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海洋地震资料处理中,通常采用的提取远场子波方法是从地震资料中直接提取和根据自由气泡震荡理论中不相干子波叠加算法由近场子波推算远场子波,但这两种方法都不精确。首先分析了由OBS模拟垂直观测地震系统实测得到远场子波,进而获取零相位算子(包括零相位算子、压制气泡算子和压制虚反射算子)的原理和实际效果。利用理论模型和实际数据对所述方法进行了检验,得到的结果不仅消除虚反射、气泡效应影响,而且整形为零相位。通过上述处理消除了非零相位数据对高分辨率处理和解释标定的影响,从实际数据处理效果来看此方法是切实可靠的。 相似文献
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为了研究二氧化碳物理相变技术应用于新型震源研发的可行性,在地下成层性较好的某煤田地震测区,开展了利用二氧化碳相变技术激发地震波的野外人工震源激发-接收实验．并与传统炸药震源进行了对比．地震数据利用Aries2.66型垂直分量反射地震仪和PDS-2型三分量地震仪接收．根据实测地震数据,从野外地震记录震相识别,初至波传播距离分析,震源近场地震信号时频分析,CO_2相变激发震源子波提取和基于CO_2震源子波的地震初至波波形反演实验等多个方面,进行了关于CO_2相变激发技术能否产生地震波信号以及能否将其应用于新型震源研发的可行性研究．研究结果表明CO_2物理相变膨胀能够产生能量集中的地震波信号;在实验区地质条件和激发参量下地震记录中初至波的可识别的传播距离约为1km;震源近场地震信号的主频集中在8～13Hz;利用震源近场数据提取了CO_2震源子波;通过地震初至波波形反演实验认为这种震源子波能够应用于波形反演等方面的研究．因为CO_2相变激发具有绿色、环保、安全等方面的优点,若能进一步在激发能量、激发—延迟时间一致性等方面加以改进,该技术有望在城市隐伏活动断层探测、城市地下空间探测、煤矿高瓦斯环境人工地震勘探等领域发挥重要的作用． 相似文献
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本文对利用强震近场加速度记录确定时,空、强三个完整的震源参数。文中给出一种利用计算机自动识别地震记录的Ｐ波初动到时和Ｓ波震相到的算法。根据新近发表的Ｗｏｏｄ－Ａｎｄｅｒｓｏｎ地震仪器的最新参数,修牍正唐山地区量规函数。利用唐 山数字震观测台阵得到的近场加速度数据,计算了１０次地震的震源位置和震级,并对定位误差进行了综合分析,将强震台网测定的震源参数与地震台 相似文献
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利用数字盒式磁带记录加速度仪组成的流动地震台网所记录的三分向近场加速度图,通过矩张量反演确定了1985年4月18日云南禄劝 Ms=6.1地震的部分余震的震源机制.以均匀半无限弹性介质的格林函数解释路径效应,并通过正演计算识别由两次积分得到的位移地震图中的直达 P 波、直达 S 波和 SP 转换波震相,然后用这些震相进行矩张量反演.反演结果表明,在解超定线性方程组时,采用适当的加权系数,可使上述直达波和转换波的理论计算值与观测值拟合得较好.尽管用以反演的三个余震大小不同(震级 ML48,3.2,3.5),震源位置也有差别,但它们的震源机制却非常接近,且与主震的震源机制相当一致.这一特征显示了余震的发生与主震发震构造的内在联系.这些实例说明,由震源球球面上分布适宜的数字地震台网取得的近场加速度资料,借助于即使是简单的介质模型,通过地震矩张量反演,不但可以得出这些地震震源的主要成份————剪切位错源,同时还可得出震源所含的其它成分,如膨胀源和补偿线性向量偶极. 相似文献
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本文针对弹性波逆时偏移,提出稳定的激发振幅成像条件.在震源波场的正向传播过程中,计算每个网格点的能量,并保存最大能量密度的时刻和相应的波场值;在检波器波场的逆时传播过程中,在每个网格点提取最大能量密度时刻的检波器波场值,并利用保存的最大能量震源波场做归一化,获得角度依赖的反射系数成像剖面.相比于归一化互相关成像条件,该成像条件在震源波场的正向传播过程中无需存储波场快照,节省大量磁盘空间和I/O吞吐任务,提高了计算效率;相比于弹性波的激发时间成像条件,该成像条件自动校正了水平分量在震源两侧的极性反转,在多炮叠加时避免振幅损失.数值试验表明,与归一化成像条件相比,稳定激发振幅成像条件具有更小的计算量,偏移剖面的低频假象更弱,水平分量的成像能力更优,具有更高的空间分辨率. 相似文献
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通过研究打桩公式法和应力波动法 (如CASE法 ) ,提出单次冲击能量及P S曲线测桩法 :用重锤或小型火箭筒一次冲击桩顶 ,用桩顶附近的检波器记录振波图和检测静、动位移 .通过实测冲击能 (总能量 )转换系数、波动和振动各自消耗的能量等各物理量 ,测定计算单桩竖向承载力 .利用振波图计算力 (P)与位移 (S)动态关系曲线 ,确定屈服点 ,并利用静载荷试验检验动测结果和确定动静P S曲线的相关常数 ,进而确定与承载力相应的沉降量 .而且 ,可由PS曲线的形态判定桩身成型质量 . 相似文献
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《地球物理学进展》2020,(3)
微地震震源机制解包含储层及裂缝特征信息,对于地质力学建模和水力压裂储层评价都有十分重要意义.然而,目前微地震震源机制类型仍存在争议,该方面的基础实验仍需要进一步的研究.本文针对花岗岩和页岩两类岩石,开展了水力压裂微地震实验研究.在实验进行前,分析了实验条件和数据采集方式.根据实验室测定的岩石物性参数和各级检波器微震事件的P波初动信息等,利用射线追踪进行微震事件的反演定位.定位的结果同岩石CT扫描观测到的裂缝有较高吻合度.利用微震事件在各级检波器处的P波初动极性及检波器在岩石表面的位置信息,进行微地震事件的震源机制反演,得出了水力压裂实验下微地震震源机制以剪切型占优的结论.结合微地震事件定位结果,震源机制反演结果和岩石CT扫描裂缝结果等,进行对比和分析,得出了一些新的结论和认识,为今后的实际微地震监测裂缝解释提供指导意见. 相似文献
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针对电磁式可控震源地震数据的相关检测,研究发现,在地下结构复杂、基板-大地耦合不佳时,常规方法——基于震源控制信号或基板附近信号作为参考信号检测得到的地震记录中,存在子波到时误差和虚假多次波问题.本文分析了上述问题的理论原因,并提出基于重构激发信号的相关检测参考信号方法(Correlation Detection Reference Signal Based on the Reconstructed Excitation Signal,CDRSBRES).首先,利用直达波与其他地震波到时不一致的特点,从震源基板附近信号中分离、提取直达波.然后,利用直达波重构震源激发信号并作为参考信号对地震数据进行相关检测.最后,应用谱白化技术提高检测结果质量.数值模拟研究表明,重构激发信号与理想激发信号的相关系数为0.9869,达到高度线性相关,CDRSBRES方法检测的地震记录在子波到时和波形特征上均与模型相符.随后,在某金属矿区开展了可控震源对比实验.与液压式可控震源MiniVib T15000检测结果相比,电磁式可控震源PHVS 500的检测结果中:基于震源控制信号的检测结果存在子波到时误差约0.012s,对应垂向精度误差约11.16m;基于基板附近信号的检测结果部分区域出现虚假多次波,信噪比降低;而CDRSBRES方法的检测结果子波到时误差约0.001s,对应垂向精度误差约0.93m,波形特征一致,相同区域无虚假多次波.综上,本方法适用于电磁式可控震源地震数据的高精度检测,尤其对于地下结构复杂区域的高分辨率地震勘探具有重要意义. 相似文献
