地球物理学基础作业03.doc

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1、地球物理学基础(2013)作业03布置时间：2013-10-8倜二)交作业时间：2013-10-24(周四)1、翻译(15分)将英文教材《FundamentalsofGeophysics^第175页的右边第二段翻译成屮文，即以“Reflectionseismologyisdirectedprimarilyatfindingthedepthsto…”开头的那一段。2、名词解释(15分)首波反射系数共屮心点排列动校正合成地震记录3・Aseismicsurveyisconductedoverlevelgroundconsistingoftwohorizontallayers.Sketchatr

2、avel-timediagramthatshowsthearrivalsofthedirectwave,thereflectedwave,andthedoublyrefractedwave.Howcantheseismicvelocityofeachlayerbedeterminedfromthediagram?(25points)4.Thefollowingtablegivestwo-waytravel-timesofseismicwavesreflectedfromdifferentreflectinginterfacesinahorizontallylayeredmedium.(3

3、0points)Geophonetoshoi-poinidistance[m]Travel-time[s]toFirstreflectorSecondreflectorThirdreflector5000.2990.3640.59210000.5660.5170.63815000.8410.7010.70820001.1170.8970.79925001.3931.0990.896.2■■2(a)Drawaplotof(travel-time)against(distance).(b)Determinetheverticaltwo-waytravel-time("echo-time”)a

4、ndaveragevelocitytoeachreflectinginterface.(c)Computethedepthofeachreflectorandthethicknessofeachlayer.(d)Computethetruevelocity(intervalvelocity)ofeachlaye匚(c)Verifyyourresultsbycomputingthetotalverticaltravel-timeforawavereflectedfromthedeepestinterface.4.Assumethatthethreehorizontalhomogeneous

5、rocklayersinthepreviousproblemshavedensitiesof1800,2200,and2500kgm"respectively.Thelowestlayeroverliesbasementwithvelocity5.8kms'anddensity2700kgm'3.(15points)(a)ComputethereflectionandtransmissioncoefficientsateachinterfaceforaplaneP-wavetravel-lingverticallydownwards.(b)Calculatewhatfractionoft

6、heinitialenergyofthewaveistransmittedintothebasement.(c)Calculatethefractionoftheinitialenergycarriedinthereflectionthatreturnstothesurfacefromthebasement.5.(附力[I题)AnincidentP-waveisconvertedintorefractedandreflectedP-andS-wavesataninterface.Calculateallthecriticalanglesinthefollowingthreecases,w

7、hereaand卩aretheP-waveandS-wavevelocities,respectively:LayerSeismicwaveCase(a)[kms-1jCase(b)[kms-1]Case(c)[kms-1]Aboveinterlacea3.54.05.502.02.33」Belowinterfacea8.56.07.0p5.03.54.06.(附加题)Thetablebelowgivesup-dipanddown-