钻井风险.本研究在分析井下钻头振动信号特点的基础上，根据现代地震观测技术的新发展，将多道勘探地震仪和流动数字地震仪的性能进行了对比分析，将天然地震的观测设备和分析方法应用到随钻地震检测中，提出了一套新的随钻地震检测方案，利用高灵敏度流动数字地震仪连续检测钻井过程中的钻头振动信号，初步现场试验表明该技术方案可行，获得的信号信噪比高，易于钻井工程师掌握，为随钻地震技术提供了新的技术路线. 相似文献
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《地球物理学进展》2017,(1)
在京津城际高铁的廊坊段,使用了1000多个数字地震检波器进行连续长时间观测.位于高铁高架桥轨道下方的检波器记录了列车通过时引起的地表振动.数据分析显示,列车经过轨道不同位置处引起的地表振动信号差异较大,而同一位置处不同列车引起的振动则具有很好的相似性,表明影响振动波形的主要因素是高架桥梁及轨道,可以利用长期观测数据来作为轨道及高架结构失稳的预警.对振动信号频率分析的结果表明,列车经过时以及经过后的十几秒时间内存在着能量较强的简谐波振动,可能和轨道及桥梁结构有关.使用轨道下方的采集信号与2~4 km外的另外一条观测测线信号进行互相关处理,可以得到信噪比很高的虚震源记录,表明列车振动信号可以沿地表传播几公里甚至更远. 相似文献
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《国际地震动态》1991,(6)
海底地震仪是一种可检测海底振动的系统。在地震学中,地震仪的用途是双重的:一种用途是通过接收已知振动源(即人工地震,也可称为可控震源,或天然地震)的地震波来研究地球内部构造。作为可控源研究的震源来说,通常采用气枪,这种气枪利用高压空气可在海中产生强大的声音。地震仪是研究地球内部的一种最有力的和最精确的观测手段。地震仪的另一种用途是研究地震活动性本身。我们已研制出了一种重60千克的小型海底地震仪,这种仪器可以保证在海中极为困难的条件下进行观测。这种海底地震仪已成功地弄清楚了过去在陆上观测一直不清楚的海底构造。海底地震仪还可成功地应用于研究深海沟地区和洋中脊地区(即板块的诞生处或消减处)的地震活动性。 相似文献
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通过对地震发生时铁路采取的应急处置措施和我国高速铁路地震监测系统现状的分析,提出建设铁路地震监测预警系统的必要性.为确定地震监测预警台站,研究在高速铁路沿线布置台站的技术方案,特在汉宜高速铁路进行列车通过噪声试验,采集列车通过测点引起的振动数据,探讨列车通过的最大振动加速度和测点与铁路正线距离之间的衰减关系.利用统计分析方法分析最大振动加速度和距离之间的衰减关系.利用频域分析方法设置低通滤波器,对列车引起的振动数据进行滤波,进一步减少列车对台站监测预警数据的影响,所提出的衰减关系及数据初步处理方法对高速铁路地震监测预警台站选取和建设具有指导意义. 相似文献
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时移地震中新提出的多道观测系统重复性，逐一应用于面元，可以给出每个面元单一的观测系统重复性，形成对应叠后成像的地震道重复性的面分布，对于评估时移地震重复性具有重要意义.前人研究抽象了多道间观测系统重复性与单道间观测系统重复性的关系，给出了多道观测系统重复性的衡量方法及其理论依据.其理论中依赖了地震数据重复性与单道观测系统重复性的线性关系模型，而这一关系在单道观测系统重复性的有限范围内较为准确.针对这一问题，本文提出了X模式拟合的关系模型，与全范围的单道地震数据重复性随观测系统重复性的变化趋势更好地吻合，并采用对大单道观测系统重复性的向X节点的收缩，使原多道观测系统重复性的相应关系在整个数据范围内基本成立.基于实际数据的研究表现了该方法的数据分析结果的新特性和应用价值. 相似文献
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多道地震反封测线穿越了中部冲绳海槽的中央裂谷带,测线位于夏岛一84海凹附近,在这里观浏到了很高的热流值,这些多道反射记录显示出一些可能是岩浆房顶邵产生的反射波. 用10台海底地震仪和4叱炸药进行了地震折射研完,结果表明,中部冲绳海槽的地壳内,在一个强烈衰减的、6.8k血/s的层上边,有一个厚5 km、6.0 km/s的层.即使在震中距大于130 km的地方,也没有观测到来自莫霍界面的信号.这里的地壳被认为是大陆型的,但是地壳下部的Q值低,而上地慢顶部的波速和Q值都狠低. 用10台海底地震仪记录了一个月的天然地震,在这个地区测到了十分活跃的微震活动.有些海底地震仪记录到一些特殊震相,怀疑它们是来自岩浆席的反射波,类似于火山氮动产生的特珠波. 相似文献
8.