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利用中、小容量气枪组成的立体气枪阵列延迟激发震源和海底地震仪(OBS)在我国北部浅海海域开展了人工地震深部地球物理探测试验.基于水深条件和压制水体虚反射、提升低频能量的需要,使气枪震源有足够的输出能量和高品质子波特性,研究了立体气枪阵列延迟激发震源工作机理,经远场子波理论模拟优选了组合参数并进行了海上试验工作.结果表明,中、小容量气枪组成的立体气枪阵列延迟激发震源,适应了浅水海域的激发环境,降低了由虚反射造成的局部陷波和干扰作用,有效地改善了OBS信号的品质,获得了Ps,Pg,PmP,Pn等多种震相.创新了由中、小容量气枪组成的立体气枪阵列延迟激发震源在浅海区OBS探测中的应用,也填补了南黄海海域深地震探测数据的空白,为南黄海、渤海深部地壳结构研究及含油气盆地形成演化研究提供了重要的基础资料. 相似文献
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Air-gun arrays are used in marine-seismic exploration. Far-field wavelets in subsurface media represent the stacking of single air-gun ideal wavelets. We derived single air-gun ideal wavelets using near-field wavelets recorded from near-field geophones and then synthesized them into far-field wavelets. This is critical for processing wavelets in marine- seismic exploration. For this purpose, several algorithms are currently used to decompose and synthesize wavelets in the time domain. If the traveltime of single air-gun wavelets is not an integral multiple of the sampling interval, the complex and error-prone resampling of the seismic signals using the time-domain method is necessary. Based on the relation between the frequency-domain phase and the time-domain time delay, we propose a method that first transforms the real near-field wavelet to the frequency domain via Fourier transforms; then, it decomposes it and composes the wavelet spectrum in the frequency domain, and then back transforms it to the time domain. Thus, the resampling problem is avoided and single air-gun wavelets and far-field wavelets can be reliably derived. The effect of ghost reflections is also considered, while decomposing the wavelet and removing the ghost reflections. Modeling and real data processing were used to demonstrate the feasibility of the proposed method. 相似文献
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To specify intelligently a nondynamite source in a marine seismic data-collection system, it is important to use all known parameters of the system—source, receiver, and recording-system characteristics. A technique has been developed to design the far-field pressure pulse of an air-gun array by taking these parameters into account. Important source variables to consider are interaction among guns in the array and the depth of the array. Near-field pressure signatures of individual guns, which are relatively unaffected by boundaries, have been used to‘construct’the far-field pressure pulse of the array by considering these variables. Comparison between constructed pulses and measured far-field pulses shows substantial agreement. Streamer depth and recording-system bandpass should also be considered when designing an air-gun array. Comparison of far-field pressure pulses for several bandpasses clearly shows the importance of considering this variable; e.g., the initial pulse is severely attenuated when a high-cut filter is used. Likewise, an additional filtering effect due to the streamer's proximity to the surface should be taken into account. Design of an air-gun array using the principles just outlined are illustrated by an example. 相似文献
