海洋地球物理第一章緒論()

1、11 Preview 緒論緒論1.1 INTRODUCTION1.2 SEABED MORPHOLOGY: A FRAMEWORK FOR GEOPHYSICAL OBSERVATIONS1.3 DEVELOPMENT OF MARINE GEOPHYSICS1.3.1 Major contribution of marine geophysics to global geology1.3.2 Impact of military science1.3.3 Demand for petroleum and other offshore minerals1.3.4 Availability of

2、 research vessels （船、艦）（船、艦）and other platforms 1.3.5 Advances in navigation1.3.6 Internationalization of oceanography1.3.7 Introduction of new technologies1.3.8 Increased awareness of the human impact on oceanic environments21.3 DEVELOPMENT OF MARINE GEOPHYSICS海上地球物理測量的興起與發(fā)展海上地球物理測量的興起與發(fā)展Outline: n

3、磁偏角測量磁偏角測量 Measurements of magnetic declinationn海上重力調(diào)查海上重力調(diào)查 Investigations of the Earths gravity field at sean海上電法和地震探測海上電法和地震探測 electrical and seismic methodsn第二次世界大戰(zhàn)以后海洋地球物理的快速發(fā)展第二次世界大戰(zhàn)以后海洋地球物理的快速發(fā)展 The period since World War II has seen enormous advances in marine geophysics31.3 DEVELOPMENT OF M

4、ARINE GEOPHYSICSn海上磁偏角測量海上磁偏角測量 Magnetic declination the angle between a compass needle and geographic north -the first geophysical observations aboard ship to provide clues about the nature of the solid Earth. Measurements of magnetic declination-The earliest world chart showing the magnetic field

5、at sea as lines of equal declination was published by Sir Edmond Halley (1702)lfollowing three expeditions on the naval vessel Paramore between 1698 and 1701. - a basis for navigationlwhen astronomical and visual sightings on landmarks were not possible. -declination changes with timelHalley argued

6、that this phenomenon arises from the westward rotation of the Earths deep interior with respect to its outer shell, an idea focusing on a dynamic planet that remains central to modern geomagnetism. -To keep charts of oceanic declination up to datelshipboard measurements continued from Halleys time w

7、ell into this century, providing further insights into secular changes(長期變化)and the origin of the geomagnetic field. 4DEVELOPMENT OF MARINE GEOPHYSICSn海上重力調(diào)查海上重力調(diào)查 Investigations of the Earths gravity field at sea -began in the late 19th century l with the experiments of C.W. Siemens (1876) lbuilt a

8、 gravity-measuring bathometer(重力測深計(jì)） as a means of determining water depth.lfailed to match the accuracy of lead-line sounding（鉛錘測深） and was never developed for routine use. -The first gravity measurements to prove of value for studying the seabedlbegan some 50 years later when F.A. Vening Meinesz (

9、1948) used pendulum apparatus aboard a submarine. lHis careful observations revealed substantial lateral changes in density below the ocean floor which he related to tectonic processes. 5DEVELOPMENT OF MARINE GEOPHYSICSn海上電法和地震探測海上電法和地震探測 electrical and seismic methods-It was during the 1930s that l

10、and-based electrical and seismic methods were adapted for use at sea. C. Schlumberger, M. Schlumberger and E.G. Leonardon (1934)：-ran cables a short distance out from the Algerian（阿爾及利亞）coast to find the depth of bedrock基巖 from readings of electrical current and potential differencesM. Ewing, A.P. C

11、rary and H.M. Rutherford (1937) E.C. Bullard and T.F. Gaskell (1938)：-pioneering seismic measurements were made in the shallow waters off the eastern USA (1937) and off southwest Britain (1938). -By timing the passage of elastic waves（彈性波傳播過程） from underwater explosions they demonstrated the presenc

12、e of thick low-velocity sediments beneath the continental shelf, thus laying the foundations of the modern offshore petroleum industry. 6DEVELOPMENT OF MARINE GEOPHYSICSn第二次世界大戰(zhàn)以后海洋地球物理的快速發(fā)展第二次世界大戰(zhàn)以后海洋地球物理的快速發(fā)展 The period since World War II has seen enormous advances in marine geophysics -Exploratio

