Pub Date : 2005-11-25DOI: 10.11867/J.ISSN.1001-8166.2005.11.1234
Niu Hecai, Zhang Hai-xiang, Zhang Boyou
Nb-enriched basalt is a kind of arc basalt that has special geochemical characteristics.It is silica-saturated with high Na_(2)O contents and differs from the typical arc basalt by the extremely high Nb(7×10~(-6)),TiO_(2)(1%～2%) and P contents with HFSE enrichment.In the primitive mantle-normalized trace element spider diagram,Nb-enriched basalts show weakly negative(sometime positive) Nb,Ta anomalies.The primitive mantle-normalized La/Nb ratios of the Nb-enriched basalts are smaller than 2(but smaller than 0.7,occasionally).It is derived from the partial melting of mantle peridotite metasomatized by slab melts.Since Nb-enriched basalts and adakites are the direct products of subducted oceanic slab,the characteristics of magma activity and interaction between slab melts and mantle wedge can be demonstrated by the studies of this association and the nature of the relative fluids and melts.
{"title":"Nb-ENRICHED BASALT: THE PRODUCT OF THE PARTIAL MELTING OF THE SLAB-DERIVED MELTMETASOMATIZED MANTLE PERIDOTITE","authors":"Niu Hecai, Zhang Hai-xiang, Zhang Boyou","doi":"10.11867/J.ISSN.1001-8166.2005.11.1234","DOIUrl":"https://doi.org/10.11867/J.ISSN.1001-8166.2005.11.1234","url":null,"abstract":"Nb-enriched basalt is a kind of arc basalt that has special geochemical characteristics.It is silica-saturated with high Na_(2)O contents and differs from the typical arc basalt by the extremely high Nb(7×10~(-6)),TiO_(2)(1%～2%) and P contents with HFSE enrichment.In the primitive mantle-normalized trace element spider diagram,Nb-enriched basalts show weakly negative(sometime positive) Nb,Ta anomalies.The primitive mantle-normalized La/Nb ratios of the Nb-enriched basalts are smaller than 2(but smaller than 0.7,occasionally).It is derived from the partial melting of mantle peridotite metasomatized by slab melts.Since Nb-enriched basalts and adakites are the direct products of subducted oceanic slab,the characteristics of magma activity and interaction between slab melts and mantle wedge can be demonstrated by the studies of this association and the nature of the relative fluids and melts.","PeriodicalId":415150,"journal":{"name":"Advance in Earth Sciences","volume":"123 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2005-11-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114770546","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2005-11-25DOI: 10.11867/J.ISSN.1001-8166.2005.11.1226
HU Yong-yun, Wen Xin-yu
Had Earth ever been completely covered by snow and ice and become a giant "snowball Earth" during the Neoproterozoic about 600~700 million years before? If it had,what caused this global freezing? What led it to melt? What had the violate climate changes during the Neoproterozoic impacted on the Cambrian life explosion? In the past few years,these problems have drawn extensive studies and intensive controversies in the fields of paleo-geology,paleontology,and paleoclimatology.According to existing results,it is generally thought that during the Neoproterozoic Earth had experienced several most severe global glaciations in Earth's history.However,it needs further geological and paleo-biological evidence to prove whether Earth had been completely frozen or not;numerical simulations with various external forcings showed that the formation of a hard "snowball Earth" is almost impossible,and if Earth runs into complete freezing,it is hard to get back out;there are two controversial points of views that such violate climate changes during the Neoproterozoic might have important impacts on the Cambrian life explosion.One is that the climate changes can induce mutations that fuel biological innovation,and the other one is that the impacts are on ecosystems.
