用多道反褶积方法测定台站接收函数

本文提出了一种在时间域用多道反褶积测定台站接收函数的方法, 以提高台站接收函数的测量精度与分辨率.在单道反褶积的基础上,选取若干个质量较好的远震P波波形事件,构成多道信号,以垂直分量为输入,径向和切向分量作为期望输出,依据最小二乘,设计多道滤波器,提取接收函数.合成地震图与观测地震图的检验表明, 多道滤波方法能有效地测定台站接收函数,特别是多道反褶积能够有效地恢复地壳上地幔间断面所产生的弱转换波震相.     

基于构建虚同相轴压制地震层间多次波

基于构建虚同相轴来估计层间多次波的方法是克希霍夫积分表示定理的一个延伸发展.本文通过构建虚地震同相轴巧妙地将散射点从地下移到了表面,利用表面的散射点来预测层间多次波.由于预测与实际地震记录中的层间多次波振幅存在偏差,采用了多道的L1范数匹配算法来实现真振幅的多次波压制.对简单模型和南黄海地质模型的数据处理实例验证了本文研究方法的正确性和有效性.     

Effect of lateral heterogeneity on surface wave testing: Numerical simulations and a countermeasure

The surface wave (S-wave) method has gained popularity in engineering practice for determining S-wave velocity depth profiles. A growing trend is towards the application of S-wave testing for spatially 2-D S-wave velocity tomography, ignoring the assumption of horizontally layered medium. A fourth-order velocity-stress finite difference method is used to perform numerical simulations of S-wave testing in earth models with lateral variation. Results show that the lateral heterogeneity induces a non-stationary property in the space domain, resulting in false depth-related dispersion or higher modes if conventional approach based on stationary assumption is used for the dispersion analysis. Artifacts maybe introduced in spatially 2-D S-wave velocity imaging if the effect of lateral heterogeneity is not accounted for. As a potential countermeasure, a high-lateral-resolution S-wave method is proposed to reduce the effect of lateral heterogeneity while maintaining the resolution and depth range of dispersion analysis. It consists of a walk-away survey and a phase-seaming procedure when synthesizing seismograms with different nearest source-to-receiver offset, allowing wide-wavelength dispersion analysis within a small spatial range. The proof of concept is given with several numerical examples. They show that the high-resolution S-wave method can greatly alleviate the effect of lateral heterogeneity and increase spatial resolution.     

Sequence model and its application to a Miocene shelf–slope system in the tectonically active Ulleung Basin margin, East Sea (Sea of Japan)

In a broader application of sequence stratigraphic concept to a tectonically active margin setting, this study presents a sequence model that considers all three controls on sequence development (i.e. eustasy, tectonic movement and sediment supply) as independent variables. The model introduces six sequence types (A to F) including type 1 and type 2 sequences defined in the original Exxon scheme. Each sequence shows a variety in number and stacking pattern of its constituent parasequence sets reflecting combined effects of accommodation change and sediment supply. This model is applied to a seismic sequence analysis of the shelf–slope system (middle to upper Miocene) in the southwestern margin of Ulleung Basin which has experienced significant crustal deformation during the Tertiary back-arc opening and subsequent closing of the East Sea (Sea of Japan). The model application delineates four sequence types whose development is closely associated with the tectonic evolution of the Ulleung Basin margin. During the back-arc opening (early to middle Miocene), type A and B sequences were emplaced as a result of steady creation of accommodation space due to a rapid subsidence combined with a tectonic-controlled high to moderate rate of sediment supply. The sequences associated with the extensional tectonism are characterized by active progradation and aggradation without forced regressive phases. In the initiation stage of back-arc closure (middle to late Miocene), subsidence rates were significantly reduced because of a widespread contractional deformation, while subaerial erosion of the uplifted thrust belt resulted in an increase in sedimentation rate. As a result, steady prograding type-E sequences were formed by alternating normal and forced regressions. During the quiescent phase of back-arc closure in the late Miocene, rise-dominant fluctuating relative sea-level change and moderate to low sediment supply gave rise to type-F sequences (similar to type-1 sequences of the Exxon group) reflecting a major control of eustatic sea-level change.     

