20 April 2018
Further information about the Castell de Mur landslide in Spain
Over the last couple of days more information has emerged about the Castell de Mur landslide in Spain, which killed two people earlier this week. My friends at UPC, Jordi Corominas and Marcel Hurlimann and colleagues have provided two drone images of the landslide, which I post here with their permission. This image shows the rear scarp of the landslide:
Note that the face is weathered, indicating that detachment has occurred via a pre-existing surface. Lower down there are clear signs of fresh fractures. The UPC interpretation, with which I agree, is that this is a toppling failure primarily of an existing jointset, with fracture of rock generating the final landslide event. The image below shows the resultant landslide deposit:-
There are several really interesting features here. In the images the remains of the former village can be seen, including ruined houses and the tiny chapel, which was destroyed in the landslide. It is also clear that the Castell de Mur landslide occurred in an area of undercutting and rockfall events.
The final failure was recorded on seismic instruments. ICTJA have posted the seismic records online:
The translation of their text states:-
In this image you can observe the seismic wave caused by the detachment of land that occurred in the area of Castell de Mur, in the Pallars Kussà and which could be recorded by different stations of the seismic network of catalonia of catalonia . It can be established, from these records, that the landslide occurred at 14:33 p.m. on 16 April.
The image, made from the data processing made by our researcher Jordi Diaz Cusi, shows the vibration of the floor in the vertical direction recorded by the stations located near Balaguer, Pont de Suert, Sort and Organyà, at Between 25 and 40 km from the place where the event occurred.
“the signal is weak and can only be identified after properly processing the data”, explains Jordi Diaz.
Although it is not easy to attribute a magnitude value to this type of signals, from the ICGC they indicate that it would be the equivalent of a very small earthquake, of local magnitude 0.8. Thus, the vibrations produced by the detachment could only be perceived near the place where it occurred.