New Insight into Post-seismic Landslide Evolution Processes in the Tropics

Tolga Görüm,Dalia Kirschbaum,Hakan Tanyaş,Luigi Lombardo,Cees J Van Westen

doi:10.3389/feart.2021.700546

Abstract

Earthquakes do not only trigger landslides in co-seismic phases but also elevate post-seismic landslide susceptibility either by causing a strength reduction in hillslope materials or by producing co-seismic landslide deposits, which are prone to further remobilization under the external forces generated by subsequent rainfall events. However, we still have limited observations regarding the post-seismic landslide processes. And, the examined cases are rarely representative of tropical conditions where the precipitation regime is strong and persistent. Therefore, in this study, we introduce three new sets of multi-temporal landslide inventories associated with subsets of the areas affected by 1) 2016 Reuleuet (Indonesia, Mw = 6.5), 2) 2018 Porgera (Papua New Guinea, Mw = 7.5) and 3) 2012 Sulawesi (Indonesia, Mw = 6.3), 2017 Kasiguncu (Indonesia, Mw = 6.6) and 2018 Palu (Indonesia, Mw = 7.5) earthquakes. Overall, our findings show that the landslide susceptibility level associated with the occurrences of new landslides return to pre-seismic conditions in less than a year in the study areas under consideration. We stress that these observations might not be representative of the entire area affected by these earthquakes but the areal boundaries of our study areas.

Highlights

Based on the number of casualties, earthquakes and precipitation are the most common landslide triggers (Petley, 2012) and near-real-time global landslide susceptibility assessment methods are separately available for both earthquake- (e.g., Nowicki Jessee et al, 2018; Tanyas et al, 2019) and rainfall-triggered (Kirschbaum and Stanley, 2018) landslides
For the area affected by the Reuleuet (December 6, 2016) earthquake, we compiled one landslide inventory associated with pre-earthquake conditions, a co-seismic landslide inventory and three post-seismic ones (Table 1)
This shows that landslide rates that we calculated for the occurrences of new landslides return to pre-seismic levels by February 12, 2018 (Figure 5)

Summary

Introduction

Based on the number of casualties, earthquakes and precipitation are the most common landslide triggers (Petley, 2012) and near-real-time global landslide susceptibility assessment methods are separately available for both earthquake- (e.g., Nowicki Jessee et al, 2018; Tanyas et al, 2019) and rainfall-triggered (Kirschbaum and Stanley, 2018) landslides. None of these statistically based methods are capable of accounting for the coupled effect of earthquakes and precipitation. Earthquakes are recognized as an important predisposing factor increasing postseismic landslide susceptibility either by disturbing the strength and/or geometry of hill slope materials or by producing co-seismic landslide deposits, which are prone to instabilities mostly due to subsequent rainfall events (e.g., Lin et al, 2004; Parker et al, 2015; Tanyas et al, 2021).

Objectives

Methods

Results

Discussion

Conclusion