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1.
断层带结构研究对于认识地震的孕育发生、地震破裂过程及其地震灾害具有重要的意义,因而多种方法被用来观测和研究断层带结构,其中断层带围陷波就是有效方法之一.断层带围陷波是由地震波入射到断层带内低速介质与高速围岩之间的界面时在界面内侧经多次反射相干叠加形成,具有大振幅、低频率和频散的特点.由于断层带围陷波在断层带的内部传播,它携带有断层带的介质物性和结构的重要信息,因此可以利用围陷波的波形特征研究断层带的精细结构.本文详细介绍了断层带围陷波的形成机制、传播和特性,全面阐述了断层带围陷波在观测研究、传播和特性理论研究和利用围陷波反演断层带结构的方法及应用三个方面的进展,并探讨了断层带围陷波研究方面存在的不足和问题. 相似文献
2.
汤西断裂的断层围陷波初步研究 总被引：6，自引：0，他引：6
作为断层围陷波方法在城市活断层探测中的首次尝试,我们针对太行山山前断裂带南段的汤西断裂开展了爆炸震源的观测试验。运用数字滤波和频谱分析等技术,由地震记录图分离出了断层围陷波。根据2横测线的观测结果,可确定断层的位置,并可推测断层在该处宽度为200～300m。破裂面较宽,可能与其张性特征有关。分频道地震图显示,断层围陷波具有正频散现象,其低频分量传播较快。这表明断层围陷波是一种面波,可利用其频散规律研究断裂带内介质的物理性质。这次的观测结果也表明,断层围陷波并不局限于新破裂带,在老断层中也能形成和传播。事实上,只要断层带内外的介质在物理性质上有较大的差异,均能产生沿断层传播的围陷波。在城市活断层探测中,断层围陷波的方法具有非常独特的优越性 相似文献
3.
《世界地震译丛》2017,(4)
在地震断层带台阵记录的数据中,研究出了断层带围陷波的一种自动识别算法。使用自动的S波最佳选择来识别地震图中的时间窗,以用于断层带围陷波的后续搜索。该算法计算每个台站记录的各个地震图的5个特征:卓越周期、1s持续时间的能量(代表围陷波)、相对波峰强度、到时延迟以及6s持续时间的能量(代表整个地震图)。共同用这些特征来识别台阵中地震图有统计离群值的台站。将此算法应用于大数据集可以从其他台站地震图中的偶然局部场地放大中识别出真正的围陷波。此方法在1992年美国兰德斯地震破裂区上记录的测试数据集上进行了验证,以前曾在此波形上人工识别出围陷波,然后应用到圣哈辛托断层带上记录的几千个地震事件的更大数据集上。所开发的技术为断层带附近记录的大型地震波形数据集的系统客观处理提供了一个重要工具。 相似文献
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利用横跨地表破裂带的小点距的地震测线, 对2001年11月14日昆仑山口西8.1级地震进行了断层围陷波的观测实验. 经过数字滤波和频谱分析等技术, 由地震记录图中分离出了断层围陷波. 资料处理结果表明: ① 无论是人工地震震源还是天然地震震源, 只要位于断层带内或紧靠断层带, 均能激发断层围陷波; ② 断层围陷波的能量主要集中于断层带内, 其振幅随测点与断层带距离的增加而急剧衰减; ③ 断层围陷波的优势频率与断层的宽度及断层带内介质的速度有关, 断层带越宽, 或断层带内部介质速度越低, 则观测到的断层围陷波的优势频率越低; ④ 断层围陷波存在着频散现象; ⑤ 根据昆仑山口西地震测线断层围陷波的观测结果, 可推断该处破裂面宽度为300 m左右, 远远大于地表破裂带的宽度. 相似文献
5.
利用交错网格有限差分方法对昆仑山断裂带人工爆破产生的围陷波进行了三维数值模拟解释.为提高断裂带最终模型的可信度，在围陷波模拟的同时考虑了人工爆破记录的三个分量.对昆仑山断裂带围陷波的模拟结果表明，影响围陷波特性的断裂带深度主要在10 km以内.S波速度和断裂带宽度对围陷波的到时、频率、振幅和相位影响较大.数值模拟解释获得的昆仑山断裂带的细结构参数是：浅部断裂带宽度为300 m，深部为250 m；深度在400 m以上断裂带内S波速度为098 km/s，外部围岩S波速度为170 km/s，Q值为138；S波速度和Q值随着深度的增加而增加；1000 m以下断裂带内S波速度为280 km/s，围岩S波速度为33 km/s. 相似文献
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7.
