Liquefaction array observation has been conducted since 1990 at two adjacent sites on soft soil in Tomakomai, Hokkaido. Several records during earthquakes including the 1993 Kushiro-oki earthquake were successfully obtained. This paper shows that the orientation errors of accelerometers varied between -9 and +64 degrees. And it illustrates that excess pore water pressure starts to be built up more than 20cm/s² in acceleration at the ground surface and suddenly increase over 100cm/s² as part of conclusions.