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1.
Panzera F. Lombardo G. Longo E. Langer H. Branca S. Azzaro R. Cicala V. Trimarchi F. 《Natural Hazards》2016,86(2):385-399
A preliminary study targeting to evaluate the local seismic response was performed in the eastern flank of Mt. Etna (southern Italy) using ambient noise measurements. The obtained spectral ratios were subdivided through cluster analysis into different classes of fundamental frequency permitting to draw an iso-frequency contour map. The analysis set into evidence the extreme heterogeneity of lava sequences, which makes difficult to identify a single seismic bedrock formation. Another important outcome, concerning the local seismic effects in terms of frequency and azimuth, is the important role played by the fracture fields associated with the main structural systems of the area. The existence of two zones with strong directional effects striking WNW–ESE and NW–SE, nearly orthogonal to the orientation of the main fracture fields, corroborate such hypothesis.
相似文献2.
提高地震资料的信噪比是地震资料处理的关键,叠前去噪是进行噪声压制的主要处理技术。小波变换方法由于具有同时在时间域与频率域分析的特点,在信号的分析处理方面得到广泛的应用;笔者采用小波变换把叠前地震数据分为不同的频段,并对包含干扰波的频段采用中值滤波消除干扰,再运用小波反变换来重构去噪后的记录;该技术不仅实现了噪声压制,还达到了保持宽频带的目的,应用于实际资料处理中,取得了很好的去噪效果。 相似文献
3.
利用多尺度边缘检测研究碳酸盐岩裂缝分布 总被引：14，自引：1，他引：13
裂缝检测与图像分析中的边缘检测有许多相似之处,因此,能够借助某些边缘检测理论并结合实际地震资料形成有效的裂缝检测方法。作者基于小波多尺度边缘检测理论,结合地震波场对裂缝的多尺度特性,提出了碳酸岩裂缝预测的多尺度边缘检测方法。方法的主要思想是：利用小波变换械的局部极值,检测出三维地震记录裂缝点特征位置,并通过调整模值在图像中的灰度,自动识别裂缝发育区的范围。 相似文献
4.
岩浆岩体严重影响井田的煤质、储量等,对采区工作面布置、巷道掘进及回采工作造成严重的影响,因而探测岩浆岩侵入煤层的范围对煤矿安全高效生产具有重大意义。在总结岩浆岩侵入体的地质特征基础上,建立岩浆侵入煤层地震地质模型,通过正演,对多种属性进行交互分析,发现主频能量属性与振幅类属性对岩浆岩反应较为敏感,并且随着岩浆岩厚度的逐渐增加能量类与振幅类属性逐渐降低。通过对QN煤矿103工作面高密度三维地震资料连井剖面10煤进行属性分析,发现频带宽度、中心频率、主振幅属性可以较好地识别岩浆侵入区。通过对勘探区10煤层进行频带宽度、中心频率和主振幅属性分析识别岩浆侵入区,其识别结果与钻孔实际揭露吻合较好,证明采用地震属性识别技术可以识别煤层岩浆岩侵入区范围。 相似文献
5.
时频域高分辨地震层序识别 总被引：5，自引：0，他引：5
地震信号频率随着时间的不稳定变化包含了地下反射层序特征的重要信息,时频分析是检测地震信号局部谱特征的重要工具。为适应实际地震信号处理,对S变换改进后得到一种新的广义S变换,用于分析和补偿地震信号的高频成分,得到了精细的地震层序识别剖面。实际资料处理表明,它对砂岩油气藏的成层特征的分析具有分辨率高和高信噪比的优点。地震信号的广义S变换时频谱分解可作为地震层序识别和解释的重要补充。 相似文献
6.
在Hudson理论的基础上推导出基于弹性—声学近似的裂缝模型反射系数计算公式,然后用变参考慢度Rytov近似波场延拓算子,对给定裂缝模型进行正演和偏移,并分析其波场特征,得到以下三点结论:1在当前地震分辨率下,不能识别单个裂缝,但可以探测裂缝发育带;2裂缝带达到一定的宽度和密度,可以用地震方法检测裂缝的分布,潜山内幕反射波的范围与强弱,有利于研究裂缝发育带的宽度和密度;3裂缝带的低频复波反射,表明在裂缝发育带,地震波频率减低,意味着用地震波的频率特征是可以检测裂缝。 相似文献
7.
