川滇地块边界构造带形变速率变化与成组强震
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摘要
利用川滇地区 1982～ 2 0 0 1年断裂带附近的短水准、短基线、连续蠕变场地每年定期复测的观测资料 ,计算各场地的形变年速率值及随时间的变化曲线 ,分析川滇地块主要边界构造带水平或垂向活动状态及与地震活动的关系。结果是 :现今滇西地区和滇东南地区形变反映的构造活动剧烈 ;川滇地块东测边界带 ,由曲江、小江至鲜水河断裂带自南而北现今水平形变量逐渐减小 ;鲜水河断裂带、小江断裂带、龙门山断裂带每年垂向变化速率值小 ,而安宁河—则木河断裂带变化幅度相对较大 ;多个地震构造带附近的一些形变场地呈现形变速率的陡变则往往是成组强震发生的前兆。
Deformation measurements such as short range leveling, short baseline, continuous cross fault strain measurement are carried out at regular interval from 1982 to 2001.All these measurement sites are built across the boundary tectonic belts of Yunnan Sichuan block. On the basis of these deformation data annual deformation rate value at each site are calculated and change curves with time are plotted respectively. With these calculated results, we analyze the vertical and horizontal movements of boundary tectonic belts of Yunnan Sichuan block and the relationship to earthquakes occurred in the block are discussed as well. These results show that the tectonic activities in the western and southeastern Yunnan are intensive. Along some eastern boundary belts: Qujiang, Xiaojiang fault belts in the south of Yunnan to Xianshuihe fault belts in northwestern Sichuan, the present horizontal deformation rate decreases. The vertical change rates are small along Xianshuihe, Xiaojiang and Longmenshan fault belts, but the vertical change rates along Anninghe and Zemuhe fault belts are comparatively large. The comprehensive analysis shows that strong grouped earthquakes will occure mostly when the deformation rate at measured sites along several seismic tectonic belts changes sharp.So we think that the sharp changes of deformation rates may be one of the seismic precursors.
Deformation measurements such as short range leveling, short baseline, continuous cross fault strain measurement are carried out at regular interval from 1982 to 2001.All these measurement sites are built across the boundary tectonic belts of Yunnan Sichuan block. On the basis of these deformation data annual deformation rate value at each site are calculated and change curves with time are plotted respectively. With these calculated results, we analyze the vertical and horizontal movements of boundary tectonic belts of Yunnan Sichuan block and the relationship to earthquakes occurred in the block are discussed as well. These results show that the tectonic activities in the western and southeastern Yunnan are intensive. Along some eastern boundary belts: Qujiang, Xiaojiang fault belts in the south of Yunnan to Xianshuihe fault belts in northwestern Sichuan, the present horizontal deformation rate decreases. The vertical change rates are small along Xianshuihe, Xiaojiang and Longmenshan fault belts, but the vertical change rates along Anninghe and Zemuhe fault belts are comparatively large. The comprehensive analysis shows that strong grouped earthquakes will occure mostly when the deformation rate at measured sites along several seismic tectonic belts changes sharp.So we think that the sharp changes of deformation rates may be one of the seismic precursors.
引文
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2 WuYilin,LiPingandLiXudong.Researchonlargeearth quankeprecursorandphysicalchangesofrockusinginde formationdatainstations[A].ResearchofEarthquankepre dictionmethodinChina[C].Beijing:SeismologicalPress,1991.(inChinese)
3 CheZaohongandZhangYanmei.TherecentfaultactivityalongthemiddleandsouthernsegmentsofSouth-Northseismicbelt[J].Earthquake,2001,21(3):31-37.(inChinese)
4 LuYipei,LiaoHua,SuQinandWangLan.TherecentcrustaldeformationinSichuan-Yunnanrhombicblockboundary[J].EarthquakeResearchinChina,2002,18(1):28-37.(inChinese)
5 LiuBenpei,ZhuZhiqin,LiaoHua,etal.TectonicgeodeticsurveyalongtheXianshuihefaultzone[J].CrustalDeforma tionandEarthquake,2001,21(4):17-25.(inChinese)
6 ZhuZhiqin,LiaoHuaandLiJianzhong.StudyonactivitycharactersofXianshuihefaultzonebyusingobserveddateofsmalllaser rangemeasurementnetworks[J].CrustalDefor mationandEarthquake,2001,21(2):77-82.(inChinese
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