2 May 2016
The location of the Kyrgyzstan loess landslide
The mainstream media has not really caught up with the Kyrgyzstan loess landslide as yet (it is only a matter of time I suspect – it has to be worth a shock-horror headlline in the Daily Mail, surely?), although a news report is now available on the Cihan website. Sadly it provides no additional information. As a reminder this is the video:
“Uch-Chat Pasture located nearby the village of Almaluu-Bulak in Jalal-Abad region”
Google Maps locates Almaluu-Bulak at 41.144 N, 73.022 W. On that basis I think the most likely location is shown in the Google Earth image below:
The valley that best seems to fit the video is this one, also from Google Earth:
If so I believe that this would be the slope that generated the landslide. Note the small slip in the lower part of the slope, and the other adjacent landslides (of which more below):
This little corner of Kyrgyzstan has an extraordinary range of landslides. This is a Google Earth image of the wider area. The valley containing the most recent landslide is in the upper left corner of the image:
Whilst some of these landslides seem to have had a high level of mobility, they do not appear to have been as mobile as the one last week. In the next valley over lies the set of landslides shown below. The one in the centre of the image has also shown a very high level of mobility. Note the house built right in the middle of the landslide deposit, which goes beyond the road. The smaller landslide on the left has also moved a significant distance:
1 May 2016
A video of a catastrophic landslide in loess in Kyrgyzstan
A video has appeared on Youtube that shows a catastrophic landslide in loess (I am assuming it is loess) in Kyrgyzstan. I keep thinking that I have seen it all in landslide videos, and then one pops up to shock. This is genuinely astounding, without doubt the most amazing of the year so far, and probably in my all time top ten:
The text that goes with the video says the following:
Two landslides occurred on April 27, 2016 at the Uch-Chat Pasture located nearby the village of Almaluu-Bulak in Jalal-Abad region. The first landslide came down at about 5.40 pm local time, amounting to at least 100 thousand cubic meters. It vanished a summer house built on the pasture. The second landslide came down at about 6.00 pm. Its volume reached 1 million 600 thousand cubic meters, which killed the 14-year-old boy who was grazing the livestock in the area.
I am unsure as to whether this is the first or second landslide – my assumption is the second given its size and given the existing landslide deposit visible in the video:
The landslide appears to be dry given the amount of dust being generated. Note the way that the loess is behaving like a fluid – the wave form evident in the video is remarkably reminiscent of a tsunami making landfall.
The first of these two videos has a decent shot of the provides an overview of the landslide:
Note the way that the landslide has super-elevated (travelled up the slope) as it has going around the bends in the valley. This is an indication of high velocities. The cause of the landslide is of course deeply intriguing, but with a lack of ability to understand any of the television footage I can provide no insight. I will try to find out more.
28 April 2016
Forecasting the time of failure: the Preonzo rockslide
In recent years there has been increasing interest in the development of techniques, and of the understanding that underpins them, to provide early warning of large landslides. One key component of this has been the use of ground movement monitoring, typically using a combination of extensometers and surface movement markers, to detect movements and to infer likely future behaviour. In a paper just published in Landslides (Loew et al. 2016), Simon Loew and his colleagues from ETH have provided details of an unusually detailed – and successful – monitoring campaign for a rockslide in Switzerland. The landslide in question is the Preonzo rockslide, a 210,000 cubic metre rockslope failure that occurred near to the village of Preonzo on 15th May 2012. I featured this landslide at the time, so won’t describe it again here, but the one of the failure events (but neither of the main collapses) was captured in a spectacular video:
Movement of this slope was first noted in 1989, with more substantial movements starting in 2006. To protect the population and infrastructure in the valley, a early system was installed in 2010. The landslide itself was anticipated and the roads below were closed. The failure occurred in two phases – an initial rockslope collapse followed, three hours later, by a remobilisation event that generated a rock avalanche (note that the events caught on video were neither of these two main failures). No-one was injured and no infrastructure was damaged.
The evolution of the rockslope failure is shown in three images in the paper:
There is much to admire in this paper, but I will focus on just one element, the movement record. The authors present a wide range of fascinating data capturing the evolution of the failure over a 10 year period. One set of data comes from measurements using a robotic total station and prisms on the rockslide, whilst another (shown below) captures the opening of the main tension crack at the rear of the mobile body of rock:
These data are amazing – note the gradual acceleration of the landslide over time, the response of the slide to rainfall events (which create bumps in the displacement plot), and the change in behaviour into rapid movement at the end of the record. It was this change that allowed the impending collapse of the slope to be observed. Loew et al. (2016) note that a distinct change in behaviour occurred in 2006, when the systematic acceleration to failure started. In fact, the authors observe that use of the inverse velocity technique from the data from 2006 onwards provides a forecasted failure in 2012, although this give no more than an approximation:
Loew et al. (2016) also look carefully at the data for the final failure event. In this case the progression to failure is clearly evident:
But note also that the data is very noisy. Failure is a complex process, and forecasting the time of failure is immensely challenging, even with the very best data. I think this paper should be read by anyone planning to use surface monitoring techniques to forecast landslide failure.