{"title":"ON STUDIES OF SNOWBALL EARTH","authors":"HU Yong-yun, Wen Xin-yu","doi":"10.11867/J.ISSN.1001-8166.2005.11.1226","DOIUrl":"https://doi.org/10.11867/J.ISSN.1001-8166.2005.11.1226","url":null,"abstract":"Had Earth ever been completely covered by snow and ice and become a giant \"snowball Earth\" during the Neoproterozoic about 600~700 million years before? If it had,what caused this global freezing? What led it to melt? What had the violate climate changes during the Neoproterozoic impacted on the Cambrian life explosion? In the past few years,these problems have drawn extensive studies and intensive controversies in the fields of paleo-geology,paleontology,and paleoclimatology.According to existing results,it is generally thought that during the Neoproterozoic Earth had experienced several most severe global glaciations in Earth's history.However,it needs further geological and paleo-biological evidence to prove whether Earth had been completely frozen or not;numerical simulations with various external forcings showed that the formation of a hard \"snowball Earth\" is almost impossible,and if Earth runs into complete freezing,it is hard to get back out;there are two controversial points of views that such violate climate changes during the Neoproterozoic might have important impacts on the Cambrian life explosion.One is that the climate changes can induce mutations that fuel biological innovation,and the other one is that the impacts are on ecosystems.","PeriodicalId":415150,"journal":{"name":"Advance in Earth Sciences","volume":"115 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2005-11-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115185929","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The research and developing history of China's submarine instruments are reviewed.The present research status and tendency of sonar-techniques for submarine exploring,such as multi-beam sounding,sub-profiler sonar and side-scan sonar etc,are summarized and contrasted with the international status.Although many papers about the marine technique or theory are published and a lot of marine instruments are made in China in the last decades,there are still a great many urgent unfathomed issues about China's marine techniques.The current level of China's ocean techniques still lags behind the overseas ocean techniques.The main forces to impel China's ocean techniques developing quickly in recent years are that China's deep-sea resources researches are carried out deeply and quickly and a series of important survey projects to protect the ocean rights and interests have been brought into effect in China Sea.Since the late 1990s,a series of marine research projects under the "863" Program have been initiated,with lots of key instruments and softwares being developed serving China's survey projects.China's submarine techniques are developing quickly.Multi-beam sounding,sub-profiler sonar and side-scan sonar are convenient tools to explore the submarine quickly.They are based on similar detecting principles,but different acoustics information near submarine are obtained for different frequencies,and powers are used in these instruments.The datum about water depth,amplitude and backscatter are obtained with multi-beam sounding,the reflecting profiles from underlain sediment layer just like single seismic profile are detected with sub-profiler sonar.The seafloor images are obtained with side-scan sonar.These data are the base to study many issues about submarine geosciences.Seabed acoustics classification techniques,submarine acoustics in-situ test,dynamic geomorphologic and morphology tectonic are several hot-topics of application research based on the data of sonar-detecting near submarine.In the end,several sustainable development ideas about China's marine techniques are proposed: ①More articles about theory and technique of submarine techniques should be published to promote the research ability and level;②More submarine detecting instruments and equipment should be invented and produced quickly in China to quicken the homemade progress;③The data-processing software of submarine instruments should be built in China to enhance the copyright of our own;④The data of sonar-detecting near seafloor should be studied and applied deeply to widen the realms of submarine geosciences.
{"title":"RESEARCH STATUS AND PROSPECT OF SONAR-DETECTING TECHNIQUES NEAR SUBMARINE","authors":"Wu Ziyin, Zheng Yu-long, Chu Feng-you, Gao Jin-yao","doi":"10.11867/J.ISSN.1001-8166.2005.11.1210","DOIUrl":"https://doi.org/10.11867/J.ISSN.1001-8166.2005.11.1210","url":null,"abstract":"The research and developing history of China's submarine instruments are reviewed.The present research status and tendency of sonar-techniques for submarine exploring,such as multi-beam sounding,sub-profiler sonar and side-scan sonar etc,are summarized and contrasted with the international status.Although many papers about the marine technique or theory are published and a lot of marine instruments are made in China in the last decades,there are still a great many urgent unfathomed issues about China's marine techniques.The current level of China's ocean techniques still lags behind the overseas ocean techniques.The main forces to impel China's ocean techniques developing quickly in recent years are that China's deep-sea resources researches are carried out deeply and quickly and a series of important survey projects to protect the ocean rights and interests have been brought into effect in China Sea.Since the late 1990s,a series of marine research projects under the \"863\" Program have been initiated,with lots of key instruments and softwares being developed serving China's survey projects.China's submarine techniques are developing quickly.Multi-beam sounding,sub-profiler sonar and side-scan sonar are convenient tools to explore the submarine quickly.They are based on similar detecting principles,but different acoustics information near submarine are obtained for different