岩石圈塑性流动波的实验研究(Ⅰ)
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摘要
实验采用了适当配比的塑化松香 ,模拟岩石圈延性层 ,研究边界驱动条件下塑性流动波的传播过程。实验表明 ,塑性流动波类似于粘性重力波 ,并有“快波”和“慢波”之分 ,二者分别由主波和辅波叠加而成。主波类似于孤立波或涌波。根据相似原理 ,“快波”主波的外推波速约为 0 .12～2 .5km/a ,在波速量级上大致相当或接近于岩石圈下层某些控制地震迁移的塑性流动波。
In order to study the propagation processes of plastic-flow waves in the lithosphere, plasticized rosin, i.e. the mixture of rosin (R) and plasticizer (P ) with proper ratio of P/R, is used as analogue material for modeling ductile layer in the lithosphere. The mixture is poured into a rectangular shallow trough (280～300mm long and 190～200mm wide), forming ductile one layer model (1) with a thickness of 8～9mm, as shown in Fig. 1. The bottom (2) and walls (3 and 4) of the trough are made up of glass plates. Some models are covered by a 0.1～0.2mm-thick brittle layer composed of dried consolidated talc-powder slurry, forming brittle/ductile two-layer models. The driving boundary of the model, a movable wall (4) of the trough, is pushed by the springs (6), which are compressed by screw-pushers (7) (micrometer screws) or adding spacers. A number of measuring points (8) are placed on the models surface and their displacements are measured by using a coordinate-system micrometer with the horizontal accuracy of 0.002mm and vertical accuracy of 0.01mm. The tests are carried out at constant temperature with the errors within the range of ±0.5℃ for most of the models. According to the similarity criterion and considering the Stokes number, S t (the ratio of viscous force to gravitational force) for viscous flow, the time ratio of prototype to model, K t , is calculated from K t=K η/(K ρK gK L), and hence the velocity ratio K V=K L/K t, where K η, K ρ,K g and K L are the ratios for viscosity, density, gravitational acceleration and length, respectively. The results of the experiments indicate that plastic-flow waves, being similar to gravity waves in viscous media, include "fast" and "slow" waves and both of them are the superposition of major and subsidiary waves. The major wave is similar to solitary wave or surge. The "fast" waves, including the major and subsidiary ones, are originated from the boundary of the model. The periods of them depend mainly on the pulsative driving period at the boundary, while the wave velocities and strain rates of them are not associated with the pushing velocity of the boundary. In terms of the theory of similarity, the velocities of the major "fast" waves inferred from the models are about 0.12～2.5km/a, corresponding or close in the orders of magnitude to those of some plastic-flow waves in the lower lithosphere, which control the migration of seismic activities (Wang et al., 1994). The major and subsidiary "fast" waves decay in general tendency with their propagation, showing the descend of strain rates, whereas they ascend again locally in a certain range of distances. As is inferred from the models, for instance, the strain rates ascend again in the range of 1 500～2 250km away from the driving boundary for the situation of the waves propagating in the lower lithosphere. Its upper limit corresponds roughly to the distance from the Himalayan collision boundary to the North China Plain. The strong seismic activities in the North China region may be associated, as one of the important factors, with the local ascent of strain rates in the propagation process of plastic-flow waves. Although what has been done in the experimental studies so far stays with qualitative or semi-quantitative simulation, the results of the physical modeling stated above have provided the powerful experimental evidences for understanding the generation and propagation of the plastic-flow waves in continental plate, which control the migration and fluctuation of seismic activities.
