Seismic Wave Attenuation in Germany's Deep Borehole Area from VSP Data

VSP 数据显示德国深井区域的地震波衰减

• 批准号: 9219208
• 负责人: Jose Pujol
• 金额: $ 5.26万
• 依托单位: University of Memphis
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1993
• 资助国家: 美国
• 起止时间: 1993-08-01 至 1996-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9219208&HistoricalAwards=false
• 关键词: Seismic; Wave; Attenuation; Germany; Deep

9219208 Pujol This project involves the determination of seismic wave attenuation using VSP (Vertical Seismic Profiling) data recorded in a 4-km-deep pilot borehole next to the super-deep borehole currently being drilled in Germany (expected to reach between 10 and 12 km). In spite of extensive research, attenuation mechanisms are not well understood, and even its measurement is plagued with uncertainty, as wave amplitudes are also modified by wave propagation effects generally only approximately known. For this reason, VSP data offer the best chance to observe the actual change in the amplitude and shape of seismic waves with the minimum amount of interference. The importance of the German deep- drilling program for this proposal is two-fold. (1) The borehole is one of the very few drilled in crystalline rocks. Very little information about attenuation in this type of rocks is available. (2) Several zero-offset VSP data sets for different seismic sources have been collected. Explosive, vibrator, and impact sources have been used to generate P and S waves. This is an exceptional data set that will be used to study the influence of the type of source and the frequency content of the waves on the measurement of attenuation, a matter on which little or no research has been carried out so far because of the unavailability of data. Although the measurement of attenuation (Q) using VSP data is the most reliable technique and getting a number for Q is a rather straightforward procedure, there are a number of factors that affect the measurements. In fact, different methods of measurement (e.g., spectral ratio, rise time) and even the choice of a tapering window may affect the results. In addition, wave propagation in the real earth affects wave amplitudes and frequency content because of scattering and the filtering effect of thin layers. For this reason, the main goal of this research will be the computation of reliable intrinsic Q values and a study of the factors that affect it. This will be the most detailed information on attenuation in crystalline rocks and will be extremely useful to calibrate the attenuation that may be determined from the analysis of high-quality reflection seismic data collected in the borehole area. ***

9219208 Pujol 该项目涉及使用在德国目前正在钻探的超深钻孔（预计深度在 10 至 12 公里之间）旁边的 4 公里深先导钻孔中记录的 VSP（垂直地震剖面）数据来确定地震波衰减。 尽管进行了广泛的研究，但衰减机制仍不清楚，甚至其测量也受到不确定性的困扰，因为波幅也会受到通常仅近似已知的波传播效应的影响。 因此，VSP数据提供了以最小干扰量观察地震波振幅和形状实际变化的最佳机会。 德国深钻计划对该提案的重要性有两个。 (1) 该钻孔是在结晶岩中钻探的极少数钻孔之一。 关于此类岩石的衰减的信息非常少。 (2) 收集了多个不同震源的零偏移距VSP数据集。 爆炸源、振动源和冲击源已被用来产生 P 波和 S 波。 这是一个特殊的数据集，将用于研究声源类型和波的频率内容对衰减测量的影响，由于缺乏数据，迄今为止很少或根本没有对此问题进行研究。 尽管使用 VSP 数据测量衰减 (Q) 是最可靠的技术，并且获取 Q 值是一个相当简单的过程，但仍有许多因素会影响测量结果。 事实上，不同的测量方法（例如光谱比、上升时间）甚至锥形窗口的选择都可能会影响结果。 此外，由于散射和薄层的过滤效应，波在真实地球中的传播会影响波幅和频率内容。 因此，本研究的主要目标是计算可靠的内在 Q 值并研究影响它的因素。 这将是有关结晶岩石衰减的最详细信息，并且对于校准可以通过分析在井眼区域收集的高质量反射地震数据来确定的衰减非常有用。 ***