2005 Volume 58 Issue 1 Pages 3-13
This study examined the relationship between slope failure and precipitation using long-term data for the Chitou tract, which is in the Experimental Forest of National Taiwan University, located 20 km south of the Chi-chi Earthquake epicenter. The University Forest maintains a variety of records that are a useful source of long-term data. Repair records for forestry roads, which assure long-term uniformity of temporal data owing to the high priority given to repairing forestry roads, were used to discuss the characteristics of slope failure. The relationship before and after the earthquake was compared to clarify the indirect influence of the Chi-chi Earthquake on subsequent slope failures. As a result, we showed that the earthquake affected subsequent slope failures, although the earthquake itself caused no slope failures directly when it happened on 21 September 1999. After the earthquake, the first slope failure was triggered by a precipitation event involving 91.5 mm of rain over 5 days in February 2000. By contrast, the smallest precipitation event that triggered slope failure before the earthquake was 210.5 mm over 5 days. In July 2001, the second slope failure event following the earthquake set a record for the most slope failures in the history of the Chitou tract. By the time of the slope failure event in May 2002, the earthquake no longer had any notable influence.