Loew, S., Gschwind, S., Gischig, V., Keller-Signer, A. and Valenti, G. 2016. Monitoring and early warning of the 2012 Preonzo catastrophic rockslope failure. Landslides. Doi: 10.1007/s10346-016-0701-y
26 April 2016
The distribution of landslides from the M=7.0 Kumamoto Earthquake
With impressive efficiency, analyses are now appearing of the distribution of landslides triggered by the M=7.0 Kumamoto Earthquake, and its foreshock and aftershock sequence. The team at DPRI at Kyoto University have put a large body of information online (in Japanese, but Google Translate does a good job). I have tried to turn some of the explanation of the landslides into understandable English from the machine translation:
Many of the slope failures, occurred on tephra covering the slopes. Many of the collapses occurred on the steep part of the slopes with a gradient of more than 30°, such as the Aso caldera wall and the incised valley wall…Near to the Kyoto University research facilities, shear fracture on the gentle slopes of about 10 ° tilt occurred, with fluid sediment movement seeming to have happened. This is believed to be due to tephra containing water being subjected to ground motion, inducing liquefaction
The team have generated a stunning contour map with the earthquake-induce landslides highlighted in red:
Note the high incidence of landslides on the western wall of the caldera, and on the steep southern flanks of the volcano. The data are available as a (zipped) KML, so I have imported them into Google Earth along with the USGS seismic intensity contour data:
This visualisation of the landslides from the M=7.0 Kumamoto Earthquake does help explain the distribution of slope failures. The highest density is in the area of intersection of the MMI=IX region and the steep slopes that mark the wall of the caldera. In the MMI=XIII zone landslides appear to have occurred in the tephra deposits on the southern edge of the volcanic complex. But note the boundaries of the area mapped on the contour image above – there may be further landslides to be found yet.
There is a great deal of work still to do on understanding these landslides, but the mapping work of this team is an amazing start.
Meanwhile, Japan Asia Group have placed an amazing digital elevation model (DEM) map online, showing the landslide at Mimami-Aso:
The most interesting aspect of this is the very extensive slope deformation around all of the ridges surrounding the actual failure, as evidenced by large numbers of cracks that the DEM data highlights beautifully.. In effect that landslide is part of a much larger landslide complex, However, experience tells us that although this situation looks extremely hazardous, these cracked slopes often prove to be more stable than one might expect. Thus, it is hard to say what will happen when heavy rainfall arrives. This is a site that will need both detailed investigation and active monitoring.
25 April 2016
Espirito Santo rock joint collapses
There is an extraordinary video on Facebook showing massive collapses of sheeting joints in Espirito Santo Brazil. I cannot embed the video, but really recommend that you take a look. This is the moment of collapse:
The collapse occurred in Pancas County of Espirito Santo in an area of granite massifs. The video was posted by Heinrich Theodor Frank, who provides the following comment (this is a tidied up Google Translation):
Yesterday, in the city of Pancas (ES), something happened very scary – and was filmed! Granites and other rocks, when they change of course they do so from the outside. Successive rock levels are changed and the rock begins to form “shells” like an onion [this is exfoliation jointing].
The same process happens with whole mountains, where there is a stress relief process. There are good internet pictures of granites in arid regions, where the “shells” are well exposed because they are not hidden beneath vegetation (search for “spheroidal exfoliation”). In Pancas the “shells” of granite changed collapsed down the hill – with everything that was in them. The news is available on the network, but the footage of this is an extraordinary record of this event. After an initial collapse, the staff began to film the dust cloud and therefore, succeeded in filming the next “shells” sliding downhill. An unpublished video in the world!
The video starts after the first collapse (which has clearly generated a vast amount of dust). After a hiatus there is then a series of successive collapses as the joints unload. This is the second major collapse event:
A cliff collapse from SW China
I don’t think I have come across this one before (but it is now hard to keep track!). It is a dramatic cliff collapse from China, but the commentary provides no additional information.
This is a classic rock topple. The slope has clearly been cut, allowing a collapse on a pre-existing set of joints. Look carefully for the was that the landslide destroys the building on the right side:
Thanks to Dave Milledge of Durham University for pointing out the Espirito Santo video.