地震仪灵敏度参数的精度直接决定了地动量记录恢复的准确度.在中国国家地震台网的四个台站布设了多套参考地震仪,分别用地震事件和地脉动噪声作为信号源,用相关分析方法计算了在线地震仪相对于参考地震仪的灵敏度.结果表明:地震事件和地脉动噪声在垂直、南北、东西三个分量均可稳定获取在线地震仪灵敏度的可靠估计,并且两种方法表现出良好的一致性.对于无法中断观测的在线地震仪而言,本文提出的利用地脉动噪声相关分析估计仪器灵敏度是一个有效方法.在测试的四个台站中,蒙城台和九江台两个台站部分分量灵敏度误差超过3%,其中蒙城台的垂直向和南北向误差将近 10%.分析结果表明,对中国国家地震台网地震仪的灵敏度进行普查非常有必要,这项工作对提高我国地震台站的观测数据质量具有重要意义. 相似文献
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Seismic features of vibration induced by train 总被引：2，自引：0，他引：2
Introduction Collisions can be generated continuously by the passage of trains due to the surface irregu-larities of wheels and rails. When a fully loaded train or freight with weight of thousands tons runson deformed rails, it may induce strong vibrations. Such vibrations may transmit several kilome-ters to result in building damage. For instance, the famous Longmen Grottoes near the Luoyangcity in China has been seriously damaged by the ground trembling by trains pasting near it(http:… 相似文献
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通过在上海地区开展深、浅地震反射、地震宽角反射/折射、高分辨地震折射和大地电磁测深等联合剖面探测, 获得了该地区近地表至Moho面的精细速度结构、电性结构和深浅构造关系.结果表明, 该地区地壳可划分为上、中、下三个组成部分.其中，上地壳厚为12～14 km，波速为57～59 km/s；中地壳厚度约为10 km，波速为59～62 km/s；下地壳厚为10～11 km, 波速为62～63 km/s，Moho面深度约为32 km.剖面浅部地质构造复杂，共解释出12条特征明显的断裂.其中，除3条断裂错断结晶基底（G界面）并向下延伸至上地壳底界面外，其他断裂均在深度3～5 km以上终止或收敛于G界面之上.此外，仅在剖面西侧基底下部约13～15 km埋深处发现一厚度在2 km左右的壳内高导层.所以，在综合各方面资料后分析认为，在剖面经过地区不存在发生大地震的深部构造条件，近地表所存在的活动断层是未来产生对该区有影响地震的震源区. 相似文献
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《中国科学:地球科学(英文版)》2017,(10)
The active sources generate seismic waves transmitting appropriate through the deep is underground key and can be used to image Abstract high-resolution subsurface structures.Therefore,an seismic source the factor to active source exploration.In order to study the structure of continental crust and its temporal variations,we selected an artificial seismic source generated from releasing air bubbles in water(airgun source hereinafter)out of a variety and of artificial sources like the is explosion,new electronic sparkers,source hammering,eccentric proven vibration,be heavy-duty train vibration,vibroseis etc.Airgun Three source Fixed a type of artificial that have been to environmentally friendly,safe,and highly efficient.Airgun western Signal China Transmission and Stations(FASTS)have been for built a few years ago in Yunnan,Xinjiang,and Gansu provinces in have been continuously them running several years.Seismic waves generated away by the the airgun sources are highly seismic reproducible waves and stacking in of can produce can good seismograms on 1300 stations km far from source,for instance,an produced Xinjiang FASTS be well about recorded 60 nearly away after 5000 stacking,China covering area of 6 million km2 and penetrating down to of a depth of km.Establishing about 10 FASTSs in would enable long-term illuminate continuous subsurface underground structures,monitoring can all 9.6 million km2 of land area.Treating from airgun sky active sources as lanterns to we achieve the situation with"Beidou surveys the and lantern illuminates underground". 相似文献
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利用中、小容量气枪组成的立体气枪阵列延迟激发震源和海底地震仪(OBS)在我国北部浅海海域开展了人工地震深部地球物理探测试验.基于水深条件和压制水体虚反射、提升低频能量的需要,使气枪震源有足够的输出能量和高品质子波特性,研究了立体气枪阵列延迟激发震源工作机理,经远场子波理论模拟优选了组合参数并进行了海上试验工作.结果表明,中、小容量气枪组成的立体气枪阵列延迟激发震源,适应了浅水海域的激发环境,降低了由虚反射造成的局部陷波和干扰作用,有效地改善了OBS信号的品质,获得了Ps,Pg,PmP,Pn等多种震相.创新了由中、小容量气枪组成的立体气枪阵列延迟激发震源在浅海区OBS探测中的应用,也填补了南黄海海域深地震探测数据的空白,为南黄海、渤海深部地壳结构研究及含油气盆地形成演化研究提供了重要的基础资料. 相似文献
