【摘要】 介绍了地幔电性结构、地幔温度、地幔含水量等参数对地球动力学和地幔动力学过程的重要科学意义,综述了近年来利用海底电缆在该领域的主要研究进展.本文首先介绍了日本利用海底电缆探测地幔深部结构的方法原理与发展历程,然后阐述了该方法的观测方式、观测系统与仪器,综述了国际上近年来利用海底电缆在环太平洋地区海底的观测资料进行地幔一维电导率结构、三维电导率分布的研究进展.基于海底电缆的观测数据进行反演的结果表明,太平洋海域地区地球深部存在410km,660km的电导率不连续面,此不连续面与地震资料的波速不连续面基本一致,为地幔不连续面提供了新的地球物理证据.在根据由海底电缆观测数据反演得到的太平洋地区地球内部电导率分布基础上,综述了综合深部地震波速、岩石高温高压实验等,将电导率的分布转换为地球内部的温度场分布、推导地幔过渡带水的浓度进而转换为地幔过渡带的含水百分比(含水量)的方法技术与研究进展.研究结果表明,夏威夷和北日本海地幔过渡带电导率异常主要受温度控制,菲律宾海域地幔过渡带的电导率异常除了和温度有关外,还受含水量影响,该处地幔过渡带的含水量大约在1%左右.这些研究表明,海底电缆探测方法,在地球深部探测尤其是地幔不连续面的探测、地幔温度场分布与特征、地幔含水量等方面有重要的作用.最后,展望了海底电缆探测方法的研究与发展,这些研究方法及成果对认识中国海域地球内部机构提供一定的参考.更多还原

【Abstract】 The knowledge on electrical conductivity in the mantle are very significant parameters for understanding the geodynamics and the evolution of the earth,as it is strongly sensitive to temperature,the presence of melt,water content,etc.This paper first introduces the general principle of the submarine cable method for exploring the Pacific Ocean mantle structure in Japan and its development.And then,it describes the recent progress in the studies,such as observation system of this novel method and mantle conductivity structure referred from the data of submarine cables in the Pacific Ocean.Including the results of the submarine cable study,the research progresses in the mantle transition zone below the Pacific Ocean are reviewed at the same time.Also the 1-D conductivity structure,which is inverted from the data recorded by the submarine cable,reveals that there are two discontinuity surfaces in the depth of 410 km and 660 km of the earth,which are even in accordance with the discontinuity surfaces inferred from the ocean bottom seismic data.All these two evidences describe the mantle structures in details.Moreover,through combining with the results of the seismic velocity studies in the depths of the earth,the rock experiments in high-temperature and high-pressure laboratory and the conductivity distribution in the Pacific Ocean mantle,it reveals that the mantle 3-D conductivity distribution,inverted from the submarine cable data,can be transformed into temperature distribution and even the percentage of the water content in the mantle transition zone.These results of the relevant studies and the related research progresses show that the anomaly conductivity distribution in the mantle transition zone of Hawaii and north Japan Sea is mainly influenced by temperature;however,that of the Philippine Sea is also influenced by the water content in the mantle transition zone,besides the factor of temperature anomaly in the mantle transition zone.In addition,the results of the related studies also reveal the percentage of the water content in the mantle transition zone of the Philippine Sea is about 1%.All these progresses in the electrical conductivity of the Pacific Ocean mantle transition zone evidently reveal that the submarine cable method is of vital usefulness to explore the characteristics of the mantle physical parameters,especially in the areas such as the temperature distribution,the water content etc.in the mantle transition zone and even in the deeper earth.The relevant improvement and further development are finally discussed,which may enlighten the relevant research and study in China Sea.更多还原