Landslides triggered by the 2018 Lombok earthquake sequence, Indonesia

Abstract

During July and August 2018, a series of four Mw > 6.0 earthquakes (Event I − 2018.07.28 Mw 6.4, Event II − 2018.08.05 Mw 6.9, Event III − 2018.08.19 Mw 6.3, and Event IV − 2018.08.19 Mw 6.9) struck Lombok Island, Indonesia. A detailed interpretation of satellite imagery reveals that the Lombok earthquake sequence triggered 10,521 landslides with a cumulative extent of 28.0 km2 over an affected area reaching approximately 1850 km2, which are divided into seismic earthflows, topography-based landslides and gully-based landslides. A total of 5621 and 2980 landslides were triggered by Event II and Events III-IV, respectively, and 1920 landslides were concentrated in the 2018.08.10 cloud-covered area. Event II caused most of the landslides. The landslide areas of all the events follow an exponential distribution. The cumulative landslide number (N) and landslide area (A) exhibit a linear logarithmic relationship of Log(N) = −1.341*Log(A) + 3.9. The western section of Mount (Mt.) Rinjani is clearly a landslide-prone area that contains mainly seismic earthflows. Rainfall is a dominant factor influencing the landslide distribution, and generally, higher rainfall corresponds to a higher landslide concentration. Seismic shaking is not a key factor in deposit failure, while in the lower gently sloping section (elevation < 1500 m), the peak ground acceleration (PGA) of landslides increases with a decrease in elevation. Moreover, the top section of the mountain with a steeper slope (Subzones II and V) caused a stronger seismic amplification effect, resulting in numerous landslides.