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Exceptionally high ground motions (horizontal peak ground acceleration (PGA) of 1.82g) were recorded at the Tarzana Station during the main shock of the 1994 Northridge earthquake (moment magnitude 6.7 at an epicentral distance of 6 km). At the time of the main shock, the instrument was located near the edge of a 21 m-high ridge with side slopes ranging from 3H:1V to 15H:1V. The ridge is underlain by shallow fill and soft rocks of Medelo Formation.
The objectives of this study were to (1) identify the relative contributions of various factors such as local geology, topography, source mechanism, and travel path on the large ground motions recorded at Tarzana Station and (2) develop an analytical model that could adequately predict observed ground motions at the Tarzana site during the Northridge earthquake and at similar sites during future earthquakes. This study is an integral part of a series of inter-related studies referred to as the ROSRINE research (Resolution of Site Response Issues during Northridge Earthquake) project.
The PGA at the surface of competent bedrock (1 km/s shear wave velocity found about 100 m below ground surface) is estimated by Silva [ROSRINE Study (2000)] at 0.46 gravity (g). To identify the source of ground motion amplification, one-dimensional ( ), two-dimensional (TELDYN and SASSI), and three-dimensional (SASSI) analyses were conducted using both recorded aftershock data and an estimated ground acceleration time histories at a 100 m depth.
The results of the analyses indicate that (1) local geology and topography could only partially account for the observed ground motion amplification, and (2) the PGA and response spectra at a point near the edge of the ridge (the location of the instrument at the time of the main shock) is in good agreement with recorded values when the angle of incident of shear waves (SV waves) at 100 m depth is assumed at 30° from vertical. Considering the local geology and variation of shear wave velocity with depth, the 30° incident angle at 100 m depth corresponds to an 8° incident angle of shear waves at the ground surface. This observation is, in general, consistent with the incident angles of shear waves reported from study of the recorded aftershock data. 相似文献
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Markus Bth 《Physics of the Earth and Planetary Interiors》1975,10(4):369-376
Short-period fundamental-mode Rayleigh waves (Rg) are generally well recorded by short-period seismographs within about 600 km of seismic events, such as explosions, rockbursts and earthquakes, which occur in the upper 3 km of the crust. Studies of these waves from records at the Swedish seismograph network revealed their usefulness to elucidate both path and source properties. They exhibit normal dispersion which requires a superficial low-velocity layer of about 1 km thickness, in part probably weathered and fractured granite. This layer has considerably higher attenuation than underlying more competent rock. The existence of Rg in regional short-period records is a reliable indication of shallow focal depth, and, provided adequate calibration is available, quite accurate depth estimation would be possible from the amplitude ratio of Rg to Sg1. 相似文献
18.
