摘要
TheeasternmarginofTibetanPlateauisoneofthemostactivezonesoftectonicdeformationandseismicityinChina.Tomonitorstrainbuildupandbenefitseismicriskassessment,weconstructed14survey-modeglobalpositionsystem(GPS)stationsthroughoutthenorthwestofLongmenshanfault.AnewGPSfieldover1999–2011isderivedfrommeasurementsofthenewlybuiltandpre-existingstationsinthisregion.Sequentially,twostrainratefields,oneprecedingandtheotherfollowingthe2008MW7.9Wenchuanearthquake,areobtainedusingtheGausianweightingapproach.Strainfieldover1999–2007showsdistinctstrainpartitioningpriortothe2008MW7.9Wenchuanearthquake,withcompressionspreadingoveraroundLongmenshanarea.Strainfieldderivedfromthetwomeasurementsin2009and2011showsthattheareaaroundLongmenshancontinuestobeunderstrikingcompression,asthepatternprecedingtheWenchuanearthquake,implyingacausativefactorofthesequentof2013MW6.7Lushanearthquake.OurGPSderiveddilatationshowsthatboththeWenchuanandLushanearthquakesoccurredwithinthedomainofpronouncedcontraction.TheGPSvelocitiesdemonstratethattheLongribafaultunderwentslightmotionwiththefaultnormaland-parallelratesat1.0±2.5mmand0.3±2.2mm/a;theLongmenshanfaultdisplayedslowactivity,withafault-normalrateat0.8±2.5mm/a,andafault-parallelrateat1.8±1.7mm/a.LongribafaultisonaparwithLongmenshanfaultinstrainpartitioningtoaccommodatethesoutheastwardmotionofeasternmarginoftheTibetanPlateau.Integratedanalysisofprincipalstraintensors,meanprincipalstress,andfastdirectionsofmantleanisotropyshowsthatwestofSichuanischaracterizedasmechanicallystrongcrust-mantlecoupling.更多还原
出版日期
2015年01月11日(中国期刊网平台首次上网日期,不代表论文的发表时间)