24 April 2016
The first anniversary of the Gorkha earthquake in Nepal: the Langtang rock and ice avalanche
25th April marks the first anniversary of the Gorkha earthquake in Nepal, undoubtedly the most important landslide-generating event of 2015. According to ICIMOD, the earthquake triggered 5,159 significant landslides in 14 districts. Of these, 464 landslides directly impacted physical infrastructure. The earthquake killed over 9000 people, with 255 still missing. Many of this latter group are likely to have been killed by landslides.
The most dramatic and significant landslide was the Langtang rock and ice avalanche, which was probably the earthquake triggered event that killed the most individuals. I featured a very preliminary analysis of this event back in May based on the initial satellite imagery that was available at the time. Since then the USGS have published an exceptionally useful review of the types and impacts of landslides in the Gorkha earthquake (Collins and Jibson 2015), which includes a description and analysis of the Langtang rock and ice avalanche. The report can be downloaded from here, and there is a set of accompanying (and very useful) videos on youtube as well.
This analysis provides detailed insight into the mechanisms and processes of the Langtang rock and ice avalanche. Included, and in the public domain, is a youtube video of a helicopter overflight of the site:
The helicopter reaches the site after about 6 minutes, and then overflies both the glacier and the landslide deposit.
The analysis takes my initial interpretation and develops it properly, providing the sort of detailed observations that I could not. Thus, it supersedes my interpretation, although I will leave mine online. The most important key insight here is that the rock avalanches started much higher up the mountain than I had observed. As Collins and Jibson (2015) wrote:
Although the exact location of the uppermost source is difficult to identify, the landslide appeared to initiate at an elevation above 5,000 m on the flank of Langtang Lirung, a 7,227-m-high peak on the north wall of the valley (fig. 19). Large masses of glacial ice broke loose from multiple source areas during the earthquake shaking, and as the ice rapidly descended the steep slopes above the valley it entrained a mixture of rock and soil from the ground surface and surrounding valley walls. The mixture of ice, rock, and soil accelerated down an approximately 35° slope and then became at least partially airborne at a point 500 m above the valley floor where the slope steepens to about 50°–55°.
This is best understood with reference to this image, also from the report:
This was a large and very mobile landslide:
The map distance from the crown of the landslide to the distal tip of the deposit was 3,700 m. The total vertical drop over that length was at least 1,850 m. The deposit covered an area 400 m wide by 900 m long. A preliminary estimate of the total volume of the deposit (based on depth estimates in different parts of the deposit made during our ground investigation) is 2,000,000 cubic metres. We estimate that more than half of the deposit was ice; the remainder was a mixture of soil and rock fragments in roughly equal proportion.
The landslide was sufficiently mobile to create an air blast that knocked over huge numbers of trees on the opposite valley wall, as this image from the report shows:
The landslide killed over 200 people in the village of Langtang, which was, with the exception of a single dwelling, destroyed completely. The village would have been strongly shaken by the earthquake, then hit by the air blast before being over-run by the rock avalanche. Once again the destructive and under-appreciated nature of earthquake-triggered landslides is clear.
Collins, B.D., and Jibson, R.W., 2015, Assessment of existing and potential landslide hazards resulting from the April 25, 2015 Gorkha, Nepal earthquake sequence (ver. 1.1, August 2015): U.S. Geological Survey Open-File Report 2015–1142, 50 p., http://dx.doi.org/10.3133/ofr20151142.
23 April 2016
Liuliao Village, China: a rockfall strikes a crowded school
Xinhua yesterday carried a story about a rockfall in Liuliao village, Rong’an County in Guangxi Zhuang Autonomous Region in southern China that struck a primary school on Thursday. At the time the school contained 149 pupils and 12 teachers, of whom 23 people were injured, seven of them seriously. This image from Xinhua gives an overview of the rockfall, which was triggered by heavy rainfall:
The landslide, which is clearly in limestone, has a volume of 1,600 cubic metres. The source area appears to be heavily weathered, suggesting failure in an existing joint. it is fortunate that part of the debris flowed to one side of the school.
The Daily Mail has a good image of the rockfall from the other side. The boulders are notably large, although again that so many missed the school is fortunate:
The structure appears to have withstood the impacts quite well. The location of the school is the one shown below, via Google Earth:
The proximity of the school to the slope is of course questionable, although the dense forest might have led to the conclusion that rockfall activity was rare. It is also notable that in this area most of the older settlements are built close to the valley edges – this may be to preserve agricultural land and to avoid flooding, perhaps.
This rockfall was triggered by a long period of heavy rainfall in southern China. There are further warnings of heavy rainfall today, and it is forecast that there will be further heavy rainfall to the end of the month. There are associated warnings of rockfalls and landslides. A landslide late on Friday has probably killed six people at Guoli Village, Nujiang Lisu Autonomous Prefecture in Yunnan Province.