This paper highlights the seismic microzonation carried out for a nuclear power plant site. Nuclear power plants are considered to be one of the most important and critical structures designed to withstand all natural disasters. Seismic microzonation is a process of demarcating a region into individual areas having different levels of various seismic hazards. This will help in identifying regions having high seismic hazard which is vital for engineering design and land-use planning. The main objective of this paper is to carry out the seismic microzonation of a nuclear power plant site situated in the east coast of South India, based on the spatial distribution of the hazard index value. The hazard index represents the consolidated effect of all major earthquake hazards and hazard influencing parameters. The present work will provide new directions for assessing the seismic hazards of new power plant sites in the country. Major seismic hazards considered for the evaluation of the hazard index are (1) intensity of ground shaking at bedrock, (2) site amplification, (3) liquefaction potential and (4) the predominant frequency of the earthquake motion at the surface. The intensity of ground shaking in terms of peak horizontal acceleration (PHA) was estimated for the study area using both deterministic and probabilistic approaches with logic tree methodology. The site characterization of the study area has been carried out using the multichannel analysis of surface waves test and available borehole data. One-dimensional ground response analysis was carried out at major locations within the study area for evaluating PHA and spectral accelerations at the ground surface. Based on the standard penetration test data, deterministic as well as probabilistic liquefaction hazard analysis has been carried out for the entire study area. Finally, all the major earthquake hazards estimated above, and other significant parameters representing local geology were integrated using the analytic hierarchy process and hazard index map for the study area was prepared. Maps showing the spatial variation of seismic hazards (intensity of ground shaking, liquefaction potential and predominant frequency) and hazard index are presented in this work. 相似文献
8.
《地学前缘(英文版)》2020,11(3):989-998
Regions of slow strain often produce swarm-like sequences, characterized by the lack of a clear mainshock-aftershock pattern. The comprehension of their underlying physical mechanisms is challenging and still debated. We used seismic recordings from the last Pollino swarm (2010–2014) and nearby to separate and map seismic scattering (from P peak-delays) and absorption (from late-time coda-wave attenuation) at different frequencies in the Pollino range and surroundings. High-scattering and high-absorption anomalies are markers of a fluid-filled fracture volume extending from SE to NW (1.5–6 Hz) across the range. With increasing frequency, these anomalies approximately cover the area where the strongest earthquakes occurred from the sixteenth century until 1998. In our interpretation, the NW fracture propagation ends where carbonates of the Lucanian Apennines begin, as marked by a high-scattering and low-absorption area. At the highest frequency (12 Hz) the anomalies widen southward in the middle of the range, consistently marking the faults active during the recent Pollino swarm. Our results suggest that fracture healing has closed small-scale fractures across the SE faults that were active in the past centuries, and that the propagation of fluids may have played a crucial role in triggering the 2010–2014 Pollino swarm. Assuming that the fluid propagation ended at the carbonates barrier in the NW direction, fractures opened new paths to the South, favoring the nucleation of the last Pollino swarm. Indeed, the recently active faults in the middle of the seismogenic volume are marked by a high-scattering and high-absorption footprints. Our work provides evidence that attenuation parameters may track shape and dynamics of fluid-filled fracture networks in fault areas. 相似文献
9.
山前复杂构造须家河组致密储层裂缝发育带综合预测 总被引：2，自引：1，他引：1
川西龙门山山前的须家河组气藏为受断层和构造控制的裂缝-岩性气藏,针对这类裂缝性复杂气藏利用基于地质成因的地史时期应力场(应变)分析、沿层构造属性分析和叠前三维地震数据相干体分析等手段进行分析处理可以达到气藏裂缝发育带预测目的.实践表明,虽然在山前复杂构造带利用地震资料研究储层裂缝及其发育带确实有较大的难度,但联合运用基于应力场和断层与构造属性的裂缝综合预测方法,仍然在龙门山前须家河组气藏的应用研究中取得到令人满意的地质效果. 相似文献
10.
