简介:WeusedearthquakecatalogsrecordedbyGuangdongSeismologicalNetworkfrom2008to2014toresolvethespatialvariationsofb-valuesinthecoastalareaofGuangdong,particularlyinthreekeyresearchareas(Yangjiang,Heyuan,andoffshoreNanaoIsland)withstrongseismicity.Ourresultsrevealedthatb-valuesexhibitedsignificantspatialvariations,andzoneswithlowb-valuescouldindicatethemostlikelyseismogenicareaoflargeearthquakes.Weobservedthreeclearlowb-valuepatchesintheoffshoreNanaoIsland.Wefoundadistincthighb-valuepeakatthedepthof11kmandtwominimumpeaksatabout14and7–8kmintheYangjiangarea.Theoverallb-valuesgenerallydecreasewithdepthintheHeyuanarea.Thespatialvariationsofb-valuesreflecttectonicanomalies;thatis,the‘low-high-low’distributionofb-valuesintheoffshoreNanaoIslandandtheYangjiangareamayindicatetheanomalyofthecrustalstructurewithaweaklayer.Theb-valuesofreservoir-inducedseismicityareobviouslylowerthanthatinducedbytectonism.Thisfindingindicatesthatthereservoirareaisgenerallyathighstressstateundertheconditionofhighporepressure.Weinferredthatlargeearthquakesmightbepronetooccurat10–12kmdepthintheoffshoreNanaoIsland,at12–15kmdepthintheYangjiangarea,andatthelowerpartoftheseismicactivityzoneintheHeyuanarea.Moreover,theupstreamareaoftheXinfengjiangreservoiristhemostlikelyareaoffuturelargeearthquakesintheHeyuanarea.
简介:导读:千百年来,祁连山雪水丰盈厚实的膏脂,养育了一代又一代河西生灵,也构建起了我国西部生态的安全屏障。然而,祁连山无休止探矿采矿、截流发电、过度放牧等造成的破坏,却让这座美丽的“母亲山”变了容颜。2017年,中办、国办就甘肃省自然保护区生态问题发出通报,甘肃省3名副省级官员和上百名干部因祁连山生态破坏问题受到严厉问责,处罚力度之大前所未有。一年时间过去了,祁连山整改复绿进展如何?发生了哪些变化?取得了哪些成效?近日,本刊记者再次深入祁连山进行了探访,真切感受到当地干部群众正在逐渐树立起“绿水青山就是金山银山”的新理念。5月,自然资源部有关领导在甘肃调研时,对张掖矿业权分类退出的举措给予充分肯定,认为甘肃在自然保护区矿业权退出上,“蹬出了一条新路,为全国积累了经验”。
简介:为了研究蛇绿岩型豆荚状铬铁矿床的成因和构造环境,对西藏雅鲁藏布构造带中段的日喀则蛇绿岩大竹曲岩体中的铬铁矿化进行了研究。通过岩相学和地球化学研究,发现大竹曲地幔橄榄岩中铬尖晶石为不规则它形,且全岩的CaO和Al2O3,含量与铬尖晶石Cr^#分别呈正相关和负相关关系,这表明地幔橄榄岩中铬尖晶石为地幔部分熔融的残余。然而,纯橄岩和矿石中铬尖晶石显示自形一半自形,并可见橄榄石包裹自形铬尖晶石,且纯橄岩与矿石的CaO和Al2O3和Cr^#均无相关性,均说明纯橄岩和铬铁矿石形成于岩石-熔体反应。高Cr^#矿石和纯橄岩的母岩浆性质接近于玻镁安山质熔体,而低Cr^#纯橄岩的母岩浆则类似于MORB,表明大竹曲铬铁矿可能形成于弧后扩张中心。
简介:SequencevariationofpartialcytochromebgenesbetweentwoCoiliaspecies,C.ectenesandC.mystus,wasinvestigated.Ofthe402nucleotides,twenty-seven(6.72%)arepolymorphicandallaresynonymoussubstitutions.Atthethirdpositionsofgeneticcondonofcytochromebgene,thetwospeciesshowanextremeanti-Gbias(<4%)andapronouncedbiastowardsAandC(>68%).Thereisnoaminoacidsequencedivergencebetweenthepartialcytochromebgenesofthetwospecies,indicatingaclosegeneticrelationshipbetweenthem.Thek-2pgeneticdistanceofpartialcytochromebsegmentofthetwospeciesis0.072,suggestingthatthespecieswereseparated3.6Maago,inthemiddlePliocene.Ourresultrevealsthatthecytochromebgeneisanappropriatemarkerforstudiesofpopulationgeneticstructuresandphylogeographicpatternsofthetwospecies.
简介:当洋盆闭合洋壳残片构造侵位于陆壳之上时,共同组成蛇绿混杂岩带。由于构造破坏,蛇绿岩及伴生的深海沉积物(放射虫硅质岩、粘土等)往往呈构造包体形式赋存在古大陆边缘沉积的陆源碎屑物基质中,基质是混杂岩带的主体。它们属构造无序岩层,不服从层序律。在造山带1∶25万区域填图中,首先考虑蛇绿混杂岩的产出特点,划分出构造包体和基质两大类,分别建立“岩群”;其次根据填图精度的要求,按照它们各自组成的地质单元分别建立“岩组”、“岩段”,对于基质中不同时代的地层单元能够恢复原始层序的可以建立“组”、“段”。为达到蛇绿混杂岩带的研究目的,测制大比例尺地质图作为补充图件
简介:Effectsofthemixtureofβ-ecdysoneandpolypodine-B(2:1W/W)onthemoultingandgrowthofprawn,Penaeusorientalisswerestudiedinlaboratorybyrearingtheanimalwiththeaddedcompounddiets.Theresultsshowedthattheadditionofthemoultinghormone(M.H)mixturetocompounddiets,from1.33×10-6to30×10-6,couldincreasemoultingactivityandgrowthrateoftheprawntodifferentextents,amongwhichthe5.33×10-6-10.67×10-6additionhadstatisticallysignificanteffects.However,60×10-6addeddietscausedmoultingandgrowthinhibitionsandcuticlethickening.Theanalysesofprotein,waterandashcontentsoftheprawnshowednoremarkabledifferencesbetweenhormonedosedanimalsandthecontrol.
简介:Basedonisotropiclinearporoelastictheoryandundertheundrainedcondition,wesummarizethreeequationsconnectingtheSkempton’scoefficientBwiththegroundwaterlevel.Afteranalysis,weproposeamethodtocalculatetheSkempton’scoefficientBaccordingtotherelationshipbetweenwaterlevelandtidalstrain.WiththismethodwecangetthevalueofBwithouttheearthquakeoccurrence,whichcanprovidethehighfrequencywavesforresearch.Besides,wecanalsogetthein-suitSkempton’scoefficientBwithouttheexperimentofrockphysics.Inaddition,weanalyzetheobserveddataofChangpingstationrecordedingroundwatermonitoringnetwork(abv.,GMN)beforeandaftertheWenchuanMS8.0withthismethod,andfindoutthere’saslightchangeofthevalueofBaftertheseismicwavespassedby,whichimpliesthatthepropagationofseismicwavesmayhavebroughtsomevariationstotheporoelasticmediumofthewell.