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.
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