《Physics and Chemistry of the Earth, Part A: Solid Earth and Geodesy》2000,25(3):325-328
The observations of the disturbances of the acoustic, electric and magnetic fields at various distances from a vibroseismic source (5–12 Hz frequency range) are presented. Two centrifugal vibrosources (VS) with sinusoidal vibrational force onto the ground of 100 and 40 tons are used. Infrasonic signals are reliably recorded at distances up to 50 km. When the acoustic signal is large, a seismic signal with the same arrival time is also detected. Magnetic and atmospheric electric fields are detected at distances of several kilometers. These signals have practically zero lag time and precede the acoustic and seismic signals. The disturbances caused by the VS were also registered by telluric field measurements at distances up to 2 km from the source. 相似文献
11.
In the fracture pattern of the Sydney Basin, various fracture and stress domains that are spatially related can be recognised. At least for the western region of the Basin, periodic, relatively narrow domains (termed fault and joint swarms) that have a submeridional trend are believed to be similar to the Lapstone Monocline‐Kurrajong Fault structures, and may extend into the Lower Palaeozoic basement. An overall, horizontal N‐S and NE‐SW oriented principal compressive stress (σ1) measured in collieries and inferred from earthquake events at depths of 10–20 km is a regional phenomenon (possibly Basin‐wide), which can be expected to be locally modified close to geological structures, especially in and close to fault and joint swarms, near major normal faults, and near minor thrust and strike‐slip faults. The interaction of colliery roadway drivage, local structures (faults and/or cleat) and the stress field permits inferences to be made about virgin stresses in coal seams. Some earthquakes coincide with fault and joint swarms, and others tend to have occurred close to or at swarm endpoints. It is concluded that the overall fracture pattern resulted from the cumulative development of fault and joint systems from mid‐Permian to Recent time. The comprehensive analysis of this pattern and its relationship to stress fields and seismic activity will require much more information. 相似文献
12.
目前国内、外油气勘探已经进入岩性油气藏勘探阶段,其中致密碳酸盐岩或页岩油气勘探具有远大前景。这类致密储层中裂缝是油气储集的主要空间。用模拟地震子波的小波函数对原始三维地震数据体作小波变换,可以得到不同频带（分辨率）的地震数据体。分别对具有不同分辨率的三维地震数据体进行C3相干处理,其中低频相干体突出了断裂的信息,而高频相干体则突出反映了受断裂控制下的小断裂或裂缝的发育信息,通过合理的融合系数有选择地对C3相干数据进行融合,获得了能够高精度分辨裂缝发育特征的相干数据体,由此提高了裂缝检测和储层预测的精度。 相似文献
13.
Nuclear power plants are designed to prevent the hazardous effects of the earthquakes and any external events to keep the safety of the plant. Ninety-one shallow seismic refraction profiles were performed to determine shear wave velocity of the engineering layers at the site of El Dabaa area that is situated to the northern coastline of Egypt for seismic hazard microzonation evaluation according to hazard index values. A microzonation is a procedure of delineating an area into individual zones having different ranks of numerous seismic hazards. This will aid in classifying areas of high seismic risk which is vigorous for industrial design of nuclear structures. The site response analysis requires the characterization of subsurface materials considering local subsurface profiles of the site. Site classification of the area under investigation was undertaken using P- and S-waves and available borehole data. The studied nuclear power plant site has been characterized as per NEHRP site classification using an average velocity of transverse wave (V s 30 ) of depth 30 m which acquired from seismic survey. This site was categorized into two site classes: the major one is “site class B,” and the minor one is “site class A.” The attenuation coefficient, the damping ratio and the liquefaction potential are geotechnical parameters which were derived from P- and S-waves, and have their major effects on the seismic hazard contribution. 1D ground response analysis was carried out in the places of seismic profiles inside the site for estimating the amount of ground quaking using peak ground acceleration (PGA), site amplification, predominant frequency and spectral accelerations on the surface of ground by the DEEPSOIL software package. Seven factors (criteria) deliberated to assess the earthquake hazard index map are: (1) the peak ground acceleration at the bedrock, (2) the amplification of the site, (3) the liquefaction potential, (4) the main frequency of the earthquake signal, (5) the average V s of the first 30 m from the ground surface, (6) the depth to the groundwater and (7) the depth to the bedrock. These features were exemplified in normalized maps after uniting them to 0–1 scores according to some criteria by the minimum and maximum values as linear scaling points. Multi-criteria evaluation is an application of multi-criteria decision analysis theory that used for developing a seismic hazard index map for a nuclear power plant site at El Dabaa area in ArcGIS 10.1 software. Two models of decision making were used in this work for seismic hazard microzonation. The analytic hierarchy process model was applied to conduct the relative weights of the criteria by pairwise comparison using Expert Choice Software. An earthquake hazard index map was combined using Weighted Linear Combination model of the raster weighted overlay tool of ArcGIS 10.1. The results indicated that most of the study site of the nuclear power plant is a region of low to moderate hazard; its values are ranging between 0.2 and 0.4. 相似文献
14.
