共查询到18条相似文献，搜索用时 140 毫秒
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多种岩石的Qp,Qs,Qc 总被引：2，自引：0，他引：2
本采用脉冲传播谱振幅比法、能量法、尾波法分别测多种岩样的Ｐ波Ｑ值、Ｓ波Ｑ值及尾波Ｑ值。结果表明，能量法所得Ｑｐ、Ｑｓ较小。谱振幅比法所得Ｑｐ一般居中，Ｑｓ较大。尾波Ｑｃ有的偏大，有的偏小。 相似文献
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利用中法合作建立的微震数字地震台的资料研究了海原西断层松山附近地区的微震尾波的衰减特征．计算了１７０次地震的７个频带的尾波Ｑｃ值，得出该地区尾波衰减可用Ｑｃ＝５２ｆ１．０９表示，表明这个地区是构造活动水平较高的地区． 相似文献
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大震前后尾波Q值变化的又一震例 总被引：1，自引：0，他引：1
本文根据Ａｋｉ的尾波散射理论，利用澜沧－耿马７．６、７．２级大震前后近１２年的时间，对大震区域及外围的７个地震台３０００多张地震记录图的尾波进行了测量，计算出尾波Ｑ值随时间的变化。结果表明：澜沧、耿马大震前有３～５年左右的低Ｑ值异常；在大震前一年左右，Ｑ值处于回升阶段；大震后多数台Ｑ值明显增大。在对两次大震震中和两次强震震中的不同距离的台站测出的Ｑ值，确定存在主震前低Ｑ值或高Ｑ值，主震后高Ｑ值或低 相似文献
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甘肃近期2次中强震前后震源区微震尾波（Qc）的变化特征 总被引：4，自引：0，他引：4
利用张掖台网和天祝－古浪台网的记录资料研究了１９８８年１１月２２日肃南５．７级地震和１９９６年６月１日天祝－古浪５．４级地震前台震源区微震尾波Ｑｃ值的变化特征,结果表明：５．７级地震前源及邻近地区介质１／Ｑｃ值趋于一致,认为这是该次地震的一种前兆表现,结合该次地震的震源机制和构造情况进行了讨论。天祝－古浪５．４级地震震源区附近地区微震尾波Ｑｃ值民频率的关系表明,这一地区属于构这活动地区。 相似文献
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本文根据Ａｋｉ的尾波散射理论，利用澜沧—耿马７．６、７．２级大震前后近１２年的时间，对大震区域及外围的７个地震台３０００多张地震记录图的尾波进行了测量，计算出尾波Ｑ值随时间的变化。结果表明：澜沧、耿马大震前有３～５年左右的低Ｑ值异常；在大震前一年左右，Ｑ值处于回升阶段；大震后多数台Ｑ值明显增大。在对两次大震震中和两次强震震中的不同距离的台站测出的Ｑ值，确实存在主震前低Ｑ值或高Ｑ值，主震后高Ｑ值或低Ｑ值的两种相互矛盾的现象。并得出地震强度与Ｑ值异常幅度无关，与Ｑ值异常的持续时间成正比。 相似文献
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采用脉冲传播谱振幅比法、能量法和尾波法分别测定片麻岩破裂孕育过程中的Ｑ值变化．结果表明:谱振幅比法所得Ｑ值呈现相对平稳值——升高至甚高值(极大值)——回降——破裂的变化形式；能量法所得Ｑ值变化形态与上述相反，即平稳值——低值——回升——破裂；而尾波法所得Ｑ值，主频Ｑ值呈现相对高值——下降至低值(极小)——回升——破裂，与能量法Ｑ值变化大体一致．而对于高频(大于主频)Ｑ值则呈现平稳值——升高至极大值——回降——破裂．同时尾波振幅谱还表明:应力达70％破裂应力后，首先是高频Ｓ波迅速减少(QC)变大)，临近主破裂时主频Ｓ波则大幅度减少(QC回升)，这可能是两种尾波QC变化形态不同的原因所致．而P，S波(初至波)振幅谱也表明，随着裂隙出现，Ｓ波频带变窄，高频成分迅速减少．即S波谱变化不同．这使采用不同方法所得的QS的变化特征不同． 相似文献
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滇西实验场两次中强地震前后尾波衰减的区域特征分析 总被引：9，自引：0，他引：9
本文在地方震尾波散理论模式的基础上，研究了１９９２年１２月发生在滇西地震预报实验场永胜期纳地区的两次Ｍｓ５．４，５．１地震前后的序列地震尾波振幅衰减率β和尾波Ｑ＾－１值随时间和空间变化的衰减特征。结果表明，尾波衰减率在空间分布上表现出明显的小区域范围的非均匀性，在主震震中附近的近场区内，主震期间的β值是０．００７６ｓ＾－１，相应的Ｑｃ＾－１值是０．００５６；余震期间的β值是０．０２０９ｓ＾－１，相 相似文献
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近震尾波是地壳和上地幔介质的不均匀性的一种标志，而尾波Ｑ（Ｑｃ）则是反映尾波介质衰减的参数。然而，用常规的最小二乘法估算的Ｑｃ缺乏统计背景。利用１９８６年长野县西部联合地震勘测资料，本文提出了一种统计可靠的Ｑｃ估算法－最大似然法，并证明了该方法的可靠性和实用性。首先，我们发现用最大似然法估算的Ｑｃ是静态有效的，并可用Ｘ＾２检验法验证其可靠性。首次我们用最大似然法估算了勘测区Ｏｈｔａｋｉ村周围的Ｑｃ 相似文献
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通过微小地震尾波Ｑ值的变化,可以推测出发生在丹波山周围因兵库县南部地震引起的地壳介质非均匀性变化。１９８７￣１９９６年,统计上可置信的尾波Ｑ值变化是,兵库县南部地震前后患前后,只出现在３．０Ｈｚ和４．０Ｈｚ两个中心频段的频率上。通过尾波Ｑ值变化和地震活动变化,推测出非均匀区域的尺度为百米至千米,这表明了这个地区介质非均匀性的特征尺度。 相似文献
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EXPERIMENTAL STUDY ON THE CHANGES OF ULTRASONIC CODA WAVE AND ACOUSTIC EMISSION DURING ROCK LOADING AND DEFORMATION 
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下载免费PDF全文 YANG Hai-ming CHEN Shun-yun LIU Pei-xun GUO Yan-shuang ZHUO Yan-qun QI Wen-bo 《地震地质》1979,42(3):715-731
