The Effect of Earthquake to Stability and Run Out Distance of Landslide During Rainfall : a case study of landslide prone area in West Java, Indonesia

The effect of earth quake to landslide stability and run out distance on landslide zones in West Java-Indonesia during rainfall was investigated considering different slope angle. An earthquake peak ground acceleration 0.3 gal for 20 s is applied on landslide zones under a rainfall intensity of 10mm/h for 4 hour. In this study, the slope angles of 26°, 33°, 45°, 56° and 68° are considered. We found that the safety factor decreases as the slope angle increases. With the introduction of rainfall and earthquake, the safety factor of the slope drops below 1.0 at slope angle higher than 33°. The calculations of run out distance during rainfall and earthquake shows the landslide masses generated from the slope 45° will travel more than slope 68° for the same soil characteristic. This is due to the landslide masses from the slope 45° is smaller than that from in the slope of 68°. We found that combination rainfall and earthquake makes the stability of the slope smaller than due to rainfalll alone. However, the run-out distance of landslide masses due to the combination of rainfall and earthquake has no significant different when compared with due to rainfall alone. (paper)