Amrita Yadav D. Shashidhar K. Mallika N. Purnachandra Rao Sunil Rohilla H. V. S. Satyanarayana D. Srinagesh Harsh Gupta 《Natural Hazards》2013,69(1):965-979
New empirical relations are derived for source parameters of the Koyna–Warna reservoir-triggered seismic zone in Western India using spectral analysis of 38 local earthquakes in the magnitude range M L 3.5–5.2. The data come from a seismic network operated by the CSIR-National Geophysical Research Institute, India, during March 2005 to April 2012 in this region. The source parameters viz. seismic moment, source radius, corner frequency and stress drop for the various events lie in the range of 1013–1016 Nm, 0.1–0.4 km, 2.9–9.4 Hz and 3–26 MPa, respectively. Linear relationships are obtained among the seismic moment (M 0), local magnitude (M L), moment magnitude (M w), corner frequency (fc) and stress drop (?σ). The stress drops in the Koyna–Warna region are found to increase with magnitude as well as focal depths of earthquakes. Interestingly, accurate depths derived from moment tensor inversion of earthquake waveforms show a strong correlation with the stress drops, seemingly characteristic of the Koyna–Warna region. 相似文献
15.
塔里木盆地塔中北斜坡奥陶系鹰山组深部优质岩溶储层的形成与分布 总被引：2，自引：0，他引：2
塔中地区是塔里木盆地的重点勘探区域,奥陶系鹰山组蕴藏了丰富的油气资源。鹰山组发育大套台地相碳酸盐岩,以高能相的台内滩沉积为主。鹰山组埋藏较深,但岩溶储层呈大面积厚层状分布。早奥陶世塔中I号断裂使得塔中隆起隆升并遭受强烈剥蚀形成下奥陶统鹰山组顶部风化壳,以孔洞型和裂缝-孔洞型储层为主。通过古地貌恢复、地震属性分析和地震测井联合波阻抗反演技术和方法识别溶洞发育带和断层裂缝发育带,确定出有利储层的分布范围。研究认为,岩性岩相是岩溶型储层发育的重要基础,层间岩溶控制了储层的成层性和横向展布规模,断裂和裂缝网络是岩溶水的主要渗滤通道,埋藏岩溶形成大量有效的缝洞空间,极大地提高了储集性能。研究发现,优质储层主要分布在鹰山组顶面以下120m地层厚度范围内,横向有一定连通性,在断层、构造裂缝和溶蚀作用下形成统一的储集体,呈准层状展布。 相似文献
16.
利用间接边界元方法,在频域内求解了层状场地中局部不均体对平面P波的散射。利用精确的土层动力刚度矩阵进行自由场反应分析,求得位移和应力响应。通过计算虚拟分布荷载的格林影响函数,求得相应位移和应力;根据边界条件确定虚拟分布荷载,最终得到问题的解答。研究了入射P波时,不均体宽度、埋深、厚度、入射角、入射频率度等参数对地表位移幅值的影响,并与相应自由场的结果进行了比较。不均体对P波散射有重要影响,在工程场地地震安全性评价中,应合理考虑局部不均体对场地设计地震动参数确定的影响。 相似文献
17.
