10 September 2021
Landslides from the 7 September 2021 M=7.1 Guerrero earthquake in Mexico
Posted by Dave Petley
Landslides from the 7 September 2021 M=7.1 Guerrero earthquake in Mexico
In the evening of 7 September 2021 (local time) a M=7.1 earthquake struck close to the city of Acapulco in Mexico. This event was shallow, leading to potentially high levels of damage in the worst affected areas. Wikipedia is calling this the 2021 Guerrero earthquake, but time will tell as to whether this is adopted as the formal name for the event.
At least three people were killed and 20 more were injured, a comparatively light toll for an event of this magnitude. Interestingly, one of the major impacts appears to have been landslides, although fortunately there are no known fatalities from these events.
Some images are emerging of landslides triggered by this event. The best set I have found so far is in the Daily Sabah, which has a gallery of images of the impacts of the earthquake, several of which show landslides:-
A major rockslide on a highway, triggered by the 7 September 2021 M=7.1 Guerrero earthquake in Mexico. Image by Reuters via the Daily Sabah.
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A fill slope collapse on a road, triggered by the 7 September 2021 M=7.1 Guerrero earthquake in Mexico. Getty Images via the Daily Sabah.
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Minor slope collapses in a residential hillside, triggered by the 7 September 2021 M=7.1 Guerrero earthquake in Mexico. Getty Images via the Daily Sabah.
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Damage to a car triggered by a slope failure triggered by the 7 September 2021 M=7.1 Guerrero earthquake in Mexico. Image by Reuters via the Daily Sabah.
Given the topography and the scale of the earthquake, it seems likely that larger landslides will have occurred in the more remote mountainous areas of the epicentral zone. As yet I have not seen any images of such events, but it is likely that reconnaissance and fact-finding visits will be organised in the coming days. I would welcome any information that loyal readers can provide.
Dave Petley is the Vice-Chancellor of the University of Hull in the United Kingdom. His blog provides commentary and analysis of landslide events occurring worldwide, including the landslides themselves, latest research, and conferences and meetings.
I’ve in-laws near there. IIRC, they were so proud of their new-build multi-storey apartment’s ‘gated’ complex, with its private pool and whatever.
When I glanced at their photos, I realised the site was on a ‘bench’ cut into a rather steep slope. The retaining wall did not seem tall enough, sufficiently angled, buttressed, drained, or even anchored. It just looked like a garden wall. There seemed scant or no geo-stuff stabilising the raw slope. And, when I asked if the nice concrete pool, intended as an emergency resource, was ‘isolated’, with a flexible membrane against cracking, emerged that, too, was planned but, like the full code ‘geo-technic’ stuff, lost to ‘economising’.
So, one little quake, all their precious pool water might gurgle, gurgle down the splits and cracks. Hopefully harmlessly. While any or all of that raw slope, plus the perched properties at the top, could impact rear of building. Oops…
A year along, we got a ‘change of address’ card: They’d not renewed their tenancy…