共查询到19条相似文献，搜索用时 125 毫秒
1.
应用包含在小波变换系数中的信号偏振信息,提出了一种确定单台三分向记录图中Ｐ波和Ｓ波震相的小波变换方法．主要的思路是寻找地震信号在不同尺度下小波变换系数的显著特性．通过对小波变换系数主成分的分析,得到不同尺度下的Ｐ波和Ｓ波识别因子,进而形成确定Ｐ波和Ｓ波初至的定位函数．通过对模拟资料和实际地震资料的分析,认为由小波变换方法形成的定位函数具有一定的抗噪声能力,在精确识别Ｐ波和Ｓ波初至方面是非常有效的．本文首先介绍了小波变换的基本概念和详细方法,然后应用小波变换对实际资料进行处理,并给出了研究结果． 相似文献
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数字化地震记录震相自动识别的方法研究 总被引：10，自引：3，他引：7
针对目前震相自动识别方法不能自动给出震相识别区间,以及不能确定识别出震相名称的问题,运用震相的运动学特征,由平均速度模型和J-B走时表数据,自动计算近震、远震和极远震的震相走时及震中距。对多尺度小波分解进行单支重构作为识别不同震相的分析信号。先求出初至震相和最大面波到时,估算出震中距,然后找到S波或PP波到时,求出准确的震中距,即可自动给出各震相的识别区间,采用线性偏振法在给定区间中识别出震相的初至时刻。由于该方法采用的是先明确要找什么震相,再由该震相的走时确定寻找区间,所以找出的初至就是要寻找的震相,自然解决了识别出震相的名称问题,从而实现了对震相的全程自动识别。 相似文献
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基于小波包和峰度赤池信息量准则的P波震相自动识别方法 总被引：2，自引：2，他引：0
基于小波包变换和峰度赤池信息量准则(AIC), 提出了一种新的自动识别P波震相的综合方法, 即小波包-峰度AIC方法． 首先对由加权长短时窗平均比(STA/LTA)法粗略确定的P波到时前后3 s的记录进行小波包三尺度的分解与重构, 分别计算每个尺度重构信号的峰度AIC曲线并将其叠加, 叠加曲线的最小值则为P波震相到时; 然后对原始地震记录进行有限冲激响应自适应滤波以提高信噪比和识别精度; 最后将小波包-峰度AIC方法应用到合成理论地震图及实际地震记录的P波初至自动识别中. 结果表明: 初至清晰度对识别精度的影响比信噪比对其影响更大; 与单独使用加权STA/LTA方法和峰度AIC法相比, 小波包-峰度AIC法具有更强的抗噪能力, 识别精度更高; 当初至清晰时, 小波包-峰度AIC法自动识别与人工识别的P波到时平均绝对差值为(0.077±0.075) s． 相似文献
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利用sym5小波包基函数对小震级天然地震和人工爆破波形进行4层小波包分解并绘制了时频谱图.通过时频谱图可直观得出, 爆破频率成分简单, 时频谱聚集性较好. 为寻求定量的识别指标, 综合P波和S波小波包变换结果, 提出并定义了P/S能量比. 分析识别效果较好的 P/S能量比判据得出爆破的P波主频集中在频段3.125—9.375 Hz处, 地震频率成分较复杂, S波在高频12.5—23.4375 Hz处也较发育, 在这些频段上, 爆破的P波与S波差异要大于地震的P波与S波差异. 作为小波包判据研究的补充, 文中也提取分析了P波的能量比与S波的能量比. 能量比判据识别结果表明, 人工爆破与天然地震的频率成分存在差异, 通过小波包变换能够提取有效的识别判据. 相似文献
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互相关函数在单孔法剪切波速测量中的应用 总被引：6，自引：1，他引：5
本文系统论述了单孔法剪切波速测量信号处理中的一种到时差识别方法。对带通滤波后的触发传感器信号和探头信号进行互相关分析,可以准确地识别S波的到时。针对实际波速测试工作中两道水平信号到时差相差比较大、测点的波速计算值为负数或者计算波速数值远大于或小于现场岩样的经验实际数据等不合理因素,编制了相应的计算程序．提高了波速分析的效率和精度。 相似文献
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本在地震数据自动化处理中，给出一种基于自回归模型的Akaike information criteria(AIC)算法和信号平均幅值比的混合方法来估计地震信号的初至．用信号的AIC曲线和平均幅值比曲线构造一种叠加曲线，再进行类似于坐标旋转的校正，可以准确估计低信噪比记录中信号的初至，尤其对于震相类型比较复杂的后续震相(如S波、Lg波)的初至估计结果很好．通过对中国数字地震台网乌鲁木齐台记录到的23次天然地震中P波、S波和Lg波的初至估计，与人工分析结果相比，P波初至估计的均方误差为0．71s，后续震相(S波、Lg波)的均方误差为1．64s，优于传统AIC算法的估计结果． 相似文献
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土是由一定尺寸大小颗粒所构成的多孔介质,具有明显的颗粒特性,当土颗粒间的孔隙被流体（如水或油）充满时则成为饱和土.利用微极理论和Biot波动理论的研究成果,把饱和土中多孔固体骨架部分近似地视为微极介质,孔隙中的流体部分视为质点介质,获得饱和多孔微极介质的弹性波动方程.借鉴Greetsma理论,建立了饱和多孔微极介质弹性本构方程力学参数与相应单相介质弹性参数的相互关系,使饱和多孔微极介质弹性波动方程中的物理参数具有明确的物理意义,易于在试验中确定.运用场论理论把饱和多孔微极介质的波动方程简化为势函数方程,建立了饱和多孔微极介质中五种弹性波的弥散方程,数值分析了五种简谐体波在无限饱和多孔微极介质中的传播特性. 结果表明,P1波、P2波和剪切S1波的波速弥散曲线与经典饱和多孔介质基本相同,当频率小于临界频率ω0时旋转纵波θ波和横波S2波不存在,当频率大于临界频率ω0时,θ波和S2波的传播速度随频率增加而减小. 相似文献
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小波变换是近年兴起的信号处理方法,具有良好的时频局部化特征。它不但可以准确地描述瞬变信号的局部特征,还可以通过多尺度变换,从不同频带上观察信号的特征。利用小波变换的以上特征将其运用于数字化水位观测资料不同频率潮汐波的分离、同震水震波及震前水位长周期“前驱波”的识别、干扰与同震效应的识别等方面,都取得了较好的效果。 相似文献
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选取了几种常见的小波母函数,分别提取了同一理论下的面波数据的群速度,并与理论群速度进行对比,结果表明Morlet小波提取面波群速度的效果最好.此外,将Morlet小波与常用的多重滤波提取群速度的结果进行了比较,结果表明: ① 多重滤波法非常依赖高斯滤波系数α的取值,α的取值应随面波周期的增大而减小;② 在α取值得当的前提下,在20—35 s周期范围内多重滤波法提取面波群速度的相对误差比Morlet小波小,在周期大于35 s时,两者相对误差相近; ③ 合适的α值的选取需在不同周期段耗费大量时间进行大量试验,这说明多重滤波法不具备自适应性;而采用小波变换分析短周期信号时,时间窗变窄,频率窗变长,当分析长周期信号时,时间窗变长,频率窗变窄,具有对信号的自适应性,这是小波变换相比多重滤波法的最大优点. 相似文献