18.
通过在九寨沟县聚宝山不同位置处布设微震监测仪器,采集到了九寨沟MS7.0级地震后几次典型的余震监测数据。对地震动监测剖面上1#（1414 m）和2#（1551 m）监测点的余震加速度响应数据进行系统的研究,表明:（1）孤立突出山体的地形放大效应显著,各监测点的水平向加速度幅值一般要大于竖直向;（2）在地震过程中,聚宝山近SN走向的山脊沿水平东西方向震动更为猛烈,即沿东西两侧发生猛烈"甩动",形成沿山脊走向发育的地震裂缝。对余震监测数据的研究证实了斜坡地震动方向效应的存在,聚宝山山顶处的2#监测点水平东西向峰值加速度放大效应明显强于其他方向,地震波能量在水平东西向上得到显著放大,因而坡顶处建筑物也更容易沿该方向发生破坏,证明了局部地形对斜坡地震动力响应具有控制效应;（3）2#监测点竖直向主频值主要为6~12 Hz,水平东西向主频值主要为5~8 Hz,水平南北向主频值主要为5~10 Hz,其水平东西向主频率值主要为低频成分;相较于1#监测点,2#监测点各向的主频值发生明显衰减,即随着高程的增加,地震动主频值呈现出减小趋势,在斜坡上部地震波以中低频为主。通过进一步地计算分析得出,九寨沟地震诱发单薄山脊、条形山体、多面临空山体等地形放大效应与地震波半波长密切相关,斜坡在局部地形尺寸与地震波丰富的波长成分的耦合作用下,地形放大效应显著,山体震害发育。 相似文献
19.
Propagation of seismic waves through soil layers would drastically change the frequency content and amplitude-based features of ground motions at the surface. These alterations are known as seismic site effects. Computation of site effects of high-populated areas such as large cities is of great importance (e.g., it is used in development of seismic microzonation of a region). Shiraz is one of the most populous cities of Iran and is located in a high seismic hazardous region. A representative clay site in this city is selected to assess local site effects. The time series and random vibration theory procedure in the frequency domain are implemented to analyze the aforementioned site. Furthermore, the nonlinear dynamic soil behavior is simulated by the equivalent linear method and the nonlinear method via DEEPSOIL program. Three types of soil column uncertainties such as shear wave velocity, modulus reduction, and damping ratio of soil layers as well as depth of underlying rock half-space (D bed) are considered herein. The mean amplification and standard deviation of natural logarithm of amplification factors are computed for a variety of analysis types. The results of the current study show that the computed mean and standard deviation of amplification factor in ln units by considering only V S uncertainty are in good agreement with the corresponding ones by considering V S and modulus reduction and damping ratio variabilities simultaneously for the studied site. Furthermore, it seems that the effect of bedrock depth in definition of spectral shapes of the Iranian seismic building code should be taken into account. 相似文献
20.
页岩储层由于骨架和孔隙结构的微观非均质性,能够在地震频段内引起波诱导的孔隙流体流动相关的弹性频散和衰减,但声波测井和实验室超声实验测量频率段远超地震频段,不可避免产生测量速度和衰减差异。这里基于澳大利亚惠灵顿地区的页岩岩心在干燥和水饱和条件下地震频段的弹性和衰减测量结果,考虑频变反透射系数和衰减对地震波反射的影响,针对不同层厚的页岩储层开展地震响应计算,并利用Wigner-Ville分布时频分析技术讨论了页岩频散、衰减性质及层厚对其地震响应规律的作用。对于无明显速度频散和衰减的页岩储层,顶、底反射振幅的频变属性受调谐效应控制,主要呈现出低频异常和陷频特征;而对于速度频散和衰减强烈的储层,顶、底反射振幅的频变属性同时受到调谐效应与储层本身频散衰减性质的作用。干燥和含水页岩储层地震响应的频变性质差异有助于加深对含流体页岩地震响应特征的理解,而基于地震频段实测数据正演和时频分析技术,对于提高页岩的地震勘探精度和流体识别具有重要的作用。 相似文献