frequencies,and powers are used in these instruments.The datum about water depth,amplitude and backscatter are obtained with multi-beam sounding,the reflecting profiles from underlain sediment layer just like single seismic profile are detected with sub-profiler sonar.The seafloor images are obtained with side-scan sonar.These data are the base to study many issues about submarine geosciences.Seabed acoustics classification techniques,submarine acoustics in-situ test,dynamic geomorphologic and morphology tectonic are several hot-topics of application research based on the data of sonar-detecting near submarine.In the end,several sustainable development ideas about China's marine techniques are proposed: ①More articles about theory and technique of submarine techniques should be published to promote the research ability and level;②More submarine detecting instruments and equipment should be invented and produced quickly in China to quicken the homemade progress;③The data-processing software of submarine instruments should be built in China to enhance the copyright of our own;④The data of sonar-detecting near seafloor should be studied and applied deeply to widen the realms of submarine geosciences.","PeriodicalId":415150,"journal":{"name":"Advance in Earth Sciences","volume":"38 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2005-11-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134646768","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2005-11-25DOI: 10.11867/J.ISSN.1001-8166.2005.11.1157
符淙斌, 安芷生, 郭维栋
Aridification in northern China is one of the most serious life-supporting environmental challenges.Annual economic losses caused directly by aridity-related disasters have been more than 10 billion RMB since the beginning of 1990s,which greatly restricts the application of development strategies of national economy.Under the guidance of Global Change Science,a National Key Basic Research Science Foundation(973 project)"Evolution of Life-supporting Environment in Our Nation and the Predictive Study of Aridification in Northern China" has carried out integrated studies on the living environment consisted of various components,such as water,soil,air,and life,etc.Aimed to put forward scientific bases for the evolution prediction,impact assessments and adaptation measures of aridification,the project revealed the mechanisms of the formation of aridification from the viewpoint of the comprehensive changes in monsoon environmental system.Notable results have been achieved since the application of the project over the past 5 years both in the fields of social demand meeting and scientific creativities.The main scientific issues and achievements of this project are introduced in this paper.
{"title":"我国生存环境演变和北方干旱化趋势预测研究（I）：主要研究成果","authors":"符淙斌, 安芷生, 郭维栋","doi":"10.11867/J.ISSN.1001-8166.2005.11.1157","DOIUrl":"https://doi.org/10.11867/J.ISSN.1001-8166.2005.11.1157","url":null,"abstract":"Aridification in northern China is one of the most serious life-supporting environmental challenges.Annual economic losses caused directly by aridity-related disasters have been more than 10 billion RMB since the beginning of 1990s,which greatly restricts the application of development strategies of national economy.Under the guidance of Global Change Science,a National Key Basic Research Science Foundation(973 project)\"Evolution of Life-supporting Environment in Our Nation and the Predictive Study of Aridification in Northern China\" has carried out integrated studies on the living environment consisted of various components,such as water,soil,air,and life,etc.Aimed to put forward scientific bases for the evolution prediction,impact assessments and adaptation measures of aridification,the project revealed the mechanisms of the formation of aridification from the viewpoint of the comprehensive changes in monsoon environmental system.Notable results have been achieved since the application of the project over the past 5 years both in the fields of social demand meeting and scientific creativities.The main scientific issues and achievements of this project are introduced in this paper.","PeriodicalId":415150,"journal":{"name":"Advance in Earth Sciences","volume":"62 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2005-11-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129242933","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2005-10-25DOI: 10.11867/J.ISSN.1001-8166.2005.10.1106
Xu Yong-fu, Zhao Liang, PU Yi-fen
This paper briefly reviews the history of development of ocean carbon-cycle models from the beginning of the simplest three-box model,discusses the features of various models at different times,and points out the ability of oceanic uptake of atmospheric CO_(2.)In recent years,the global ocean-circulation model of carbon cycle often uses a simple biogeochemical model,while in the process-based model and one-dimensional model the role of ecosystem in the ocean carbon cycle is explored in relative detail.In 1995,the Ocean Carbon-Cycle Model Intercomparison Project(OCMIP) was initiated by IGBP/GAIM.Two phases have been completed.In the second phase,13 modeling groups participated in the project.Although OCMIP is now in its third phase,some papers from the first or second phase are still in preparation.The newest global ocean-circulation models estimate an annual mean oceanic uptake of 1.5-2.2 GtC of anthropogenic CO_(2) for the 1980s.In spite of many achievements,which have revealed the basic features of oceanic uptake and distributions of atmospheric CO_(2),many challenges still remain that require further research,which is discussed.One of serious issues is the consistency of physical fields,which can be assessed through examination of anthropogenic tracers.The parameterization of air-sea exchange of CO_(2) still needs to be further studied.The use of the carbon cycle model with an explicit ecosystem is a developing trend in the study of biogeochemical cycle of carbon dioxide and its response to global change.