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J. E. MARTIN 《Geophysical Prospecting》1993,41(8):943-967
An experiment was undertaken at BP's Fulbeck Geophysical test site to compare the viability of various simultaneous vibroseis recording techniques, which are often recommended as a means of improving data acquisition production rates for 3D seismic surveys. Of particular interest were: (a) the ability to separate the signals from each source during processing, (b) the generation and suppression of harmonics and (c) the effects of any source interaction. Two vibrators were deployed with a baseplate separation of 10 m, about a borehole containing a vertical array of geophones. Our analysis concentrated on the groundforce signals measured at each vibrator and the far-field signatures measured using a vertical geo-phone at a depth of 204 m. By comparing single vibrator records with similar but separated records from a simultaneous recording sequence, signal separability, harmonic suppression and vibrator interaction could be fully studied. Separated far-field signatures from simultaneous vibroseis methods using combinations of up and downsweeps exhibited unsuppressed harmonics and substantial energy from the undesired source which leaked through the correlation process. The ‘up/down’ method was capable of separating the signal from each source by only 12.7 dB, and is therefore unsuitable as a field technique. The variphase simultaneous vibroseis methods studied afforded some harmonic suppression and gave signal separations of about 30.0 dB. Use of variphase simultaneous vibroseis methods will compromise the quality of the data recorded, when compared with single-source acquisition methods. None of the simultaneous vibroseis methods tested provided adequate signal separation and, therefore, cannot be recommended as data acquisition techniques. The ‘alternate sweeping’ method coupled with multispread recording will give the desired improvement in data acquisition rates, while preserving the necessary quality of our seismic data. 相似文献
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M. H. SAFAR 《Geophysical Prospecting》1976,24(2):328-333
The absolute amplitude of the pressure pulse radiated by a marine seismic source is one of the prime criteria used in evaluating its performance. A technique for this measurement is proposed which is applicable to all sources which radiate a bubble pulse. The technique is described with reference to an air-gun array in which the pulse radiated from a single gun is compared with that radiated by the full array. The advantage of the method is that absolute values of pressure are obtained without any need for a calibrated hydrophone. In theory this may seem a trivial advantage but in practice sensitivity factors for the hydrophone channel cannot always be relied upon. The proposed technique is illustrated by an example. 相似文献
