简介:AstudyoftheKunlunshanearthquakeofMS=8.1basedonobservedcoseismicstrainstepsfromtheboreholestrainmonitoringnetworkoverChinahasbeencarriedoutwithsomeinterestingresults.Firstly,manyrecordingsdisagreewiththeoreticcalculationusingstaticdislocationmodel.Secondly,abnormallylargestrainstepsareobservedatquiteafewstationsinthetectonicallyactiveeast-northernChina,whileintherelativelyinactiveeast-southernChinanoobviousstepsarerecorded.Itisinferredthatseismicstresstriggeringmaysignificantlyaffectremoteseismicstrainfield.Inotherwords,whetherremotefaultingbeseismicallytriggeredornotmaydeterminethepatternoflocalseismicstrainchanges.FurthercomparisonstudyresultsofMarch11,1999ZhangbeiearthquakeandNovember1,1999Datongearthquakeshowthatthespecificpatternofseismiczoneshasobviousinfluenceonseismicstrainchangesintheregion.Thissupportstheideathatobservedabnormalstrainstepsmightbeproducedbycoseismiclystress-triggeredlocalfaulting.
简介:IonosphereicfoF2variationsareverysensitivetotheseismiceffectandresultsofionosphericperturbationsassociatedwithearthquakesseemtoveryhopefulforshort-termearthquakeprediction.OnJanuary18,2011at20:23UTagreatearthquake(M=7.2)occurredinDalbandin(28.73°N,63.92°E),Pakistan.Inthisstudy,wehavetriedtofindoutthefeaturesofpre-earthquakeionosphericanomaliesbyusingthehourlydaytime(08.00a.m.-05.00p.m.)dataofcriticalfrequency(foF2)obtainedbythreeverticalsoundingstationsinstalledinIslamabad(33.78°N,73.06°E),Multan(32.26°N,71.51°E)andKarachi(24.89°N,67.02°E),Pakistan.TheresultsshowthesignificantanomaliesoffoF2intheearthquakepreparationzoneseveraldayspriortotheDalbandinearthquake.ItisalsoobservedthattheamplitudeandfrequencyoffoF2anomaliesaremoreprominentattheneareststationtotheepicenterascomparedtothosestationsneartheoutermarginoftheearthquakepreparationzone.TheconfidencelevelforionosphericanomaliesregardingtheseismicsignaturescanbeenhancedbyaddingtheanalysisofsomeotherionospheicparametersalongwithcriticalfrequencyofthelayerF2.
简介:On26thOctober2015,anMw7.5earthquakestrucknorthernPakistan,withitsepicenterlocated45kmsouthwestofJarmintheHinduKushregionofAfghanistan.Theearthquakeresultedfromreversefaultingatadepthof210km,resultingin280fatalitiesandsubstantialdamagetosome109,123buildings.Regionalseismicity,characteristicsofrecordedstrongmotions,damagestatistics,andbuildingperformanceobservationsarepresented.Earthquakedamagewasmostlyconstrainedtoseismic-deficientunreinforcedmasonry(URM)buildings.Typicalfailuremodesincludedtoppledminarets,partialorcompleteoutofplanecollapseofURMwalls,diagonalshearcrackinginpiers,flexuralcrackinginspandrels,cornerdamage,poundingdamage,anddamageduetogroundsettlement.ThemajorityofhumanlossresultedduetofailureofURMwallsandsubsequentroofcollapse.URMbuildingslocatedinruralhillyareasclosertotheepicentersufferedmoreintenseandfrequentdamagethanurbanURMbuildingslocatedfartherawayinlargercities.
简介:Crack-inducedanisotropyinthecrustfromshearwavesplittingobservedinTangshanregion,NorthChinaYuanGAO(高原)Si-HuaZHENG;(郑斯华)andYong...
简介:ThedataofionosphericperturbationsobservedonDEMETERbeforethe2007Pu'erearthquakeareanalyzed.Thethree-componentplasma(ions,electronsandheavyions)isstudiedinthefluidconcept.Thelineardispersionrelationforion-acousticwaveisfoundinthepresenceofheavyions.Thenonlineardynamicsisstudiedforarbitraryamplitudeofthewave.TheSagdeevpotentialiscalculated,whichshowsthatsolitarystructureexistsforMachnumberwithinarangedefinedbythepresenceofheavyions.Thedevelopedion-acousticsolitonsmaybeusedasprecursorforearthquakeprediction.
简介:Thisstudyinvestigatesdata-processingmethodsandexaminestheprecipitationeffectongravitymeasurementsattheDaligravitynetwork,establishedin2005.High-qualitygravitydatawerecollectedduringfourmeasurementcampaigns.Tousethegravitydatavalidly,somegeophysicalcorrectionsmustbeconsideredcarefully.Wefirstdiscussdata-processingmethodsusingweightedleastsquaresadjustmentwiththeconstraintoftheabsolutegravitydatum.Resultsindicatethatthegravityprecisioncanbeimprovedifallabsolutegravitydataareusedasconstraintsandifcalibrationfunctionsofrelativegravimetersaremodeledwithintheobservationfunction.Usingthisdata-processingscheme,themeanpointgravityprecisionisbetterthan12lgal.Afterdeterminingthebestdata-processingscheme,wethenprocessthegravitydataobtainedinthefourmeasurementcampaigns,andobtaingravitychangesinthreetimeperiods.Resultsshowthatthegravityhasaremarkablechangeofmorethan50lgalinthefirsttimeperiodfromApr–Mayof2005toAug–Septof2007.Tointerpretthelargegravitychange,ameanwatermasschange(0.6minheight)isassumedintheETOPO1topographicmodel.Calculationsoftheprecipitationeffectongravityshowthatitcanreachthesameorderoftheobservedgravitychange.ItisregardedasamainsourceoftheremarkablegravitychangeintheDaligravitynetwork,suggestingthattheprecipitationeffectongravitymeasurementsmustbeconsideredcarefully.