Many crucial tasks in seismology, such as locating seismic events and estimating focal mechanisms, need crustal velocity models. The velocity models of shallow structures are particularly important in the simulation of ground motions. In southern Ontario, Canada, many small shallow earthquakes occur, generating high-frequency Rayleigh (Rg) waves that are sensitive to shallow structures. In this research, the dispersion of Rg waves was used to obtain shear-wave velocities in the top few kilometers of the crust in the Georgian Bay, Sudbury, and Thunder Bay areas of southern Ontario. Several shallow velocity models were obtained based on the dispersion of recorded Rg waves. The Rg waves generated by an m N 3.0 natural earthquake on the northern shore of Georgian Bay were used to obtain velocity models for the area of an earthquake swarm in 2007. The Rg waves generated by a mining induced event in the Sudbury area in 2005 were used to retrieve velocity models between Georgian Bay and the Ottawa River. The Rg waves generated by the largest event in a natural earthquake swarm near Thunder Bay in 2008 were used to obtain a velocity model in that swarm area. The basic feature of all the investigated models is that there is a top low-velocity layer with a thickness of about 0.5 km. The seismic velocities changed mainly within the top 2 km, where small earthquakes often occur. 相似文献
19.
Saman Tavakoli Mahdieh Dehghannejad María de los Ángeles García Juanatey Tobias E. Bauer Pär Weihed Sten-Åke Elming 《Acta Geophysica》2016,64(6):2171-2199
Multi-scale geophysical studies were conducted in the central Skellefte district (CSD) in order to delineate the geometry of the upper crust (down to maximum ～ 4.5 km depth) for prospecting volcanic massive sulphide (VMS) mineralization. These geophysical investigations include potential field, resistivity/induced polarization (IP), reflection seismic and magnetotelluric (MT) data which were collected between 2009 and 2010. The interpretations were divided in two scales: (i) shallow (～ 1.5 km) and (ii) deep (～4.5 km). Physical properties of the rocks, including density, magnetic susceptibility, resistivity and chargeability, were also used to improve interpretations. The study result delineates the geometry of the upper crust in the CSD and new models were suggested based on new and joint geophysical interpretation which can benefit VMS prospecting in the area. The result also indicates that a strongly conductive zone detected by resistivity/IP data may have been missed using other geophysical data. 相似文献
20.
O. V. Pavlenko 《Izvestiya Physics of the Solid Earth》2009,45(10):874-884
For evaluating the parameters of the vibrations of the Earth’s surface in the case of strong earthquakes, which are possible in the future, the regular patterns of the emission and propagation of seismic waves in the North Caucasus regions are investigated. The regional parameters of emission and propagation of seismic waves are evaluated by solution of the inverse problems of stochastic modeling of the accelerograms of the earthquakes, recorded by the seismic station in Sochi. The horizontal components of the strongest earthquakes (M w ～ 3.9?5.6), that occurred in 2002–2006 within a radius of ～300 km from the seismic station, with source depths up to 60 km are modeled. For calculations of accelerograms, estimates of the quality are used, obtained earlier for this region in the form: Q(f) ～ 80 ～ f 0.9. The parameter settings are carried out, which determine the shapes of the source spectra, the amplification of the seismic waves in the Earth’s crust, the weakening of the waves at high frequencies (κ), the parameters that determine the shape and duration of accelerograms, etc. Sufficiently good agreement of the calculated and recorded accelerograms is obtained, the regional characteristics of emission and propagation of seismic waves, which can be used for prediction of the parameters of strong motions in the North Caucasus, are evaluated; however, in the future these characteristics should be studied in more detail. 相似文献