远震相对走时数据快速计算方法及应用

远震层析成像技术已成为研究地球深部速度结构最为主要的方法,而其所用数据通常为初至震相的相对走时残差值.本文针对信噪比差的远震波形资料提出一种计算远震相对走时残差数据的快速方法,整个计算过程全部由计算机自动完成.该方法主要有两大特点:(1)利用互相关方法计算波形间的偏移时间时引入波形相位信息,有效压制噪声,增强有用震相的识别;(2)改进常规方法中计算相对走时残差的理论公式,避免求解超定方程组,提高计算精度.为验证新方法的可行性和实用性,以长江中下游地区远震波形资料为例,采用常规方法和新方法分别计算相对走时残差数据,对比结果显示:新方法比常规方法的工作效率和数据精度都高.     

南海西南部深水水道的多波束地形与多道反射地震研究

基于高分辨率多波束地形与多道地震资料精细解释,发现了南海西南部陆坡区5条大型深水水道.这5条水道可分成两类：1、5号水道延伸短,横剖面呈V形,弯曲度低,属顺直水道,侵蚀作用主导;2-4号水道延伸长,横剖面呈U形,弯曲度高,属弯曲水道,侵蚀-沉积作用主导.水道走向NEE-NE,长度大于350 km的有2条,宽度最大达2 km,切割深度最大达150 m.推测这些水道是陆源物质重力流作用形成的,是该区陆源物质通过陆架输送到南海西南次海盆的重要通道.陆坡区这些水道基本发育天然堤.在下游区域第二长的2号水道谷底明显高于周缘海底,水道-天然堤沉积已逐渐演变为朵叶沉积.这些水道的深部对应基底隆起区,说明深部构造的晚期活动控制了水道的平面位置,重力流与深部构造晚期活动共同控制了水道的形成演化.     

多道瞬变电磁法(MTEM)虚拟波场提取技术

多道瞬变电磁法（MTEM）是近年来发展起来的一种新的地球物理勘查技术,其数据采集方式与地震法类似,因此,采用瞬变电磁拟地震解释方法对MTEM数据进行处理解释具有一定的优越性.研究MTEM虚拟波场有效提取方法具有重要意义.在以往奇异值分解法、预条件正则化共轭梯度法两种不同的常规提取方法研究基础上,本文提出采用相关叠加法提取MTEM虚拟波场信息.首先采用预条件正则化共轭梯度法对全时段MTEM数据进行虚拟波场提取,然后采用同种方法对划分的各时间段数据进行虚拟波场提取,最后对全时段提取结果与各个时间段提取结果进行相关性叠加,叠加结果作为最终的提取结果.实测MTEM数据虚拟波场提取结果表明,采用相关叠加法可以得到稳定、光滑的虚拟波场波形曲线,且抗干扰能力强.     

基于矢量波数变换法(VWTM)的多道Rayleigh波分析方法

在近二十年来,多道面波分析法（MASW）由于其便捷、高效等特性在浅层地震勘探领域得到了广泛的应用.本文基于多道面波勘探的采集方式,提出了一种新的面波多道分析方法——矢量波数变换法（VWTM）.该方法通过对震源的近似,基于水平层状模型得到台站与震源间近似格林函数,然后进行矢量波数变换得到含有高阶模态Rayleigh波（频率-相速度）频散能量图.本研究首先利用合成地震数据到频散能量图与理论频散曲线进行叠加分析该方法的有效性和正确性;然后与相移法进行对比分析,我们发现在频散能量图中VWTM法对基阶、高阶模态成像均具有更高的分辨率和成像质量;最后我们将其应用于实际多道瞬态面波探测中,通过与相移法进行对比分析,发现VWTM法是一种方便、实用、有效的Rayleigh波频散提取方法.VWTM法提取多模态的Rayleigh波频散特征具有巨大潜力,可为基阶、高阶面波频散联合反演提供丰富的高阶模态频散信息.

     

基于多通道奇异谱分析的GNSS坐标时间序列共模误差的提取

共模误差是区域连续GNSS网中存在的一种与时空相关的主要误差源.为了有效的剔除共模误差,提高坐标时间序列的精度,本文提出了利用多通道奇异谱分析（Multi-channel Singular Spectrum Analysis,MSSA）提取共模误差的新思路,并利用实验区域18个测站9年（2002年到2010年）的GPS坐标时间序列进行实验,分析了共模误差对时间序列的影响和测站噪声特性的影响,并对共模误差序列进行周期探测,结果显示：通过MSSA能够有效的剔除共模误差,提高坐标时间序列的精度.