The coda wave propagation path has received extensive attention as it is more sensitive to small changes in the medium than the direct wave. During the process of loading, the wave velocity, medium or source changes may cause the coda wave to change. The physical mechanism of change in the ultrasonic coda wave varies during different deformation stages. Meanwhile, there exist local damages in the rock sample during the deformation, and it will be accompanied by acoustic emission. Combining the ultrasonic coda wave and acoustic emission is beneficial to characterize the coda wave characteristics and damage degree of the sample at different deformation stages. In this paper, three kinds of rocks, including granodiorite, marble and sandstone with the sizes of 50mm×50mm×150mm, are used to carry out observations of ultrasonic coda wave and acoustic emission during the whole process of loading so as to study characteristics of the coda wave at different deformation stages. The major results are given below: 1)There is a good correspondence between the coda wave variation and the acoustic emission evolution process. When the acoustic emission frequency increases, the coda wave changes accordingly. In particular, the coda wave changes in the early stages of increased acoustic emission frequency, which indicates that the early damage information of rock can be obtained by analysis of the coda wave. 2)The physical mechanism of the coda wave change is different in different deformation stages. At the initial stage of loading, there are obvious scatterer changes in the coda wave change; then, in the linear elastic deformation stage, the wave velocity change is dominating; in the late-stage of loading, the scatterer change increases and coexists with the wave velocity change, the scatterer change effect is related with the rock micro-fracture degree, the rock will locally be damaged before rupturing, and the role of the scatterer will be enhanced. 3)With the increase of loading, the amplitude of increase of the wave velocity generally decreases gradually, which is basically consistent with the understanding obtained through the direct wave. The interference of acoustic emission can be eliminated because of the Kaiser effect when analyzing the coda wave. The consistency of the wave velocity change and stress loading and unloading is further verified. 4)The micro-fracture generated during rock deformation will change the physical mechanism of the coda wave change, and the scatterer effect will be significantly enhanced. At the same time, the acoustic emission waveform will cause interference to the ultrasonic coda wave. This means that attention needs to be paid when analyzing rock damage using only coda wave data. In short, the ultrasonic coda wave and acoustic emission can reflect the damage inside the rock, and the change mechanism of the coda wave in different deformation stages is different. The joint observation of the two can play a mutual verification role, which is conducive to improving the reliability of the observation results. 相似文献
