The raw statistics are important.\u00a0 Martha et al.<\/em> (2016)<\/a> have mapped 15,551 landslides triggered by the\u00a0M=7.8 Gorkha Earthquake in total, including 213 landslides triggered by the large aftershock in Dolakha.\u00a0 The total volume of the landslides is about 620 million cubic metres.\u00a0 Whilst this number of landslides sounds high, it is probably much lower than we had anticipated for an earthquake of this magnitude in the highly unstable mountains of Nepal.\u00a0 The reasons for this remain unclear.<\/p>\n The most interesting aspect of the paper though is that the spatial correlation between the landslides triggered by the earthquake and the peak ground acceleration is weak.\u00a0 There is a strong correlation with slope angle (this is always the case), but the landslides occurred in a zone to the north of the earthquake affected area that does not correspond with the high peak ground accelerations.\u00a0 This diagram, from the paper, shows this rather nicely:-<\/p>\n The landslide distribution in relation to the Peak Ground Acceleration, from Martha et al (2016)<\/em><\/p><\/div>\n .<\/p>\n Whilst it might be tempting to explain this by the distribution of steep slopes, I do not think that this alone explains the result.\u00a0 Thus, in the case of the M=7.8 Gorkha Earthquake, the landslide distribution is more complex than one might have expected.\u00a0 Martha et al.<\/em> (2016)<\/a> make the point that the landslide distribution seems to have been strongly controlled by the behaviour of the fault rupture, and that the spatial termination of the landslides towards the east seems to be controlled by the termination of the rupture event.\u00a0 I think this is spot on.\u00a0 Below is an INSAR map of the tectonic ground deformation caused by the earthquake<\/a>.\u00a0 You can get an idea of the location in relation to the map above using the location of the epicentre of the mainshock to the west and the M=7.3 Dolakha aftershock to the east (with the cluster of aftershocks that followed that event:<\/p>\n INSAR data showing tectonic deformation from the M=7.8 Gorkha Earthqhquake in Japan, via GSI Japan<\/a><\/p><\/div>\n .<\/p>\n And this is a map of the aftershocks, published in an open access paper by Ichiyanagi et al.<\/em> (2015)<\/a>.\u00a0 Note that this is from an array in Kathmandu, so the distribution towards the west may not be as complete:<\/p>\n The distribution of aftershocks from the M=7.8 Gorkha earthquake in Nepal, from Ichiyanagi et al.<\/em> (2016)<\/a><\/p><\/div>\n .<\/p>\n In general the high density of aftershocks lies in the northern area of the fault rupture, as does the landslides.\u00a0 These aftershocks did not trigger the landslides, but the similarity in extent suggests that the dynamics of the behaviour of the fault plays a strong role in controlling the landslide distribution.<\/p>\n The authors of the paper in landslides have made the inventory data available via the Bhuvan tool<\/a>.<\/p>\n Ichiyanagi, M., Takai, N., Shigefuji, M., Bijukchhen, S., Sasatani, T.,\u00a0 Rajaure, S., Dhital, M.R. and Takahashi, H. 2015. Aftershock activity of the 2015 Gorkha, Nepal, earthquake determined using the Kathmandu strong motion seismographic array<\/a>. Earth, Planets and Space<\/em>, 68<\/strong>, 25. DOI: 10.1186\/s40623-016-0402-8.<\/p>\n![\"M=7.8](\"https:\/\/blogs.agu.org\/landslideblog\/files\/2016\/12\/16_12-Nepal-1.jpg\")
![\"M=7.8](\"https:\/\/blogs.agu.org\/landslideblog\/files\/2016\/12\/16_12-INSAR-Map-e1481271746415.png\")
![\"M=7.8](\"https:\/\/blogs.agu.org\/landslideblog\/files\/2016\/12\/16_12-aftershocks-1.jpg\")
References<\/h5>\n