18 December 2020
Arequipa, Peru: landslides from a M=5.6 earthquake on 16 December 2020
The city of Arequipa in Peru was struck by a M=5.6 earthquake at 17:48 UT on 16 December 2020. This was a comparatively deep earthquake (87 km according to the USGS) in an area with a history of significant seismicity. It is not expected that an earthquake of this magnitude at such a depth would cause large amounts of structural damage (or indeed extensive landslides), and indeed there are no reports that I can find of loss of life.
This earthquake is however interesting because it appears to have generated significant landslide activity in the mountains around the city. These were caught on a video that has been posted to Youtube, which is quite dramatic:-
The video of course is showing the clouds of dust generated by landslides (most probably rockfalls) in this extremely dry environment. We have seen this effect previously where earthquakes have occurred in very arid environments, most notably in the 2010 M=7.2 earthquake in the Sierra Cucapah, Mexico, which was also caught on video. In Mexico we studied the landslides via remote sensing and wrote up the results (Barlow et al. 2014). Whilst the videos of the event were very dramatic, and rockfalls were widespread, the volume of material moved by the failures was quite small.
It is difficult to know whether this will be the case here:-
There are some images online of rockfalls triggered by the earthquake, especially on roads, but I have not been able to track down any images of larger failures. These may of course be located in remote areas, if they have occurred.
Barlow, J., Barisin, I., Rosser, N., Petley, D., Densmore, A. and Wright, T. 2015. Seismically-induced mass movements and volumetric fluxes resulting from the 2010 Mw = 7.2 earthquake in the Sierra Cucapah, Mexico, Geomorphology, 230, 138-145. http://dx.doi.org/10.1016/j.geomorph.2014.11.012.