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在实验室内，模拟了在构造应力和引潮力的共同作用下岩石失稳破裂的过程，记录了整个过程中不同应力条件下通过岩石样品的纵波波形曲线．以此为基础，分别在时间域和频率域计算了Ｐ波波列能量随应力的变化；并根据Ｑ值的定义，导出了接收到的波列的能量与岩石衰减Ｑ的关系式，从而计算出不同应力条件下相应的Ｑ值及其变化．利用加卸载响应比的定义，得到以Ｑ为响应参数时岩石系统的加卸载响应比随应力的变化曲线，其结果和响应比理论的预测相当吻合．因此认为，Ｑ值的加卸载响应比可以表征岩石系统的稳定程度，并可以用于预测岩石的非线性失稳． 相似文献
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在岩石电阻率随压力变化的不同阶段,部份地减低轴向压力后再加压(每回总压降约为破坏应力的10%).研究这种特殊的加载方式下,即所谓应力反复对电阻率的影响.结果如下:(1)对高水饱和度岩石,随压力不断增加电阻率变化的总趋势为上升——平稳——下降的变化形态(包括饱和度为100——70%).对低饱和度岩石(实验中饱和度为70%和50%),电阻率变化的总趋势已改变.(2)对高饱和度岩石共作了十一次应力反复实验.除了水饱和度为71%的岩石在压力为30MPa 处,应力反复时电阻率无明显变化外,其余均呈现电阻率的负异常(下降幅度约2%左右),我国地电台在震前观测到的地电阻率变化以负异常为主.实验结果为解释这种负异常提供一种新的可能机制.(3)在电阻率随压力变化的下降段,特别是接近岩石破坏时,应力反复所引起的电阻率负异常与一般情况下出现的负异常相比,有以下三个特征:a)负异常的幅度要大一个数量级(约-20%);b)不仅应力下降时电阻率下降,而且应力恢复时电阻率仍然下降;c)各个方向电阻率变化的差别很大(约10%).以上这三个特征可作为岩石临近破坏的标志.而一般的电阻率负异常可能只与应力反复有关,并不意味着岩石处于临近破裂的危险状态.(4)低饱和度岩石,应力反复可能引起电阻率的正异常.作者还用 相似文献
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ＴｈｅＱｖａｌｕｅｖａｒｉａｔｉｏｎｓｉｎｔｈｅｐｒｅｐａｒｉｎｇｐｒｏ┐ｃｅｓｏｆｒｏｃｋｒｕｐｔｕｒｅＢＩＮＷＡＮＧ１）（王彬），ＺＨＡＯ－ＹＯＮＧＸＵ１）（许昭永），ＪＩＮ－ＭＩＮＧＺＨＡＯ１）（赵晋明）ＹＩ－ＬＩＨＵ２）（胡毅力）１）Ｓｅｉ... 相似文献
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The properties of rock resitivity were studied under pressure, particularly with “stress reversal”, a procedure in which the
pressure applied was increased and decreased.
It was observed that, 1) With pressure increasing, the main feature of resistivity change was increase-steady-decrease for
high-saturation rock samples (saturation 70–100%). But the main feature for low-saturation samples was different. 2) In 10
out of 11 cases of “stress reversal” for high-saturation samples the resistivity droped (about 2%). Such drop could explain
the anomalies in geoelectricity terms, which are commonly observed before earthquakes in China. 3) It was also observed shortly
before rock failure that, a) the resistivity drops more dramatically (about 20%) during “stress reversal” period, which is
much more than ordinary drops. b) these drops occurred not only during stress decrease but also during stress increase. c)
Resistivity exhibits anisotropy: the resistivity along different directions may differ by 10%. These three features may indicate
that the rock is nearing failure, while ordinary resistivity drops are only connected with “stress reversal” and may not mean
the imminence of rock failure. 4) Resistivity increase was observed during the “stress reversal” period for low-saturation
rock samples.
The results mentioned above were explained with the effect of water flowing in and out of the cracks of rock. The temporary
factors which yield a reduction of the maximum main stress, may enhence the possibility of earthquake occurrence. 相似文献