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1、热带海洋学报JOURNALOFTROPICALOCEANOGRAPHY2012年第31卷第3期:90−96海洋地球物理学doi:10.3969/j.issn.1009-5470.2012.03.012http://www.jto.ac.cn*海底地震仪实测信号特性分析121,211,21刘宏扬,牛雄伟,阮爱国,吴振利,李家彪,潘少军1.国家海洋局第二海洋研究所,国家海洋局海底科学重点实验室,浙江杭州310012;2.浙江大学地球科学系,浙江杭州310027摘要:置于海底数百米至数千米的海底地震仪(O
2、BS)的实测信号相比陆地地震仪具有不同的特性;由于水的作用或记录信号源频率的不同,短周期OBS和宽频带OBS记录的信号又有明显的差异。文章对南海西南次海盆地震探测期间记录的人工气枪震源和天然地震实测信号进行了时频分析,结果如下。1)气枪作业后在海底激发两种噪声:一是水的波动不断叠加形成的长波,周期50s左右,以水平分量为主;二是高频噪声,主要是OBS底座细微晃动引起的。2)宽频OBS对于水下移动目标激发海底波动具有很好的探测能力,特别是水平分量可以获得大振幅且周期特征清晰的记录,并能够指示方向。3)
3、宽频OBS能记录到清晰的天然地震信号,为研究调查区岩石圈结构增添了更多的信息,短周期OBS对远震直达P波有很好的记录。国产宽频I-4C型OBS碰巧记录了日本M9.0级大震。关键词:海底地震仪;实测信号;短周期;宽频带中图分类号:P716.83；P315文献标识码:A文章编号:1009-5470(2012)03-0090-07Analysisofseismicsignalsofoceanbottomseismometer121,211,21LIUHong-yang,NIUXiong-wei,RUANA
4、i-guo,WUZhen-li,LIJia-biao,PANShao-jun1.SecondInstituteofOceanography,StateOceanicAdministration/KeyLaboratoryofSubmarineGeosciences,StateOceanicAdministration,Hangzhou310012,China;2.DepartmentofEarthSciences,ZhejiangUniversity,Hangzhou310027,ChinaAbst
5、ract:Seismicsignalsofoceanbottomseismometer(OBS)ontheseafloorhundredsorthousandsmetersdeeparedifferentfromthoseoflandseismometer.Therecordsofshort-periodOBSarealsoobviouslydifferentfromthoseofbroad-bandOBSduetoeffectsofseawaterorsignalfrequency.Thisstu
6、dycarriedouttime-frequencyanalysisandcomparedtheseismicsignalsexcitedbyairgunaswellasearthquakesignalsofOBSduringaseismicsurveyinthesouthwestsub-basinoftheSouthChinaSea.Theresultsareasfollows.1)Air-gunshootinggeneratedtwokindsofnoises:oneislong-wavenoi
7、seduetothesuperpositionofwaterfluctuation,withaperiodof50smainlyinthehorizontalcomponent;theotherishigh-frequencynoise,mainlyduetofinvibrationofOBSpedestalitself.2)Broad-bandOBSisabletodetectthefluctuationcausedbymovingobjectunderwater,especiallyintheh
8、orizontalcomponentwhoseamplitudeislargeandwhosefrequencyfeatureisclear,fromwhichthedirectionofthesignalsourcecanbedistinguished.3)Duringthissurveybroad-bandOBSrecordedmanyhigh-qualityearthquakesthatwillbenefitourstudyonthelithospherestr