In order to study the propagation processes of plastic-flow waves in the lithosphere, plasticized rosin, i.e. the mixture of rosin (R) and plasticizer (P ) with proper ratio of P/R, is used as analogue material for modeling ductile layer in the lithosphere. The mixture is poured into a rectangular shallow trough (280～300mm long and 190～200mm wide), forming ductile one layer model (1) with a thickness of 8～9mm, as shown in Fig. 1. The bottom (2) and walls (3 and 4) of the trough are made up of glass plates. Some models are covered by a 0.1～0.2mm-thick brittle layer composed of dried consolidated talc-powder slurry, forming brittle/ductile two-layer models. The driving boundary of the model, a movable wall (4) of the trough, is pushed by the springs (6), which are compressed by screw-pushers (7) (micrometer screws) or adding spacers. A number of measuring points (8) are placed on the models surface and their displacements are measured by using a coordinate-system micrometer with the horizontal accuracy of 0.002mm and vertical accuracy of 0.01mm. The tests are carried out at constant temperature with the errors within the range of ±0.5℃ for most of the models. According to the similarity criterion and considering the Stokes number, S t (the ratio of viscous force to gravitational force) for viscous flow, the time ratio of prototype to model, K t , is calculated from K t=K η/(K ρK gK L), and hence the velocity ratio K V=K L/K t, where K η, K ρ,K g and K L are the ratios for viscosity, density, gravitational acceleration and length, respectively. The results of the experiments indicate that plastic-flow waves, being similar to gravity waves in viscous media, include "fast" and "slow" waves and both of them are the superposition of major and subsidiary waves. The major wave is similar to solitary wave or surge. The "fast" waves, including the major and subsidiary ones, are originated from the boundary of the model. The periods of them depend mainly on the pulsative driving period at the boundary, while the wave velocities and strain rates of them are not associated with the pushing velocity of the boundary. In terms of the theory of similarity, the velocities of the major "fast" waves inferred from the models are about 0.12～2.5km/a, corresponding or close in the orders of magnitude to those of some plastic-flow waves in the lower lithosphere, which control the migration of seismic activities (Wang et al., 1994). The major and subsidiary "fast" waves decay in general tendency with their propagation, showing the descend of strain rates, whereas they ascend again locally in a certain range of distances. As is inferred from the models, for instance, the strain rates ascend again in the range of 1 500～2 250km away from the driving boundary for the situation of the waves propagating in the lower lithosphere. Its upper limit corresponds roughly to the distance from the Himalayan collision boundary to the North China Plain. The strong seismic activities in the North China region may be associated, as one of the important factors, with the local ascent of strain rates in the propagation process of plastic-flow waves. Although what has been done in the experimental studies so far stays with qualitative or semi-quantitative simulation, the results of the physical modeling stated above have provided the powerful experimental evidences for understanding the generation and propagation of the plastic-flow waves in continental plate, which control the migration and fluctuation of seismic activities.
引文
OmegaEngineering,Inc.,1991:“ChartofDimensionlessNumbers金日光.1986.高聚物流变学及其在加工中的应用.北京:化学工业出版社
.JinRiguang.1986.RheologyofHighPolymersanditsApplicationstoProcessing.Beijing:ChemicalIndustryPublishingHouse(inChinese)
李建国,周永胜,王绳祖.1998.中东亚大陆塑性流动网络控制下构造变形的物理模拟.地震地质,20(1):63～72.
LiJianguo,ZhouYongsheng,WangShengzu.1998.Physicalmodelingofplastic-flow-network-controlledtectonicdefor mationinthecentral-easternAsiancontinent.SeismologyandGeology,20(1):63～72(inChinese).
钱令希主编.1985.中国大百科全书·力学.北京:中国大百科全书出版社QianLingxi(Chiefed.).1985.EncyclopaediaofChina,MechanicsVolume.Beijing:EncyclopaediaofChinaPublishingHouse(inChinese).
王绳祖.1993a.亚洲大陆岩石圈多层构造模型和塑性流动网络.地质学报,67(1):1～18.
WangShengzu.1993.Multi-layertectonicmodelforintraplatedeformationandplastic-flownetworkintheAsiancontinen tallithosphere.ActaGeologicaSinica(Englishedition),6(3):247～271.
王绳祖.1993b.岩石的脆性-延性转变及塑性流动网络.地球物理学进展,8(4):25～37.
WangShengzu.1993b.Brittle-ductiletransitionandplastic-flownetworksinrocks.ProgressinGeophysics,8(4):25～37(inChinese).
王绳祖.1994.大陆岩石圈的网络状塑性流动、塑性波和地震活动.见:国家地震局地质研究所编.现今地球动力学研究及其应用.北京:地震出版社.20～27.
WangShengzu.1994.Netlikeplastic-flow,plasticwavesandseismicactivitiesinthecontinentallithosphere.In:InstituteofGeology,SSB ,ed.Researchesoncontemporarygeodynamicsandtheirapplications.Beijing:SeismologicalPress.20～27(inChinese).
王绳祖.1996.地壳、上地幔变形属性的判别.地震地质,18(3):215～224.
WangShengzu.1996.Deformationpropertyrecognitionofthecrustanduppermantle.SeismologyandGeology,18(3):215～224(inChinese)王绳祖,张宗淳.1994.大陆板内塑性流动波与地震迁移(1).地震地质,16(4):289～297.
WangShengzu,ZhangZongchun.1994.Plastic-flowwavesandearthquakemigrationincontinentalplate(1).SeismologyandGeology,16(4):289～297(inChinese).
王绳祖,张宗淳.1997.亚洲中东部岩浆岩网络状分布与塑性流动网络.地震地质,19(3):235～247.WangShengzu,ZhangZongchun.1997.Netlikedistributionofmagmatiteandplastic-flownetworksincentralandeasternAsia.SeismologyandGeology,19(3):225～247(inChinese).
郑洽余,鲁钟琪.1980.流体力学.北京:机械工业出版社.ZhengQiayu,LuZhongqi.1980.LiquidMechanics.Beijing:MachineryIndustryPublishingHouse.
