Multimodal method for coseismic landslide hazard assessment

Abstract

Regional-scale coseismic landslide hazard assessments have traditionally been based on infiniteslope analyses, considering only a single mode of failure. Inventories and landslide reconnaissance work have shown a diverse range of coseismic landslide modes with significantly different consequences of failure. This paper presents a multimodal approach for regional-scale coseismic landslide hazard assessment. Through a two-step procedure, the multimodal method explicitly accounts for four general landslide types commonly observed during earthquakes: rock-slope failures, disrupted soil slides, coherent rotational slides, and lateral spreads. First, the susceptibility to each landslide mode is evaluated based on topography. Second, coseismic landslide hazards are assessed using mode-specific geotechnical models. A trial multimodal landslide assessment is presented for the seismically active country of Lebanon. Results show that the computed coseismic landslide hazard closely matches field-verified slope activity across different regions of the country exhibiting a range of failure modes. These results qualitatively demonstrate the efficacy of the procedure and suggest that multimodal coseismic landslide hazard analysis is especially well-suited for regions with varying terrain and where landslide inventories are not available.

Landslide susceptibility mapping based on triggering factors using a multi-modal approach

“…We build upon the multimodal approach presented in [9] to assess susceptibility to three types of rainfall-induced landslides on a regional scale: (1) debris flows, (2) rock slope failures, and (3) coherent rotational slides. Topographic slope and geologic formation are used to determine terrains susceptible to rainfall-induced landslides and the corresponding mode of failure.…”

“…The slope bounds adopted by [9] are used to delineate the slopes where each mode of failure is more likely to occur. Slopes from 15° to 50° are susceptible to debris flows.…”

“…To analyze coherent rotational slides, we modified the model developed by [9] and added water pore pressure to the factor of safety equation ( [rad] for slopes15° ߠ 35°, and ߚ is determined by the level of saturation.…”

“…The model studies all geologic units and uses the same soil and rock strength parameters as in [9] to predict debris flow failures but adjusts these parameters for the wedge and coherent failure modes. For debris flow, root cohesion is derived from the vegetation index across Lebanon [18].…”

“…Only few researchers employed mode-specific approaches to assess landslide susceptibility. Recently, an innovative multimodal approach was proposed to assess regional-scale co-seismic landslide hazards in the country of Lebanon [9]. The approach focused on four common types of coseismic landslides: (1) rock-slope failures, (2) disrupted soil slides, (3) coherent rotational slides, and (4) lateral spreads.…”