20 April 2016
Images of other landslides from the Kumamoto earthquakes
In addition to the major, and well-publicised, landslides triggered by the Kumamoto earthquakes this week (which I have featured in my previous posts), there appears to be a substantial number of other major failures, many of them around the flanks of Mount Aso. There are images of these on the websites of Kokusai Kogyo and Asia Air Survey. In this post I seek to highlight some of the more interesting ones that have been photographed by Asia Air Survey.
Asia Air Survey has a very clear image of the multiple landslides that formed the flow slide that I featured yesterday. These appear to be shallow slides in (probably) an volcanic deposit. Note the cracks in the slope on the left side of the image – this will be an area to watch in the forthcoming rainy season.
Asia Air Survey also has this fascinating image of three shallow landslides:
There is a huge amount going on in this slope in addition to the two obvious, and one less obvious (on the counter-slope) landslides. There is extensive cracking on the ridge top, and in the upper part of the image on the main slope. Asia Air Survey also has this image of a very extensive landslide system, including a large area of highly mobile debris movement:
Note the very extensive slope cracking here as well, including a series if cracks that appear to run through the building on the ridge. I am intrigued as to whether this is a slope deformation or a tectonic crack – the position is unusual if it is the former. The largest landslide here has flowed into two different drainage systems.
Finally, and perhaps most intriguingly, Asia Air Survey have this image of a landslide system in the vicinity of what I assume is a hot spring system:
There are signs here that the ground may have been altered (and probably weakened) by hydrothermal activity. The houses in this area will need careful assessment in light of the potential for further slope activity.
19 April 2016
Drone footage of the Kumamoto earthquake landslides
Kenichi Handa from the National Building Research Organization (NBRO) in Sri Lanka, to which he has been seconded by the Ministry of Land, Infrastructure, Transport and Tourism in Japan, added a comment to my post yesterday about the Kumamoto earthquake with some very useful links to images and videos of the landslides triggered by the quake. Particularly impressive is a set of drone footage videos collected by the Geographical Survey Institute, which provide clarity about the landslides. One of the films features the very large landslide at Mimami-Aso:
The footage shows that the upper portion of the landslide is very steep, with a planar mid section:
Whilst the lower part of the slide plane is stepped:
The video also confirms that the landslide has not blocked the river.
Perhaps more interesting is drone footage of the massive flowslide that I featured yesterday:
To me this would seem to be the most interesting landslide of all. The video suggests that the landslide might have had multiple source zones on steep forested slopes, including these two:
However, the drone footage hints there are further source zone landslides upstream, such as in the top right of this image:
This is clarified by an extraordinary photograph from the Ajiko website:
Thus, there appears to be a highly concentrated set of shallow translational landslides in the upper part of the catchment. I would suspect that this must be a case of dynamic liquefaction leading to a highly mobile flow. It has probably the most beautiful runout pattern of any of the Kumamoto Earthquake landslides:
The location of this landslide can be found on the GSI online GIS platform. This is the site on Google Earth, I think:
This suggests that the landslide has occurred on the flanks of Mount Aso, the largest active volcano in Japan. I suspect therefore that this might have been a flow of volcanic ash, so technically may be a lahar.
It is increasingly clear that the Kumamoto Earthquake landslides are remarkable. More will follow in the next few days…
18 April 2016
Landslides from the Kumamoto earthquake in Japan
The Kumamoto earthquake, the second of the two significant earthquakes that Japan over the last three days, and the associated aftershocks, appears to have generated significant numbers of landslides. Experience tells us that the area most affected by earthquake-induced landslides will be the terrain with significant slopes that has a high concentration of aftershocks. The largest landslide seems to be a very substantial slope failure close to Mimami-Aso that destroyed an important bridge. Asia One has a quite beautiful image of this landslide:
This appears to be a large rockslide in weathered rock. Note that the crown extends almost to the ridge, which is common in earthquake induced landslides. This landslide must have deposited a large volume of material in the gorge. Note also that the other slopes along the gorge have failed too, as this AP image shows. There is a reasonably large landslide towards the left side of the image that has come close to destroying another bridge:
However, this is by no means the only landslide. AFP have an image of a landslide that appears to have caused serious damage to the Kurowa Dai-ichi power station:
There are also some images of a quite peculiar and deeply intriguing flowslide. AP have this image of the debris in the fields:
Whilst the BBC has some nice video footage of it. There seems to be quite a large amount of landslide damage to roads. This appears to be a major cutslope failure:
Other road damage seems to have been caused by the failure of fill slopes:
If you have links to further images please post them in the comments.