利用断层带特有震相通过观测模拟可以得到断层带介质的性质。本文回顾了地震学领域中断层带震相研究的发展历程,对断层带首波、断层带围陷波的国内外研究现状进行了综述,并结合国际上有关断层带震相研究的最新进展,对基于地震波形研究断层性质的前景进行了展望。 相似文献
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低速断层破碎带内传播的断层围陷波是断层内部信息的重要载体,研究其波场特征是反,演断层内部结构的关键。前人对围陷波的模拟主要针对垂直断层,但实际断层大部分是倾斜的。本文利用谱元法数值模拟地震波在垂直和倾斜断层区域的传播,并分别单独改变断层破碎带或断层两盘速度差异等参数,对比分析地震动在时域和频域发生的变化,研究这些参数对波场特征的影响。对比研究表明,当存在一定宽度的低速破碎带时,倾斜断层对近断层区域波场的影响和垂直断层相比在幅值分布上有比较显著的差异,尤其是当断层两盘同时还存在速度差异时;在倾斜和垂直断层破碎带上方,均能产生断层围陷波,其幅值特征差异不大,但在跨断层平面上的质点极化方式可能会存在差异:垂直断层围陷波质点极化方向表现为单一,而倾斜断层可能会出现多个方向。这些模拟结果有助于反演真实断层破碎带结构,也能够加深对近断层的强地面运动特征的认识。 相似文献
9.
汶川地震区断层围陷波探测 总被引：3，自引：0，他引：3
对汶川地震区开展震后科考和断层围陷波探测,本文主要介绍平通镇断层围陷波探测及初步结果。平通镇处在汶川8．0级地震断层带正上方,地表破坏十分严重。该断层围陷波测线横跨断层,以地震探槽为大致中点,沿NW—SE方向两端延伸,测线长约400m。这次观测结果表明,在汶川8．0级地震的新破裂带中可以观测到断层围陷波,反映了断层带内外的介质在物理性质上有较大的差异。该测线记录的断层围陷波优势频率大约为3—4Hz。探槽附近的台站断层围陷波较强,初步推测,该地段地壳内断层的宽度大约有200m。 相似文献
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11.
Study on rupture zone of the M=8.1 Kunlun Mountain earthquake using fault-zone trapped waves 总被引：1，自引：0，他引：1
Introduction The study on deep crustal faults has been one of the most vigorous subjects in seismology. In the past, 3-D deep seismic sounding and 3-D seismic tomography were usually used for this pur-pose. But it is difficult to obtain the fine structures of the faults in deep crust by these methods. Recently, seismologists in the world pay more attention to the fault zone trapped waves. Since the fault-zone trapped waves arise from coherent multiple reflections at two boundaries of the fau… 相似文献
12.
The observation of the fault-zone trapped waves was conducted using a seismic line with dense receivers across surface rupture zone of the M=8.1 Kunlun Mountain earthquake. The fault zone trapped waves were separated from seismograms by numerical filtering and spectral analyzing. The results show that: a) Both explosion and earthquake sources can excite fault-zone trapped waves, as long as they locate in or near the fault zone; b) Most energy of the fault-zone trapped waves concentrates in the fault zone and the amplitudes strongly decay with the distance from observation point to the fault zone; c) Dominant frequencies of the fault-zone trapped waves are related to the width of the fault zone and the velocity of the media in it. The wider the fault zone or the lower the velocity is, the lower the dominant frequencies are; d) For fault zone trapped waves, there exist dispersions; e) Based on the fault zone trapped waves observed in Kunlun Mountain Pass region, the width of the rupture plane is deduced to be about 300 m and is greater than that on the surface. 相似文献
13.
