2017年地球物理学基础作业03及参考答案

2017年地球物理学基础第3次作业第1页共5页1THETECHNIQUESOFREFRACTIONANDREFLECTIONSEISMOLOGY,USINGARTIFICIAL,CONTROLLEDEXPLOSIONSASSOURCES,WEREDEVELOPEDINTHESEARCHFORPETROLEUMSINCETHE1960STHESEMETHODSHAVEBEENAPPLIEDWITHNOTABLESUCCESSTOTHERESOLUTIONOFDETAILEDCRUSTALSTRUCTUREUNDERCONTINENTSANDOCEANSTHEDEVELOPMENTOFPOWERFULCOMPUTERTECHNOLOGYENABLEDREFINEMENTSINEARTHQUAKELOCATIONANDINTHEDETERMINATIONOFTRAVELTIMESOFSEISMICBODYWAVESTHESEADVANCESLEDTOTHEMODERNFIELDOFSEISMICTOMOGRAPHY,APOWERFULANDSPECTACULARTECHNIQUEFORREVEALINGREGIONSOFTHEEARTHSINTERIORTHATHAVEANOMALOUSSEISMICVELOCITIESINTHEFIELDOFEARTHQUAKESEISMOLOGY,THENEEDTOPROTECTPOPULATIONSANDMANMADESTRUCTURESHASRESULTEDINTHEINVESTMENTOFCONSIDERABLEEFFORTINTHESTUDYOFEARTHQUAKEPREDICTIONANDTHEDEVELOPMENTOFCONSTRUCTIONCODESTOREDUCEEARTHQUAKEDAMAGETOAPPRECIATEHOWSEISMOLOGISTSHAVEUNRAVELEDTHESTRUCTUREOFTHEEARTHSINTERIORITISNECESSARYTOUNDERSTANDWHATTYPESOFSEISMICWAVESCANBEGENERATEDBYANEARTHQUAKEORMANMADESOURCESUCHASACONTROLLEDEXPLOSIONTHEPROPAGATIONOFASEISMICDISTURBANCETHROUGHTHEEARTHISGOVERNEDBYPHYSICALPROPERTIESSUCHASDENSITY,ANDBYTHEWAYINWHICHTHEMATERIALOFTHEEARTHSINTERIORREACTSTOTHEDISTURBANCEMATERIALWITHINTHESEISMICSOURCESUFFERSPERMANENTDEFORMATION,BUTOUTSIDETHESOURCETHEPASSAGEOFASEISMICDISTURBANCETAKESPLACEPREDOMINANTLYBYELASTICDISPLACEMENTOFTHEMEDIUMTHATIS,THEMEDIUMSUFFERSNOPERMANENTDEFORMATIONBEFOREANALYZINGTHEDIFFERENTKINDSOFSEISMICWAVES,ITISIMPORTANTTOHAVEAGOODGRASPOFELEMENTARYELASTICITYTHEORYTHISREQUIRESUNDERSTANDINGTHECONCEPTSOFSTRESSANDSTRAIN,ANDTHEVARIOUSELASTICCONSTANTSTHATRELATETHEM利用人工的、控制爆炸作为震源的折射地震和反射地震技术在寻找石油领域得到了发展。19世纪60年代以来，这些方法已经令人瞩目的成功应用于分辨位于大陆和大洋下的精细地壳构造。强大的计算机技术的发展使地震位置的改进和地震体波走时的测定成为可能。这些进展导致了现代地震层析成像领域的发展，这是一项强大而引人注目的技术，它揭示了地球内部具有异常地震速度的区域。在天然地震地震学领域，对人口和人造建筑的保护需求导致了在地震预测研究和制定减少地震损害的建筑规范方面投入了大量精力。想要领会地震学家是如何揭开地球内部结构的，就有必要理解什么类型的地震波可以被天然地震震源或人工地震震源（如控制爆破）产生。地震扰动在地球的传播受密度等物理特性的控制，以及地球内部物质对扰动的反应方式的控制。震源中的物质承受永久变形，但震源外的地震扰动主要通过介质的弹性位移而发生，即介质不发生永久变形。在分析不同类型的地震波之前，掌握基本弹性理论是十分重要的。这需要理解应力和应变的概念，以及与它们有关的各种弹性常数。