A closer look at factors governing landslide recovery time in post-seismic periods

Abstract

<p>Various mechanisms are proposed to explain landslide recovery time in the time following major earthquakes. However, research on prescribing possible recovery times following an earthquake is still relatively new. This paper provides an insight into factors governing landslide recovery time, which could be considered as a step forward in predictive modeling for landslide recovery time. To accomplish this, we examined 11 earthquake-affected areas based on the characteristics of both landslide events and landslide sites associated with diverse morphologic and climatic conditions. Our analyses indicate that the dominant characteristics of post-seismic landslide mechanisms determine the recovery time. The characteristics can be identified based on: (i) the fraction of area affected by landslides (%), (ii) mean relief and its standard deviation (m), (iii) average daily accumulated precipitation (mm) and (iv) rainfall seasonality index. If there are not enough co-seismic landslide deposits or not enough relief to trigger large deposits on hillslopes, then the recovery processes are mostly controlled by new landslides caused by a strength reduction of hillslope materials. In most of the cases, this brings a relatively quick recovery process in which the majority of post-seismic landslides may happen within a year or even in a month if sufficient intense rainfalls occur soon after the earthquake. If the predisposing factors create large co-seismic landslide deposits, then remobilization of material takes the role of the dominant mechanism and recovery may take years. Overall, our analyses show that the recovery takes relatively longer if a large amount of co-seismic landslide material is deposited within a high-relief mountainous environment where precipitation rate is low and not persistent.</p>

Space-time landslide susceptibility modelling in Taiwan

“…We collated 56 PGA maps from the USGS ShakeMap system (Worden and Wald, 2016), all corresponding to earthquakes with magnitude above 5.0, occurred within the spatio-temporal domain examined in this work. Thus, our initial assumption was that the effect of ground motion, be it direct or preparatory via legacy processes (Tanyaş et al, 2021). However, it appeared that the ground motion signal did not provide any explanatory information which in turn may imply that the primary landslide trigger for the period we examined uniquely consist of heavy and/or persistent rainfall.…”

Space-time landslide hazard modeling via Ensemble Neural Networks

“…The Mw 7.8 mainshock occurred on 25 th April 2015 and together with a sequence of aftershocks it was responsible for triggering more than 25,000 landslides (Roback et al, 2018). The ground motion did not only affect the Nepalese terrain right after the earthquake by co-siesmic landslides, but its disturbance increased the landslide susceptibility in the following years, a phenomenon commonly referred to as earthquake legacy (Tanyaş et al, 2021). The legacy of the Gorkha earthquake has been recently demonstrated by mapping a multi-temporal inventory, which has been publicly shared by Kincey et al (2021).…”

Coseismic Debris Remains in the Orogen Despite a Decade of Enhanced Landsliding

“…Material exhaustion may prevail in small deposits–more likely originating from weak soil covers than from bedrock. In fact, the nature of the source material defines debris properties and threshold slopes, and thus their factor of safety and residence time (Larsen et al., 2010; Montgomery & Brandon, 2002; Tanyaş, Kirschbaum, Görüm, et al., 2021).…”

“…Interestingly, although the destabilising effect of major earthquakes appears positively correlated with their magnitude (Marc et al., 2015), the decay timescale of landslide activity for even the largest disturbance appears counterintuitively short (Fan, Scaringi, Korup, et al., 2019). While multiple mechanisms may be at play (Kincey et al., 2021), post‐earthquake landslide dynamics seem essentially controlled by the coseismic landslide disturbance (sizes, locations, landcover, and hydrological conditions), the healing or removal of seismically damaged layers, morphologic and climatic factors, and the legacy of previous earthquakes (Marc et al., 2021; Tanyaş et al., 2021a, 2021b; Tian et al., 2020).…”