Costa Rica earthquake - landslides have proven to be a major threat

News continues to flow in regarding the impact of the earthquake in Costa Rica. It is increasingly evident that landslides have probably been the major problem, which is unsurprising given the topography and soils. The landslides have clearly caused substantial loss of life and are also hampering rescue operations.

The Washington Post is reporting, quite rightly, that there are now concerns about the stability of the slopes in the affected area in the next wet season. The Reuters image below shows seriously deformed ground above the crown of a seismically-triggered landslide at San Rafael de Vara Blanca:


I found the diagram below showing rainfall in San Jose, which is just a few tens of kilometres away:


Fortunately the period January to April is pretty dry, but problems will certainly start in May. Action will be needed to address this as the level of hazard will be high in many areas. At the moment the biggest problems seem to be around the village of Cinchona, on the flank of the volcano, were a family restaurant was buried (see AP images below of Cinchona):


There are certainly lots of other landslides too, as this AP image shows:


Finally, the Washington Post is carrying a slightly intriguing report:

"A wave caused by the earthquake damaged the Cariblanco hydroelectric plant and it will take at least a year to repair, local media quote a senior official as saying."

A bit of digging shows that AP are reporting that "Officials reported meanwhile that the country's leading Cariblanco hydroelectric plant will be out of operation for about a year, after its generators were buried by tons of mud from flooding and landslides unleashed by the earthquake."

According to this site, Cariblanco appears to consist of two 40 MW turbines. It came into operation in 2007 after construction costs of US$170 million. This would appear to be a very expensive set of landslides for such a new project! Unfortunately, our experience elsewhere (e.g. Taiwan) is that sediment delivery increases in the rainy season as further landslides activate, so the operators of this site would be well advised to get some landslide advice.

Magnitude Mw=6.1 earthquake in Costa Rica

At 19:21 UTC (13:21 local time) on 8th January a Magnitude Mw=6.1 earthquake struck Costa Rica. Although this is not a particularly large earthquake, it is certainly substantial enough to have triggered many landslides, especially given that it occurred very close to the surface (the USGS depth estimate is just 4.5 km). Several reports have come in already about fatalities associated with landslides. Confirmed are the deaths of two girls near the city of Alajuela, NW of San Jose, whilst less well confirmed reports suggest that a family of five may also have perished in a landslide.

The USGS has provided a shake map:
This is an area of known high levels of seismic hazard:
This area is probably particularly prone to landslides as the soils consist of heavy weathered soils and those derived from volcanic products, both of which are potentially unstable when disturbed. I have come across two very interesting resources. First, a map of damage reports (in Spanish) is being put together, based on information from Twitter. This should be visible below:


Ver mapa más grande

Second, there is an interesting Youtube video of TV footage of the aftermath, much of it shot from a helicopter. The first part of the footage shows I think attempts to recover the remains of the two girls killed in a landslide, whilst the middle section shows landslides triggered in the epicentral region. Based upon this it might well be that further fatalities become apparent when daylight reaches this area. The video should be visible below, or can be viewed here.

Guatemala landslide

As the Guatemala landslide now fades from media prominence, Reuters have released probably the best image to date of the landslide site:

It is now clear that this was a a large rockslide (not a mudslide as reported elsewhere).

AP have released a good image of the site:


Whilst this Reuters image shows the runout of the landslide quite well:



Finally, CONRED released this image of the site to show the ongoing rockfall activity that caused suspension of rescue operations:

Meanwhile the number of recovered victims has now reached 37. About 50 victims remain buried in the debris.

Finally, there are various reports that an evaluation of the site has determined that the area around the landslide is too dangerous for habitation. My suspcicion is that this is right - the landslide appears to me to have occurred in a much larger landslide scar. I will post again on this soon.

Landslide crisis in Honduras

Although it has not received any substantial coverage in the west, it appears that there is a serious landslide crisis developing in Honduras. Over the last few days Honduras has experienced intense rainfall as a consequence of a stalled tropical depression. A state of emergency has been declared.

The most serious problem appears to lie in Corquin in Copan, in the very west of Honduras. Here, both La Prensa and La Tribhuna are reporting that massive landslides have occurred. A (very rough) translation of the key parts of the La Prensa article is as follows:

"A landslide caused by rains in two hills formed a gigantic dam on a river that buried two villages, whose inhabitants had been evacuated, in a municipality in the department of Copan, 550 km northwest of the Honduran capital, reported a local official on Tuesday.

"El Suptal de Coquín and El Suptal de Belén are two communities that were nearby, one kilometer away from one to another, and they were buried, including two schools and all the houses disappeared". The mayor said that five other communities are at risk. Paz said that the land that slipped from two hills formed a dam on the river Coyol, which was formed a gigantic pool that has flooded the two communities. The earth dam is turning into mud that can slide easily endanger other five communities, which were evacuated. "The communities that are at risk are Mesitas, Pacaya, Ichotal, Higueral y El Coyol, all we have evacuated 100%, there are not a person, or anything, thank God," he said. He explained that "there is no access for machinery, or anything, the only way will be to blow it up but the thing is that as the hills are too sensitive and could cause more landslides." In the monitoring they did yesterday, the dam measured about 500 meters and the river Coyol is blocked. Every five minutes landslides occur that bring down trees and rocks, which increases the height of the blockage.

La Estrella is reporting that the landslide dam is 150 m high Needless to say a blockage like this is exceptionally concerning as it is inevitable that a breach will lead to a serious flood unless the landslide is mitigated. Urgent action may be needed to prevent a serious problem.