Earthquake-triggered landslides and Environmental Seismic Intensity: insights from the 2018 Papua New Guinea earthquake (Mw 7.5)

Abstract

ABSTRACTOn the 25 February 2018, an earthquake of magnitude Mw7.5 struck the region of Porgera in Papua New Guinea (PNG), triggering numerous landslides. Planetscope images are used to derive a partial inventory of 2941 landslides in a cloud-free area of 2686 km2. The average area of landslides in the study area is 18,500 m2. We use the Environmental Seismic Intensity (ESI) scale to assess the damage due to the triggered landslides. Local intensity values are assigned to individual landslides by calculating their volume using various area–volume relations. We observe that different empirical relations yield similar volume values for individual landslides (local ESI intensity ≥ X). The spatial variation of landslide density and areal coverage within the study area in cells of 1 km2 is investigated and compared to the probability predicted by the USGS model. We observe that high probability corresponds to a significant number of landslides. An ESI epicentral intensity of XI is estimated based on primary and secondary effects. This study represents the first application of the ESI scale to an earthquake in PNG. The Porgera earthquake fits well with past case studies worldwide in terms of ESI scale epicentral intensity and triggered landslide number as a function of earthquake magnitude.

Keywords

• Earthquake Environmental Effects (EEE)
• ESI scale 2007
• Papua New Guinea
• Earthquake-induced landslides