炸药性能对地震波品质影响的Hilbert-Huang变换分析

为检测爆炸地震波的品质（能量,主频）,探寻激发高能量、高频率地震波的炸药震源,选用梯恩梯（TNT）、梯铝（TL）、8701,黑火药（BP）进行浅埋土中爆炸试验.并利用Hilbert-Huang变换（HHT）对距离震源10-65m处地面振动速度信号进行分析,结果表明：高能量高爆速炸药8701震源激发的地震波能量大,但频带较窄,主频较低,高频率段能量随传播距离衰减较快;低能量低爆速炸药BP激发的地震波频带较宽,主频也较高,但地震波能量过低;含铝炸药TL激发的地震波能量大,且随传播距离衰减速度较慢,主频介于黑火药BP与炸药8701之间.

耦合介质对炸药震源爆炸地震波能量和主频影响规律试验研究

耦合介质对炸药震源激发的爆炸地震波的能量与频率特征有较大影响。为提高地震勘探中炸药震源激发地震波的品质,选取了空气、水、细沙和岩土4种介质作为耦合介质,进行了土中爆炸试验来对比分析耦合介质对地震波特征的影响规律。利用快速傅里叶变换(FFT)将频率分为不同的频率带,对距炸药震源5~65 m内收集到的地面震动信号进行分析。试验结果表明:以水为耦合介质的炸药震源产生的地震波能量相对要高,尤其在25~100 Hz内,能量对比差别更加明显;以空气为耦合介质的炸药震源次之;以水为耦合介质炸药震源主频最高,随传播距离衰减速度较慢;岩土全耦合炸药震源在25 m范围内主频较高,但衰减速度最快,随着传播距离下降较快。综上,以水为耦合介质与其他相介质对比可产生较高能量和主频,更加符合地震勘探要求。

Improve Q estimates with spectrum correction based on seismic wavelet estimation

Characterization of seismic attenuation,quantified by Q,is desirable for seismic processing and interpretation.For seismic reflection data,the coupling between seismic wavelets and the reflectivity sequences hinders their usage for Q estimation.Removing the influence of the reflectivity sequences in reflection data is called spectrum correction. In this paper,we propose a spectrum correction method for Q estimation based on wavelet estimation and then design an inverse Q filter.The method uses higher-order statistics of reflection seismic data for wavelet estimation,the estimated wavelet is then used for spectral correction.Two Q estimation methods are used here,namely the spectral-ratio and centroid frequency shift methods.We test the characteristics of both Q estimation methods under different parameters through a synthetic data experiment.Synthetic and real data examples have shown that reliable Q estimates can be obtained after spectrum correction;moreover, high frequency components are effectively recovered after inverse Q filtering.

Discussion on the Measurement Method for the Coda Wave Quality Factor

The Quality factor is the parameter that can be used to describe the energy attenuation on seismic wave. In theory, we can obtain the relationship between the change of the coda wave quality factor with time and the strong earthquake preparation process on the basis of the quality factor of a coda wave in a same ray path. However, in reality the coda wave quality factor measured by different seismic coda waves corresponds to different seismic wave ray paths. The change of the quality factor with time is related to non-elastic characteristics of the medium and the volume of scattering ellipsoid constrained by scattered wave phase fronts, besides the change of regional stress field. This paper discusses the relationship between quality factor, epicenter distance and different lapse time, and then discusses the relationship between quality factor and frequency. Furthermore the determination method of the coda wave quality factor is put forward. The improved determination method of the quality factor, which removes the influence of different earthquakes or propagation depth of scattered waves, may increase measurement precision, thus information pertaining to abnormal changes in quality factor and the relationship between the quality factor and earthquake preparation process can be acquired.

静载对节理煤岩体动态力学特性和应力波传播的影响

为研究地应力和节理作用下煤岩体的动态力学特性和应力波传播规律,利用改造的动静组合加载SHPB装置,针对人工构造节理试样,研究不同静载(0,2,4,6和8 MPa)和不同节理吻合系数(JMC:0.8,0.9,1.0和无节理)煤样的动态力学特性和应力波传播规律。试验结果表明:随节理吻合系数减小,反射波振幅呈现增大趋势,透射波振幅呈现降低趋势;随着静载从0 MPa增大到8 MPa,不同节理吻合系数试样的透射系数均呈现增大趋势,且节理吻合系数越小,透射系数增加值越大,静载对低节理吻合系数试样的透射系数影响更为明显;峰值应力随静载增大而增大,而峰值应变反之;节理比刚度和动态模量均随静载增大呈现增长的趋势,表明静载的存在抑制节理煤岩体劣化作用。基于应力-应变关系和标准线性固体模型分析验证了试验结果,随静载和节理吻合系数增大,地震波品质因子增大,试样耗散能量减少。研究认为在地下工程中应更为重视节理和静载共同对应力波传递特性的影响。