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1、 地球物理学基础（2013）作业 03 1 / 3地球物理学基础（2013） 作业 03布置时间：2013-10-8( 周二) 交作业时间：2013-10-24（周四）1、翻译（15 分）将英文教材Fundamentals of Geophysics第 175 页的右边第二段翻译成中文，即以“Reection seismology is directed primarily at nding the depths to”开头的那一段。 2、名词解释（15 分）首波 反射系数 共中心点排列 动校正 合成地震记录3. A seismic survey is conducted over level
2、 ground consisting of two horizontal layers. Sketch a travel-time diagram that shows the arrivals of the direct wave, the reected wave, and the doubly refracted wave. How can the seismic velocity of each layer be determined from the diagram? (25 points)4. The following table gives two-way travel-tim
3、es of seismic waves reected from dierent reecting interfaces in a horizontally layered medium.（30 points）(a) Draw a plot of (travel-time)2 against (distance)2.(b) Determine the vertical two-way travel-time (“echo-time”) and average velocity to each reecting interface.(c) Compute the depth of each re
4、ector and the thickness of each layer.(d) Compute the true velocity (interval velocity) of each layer. (e) Verify your results by computing the total vertical travel-time for a wave reected from the deepest interface. 地球物理学基础（2013）作业 03 2 / 35. Assume that the three horizontal homogeneous rock layer
5、s in the previous problems have densities of 1800, 2200, and 2500 kg m-3 respectively. The lowest layer overlies basement with velocity 5.8 km s-1 and density 2700 kg m-3. (15 points)(a) Compute the reection and transmission coecients at each interface for a plane P-wave travel-ling vertically downw
6、ards.(b) Calculate what fraction of the initial energy of the wave is transmitted into the basement.(c) Calculate the fraction of the initial energy carried in the reection that returns to the surface from the basement.6.（附加题）An incident P-wave is converted into refracted and reected P- and S-waves
7、at an interface. Calculate all the critical angles in the following three cases, where and are the P-wave and S-wave velocities, respectively:7.（附加题）The table below gives up-dip and down-dip travel-times of P-wave arrivals for refraction proles over an inclined interface. The geophones are laid out
8、in a straight line passing through the alternate shot-points A and B, which are 2700 m apart on the prole.(a) Plot the travel-time curves for each shot-point.(b) Calculate the true velocity of the upper layer.(c) Calculate the apparent velocities of the layer below the refractor.(d) In which directi
9、on does the refracting interface dip?(e) What is the angle of dip of the interface?(f) What is the true velocity of the layer below the refractor?(g) What are the closest distances to the refractor below A and B? 地球物理学基础（2013）作业 03 3 / 3(h) What are the vertical depths to the refractor below A and B?注意：1、以上所有题目（英译汉除外） ，用中文或者英文回答都可以；2、请使用 A4 打印纸或者同等大小的纸张作答，无需再抄题目，标清楚题号即可，手写或者电子打印都可以；3、请在第一页页首位置写上你的信息，格式是“姓名+单位+ 学号” 。4、附加题可以不做，但鼓励大家去做。5、要求独立完成，鼓励大家互相讨论，有不懂的可以问助教或者问老师，但是请勿抄袭，否则按照学校相关规定，记零分处理。