中国科学院地质研究所.1977.数学地质引论.北京:地质出版社.InstituteofGeology,ChineseAcademyofSciences.1977.IntroductiontoMathematicalGeology.Beijing:GeologicalPub lishingHouse(inChinese).
BullJM ,MartinodJ,DavyP .1992.Bucklingoftheoceaniclithospherefromgeophysicaldataandexperiments.Tectonics,11(3):537～548.
CobboldPR .1975.Foldpropagationinsingleembeddedlayers.Tectonophysics,27:333～351.
DavyPh,CobboldPR .1991.Experimentsonshorteningofa4-layermodelofthecontinentallithosphere.Tectonophysics,188:1～25.
RambergH .1967.Gravity,DeformationandtheEarth’sCrust(firstedition).London:AcademicPress.WangShengzu.1993.Net-likeearthquakedistributionandplastic-flownetworkincentralandeasternAsia.PhysicsoftheEarthandPlanetaryInteriors,77:177～188.
.JinRiguang.1986.RheologyofHighPolymersanditsApplicationstoProcessing.Beijing:ChemicalIndustryPublishingHouse(inChinese)
李建国,周永胜,王绳祖.1998.中东亚大陆塑性流动网络控制下构造变形的物理模拟.地震地质,20(1):63～72.
LiJianguo,ZhouYongsheng,WangShengzu.1998.Physicalmodelingofplastic-flow-network-controlledtectonicdefor mationinthecentral-easternAsiancontinent.SeismologyandGeology,20(1):63～72(inChinese).
钱令希主编.1985.中国大百科全书·力学.北京:中国大百科全书出版社QianLingxi(Chiefed.).1985.EncyclopaediaofChina,MechanicsVolume.Beijing:EncyclopaediaofChinaPublishingHouse(inChinese).
王绳祖.1993a.亚洲大陆岩石圈多层构造模型和塑性流动网络.地质学报,67(1):1～18.
WangShengzu.1993.Multi-layertectonicmodelforintraplatedeformationandplastic-flownetworkintheAsiancontinen tallithosphere.ActaGeologicaSinica(Englishedition),6(3):247～271.
王绳祖.1993b.岩石的脆性-延性转变及塑性流动网络.地球物理学进展,8(4):25～37.
WangShengzu.1993b.Brittle-ductiletransitionandplastic-flownetworksinrocks.ProgressinGeophysics,8(4):25～37(inChinese).
王绳祖.1994.大陆岩石圈的网络状塑性流动、塑性波和地震活动.见:国家地震局地质研究所编.现今地球动力学研究及其应用.北京:地震出版社.20～27.
WangShengzu.1994.Netlikeplastic-flow,plasticwavesandseismicactivitiesinthecontinentallithosphere.In:InstituteofGeology,SSB ,ed.Researchesoncontemporarygeodynamicsandtheirapplications.Beijing:SeismologicalPress.20～27(inChinese).
王绳祖.1996.地壳、上地幔变形属性的判别.地震地质,18(3):215～224.
WangShengzu.1996.Deformationpropertyrecognitionofthecrustanduppermantle.SeismologyandGeology,18(3):215～224(inChinese)王绳祖,张宗淳.1994.大陆板内塑性流动波与地震迁移(1).地震地质,16(4):289～297.
WangShengzu,ZhangZongchun.1994.Plastic-flowwavesandearthquakemigrationincontinentalplate(1).SeismologyandGeology,16(4):289～297(inChinese).
王绳祖,张宗淳.1997.亚洲中东部岩浆岩网络状分布与塑性流动网络.地震地质,19(3):235～247.WangShengzu,ZhangZongchun.1997.Netlikedistributionofmagmatiteandplastic-flownetworksincentralandeasternAsia.SeismologyandGeology,19(3):225～247(inChinese).
郑洽余,鲁钟琪.1980.流体力学.北京:机械工业出版社.ZhengQiayu,LuZhongqi.1980.LiquidMechanics.Beijing:MachineryIndustryPublishingHouse.
中国科学院地质研究所.1977.数学地质引论.北京:地质出版社.InstituteofGeology,ChineseAcademyofSciences.1977.IntroductiontoMathematicalGeology.Beijing:GeologicalPub lishingHouse(inChinese).
BullJM ,MartinodJ,DavyP .1992.Bucklingoftheoceaniclithospherefromgeophysicaldataandexperiments.Tectonics,11(3):537～548.
CobboldPR .1975.Foldpropagationinsingleembeddedlayers.Tectonophysics,27:333～351.
DavyPh,CobboldPR .1991.Experimentsonshorteningofa4-layermodelofthecontinentallithosphere.Tectonophysics,188:1～25.
RambergH .1967.Gravity,DeformationandtheEarth’sCrust(firstedition).London:AcademicPress.WangShengzu.1993.Net-likeearthquakedistributionandplastic-flownetworkincentralandeasternAsia.PhysicsoftheEarthandPlanetaryInteriors,77:177～188.
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