{"title":"ADVANCES IN THE STUDIES OF OCEAN CARBON-CYCLE MODEL","authors":"Xu Yong-fu, Zhao Liang, PU Yi-fen","doi":"10.11867/J.ISSN.1001-8166.2005.10.1106","DOIUrl":"https://doi.org/10.11867/J.ISSN.1001-8166.2005.10.1106","url":null,"abstract":"This paper briefly reviews the history of development of ocean carbon-cycle models from the beginning of the simplest three-box model,discusses the features of various models at different times,and points out the ability of oceanic uptake of atmospheric CO_(2.)In recent years,the global ocean-circulation model of carbon cycle often uses a simple biogeochemical model,while in the process-based model and one-dimensional model the role of ecosystem in the ocean carbon cycle is explored in relative detail.In 1995,the Ocean Carbon-Cycle Model Intercomparison Project(OCMIP) was initiated by IGBP/GAIM.Two phases have been completed.In the second phase,13 modeling groups participated in the project.Although OCMIP is now in its third phase,some papers from the first or second phase are still in preparation.The newest global ocean-circulation models estimate an annual mean oceanic uptake of 1.5-2.2 GtC of anthropogenic CO_(2) for the 1980s.In spite of many achievements,which have revealed the basic features of oceanic uptake and distributions of atmospheric CO_(2),many challenges still remain that require further research,which is discussed.One of serious issues is the consistency of physical fields,which can be assessed through examination of anthropogenic tracers.The parameterization of air-sea exchange of CO_(2) still needs to be further studied.The use of the carbon cycle model with an explicit ecosystem is a developing trend in the study of biogeochemical cycle of carbon dioxide and its response to global change.","PeriodicalId":415150,"journal":{"name":"Advance in Earth Sciences","volume":"6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2005-10-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131410786","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2005-10-25DOI: 10.11867/J.ISSN.1001-8166.2005.10.1127
Li Lan, Zhou Zhong-hao, Liu Gang-cai
As the criterion of judging non-erosion and erosion area,the value of soil loss tolerance(T-value) must be determined scientifically and rationally.To assign a T-value soil formation rate,relationship between soil loss and productivity and gully prevention must be considered.Current methods of evaluating the soil loss tolerance mainly include: ①soil profile thickness;②the geochemistry cycle theory;③nutrient balance;and ④ according to erosion model.The international existing T-value standards are mainly established according to the soil profile thickness and soil formation rate.The history and the main content of soil loss tolerance study are reviewed in this paper,and the method of using Barth equation and on the basis of the risk assessment are also introduced.In face of the existing problems in the evaluation method and conclusion of T-value research,future T-value study should be concentrated on the characteristic of soil formation(natural attribute),the durative of rational productivity level(social attribute) and the soil and water environment safety(social and natural attribute)is raised.