2波前WAVEFRONT；反射波REFLECTEDWAVE；高速带HIGHVELOCITYZONE；球面层SPHERICALLAYERS；积分法INTEGRALMETHOD；平面波PLANEWAVE；射线路径RAYPATH；斯奈耳定律SNELLSLAW；HEADWAVE首波；RAYPARAMETER射线参数；2017年地球物理学基础第3次作业第2页共5页TRAVELTIMECURVE走时曲线；DIRECTWAVE直达波；APPARENTVELOCITY视速度；LOWVELOCITYDISCONTINUITY低速间断面；SEISMICPHASE震相；CURVATUREOFSPHERICALRAY球面射线曲率；3ONACROSSSECTIONOFTHEEARTH,SKETCHTHEPATHSOFTHEFOLLOWINGSEISMICRAYSIPKP,IISKS,IIIPCP,IVPPP（10POINTS）4ASTRONGEARTHQUAKEOFFTHECOASTOFJAPANSETSOFFATSUNAMITHATPROPAGATESACROSSTHEPACIFICOCEANAVERAGEDEPTHD5KM（20POINTS）ACALCULATETHEVELOCITYOFTHEWAVEINKM/HRANDTHECORRESPONDINGWAVELENGTH,WHENTHEWAVEHASADOMINANTPERIODOF30MINBHOWLONGDOESTHEWAVETAKETOREACHHAWAII,WHICHISATANANGULARDISTANCEOF54FROMTHEEPICENTER（A）HRKMSMGDC/797/42211000589KMCT539850797（B）HRCLT53779763712360545THEFOLLOWINGTABLEGIVESTWOWAYTRAVELTIMESOFSEISMICWAVESREFLECTEDFROMDIFFERENTREFLECTINGINTERFACESINAHORIZONTALLYLAYEREDMEDIUM（20POINTS）2017年地球物理学基础第3次作业第3页共5页ADRAWAPLOTOFTRAVELTIME2AGAINSTDISTANCE2BDETERMINETHEVERTICALTWOWAYTRAVELTIME“ECHOTIME”ANDAVERAGEVELOCITYTOEACHREFLECTINGINTERFACECCOMPUTETHEDEPTHOFEACHREFLECTORANDTHETHICKNESSOFEACHLAYERDCOMPUTETHETRUEVELOCITYINTERVALVELOCITYOFEACHLAYEREVERIFYYOURRESULTSBYCOMPUTINGTHETOTALVERTICALTRAVELTIMEFORAWAVEREFLECTEDFROMTHEDEEPESTINTERFACE（A）01234567X1060020406081121416182TRAVELTIME2DISTANCE2FIRSTREFLECTORSECONDREFLECTORTHIRDREFLECTOR（B）ACCORDINGTOTHEPLOTOFTRAVELTIME2AGAINSTDISTANCE2OFEACHREFLECTORABOVE，THESLOPEOFEACHSTRAIGHTLINEISEQUALTO1/VA2，WHEREVAISTHEAVERAGEVELOCITY，ANDTHEITSINTERCEPTWITHTHET2AXISISEQUALTOTHESQUAREOFECHOTIMET0，THENTHEAVERAGEVELOCITYANDECHOTIMECANBECOMPUTED，THERESULTSARELISTINFOLLOWINGTABLE2017年地球物理学基础第3次作业第4页共5页THATIS，TOTHE1STLAYER,AVERAGEVELOCITYISABOUT1800M/SITSECHOTIMEISABOUT0111STOTHE2NDLAYER,AVERAGEVELOCITYISABOUT2360M/SITSECHOTIMEISABOUT0296STOTHE3RDLAYER,AVERAGEVELOCITYISABOUT3640M/SITSECHOTIMEISABOUT0576S（C）FORTHEFIRSTREFLECTOR，THEAVERAGEVELOCITYISITSTRUEVELOCITYANDITSDEPTH（D1）ISEQUALTOITSTHICKNESS（D1），THATISVA1V1，D1D1，SOMTVATVD1002/02/0D111111FORTHESECONDREFLECTORS，MTVADD3502/0D22212MDDD250112FORTHETHIRDREFLECTORS，MTVADD10492/0D33323MDDD699233（D）FORTHEFIRSTREFLECTOR，THEAVERAGEVELOCITYISITSTRUEVELOCITY（INTERVALVELOCITY）SMV/18001FORTHESECONDREFLECTORS，THEINTERVALVELOCITYISCOMPUTEDBYITSTHICKNESSANDTWOWAYTRAVELTIMEINTHESECONDLAYERSMTTD/2695002V1222FORTHETHIRDREFLECTORS，SMTTD/4996002V2333（E）THETOTALVERTICALTRAVELTIMEFORAWAVEREFLECTEDFROMTHEDEEPESTINTERFACESVDVDVDT576022203322113201