【作者】 唐杰；

【导师】 陈颙； 席道瑛；

【作者基本信息】 中国科学技术大学 ， 固体地球物理， 2008， 博士

【摘要】 区域尺度的研究对于了解和研究地壳上地幔的结构构造、物质组成、物质的物理化学性质以及热力学状态,研究大地构造,认识地球演化、强震分布规律和潜在震源区的定量化判别,寻找地下隐伏断裂、油气资源和成矿规律,发展地学理论都具有重要的理论和实践意义。天然地震受制于地域性、地震事件有限性以及震源定位误差的影响,观测的精度和分辨率受到限制。人工地震信号是一种由人工源激发出的探测信号,具有很强的确定性、可控性和可重复性,这些特性是人工震源与天然地震之间的本质区别。以人工震源构建地震雷达,从被动观测变为对地下状态和结构的主动探查,对于探测地下结构及其变化、认识灾害机理、探索地震的物理预测等,都有重要的意义。人工震源的激发能量很低,在利用人工震源进行大范围的地下探察时,如何提高人工震源的探测能力和探测距离是一个亟待解决的重要科学问题。本文针对人工震源能量小、探测能力有限,将人工地震激发过程和通信系统结合起来,从震源特性角度和信号检测角度研究了深部探测中人工震源探测遇到的问题。震源是地震勘探的重要组成部分,震源产生的地震波信号质量将直接影响地震研究的效果。炸药是陆地上使用时间最久、用途最广的震源。大当量的炸药可以实现数百公里的探测范围,而大当量炸药的破坏性以及费用高的缺点促使人们研究小药量激发实现远距离接收的可能性。研究发现炸药震源的信号具有一定的可重复性,在良好的激发和接收条件下选择小当量炸药可以作为震源,采取恰当的激发和信号处理方式能够实现远距离的信号接收。气枪是海洋地震勘探使用最广的震源,本文研究了大容量气枪在陆地水库激发的能量、频谱、探测距离、可重复性等特征。气枪单次激发能量等同于1.4-1.6kg的炸药,大容量气枪震源是具有10Hz以下低频信号的低频震源,单次激发信号可传播120km。气枪具有环保、经济、较高可操作性和高度可重复性的特点,是较理想的区域性研究的震源。界面对与气枪激发的信号有改造作用,在地震探测中,需要地震波有足够的透射能量,才能达到勘探要求的深度,获得更多的反射层信息。深部探测一般采用大容量的气枪或枪阵,本文研究了大容量气枪子波信号的模拟,并针对大容量气枪的特征作了修正。通过对子波的研究发现气泡脉冲包含的低频成分高,在深部探测中应设法增加气泡脉冲,增加低频段能量输出,这是深部探测中气枪设计和参数选择的关键。利用实验与模拟结果本文分析了工作参数对信号的影响,对阵列中气枪容量、工作压力、沉放深度和组合方式的选择等做出分析,数值模拟方法得到的阵列远场子波及其频谱分析表明数值模拟方法设计的气枪震源阵列能够满足实际生产的需要,是针对实际生产中的困难,省时、省力设计满足生产需求的不可或缺的重要手段。提高地震记录的信噪比,提取其中的有效地震信号是地震数据处理的基础性工作。规则噪声的自适应压制能适应规则噪声视速度的任意变化,可有效压制规则噪声,并且该方法对有效信号的畸变也较小,可以克服全局滤波的缺点。互信息量方法能够清晰地标示出待测信号的存在,有助于采用自动化的方法进行分析和处理。充分利用人工震源的可控性和可重复性,以现代信息科学的理论和方法为基础,探索如何通过地震信号处理指导人工震源的设计、激发和信号观测,以期提高人工震源的探察能力和探测距离,是地震学和现代信息科学的交叉领域。本文将激发方式和信号检测结合起来,激发方式采取了大当量激发地激发小当量信号,小当量多次激发以及小当量编码激发的方式,并分析了三种激发方式下的数据处理方法,包括相关处理,N次方根加权叠加,相位权重叠加以及编码技术,取得了较好的检测效果。本研究为利用小当量激发进行区域尺度深部探测提供了新的尝试和基础。更多还原

【Abstract】 Seismic waves can spread through the Earth’s interior, and it’s the most effective means to explore Earth’s interior information. The 4D map of regional structure of deep earth provides important information for earthquake prediction and understanding the continental geodynamics. Suitable seismic source and advanced recording and processing systems are necessary to produce the 4D map. Although natural earthquakes can release huge amounts of energy, the epicenters of natural earthquakes are not accurate enough to be used regional scale exploration. Artificial seismic signal is inspired by the artificial source; it is highly controllable and repeatable. These characteristics are the main difference between artificial source and natural seismic. Seismic radar built using artificial seismic source can help people observe underground state and structure initiatively; it has major significance for detecting underground structures and changes, understanding the mechanism of disasters, and studying physical forecast of earthquake. Energy of artificial source is very low. How to improve the detection ability and detection range of artificial source is very important scientific question.As active seismic source has low energy, its detecting ability is limited. We study the problem in active seismic source exploration from source character and signal detection. Explosion is the most common source for seismic exploration on the land. Traditionally, explosives are used as the seismic sources for exploring deep structure. However, explosives are expensive and have a large negative effect on the environment, so it is difficult to use them. Small explosive can be used as the seismic source for deep structure exploration if the source and receiver conditions are good enough.The airgun is the most important seismic source in marine exploration. We study energy spectrum, detection range, repeatability, and other features of high-capacity airgun firing in the reservoir. Energy of single airgun is equivalent to 1.4-1.6kg of explosives. Signal of high-capacity airgun include abundant low-frequency energy, single-shot signal can transmit to 120km. Airgun source is eco-friendly, economic, high controllable and high repeatable seismic source. It is a very useful source for regional studies. Interface can change the signal from airgun. In deep exploration, seismic waves should have enough transmission capacity to meet the requirements of the deep exploration, and help people get more information on the reflector.People use large-capacity airgun or airgun array in deep exploration. In this paper, We study simulating airgun wavelet signal, and making some amendments for high-capacity airgun. Through our study, we find that bubble pulse has more low-frequency components than pressure pulse. In deep structure exploration we should increase bubble pulse to increase low-frequency energy output. That’s the key point for airgun design and parameter selection. We analyze the influence of work parameter such as airgun volume, work pressure and set depth to airgun signal. Airgun wavelet signal and its spectrum analysis from numerical simulation showed that numerical simulation can help us design airgun array to meet the actual needs. It is an important method for actual exploration.Improving the SNR of seismic records and extracting effective seismic signal is the basic work for seismic data process. Adaptive noise suppression method can effectively suppress noise, and the methods can overcome the shortcomings of the whole filter. Mutual information method can clearly mark out the tested signal and help us analyze and process seismic data automatically.Make full use of controllability and repeatability of the artificial source, based on modern information theory and approach, we study how to use seismic signal process to guide the design, inspiring mood, and signal observation of artificial source to improve detection ability and distance of active source. This is the cross field of seismology and modern information science.We combine inspiring method and signal detection, and use the following inspiring method, inspiring small shot in big shot area, a number of small shot excitation, as well as coding inspiring methods. We analyze the data-processing methods for the three shooting mode, including cross-correlation, N-th root weighted stack, phase weighted stack, as well as coding technology.更多还原