Prediction of the area affected by earthquake-induced landsliding based on seismological parameters

Odin Marc,Niels Hovius,Patrick Meunier

doi:10.5194/nhess-17-1159-2017

Abstract

Abstract. We present an analytical, seismologically consistent expression for the surface area of the region within which most landslides triggered by an earthquake are located (landslide distribution area). This expression is based on scaling laws relating seismic moment, source depth, and focal mechanism with ground shaking and fault rupture length and assumes a globally constant threshold of acceleration for onset of systematic mass wasting. The seismological assumptions are identical to those recently used to propose a seismologically consistent expression for the total volume and area of landslides triggered by an earthquake. To test the accuracy of the model we gathered geophysical information and estimates of the landslide distribution area for 83 earthquakes. To reduce uncertainties and inconsistencies in the estimation of the landslide distribution area, we propose an objective definition based on the shortest distance from the seismic wave emission line containing 95 % of the total landslide area. Without any empirical calibration the model explains 56 % of the variance in our dataset, and predicts 35 to 49 out of 83 cases within a factor of 2, depending on how we account for uncertainties on the seismic source depth. For most cases with comprehensive landslide inventories we show that our prediction compares well with the smallest region around the fault containing 95 % of the total landslide area. Aspects ignored by the model that could explain the residuals include local variations of the threshold of acceleration and processes modulating the surface ground shaking, such as the distribution of seismic energy release on the fault plane, the dynamic stress drop, and rupture directivity. Nevertheless, its simplicity and first-order accuracy suggest that the model can yield plausible and useful estimates of the landslide distribution area in near-real time, with earthquake parameters issued by standard detection routines.

Highlights

Triggered landslides are a significant secondary hazard of earthquakes, and may be the dominant cause of damage to infrastructure and lifelines, especially roads (Bird and Bommer, 2004)
For a number of small- to moderate-magnitude earthquakes with a small Ad, the model predicts no landsliding. This may be due to uncertainties on the hypocentral depth estimation that we assume to be the depth of wave emission, R0, and assigning a < 25 % uncertainty on R0 allows for the prediction to match Ad within a factor of 2, for five out of seven cases in this category (Fig. 2)
We have presented an analytical expression for the distribution area of earthquake-induced landslides

Summary

Introduction

Triggered landslides are a significant secondary hazard of earthquakes, and may be the dominant cause of damage to infrastructure and lifelines, especially roads (Bird and Bommer, 2004). The severity of this hazard and the associated risks is clear after most large earthquakes in steep landscapes, and was underlined by the devastation and fatalities caused by landsliding induced by recent large earthquakes in Sichuan (China) 2008 and central Nepal, 2015 (Yin et al, 2009; Kargel et al, 2015). The earthquake-induced landslide hazard is defined in the first instance by the number, size, and location of landslides. Marc et al.: Prediction of the area affected by earthquake-induced landsliding

Results

Discussion

Conclusion