{"title":"THE PRESENT SITUATION AND SOME THOUGHTS OF SOIL LOSS TOLERANCE STUDY","authors":"Li Lan, Zhou Zhong-hao, Liu Gang-cai","doi":"10.11867/J.ISSN.1001-8166.2005.10.1127","DOIUrl":"https://doi.org/10.11867/J.ISSN.1001-8166.2005.10.1127","url":null,"abstract":"As the criterion of judging non-erosion and erosion area,the value of soil loss tolerance(T-value) must be determined scientifically and rationally.To assign a T-value soil formation rate,relationship between soil loss and productivity and gully prevention must be considered.Current methods of evaluating the soil loss tolerance mainly include: ①soil profile thickness;②the geochemistry cycle theory;③nutrient balance;and ④ according to erosion model.The international existing T-value standards are mainly established according to the soil profile thickness and soil formation rate.The history and the main content of soil loss tolerance study are reviewed in this paper,and the method of using Barth equation and on the basis of the risk assessment are also introduced.In face of the existing problems in the evaluation method and conclusion of T-value research,future T-value study should be concentrated on the characteristic of soil formation(natural attribute),the durative of rational productivity level(social attribute) and the soil and water environment safety(social and natural attribute)is raised.","PeriodicalId":415150,"journal":{"name":"Advance in Earth Sciences","volume":"31 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2005-10-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116016264","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2005-09-25DOI: 10.11867/J.ISSN.1001-8166.2005.09.0932
Sun Min-zhang, Lu Li, Wang Jie-min, Liu Shao-min
It is very important to determine land surface fluxes, including sensible heat fluxes and latent heat fluxes, for the issues involving many aspects of climate, agriculture, hydrology, and water resources management. However, it is still very difficult to observe and study areal fluxes in the scale of several to tens kilometers, especially on heterogeneous land surface. The Large Aperture Scintillometer (LAS), which is becoming popular in recent years, offers a new perspective to solve this problem. Based on light scintillation in the turbulent atmosphere,it can measure sensible heat fluxes by emitting a beam of light over a horizontal path. Then, latent heat fluxes can be derived according to surface energy balance equation. The LAS is adapted to different kinds of land surface, homogeneous or heterogeneous. Test comparisons of LAS flux measurement with the measurements by eddy correlation system show good agreement. There are some key factors, which influence the precision of areal evapotranspiration determined by LAS, such as beam height, wind speed, roughness length, zero plane displacement, Bowen ratio, and net radiation, etc. Basic principle and some algorithms are introduced. A prosperous utilization of LAS in recent years is in the validation of areal surface fluxes retrieved from remote sensing models, such as the SEBAL and SEBS. Finally, this paper discusses the development trend of applying the large aperture scintillometer in the future.
{"title":"ADVANCES IN THE STUDY OF AREAL SURFACE FLUXES WITH LARGE APERTURE SCINTILLOMETER","authors":"Sun Min-zhang, Lu Li, Wang Jie-min, Liu Shao-min","doi":"10.11867/J.ISSN.1001-8166.2005.09.0932","DOIUrl":"https://doi.org/10.11867/J.ISSN.1001-8166.2005.09.0932","url":null,"abstract":"It is very important to determine land surface fluxes, including sensible heat fluxes and latent heat fluxes, for the issues involving many aspects of climate, agriculture, hydrology, and water resources management. However, it is still very difficult to observe and study areal fluxes in the scale of several to tens kilometers, especially on heterogeneous land surface. The Large Aperture Scintillometer (LAS), which is becoming popular in recent years, offers a new perspective to solve this problem. Based on light scintillation in the turbulent atmosphere,it can measure sensible heat fluxes by emitting a beam of light over a horizontal path. Then, latent heat fluxes can be derived according to surface energy balance equation. The LAS is adapted to different kinds of land surface, homogeneous or heterogeneous. Test comparisons of LAS flux measurement with the measurements by eddy correlation system show good agreement. There are some key factors, which influence the precision of areal evapotranspiration determined by LAS, such as beam height, wind speed, roughness length, zero plane displacement, Bowen ratio, and net radiation, etc. Basic principle and some algorithms are introduced. A prosperous utilization of LAS in recent years is in the validation of areal surface fluxes retrieved from remote sensing models, such as the SEBAL and SEBS. Finally, this paper discusses the development trend of applying the large aperture scintillometer in the future.","PeriodicalId":415150,"journal":{"name":"Advance in Earth Sciences","volume":"58 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2005-09-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131517906","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2005-09-25DOI: 10.11867/J.ISSN.1001-8166.2005.09.0946
