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基于水库气枪震源数据的频域水准比例因子反褶积方法分析 总被引：1，自引：0，他引：1
基于2016年福建南一水库气枪实验资料,利用频率域水准因子反褶积方法和互相关时延检测技术,研究水准比例因子及台站的背景噪声水平对反褶积计算结果的影响,并对反褶积法消除不同枪压引起的震源影响效果进行分析。结果表明:(1)水准比例因子越小,反褶积计算后的波形信噪比越小,当水准比例因子取值过小时,走时识别误差较大;(2)台站气枪记录的信噪比越大,走时识别精度越高,参考台记录的信噪比对结果的影响远大于远场台,当远场台记录的信噪比大于10时,走时误差一般小于6ms,而当参考台记录的信噪比为30左右时,走时误差可能达到20ms;(3)气枪震源差异较大时,频域水准反褶积方法去除震源效应的效果较好,而在震源差异较小时,可能引入方法误差。 相似文献
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为进一步加深对大容量气枪震源激发的地震波传播特性的认知,利用福建海陆多个气枪震源固定激发点重复激发的实验数据,通过线性叠加和仿真技术得到等效单次激发高信噪比速度和位移记录,然后利用不同震中距的位移峰值计算不同固定点气枪激发的等效震级,进而建立等效震级、震中距和速度峰值的衰减关系。结果表明:(1)震中距为0~270km时,大容量气枪单次激发得到的速度峰值为700~4nm/s,位移峰值为200~0.2nm;(2)总容量为8000 in~3的气枪震源P波等效震级为0.181~0.760,S波等效震级为0.294~0.832,总容量为12000 in~3的气枪震源P波等效震级为0.533~0.896,S波等效震级为0.611~0.946,气枪震源激发产生的S波能量大于P波能量,激发环境不同,激发效能相差较大;(3)速度峰值随等效震级增大而增大,随震中距增大而减小,P波速度峰值三分量中垂直分量最大,S波相反,其垂直分量最小,二者水平分量相近。研究结果可为定量判断气枪震源激发的地震波的传播能力以及利用气枪震源进行深部探测或监测的观测系统的设计提供重要依据。 相似文献
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Three-dimensional velocity structure around the focal area of the 2021 MS6.4 Yangbi earthquake 
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下载免费PDF全文 Yunpeng Zhang Weitao Wang Wei Yang Min Liu Jinbo Su Xiaobin Li Jun Yang 《地震科学（英文版）》2021,34(5):399-412
On May 21, 2021, an MS6.4 earthquake occurred in Yangbi, Yunnan province, China, which exhibited typical foreshock-mainshock-aftershock characteristics. To better understand the velocity structure of the focal area and adjacent fault zones, Pg/Sg travel times at 12 seismic stations for the local earthquakes with ML ≥ 1.5 from 2009–2019 and the Yangbi sequence in May of 2021 were used to invert the three-dimensional (3D) structures for both vP and vP/vS. The obtained structure extends deeply to 15 km for area (25°N–26.5°N, 99.5°E–101°E) at a horizontal resolution of 10× 10 km, and the accuracy of the vP velocity was verified using airgun signals excited by the Binchuan Airgun Transmitting Seismic Station (BATSS). The resulting vP and vP/vS images correlate with existing fault zones and the Yangbi sequence, including: (1) The shallow velocity structure at 0 km agrees with local topography, where the Binchuan basin exhibits low-vP and high-vP/vS values. From 3–15 km, vP and vP/vS show variations, and the boundaries are consistent with the main faults (e.g., the Weixi-Qiaohou-Weishan, Honghe, and Chenghai faults). (2) The largest foreshock (MS5.6), mainshock (MS6.4), and largest aftershock (MS5.2) occurred near the boundaries where both vP and vP/vS have clear contrasts. (3) Small earthquakes are also concentrated in the transition zone between high- and low-vP and vP/vS anomalies, and are biased toward low-vP/vS zones. (4) Boundaries in vP and vP/vS are observed at 20 km west of the Weixi-Qiaohou-Weishan fault, indicating that there may exist one hidden fault. 相似文献
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海洋石油建设中的一个关键环节是对有关海域的工程地质条件作出准确评价。海上原位静力触探(CPT)是主要的原位勘察手段,与陆地CPT不同,其贯入方式主要有Seabed和Downhole两种形式。这两种CPT由于贯入方式不同,所得到的锥端阻力存在一定的差异。采用有限元方法对这两种形式的CPT锥端阻力和贯入模式进行计算分析。研究显示,CPT入土过程中,周围土体存在两种不同位移状态,即滑动状态和排挤状态。在入土初期,土体以滑动状态为主,土体中竖向应力随贯入深度的增加而递增。在入土一定深度以后,土体的排挤状态占主导地位,竖向应力变化趋于平稳。这两种位移状态的相互转化解释了Seabed CPT和Downhole CPT实测数据之间的差异。在贯入深度较大时,Seabed CPT受排挤状态控制,而Downhole CPT仍然受滑动状态的影响。 相似文献
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Chien-Ping Lee Yi-Ben Tsai Kuo-Liang Wen 《Soil Dynamics and Earthquake Engineering》2006,26(5):435-460