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Shear wave velocities of soils, which provide shear moduli for earthquake response calculations, can be measured clearly and accurately using the down-hole method. Such a method has been used at a number of sites in California with good results to depths of 200 ft. Seismic waves from hammer blows, delivered to the ends of a heavy plank loaded by the front wheels of a vehicle, are received by a three-component geophone in a carefully prepared vertical hole and recorded at 1 mm/ms with a six-channel seismograph. A series of records are obtained at various measured depths in the hole, allowing calculation of interval velocities. Shear waves are easily identified by a clear 180 degrees phase difference between waves generated by blows on the opposite ends of the plank. Compressional waves are routinely logged by a vertical hammer blow at each recording depth. Shear velocities are reproducible to about 5 per cent in surveys of neighbouring holes. The reading uncertainty of ± 1 msec for the S arrival gives a resolution sufficient to detect a buried layer 5–10 ft thick with a velocity contrast of only 20 per cent. 相似文献
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Elastic full waveform inversion of seismic reflection data represents a data‐driven form of analysis leading to quantification of sub‐surface parameters in depth. In previous studies attention has been given to P‐wave data recorded in the marine environment, using either acoustic or elastic inversion schemes. In this paper we exploit both P‐waves and mode‐converted S‐waves in the marine environment in the inversion for both P‐ and S‐wave velocities by using wide‐angle, multi‐component, ocean‐bottom cable seismic data. An elastic waveform inversion scheme operating in the time domain was used, allowing accurate modelling of the full wavefield, including the elastic amplitude variation with offset response of reflected arrivals and mode‐converted events. A series of one‐ and two‐dimensional synthetic examples are presented, demonstrating the ability to invert for and thereby to quantify both P‐ and S‐wave velocities for different velocity models. In particular, for more realistic low velocity models, including a typically soft seabed, an effective strategy for inversion is proposed to exploit both P‐ and mode‐converted PS‐waves. Whilst P‐wave events are exploited for inversion for P‐wave velocity, examples show the contribution of both P‐ and PS‐waves to the successful recovery of S‐wave velocity. 相似文献
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本文从数值上研究了裸眼井中弹性波传播的非对称模式,给出了合成微地震图和导波（弯曲波）的频散曲线,发现在“硬”地层和“软”地层的井中,导波都是高度频散的,其最大相速度等于地层的横波速度,其截止频率低于对称模式的伪瑞利波的截止频率;在低频（2-3kHz）和长源距（3-4m）的条件下,由非对称的声源（如声偶极子）所产生的微地震图中,初至信号是以横波速度传播的,而以纵波速度传播的信号被抑制。本文的结果对研制横波速度测井仪是有意义的。 相似文献
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Summary To derive the structure of the Lower Mantle, observations of P and S waves at epicentral distances beyond 90 degrees have been used. The arrival times and amplitude decay with distance proved to be a source of information to derive the structure near the core-mantle interface. These observations were compared with results of theoretical calculations based on full wave theory [1, 2, 5, 6]. Another important theoretical method is the reflectivity method [4]. Differences between the two methods have a direct bearing on the interpretation of the observations and therefore need to be investigated.In the two methods the wave propagation involved in diffraction is simulated in different ways. In this paper the importance of approximations involved in each of the methods will be discussed. For this purpose the calculation of the frequency-dependent decay with distance of diffracted SH waves has been chosen. The approximations are considered to be important both in P and SH diffraction. The advantage of studying SH waves is the simpler and more straightforward formulation. 相似文献
