21 December 2021

The movement of the San Isidro landslide in Peru, and a possible relationship with the 28 November 2021 Northern Peru earthquake?

Posted by Dave Petley

The movement of the San Isidro landslide in Peru, and a possible relationship with the 28 November 2021 Northern Peru earthquake?

Yesterday I wrote about the failure of the San Isidro Landslide in La Peca, Peru on 12 December 2021, which has led to the relocation of about 250 people.  Later in the day, Sotiris Valkaniotis tweeted satellite images of the site, derived from the European Space Agency Sentinel instruments, that both confirmed the location of the landslide and provided an indication of the movement of the slope.  The Tweet should be visible below:

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This provisional analysis indicates that the landslide was about 800 m in length, with displacements exceeding 20 metres in places.  The devastating impact on the village is clear, despite the low resolution of the imagery.

There is an interesting other dimension to this landslide.  On 28 November 2021 the Amazonas region suffered an M=7.5 earthquake.  The epicentre was about 215 km from the San Isidro landslide. Images posted to the La Peca Facebook page indicate that significant landsliding was triggered in the area by the earthquake.

 

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News reports suggest that there was significant landsliding near to Bagua Grande, 25 km to the south of San Isidro, for example.

Thus, it seems quite possible that the slope at San Isidro was weakened by the earthquake, and then failed in the first heavy rainfall event after the seismic event.  This is a pattern that we have seen elsewhere.

Of course this is only speculation at this point, but it is an interesting angle to explore.

As an aside, the images in the Facebook page indicate that in at least one location the valley is blocked by a landslide, possibly in the area of Bagua Grande. I hope that this has been (or is being) addressed.