Correlation between excess pore water pressure and seismic waves

On the site of the Large Scale Seismic Test at Lotung, Taiwan, an in‐situ pore water pressure measurement program has been ongoing since 1986. Its purpose is to measure the changes in ground pore water pressure due to earthquake excitations. During the July 30 (M = 6.2) and the November 15 (M = 7.0), 1986 earthquakes, which occurred in Eastern Taiwan, a total of 16 pore pressure responses had been successfully recorded. Among the data obtained, 6 sets of data were the responses of 3 sensors triggered in both earthquakes. This data was selected to investigate the characteristics of pore water pressure responses during different earthquakes. It is found that the responses of pore water pressure are highly oscillatory during earthquakes. However, each of the pore water pressure records can be roughly divided into an initial build‐up stage and a following dissipation stage. During the build‐up stage, the pore water pressure responded in higher frequencies of fluctuation and the oscillatory parts were found to be best correlated to the wave trains of ground velocity in the vertical direction.