越南地壳形变研究的若干初期成果(英文)
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摘要
详细介绍了 1984～ 2 0 0 1年间越南地球物理研究所开展的地壳形变 (应变 )监测研究工作及其初步成果。文章指出 ,研究地壳运动时 ,应针对不同的情况 (如构造运动周期 )采用不同的方法 ,而本文着重介绍了地球物理仪器方法 ,此法 (有时与大地测量方法结合 )既可用来监测从几秒到几十年的运动 ,也可监测微小的局部位移。监测用的是前苏联制造的石英管伸缩仪 ,采用光电传感器换能 ,照相记录 ,灵敏度为 10 - 8m m。在用于观测固体潮汐应变时 ,观测精度还取决于应变的周期 :对周日波及更短周期 ,精度可达 10 - 9～ 10 - 1 0 ;而对缓慢的运动则只能达到10 - 7～ 10 - 8,但此时记录具有高稳定性。但用于监测所在地区是否存在断裂活动则无疑具有肯定的效果。最后 ,根据已有的 2处台站 10余年的观测成果 ,得出下列结论 :1.Phu L ien台站位于 Dong Trieu- Cam Pha断裂与红河断裂为边界的区域内 ,而此断裂自古至今都有活动 ,发生过 6级左右地震。但这一地区在 1989～ 1991期间却构造稳定 ,只记录到缓慢的运动速率 (1× 10 - 6 /a) ,也未观测到地震前兆性的应变现象。2 .而在 1993年才开始观测的 Hoa Binth台站 ,到 1997年止 ,则观测到比较大的地壳运动速率 ;其绝对最大幅度高达约 10 0× 10 - 6 ,日均值为 6 0× 10
In this work, the authors present some results of strain monitoring within the territory of Vietnam from 1984 to 2001. Data analysis shows that (1) the Phu Lien area is tectonically stable with low strain rate, 1×10\+\{-6\} /a; (2) the Hoa Binh area has indication of tectonic instability with relatively high strain rate of the earth crust: absolute value of the strain reaching 100×10\+\{-6\}, usual average strain amplitude of 60×10\+\{-6\}, whereas the monthly average strain intensity varies in a range from 30×10\+\{-6\} to 50×10\+\{-6\}; (3) there are clear indications of the strain state of the earth crust before occurrence of earthquakes of medium or higher magnitude. This is a very important indication in the research and short term prediction of earthquakes, especially for the areas with low seismic stability like the NW of Vietnam.
In this work, the authors present some results of strain monitoring within the territory of Vietnam from 1984 to 2001. Data analysis shows that (1) the Phu Lien area is tectonically stable with low strain rate, 1×10\+\{-6\} /a; (2) the Hoa Binh area has indication of tectonic instability with relatively high strain rate of the earth crust: absolute value of the strain reaching 100×10\+\{-6\}, usual average strain amplitude of 60×10\+\{-6\}, whereas the monthly average strain intensity varies in a range from 30×10\+\{-6\} to 50×10\+\{-6\}; (3) there are clear indications of the strain state of the earth crust before occurrence of earthquakes of medium or higher magnitude. This is a very important indication in the research and short term prediction of earthquakes, especially for the areas with low seismic stability like the NW of Vietnam.
引文
1 L atyninaL A,KarmaleevaR M.Earthquake intensityvariation in areas with different tectonic conditions[A ].Selected works on contemporary motions of the earthcrust along geodynam ic studying networks[C].Novosi-birsk,1976,136-141(inRussian)
2 L atyninaL A,KarmaleevaR M.On the relationship be-tween the earth tide variation value and the characteris-tics of seism ic activities in theAlmaAta area[A].Se-lected works on contemporary motions of the earth crustalong geodynamic studying networks[C].Novosibirsk,1981,16-20(inRussian)
3 Karm aleevaR M,L atyninaL A.The study of recentcrustal m ovements from extensometric data[J].Journ.ofGeodyn.,1988,V .10,321-323.
4 BergerJ.A note on thermoelastic strains andTilts[J].Journ. of geoph.Res.1975,V.80,2,274-277
2 L atyninaL A,KarmaleevaR M.On the relationship be-tween the earth tide variation value and the characteris-tics of seism ic activities in theAlmaAta area[A].Se-lected works on contemporary motions of the earth crustalong geodynamic studying networks[C].Novosibirsk,1981,16-20(inRussian)
3 Karm aleevaR M,L atyninaL A.The study of recentcrustal m ovements from extensometric data[J].Journ.ofGeodyn.,1988,V .10,321-323.
4 BergerJ.A note on thermoelastic strains andTilts[J].Journ. of geoph.Res.1975,V.80,2,274-277
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