The observation of the fault-zone trapped waves was conducted using a seismic line with dense receivers across surface rupture
zone of the M=8.1 Kunlun Mountain earthquake. The fault zone trapped waves were separated from seismograms by numerical filtering and spectral
analyzing. The results show that: a) Both explosion and earthquake sources can excite fault-zone trapped waves, as long as
they locate in or near the fault zone; b) Most energy of the fault-zone trapped waves concentrates in the fault zone and the
amplitudes strongly decay with the distance from observation point to the fault zone; c) Dominant frequencies of the fault-zone
trapped waves are related to the width of the fault zone and the velocity of the media in it. The wider the fault zone or
the lower the velocity is, the lower the dominant frequencies are; d) For fault zone trapped waves, there exist dispersions;
e) Based on the fault zone trapped waves observed in Kunlun Mountain Pass region, the width of the rupture plane is deduced
to be about 300 m and is greater than that on the surface.
Foundation item: Joint Earthquake Science Foundation of China (201001).
Contribution No. RCEG200305, Research Center of Exploration Geophysics, China Earthquake Administration. 相似文献
14.
对2001年昆仑山口西Ms81级地震产生的断层带，布设了沿断层和横跨断层的两条人工地震测线.通过对观测资料的定量分析和处理，求得了昆仑山断层带内部的细结构.分析工作包括从S波震相开始的振幅谱计算、速度频散计算、群速度测量，并用面波频散方法反演S波速度结构，用振幅谱比的方法估计断层带的Q值.野外试验结果表明，S波震相与围陷波组的时间差随炮点与台站之间距离增大而增加，在断层带外的测点上观测到与断层带相关的场地效应.最后得出昆仑山断层带宽度为250m、速度结构为断层内低速的分层结构和Q值为15（断层内）和30（围岩）.虽然昆仑山口西地震的震级比美国加州Landers地震的震级（Ms76）大，且地震产生的破裂带长度长得多，但是这两个地震断层带的宽度却相差不大. 相似文献
15.
《地震研究进展（英文）》2021,1(4):100035
Detecting subsurface fault structure is important for evaluating potential earthquake risks associated with active faults. In this study, we propose a new method to detect faults using reflected surface waves observed in ambient noise cross correlation functions. Ambient noise tomography using direct surface waves obtained from ambient noise interferometry has been widely used to characterize active fault zones. In cases where a strong velocity contrast exists across the fault interface, fault-reflected surface waves are expected. We test this idea using a linear array deployed in the Suqian segment of Tanlu fault zone in Eastern China. The fault-reflected surface waves can be clearly seen in the cross-correlation functions of the ambient noise data, and the spatial position of the fault on the surface is close to the stations where the reflected signals first appear. Potentially reflected surface waves could also be used to infer the dip angle, fault zone thickness and the degree of velocity contrast across the fault by comparing synthetic and observed waveforms. 相似文献
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-- Fault zones are thought to consist of regions with reduced seismic velocity. When sources are located in or close to these low-velocity zones, guided seismic head and trapped waves are generated which may be indicative of the structure of fault zones at depth. Observations above several fault zones suggest that they are common features of near fault radiation, yet their interpretation may be highly ambiguous. Analytical methods have been developed to calculate synthetic seismograms for sources in fault zones as well as at the material discontinuities. These solutions can be used for accurate modeling of wave propagation in plane-parallel layered fault zone structures. However, at present it is not clear how modest deviations from such simplified geometries affect the generation efficiency and observations of trapped wave motion. As more complicated models cannot be solved by analytical means, numerical methods must be employed. In this paper we discuss 3-D finite-difference calculations of waves in modestly irregular fault zone structures. We investigate the accuracy of the numerical solutions for sources at material interfaces and discuss some dominant effects of 3-D structures. We also show that simple mathematical operations on 2-D solutions generated with line sources allow accurate modeling of 3-D wave propagation produced by point sources. The discussed simulations indicate that structural discontinuities of the fault zone (e.g., fault offsets) larger than the fault zone width affect significantly the trapping efficiency, while vertical properly gradients, fault zone narrowing with depth, small-scale structures, and moderate geometrical variations do not. The results also show that sources located with appropriate orientations outside and below a shallow fault zone layer can produce considerable guided wave energy in the overlying fault zone layer. 相似文献