金振民, 王永锋
Seismic anisotropy has received a lot of attention from seismologists in recent years and is becoming increasingly important in the field of geophysics and geology. It is regarded as the bridge between seismology and structural geology. Seismic anisotropy is discovered at all scales in the Earth's interior and may provide us with valuable information, such as the thickness and structure of lithosphere, mantle convection, and geodynamics, and since the fast wave propagation directions of shear wave correspond to flow directions as implied from plate motions, it is recognized as a good indicator of deformation and mantle flow. Seismic anisotropy plays a central role in revealing the deep structure and geodynamics in the following geological settings, such as subduction zone, continental rift, mantle transition zone and continental collisional orogenic belt (for instance, Tibet). This paper mainly reviews recent studies of the occurrence, geological interpretation and implication of seismic anisotropy for these geological settings. There is no doubt that the existing technologies will be refined and developed further to make estimates of anisotropy and related rock properties more accurate. Problems required to be further considered include the following: (1) resolution of shear wave: SKS wave is poor in vertical resolution, and it is suggested that the combination of surface wave and SKS wave may well constrain the depth of anisotropy; (2) petrofabric analysis: although great advances had been made in investigation of relationship between anisotropy and petrofabric, recent studies reveal that olivine fabric may be different from previously expected under water-rich conditions, which may then induce anomalous seismic anisotropy. Thus, efforts are still required to be taken to further study the petrofabric, and (3) other mechanisms for seismic anisotropy, such as MPO, aligned cracks, etc.. In particular, strain aligns highly anisotropic minerals, such as olivine, orthopyroxene, plagioclase, and so on, in the mantle and crust to form LPO, which is the most likely cause of splitting measured from records of distant earthquakes. As a result, it is emphasized that investigation of seismic anisotropy shall be combined with rheology of rocks and minerals at high temperature and pressure.
{"title":"地震波各向异性：窥测地球深部构造的“探针”","authors":"金振民, 王永锋","doi":"10.11867/J.ISSN.1001-8166.2005.09.0946","DOIUrl":"https://doi.org/10.11867/J.ISSN.1001-8166.2005.09.0946","url":null,"abstract":"Seismic anisotropy has received a lot of attention from seismologists in recent years and is becoming increasingly important in the field of geophysics and geology. It is regarded as the bridge between seismology and structural geology. Seismic anisotropy is discovered at all scales in the Earth's interior and may provide us with valuable information, such as the thickness and structure of lithosphere, mantle convection, and geodynamics, and since the fast wave propagation directions of shear wave correspond to flow directions as implied from plate motions, it is recognized as a good indicator of deformation and mantle flow. Seismic anisotropy plays a central role in revealing the deep structure and geodynamics in the following geological settings, such as subduction zone, continental rift, mantle transition zone and continental collisional orogenic belt (for instance, Tibet). This paper mainly reviews recent studies of the occurrence, geological interpretation and implication of seismic anisotropy for these geological settings. There is no doubt that the existing technologies will be refined and developed further to make estimates of anisotropy and related rock properties more accurate. Problems required to be further considered include the following: (1) resolution of shear wave: SKS wave is poor in vertical resolution, and it is suggested that the combination of surface wave and SKS wave may well constrain the depth of anisotropy; (2) petrofabric analysis: although great advances had been made in investigation of relationship between anisotropy and petrofabric, recent studies reveal that olivine fabric may be different from previously expected under water-rich conditions, which may then induce anomalous seismic anisotropy. Thus, efforts are still required to be taken to further study the petrofabric, and (3) other mechanisms for seismic anisotropy, such as MPO, aligned cracks, etc.. In particular, strain aligns highly anisotropic minerals, such as olivine, orthopyroxene, plagioclase, and so on, in the mantle and crust to form LPO, which is the most likely cause of splitting measured from records of distant earthquakes. As a result, it is emphasized that investigation of seismic anisotropy shall be combined with rheology of rocks and minerals at high temperature and pressure.","PeriodicalId":415150,"journal":{"name":"Advance in Earth Sciences","volume":"19 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2005-09-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132588634","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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