Both linear and nonlinear behaviors of soil deposits were evaluated by strong and weak motion data observed on the surface and at depths of 6, 11, 17, 47 m at the Large Scale Seismic Test (LSST) array in Lotung, Taiwan. The soil properties measured by well logging and by the shear wave velocity profile measured by uphole and cross-hole methods are available. Both one-dimensional equivalent-linear method and nonlinear method are used for the evaluation have been used. The synthetic records at various depths are obtained by using the records at the bottom as input motion. These synthetic records are then compared with actual records at corresponding depths. Records of 13 earthquakes are used. We find that the synthetic records obtained from a linear model match well with actual records for small input motions, but the results obtained from a nonlinear model match poorly. On the other hand, the synthetic records using both the nonlinear model and equivalent-linear model are in good agreement with the observed records for large input motions. In these cases, the predicted response spectra using the linear model consistently overestimate the observed records. The threshold distinguishing the large and small input motions is 0.04 g at depth of 47 m for the LSST data. Thus, the nonlinearity started at 0.04 g and occurred unequivocally at 0.075 g. Furthermore, the dominant frequencies shift toward lower values when input motions become large. Clearly, the observed records at the LSST site manifest nonlinearity of soil response. The hysteresis loops evaluated by the nonlinear method show a permanent strain of about 0.01% in soil layers at higher ground motion input levels in this case. 相似文献
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We design a numerical algorithm for wave simulation in a borehole due to multipole sources. The stress–strain relation of the formation is based on the Kelvin–Voigt mechanical model to describe the attenuation. The modelling, which requires two anelastic parameters and twice the spatial derivatives of the lossless case, simulates 3-D waves in an axisymmetric medium by using the Fourier and Chebyshev methods to compute the spatial derivatives along the vertical and horizontal directions, respectively. Instabilities of the Chebyshev differential operator due to the implementation of the fluid–solid boundary conditions are solved with a characteristic approach, where the characteristic variables are evaluated at the source central frequency. The algorithm uses two meshes to model the fluid and the solid. The presence of the logging tool is modelled by imposing rigid boundary conditions at the inner surface of the fluid mesh. Examples illustrating the propagation of waves are presented, namely, by using monopoles, dipoles and a quadrupoles as sources in hard and soft formations. Moreover, the presence of casing and layers is considered. The modelling correctly simulates the features—traveltime and attenuation—of the wave modes observed in sonic logs, namely, the P and S body waves, the Stoneley wave, and the dispersive S waves in the case of multipole sources. 相似文献
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Local site conditions can significantly influence the characteristics of seismic ground motions. In this study, site response analyses using one-dimensional linear elastic (LE), equivalent-linear (EQL) and nonlinear (NL) approaches are performed at different seismic hazard levels of Singapore. Two seismic stations, namely, the KAP and BES stations located at soft soil sites, are selected from the national network of Singapore. Firstly, site response estimates using the LE, EQL (SHAKE04) and NL (DEEPSOIL) approaches are compared with the borehole recordings. Results show favorable matches between the predictions and the observations at the KAP site, while under-predictions are observed for all the three site effect approaches at the BES site. Secondly, the applicability of the LE, EQL and NL models is examined at different hazard levels of Singapore. It is found that for the hazard level at a return period of 475 years, the computed maximum strain (γmax) is 0.06% and then the EQL model can provide accurate site response predictions. However, for the hazard level at a return period of 2475 years, the calculated γmax is larger than 2%, resulting in notable differences in the predictions of different site response models. This study highlights the importance of site effects in seismic hazard analysis of Singapore. 相似文献