Comparative study of different instrumental intensity algorithms for the earthquakes in Sichuan region

Strong motion observation data is classified into two categories， one is strong motion time history data, the other is seismic damage investigation data. The former is the microscopic quantitative data, and the latter is the macro-scopic qualitative indexes. Firstly we define the concept of microscopic instrumental intensity and macroscopic instrumental intensity, microscopic inspection intensity and macroscopic inspection intensity in the present paper. And then we propose it is significant to compare macroscopic instrumental intensity with macroscopic inspection intensity. Meanwhile we also conduct a comparative study about the instrumental intensity algorithms at home and abroad. The results indicate that Yuan’s instrumental intensity algorithm is more reliable. In addition, based on the strong motion records of Sichuan earthquakes, the modified Yuan’s algorithm is applied to calculate seismic intensity. The results show that it is feasible to revise and expand the Yuan’s instrumental intensity algorithm, and also prove that there exists large difference when the micro-scopic instrumental intensity is compared with macroscopic inspection intensity directly.