13、n has reached far beyond the confines of coastal areas into the deepest waters and furthest reaches of the oceans. -brought about a radical transformation（根本改變） in our understanding of geological processes, the nature of the seabed and the development of our planet. -dramatically altered the ways in

14、 which we find and exploit seabed resources. 71.3.1 Major contribution of marine geophysics to global geology-Until the 1950s our knowledge of the constitution and history of the Earth was largely inferred from studies of the continents. -Land-based research left many geological questions unanswered

15、. n陸地地質(zhì)研究留下的四個(gè)基本問題陸地地質(zhì)研究留下的四個(gè)基本問題 Among these lie four fundamental problemslDo the continents and oceans differ in their geology?lHow did the oceans form? lHow old are the ocean basins? lHow do ocean basins and their margins evolve through geological time? 8Major contributionn大陸漂移假說的提出：大陸漂移假說的提出：F.B

16、. Taylor (1910) and A. Wegener (1915)：-argued that the oceans are geologically young and have developed as continental blocks drifted apart.- an idea outlined at least two centuries earlier. Evidence:-came from studies of fossils, climatic indicators in rock sequences and the structure of mountain b

17、elts. -With a few notable exceptions, most geologists found the continental drift idea unconvincing(不易令人信服的; 沒有說服力的)and could not be diverted from(使偏離） the view that the oceans are permanent features formed early in the Earths history. 9Alfred Wegener and continental drift Scientists still do not ap

18、pear to understand sufficiently that all earth sciences must contribute evidence toward unveiling(揭開揭開)the state of our planet in earlier times, and that the truth of the matter can only be reached by combing all this evidence. . . It is only by combing the information furnished by all the earth sci

19、ences that we can hope to determine truth here, that is to say, to find the picture that sets out all the known facts in the best arrangement and that therefore has the highest degree of probability. Further, we have to be prepared always for the possibility that each new discovery, no matter what s

20、cience furnishes it, may modify the conclusions we draw. Alfred Wegener. The Origins of Continents and Oceans (4th edition)魏格納（魏格納（Alfred Lothar Wegener）是德國氣象學(xué)家、地球物理學(xué)家，）是德國氣象學(xué)家、地球物理學(xué)家，1880年年11月月1日日生于柏林，生于柏林，1930年年11月在格陵蘭考察冰原時(shí)遇難。被稱為月在格陵蘭考察冰原時(shí)遇難。被稱為大陸漂移學(xué)說之父大陸漂移學(xué)說之父.10Major contributionnGeophysical stu

21、dies in the 1950s and 1960s overturned our thinking on how the oceans and continents have evolved. -Observations at sea clearly demonstrated that the oceans are much younger than the continents and quite different in structure. -They are created by igneous activity(火成巖活動） where rigid blocks or litho

22、spheric plates forming the Earths outer shell are moving apart. Note:The interactions of Iithospheric plates and their evolution through time are embraced (包含）in the theory of plate tectonics (Le Pichon et al, 1973; Kearey and Vine,l996). 111.3.2 Impact of military sciencen滿足戰(zhàn)爭需要，影響軍事科學(xué)發(fā)展?jié)M足戰(zhàn)爭需要，影響軍事

23、科學(xué)發(fā)展Marine research for military purposes during World War II had an important influence on the development of geophysics after 1945.provided both the expertise專門知識專門知識 and some of the basic instruments for making geophysical measurements in a hostile(敵敵方的方的) marine environment.Techniques for locati

24、ng submarines and other underwater objects had advanced rapidly during wartime. -Primarily based on the detection of sound（聲波檢測） and perturbations in the Earths magnetic field（磁場攝動）-they involved the construction of some of the principal tools of marine geophysicists: sensitive magnetometers（地磁儀）, h

25、ydrophones（水聽器） and the devise capable of producing frequent underwater explosions. -Towed sound sources（拖曳聲源） and cables（電纜） producing high-intensity magnetic fields were designed to sweep acoustic and magnetic mines（水雷） by causing them to detonate（引爆） at a safe distance. -It was also necessary for tactical（戰(zhàn)術(shù)上的） reasons to learn about the propagation of sound in the oceans and, in particular, the effect of variations in the water layer and the character of the sea bottom on acoustic transmission.12Impact