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地震全波形反演(FWI)从理论走向实际面临着诸多难题,其中之一就是需要一个较高精度的初始模型,另一个难题就是需要一个较为精确的震源子波,初始模型和震源子波的准确程度严重影响着全波形反演的最终结果.为此,本文提出了不依赖子波、基于包络的FWI初始模型建立的方法,建立了相应的目标函数,推导出了反演的梯度,给出了伴随震源的表达式,理论上分析了不依赖子波FWI的可行性.在数值试验中,讨论了参考道的选取方式,通过分析归一化目标函数收敛速率,认为近偏移距参考道优于远偏移距参考道,在地震数据含干扰噪音时,平均道作为参考道要优于最小偏移距参考道.通过包络、包络对数、包络平方三种目标函数反演结果的比较,发现包络对数目标函数对深层的反演效果最好.通过不同子波的试验进一步验证了本方法的正确性. 相似文献
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波形反演是近年来较热门的反演方法,其分辨率可以达到亚波长级别.在波形反演的实际应用中,源子波的估计十分重要.传统方法使用反褶积来估计源子波并随着反演过程更新,该方法在合成数据波形反演中效果较好,但在实际数据反演过程中存在一系列的问题.由于实际数据信噪比较低,在源子波估计过程中需要大量的人为干涉,且结果并不一定可靠.本文使用一种基于褶积波场的新型目标函数,令反演过程不再依赖源子波.详细推导了针对跨孔雷达波形反演的梯度及步长公式,实现介电常数和电导率的同步反演.针对一个合成数据模型同时反演介电常数和电导率,结果表明该方法能够反演出亚波长尺寸异常体的形状和位置.接着,将该方法应用到两组实际数据中,并与基于估计源子波的时间域波形反演结果进行比较.结果表明不依赖源子波的时间域波形反演结果分辨率更高,也更准确. 相似文献
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Three methods for estimation of the pressure wavefield generated by a marine airgun array are tested experimentally and compared. In the trial a variety of radiation angles and array configurations were used and some large synchronization errors were deliberately introduced. The source was equipped with near-field hydrophones and a subsource ministreamer. A tethered far-field hydrophone was used so that the three estimated far-field signatures could be compared with an independent measurement. The knowledge of the source signature is important for on-board source array QC, deconvolution, multiple attenuation, stratigraphic trap prediction, modelling and inversion, AVO analysis and reservoir monitoring. The methods perform very well and give estimates whose frequency-domain spectra match the measured spectra to within a few dB and within a few tens of degrees of phase over the tested bandwidth of 3.5–110 Hz. The time-domain error-energy is typically only a few per cent of the signal energy for radiation angles within about 30° of the vertical. The third method proved to be sensitive to an experimental shortcoming leading to overloading of the ministreamer and meaningful comparison was not possible for some test configurations. 相似文献
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S. P. KRAVIS 《Geophysical Prospecting》1985,33(7):987-998
Deterministic deconvolution of seismic data recorded with a non-minimum phase source, such as a sparker, requires an estimate of the source signature. Present methods of deterministic signature estimation and deconvolution require additional field equipment (near- or far-field hydrophones), or else make a deterministic estimate of the effective source signature (the free-field source signature convolved with source and receiver ghosts). By analyzing the direct arrival signal to normal hydrophone groups it is shown that extraction of the free-field source signature from this signal is possible for a spherically symmetric source, and it is demonstrated that the use of this signature for a preliminary deterministic deconvolution gives better results on sparker data than minimum-phase whitening deconvolution applied on its own. The applicability of the method to non-spherically symmetric sources, such as arrays, is also discussed. This paper is published with the permission of the Director, Bureau of Mineral Resources, Geology and Geophysics, Canberra, Australia. 相似文献