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Summary The paper is intended as a contribution to the quantitative analysis of travel-time curves of seismic events recorded in the Ostrava-Karviná District (OKD). The input data represent a set of 2621 seismic events, recorded by the local seismological network of 26 mine stations DSLA and a regional diagnostic polygon consisting of five surface Lennartz stations. All the events were processed automatically in the Operational Seismological Centre of the Czechoslovak Army Mine in Karviná and stored in the seismological data base. The results are presented in the form of graphs of arrival times versus distance for the whole OKD, for two mines and one tectonic block.Travel-time curves of direct P and S waves, as well as of reflected and refracted waves are given. The direct P and S waves propagate well practically throughout the whole region studied, but their apparent velocities of propagation are affected by the properties of the rock medium.As a result of the complicated geological conditions, the recorded wave image is quite complicated. Methods of mathematical modelling, using kinematic and dynamic parameters of seismic waves, will have to be applied to identify the separate wave groups uniquely. 相似文献
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The seismic wave consists of many seismic phases, which contain rich geophysical information from the hypocenter, medium of seismic wave passing through and so on. It is very important to detect and pick these seis-mic phases for understanding the mechanism of earthquake, the Earth structure and property of seismic waves. In order to reduce or avoid the loss resulted from the earthquake, one of the important goals of seismic event detect-ing is to obtain its related information before and afte… 相似文献
17.
Bagus Jaya Santosa 《中国地震研究》2008,22(2):206-217
The S wave velocity structure of the earth below Eastern Southeast Asia has been investigated by analyzing the seismogram from surface wave to multiple depth waves in the time domain and three Cartesian components simultaneously. The wave passes across the front area of subduction zone between the Philippine plate and the Asian plate. The main data are waveform comparisons, instead of the arrival times. The synthetic seismogram is calculated using the GEMINI method. The synthetic seismogram constructed by PREMAN global earth model deviates greatly from the measured one. To solve this problem, corrections are needed for the β speed structure. Corrections cover the gradient change of βh, which turns from negative to positive in upper mantle layers as in the PREMAN, change of earth crust depth and change of zero order coefficients of β velocity function in all earth mantle layers. So, the fitting is obtained, as well as the arrival time or the waveform of Love and Rayleigh surface waves, the S wave and the repetitive depth waves ScS2 and ScS3. This result reveals that the Southeast Asia, being stretched due to tectonic release, has a mantle in some parts with negative anomaly of S wave velocity and vertical anisotropy in all earth mantle layers. 相似文献
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地震波在各向异性介质中以一个准P波(qP)和两个准S波(qS1和qS2)的形式传播.研究三种波的相速度、群速度以及偏振方向等传播性质能够为各向异性介质中的正反演问题提供有效支撑.具有比横向各向同性(TI)介质更一般对称性的正交各向异性介质通常需要9个独立参数对其进行描述,这使得对传播特征的计算更为复杂.当两个准S波速度相近时具有耦合性,从而令慢度的计算产生奇异性.因此,奇异点(慢度面的鞍点和交叉点)附近的反射与透射(R/T)系数的求解不稳定,会导致波场振幅不准确.本文首次通过结合耦合S波射线理论和基于迭代的各向异性相速度与偏振矢量的高阶近似解,得到了适用于正交各向异性介质以qP波入射所产生的二阶R/T系数的计算方法.与基于一阶近似的结果相比,基于二阶近似的方法提高了qP波R/T系数的精度,能得到一阶耦合近似无法表达的准确的qP-qS转换波的R/T系数解,且方法适用于较强的各向异性介质. 相似文献