27 July 2016

Landslides from the M=6.1 earthquake in the Atacama Desert on 25th July

Landslides from the M=6.1 earthquake in the Atacama Desert on 25th July

On Monday a M=6.1 earthquake occurred in the Atacama Desert, 53 km to the north of the town of Diego de Almagro in Chile.  This was not a very large earthquake, and it occurred at 71.5 km depth according to the USGS, meaning that the impact was low.  It is likely to have generated comparatively low intensity shaking over a large area.

On Twitter, a series of images were posted of the impact of the earthquake in El Salvador, a mining town located in the Atacama desert about 100 km from the epicentre of the earthquake.  These show large plumes of dust being generated in the mountains around the town:

Atacama Desert

Dust clouds being generated in the hills in the Atacama Desert after the M=6.1 earthquake in Chile on Monday, via Twitter

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Atacama Desert

Dust clouds being generated in the hills in the Atacama Desert after the M=6.1 earthquake in Chile on Monday, via Twitter

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Atacama Desert

Dust clouds being generated by landslides in the hills of the Atacama Desert after the M=6.1 earthquake in Chile on Monday, via Twitter

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Clearly there was significant landslide activity in this earthquake, although it is likely that the slides will mostly have been small and localised.  We know little about landslide activity during earthquakes in very arid conditions, so this is a technically interesting event.  The images suggest that the effects might have been similar to those from the 2010 Sierra Cucapah earthquake in Baja California, Mexico, which was captured on a youtube video that I posted at the time.  Working with colleagues at Durham, most notably John Barlow (who is now at the University of Sussex), we used satellite imagery to investigate at these landslides.  This work was published about 18 months ago (Barlow et al. 2014), and I posted a commentary about the paper at the time.  In that case we found that large numbers of comparatively small landslides were able to generate a large amount of dust.

Reference

Barlow, J., Barisin, I., Rosser, N., Petley, D.,  Densmore, A. and Wright, T. 2014. Seismically-induced mass movements and volumetric fluxes resulting from the 2010 Mw = 7.2 earthquake in the Sierra Cucapah, Mexico, Geomorphology, 230, 138-145, http://dx.doi.org/10.1016/j.geomorph.2014.11.012.

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25 July 2016

Gangotri and China: three fascinating new landslide videos

Gangotri – a very nice rockslide video from India

As Asia reels under extraordinary rainfall under strong monsoon conditions, three new, interesting landslide videos have been posted on Youtube.  The first shows a rather elegant rockslide on the highway to Gangotri in Uttarakhand in northern India:

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This is a classic of its type – a translational rockslide on a joint system dipping out of the slope.  It is likely that trimming of the slope to create the road has removed the natural buttress at the toe of the slide, allowing slip to occur on the existing weakness when pore pressures are high.

Gangotri

Gangotri rockslide via Youtube

 

Note also the very large amounts of dust generated by the landslide.

A spectacular landslide from China

This video first appeared on Liveleak, and has now migrated to Youtube as well.  The landslide is from a highway in China, but no other details are available:-

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The magnitude of the landslide is very large.  Note that both section of the landslide occurred on slopes that have been cut to create the road bench, and then reinforced to provide stability:-

Gangotri

Massive roadside landslide in China, via Youtube

 

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The aftermath of a landslide in China

And finally, CCTV has now posted a very nice video of the aftermath of the widely circulated video of a landslide destroying houses in a rural village in Hunan Province:

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This is the original video:

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In this case there is a railway line running across the slope – the failure appears to have occurred at the tunnel portal:

Gangotri

Landslide in China via CCTV and Youtube

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It’s hard to know whether earthworks for the line played a role in the landslide, but it seems like a prime candidate:

Gangotri

Footage of the aftermath of a landslide in China, via CCTV and Youtube

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These three landslides all rather nicely illustrate the ways on which poor slope management is exacerbating landslide problems in upland areas of Asia.

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22 July 2016

The University of Sheffield

University of Sheffield

The University of Sheffield

It is with great excitement that I can announce this morning that, as from 1st November 2016, I will be moving to take up the position of Pro-Vice-Chancellor (Research and Enterprise) at the University of SheffieldThe University has formally put out a press release with this news this morning.  A Pro-Vice-Chancellor is the equivalent of a Vice-President in the US system.  I will help to provide strategic leadership in research across the university, and will lead on all innovation (knowledge transfer, enterprise, consultancy, business generation, etc) as well.  It is a very exciting step for me.

Sheffield is a very strong, research-led Russell Group (the UK equivalent of the Ivy League) university.  It’s in the World top 100 institutions, with over 27,000 students and a research income of over £140 million.  It has a fabulous reputation for the quality of the student experience – it came third out of 117 institutions in the 2016 Times Higher Education Student Experience Survey for example.

Of course, this means that with great sadness I will leave the University of East Anglia on 31st October.  I will do so with real sorrow – I’ve loved my time at UEA.  It’s a great university, one that also focuses on the student experience (UEA came 7th in the same survey), and I have had the honour and privilege to work with some amazing people.  UEA is a university that has extraordinary strength, amazing staff and an astonishing can-do attitude.  Its location in the East of England means that it will play a fundamental role in the development of a gorgeous part of the UK.  Until I moved to Norwich I had not appreciated what an amazing city it is.  Being here has been absolutely instrumental to my career, and I have loved every minute of it.  The university has a tremendous future ahead of it, and I shall watch with great interest as the university develops.

But I see amazing opportunities in Sheffield, and I cannot wait to play a part in the development of that wonderful university.  It is an institution that is firmly rooted in its city and region, which will play a massive role in helping Britain to find a new path in the wake of the Brexit result.  I feel deeply honoured to have been asked to join the University of Sheffield, and am hugely looking forward to working with colleagues and students across the institution.

University of Sheffield

The new Diamond Building at the University of Sheffield, via De Zeen

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19 July 2016

The Aranayake landslide disaster in Sri Lanka – a JICA report

The Aranayake landslide disaster in Sri Lanka

JICA has now posted a report online (NB it’s a PDF) providing the initial results of an investigation of the May 2016 Aranayake landslide disaster in Sri Lanka, which killed 127 people.

This is a complex landslide – the image below from the report provides the best overview of the whole of the landslide, from the small failure at the crown to the debris flow at the toe:

Aranayake landslide

The Aranayake landslide in Sri Lanka, from the JICA report

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This this image shows the complex translational component of the landslide.  The report points out the unusual width of the landslide, which was not evident in most of the images at the time:

Aranayake landslide

The main part of the Aranayake landslide in Sri Lanka, via JICA

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I think there are two really revealing aspects to this report.  First, it provides a detailed aerial image of the very crown of the landslide:

Aranayake landslide,

The crown of the Aranayake landslide, via JICA

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Whilst it might on first inspection be thought that this small failure induced the overall collapse, this strange feature in the very crown of the landslide may well be a secondary failure, judging by the debris on the slope below.  However, I still believe that the landslide was initiated by a failure in the crown area (but possibly over a larger area than shown above).  It is interesting that the primary forest appears to have been removed in the areas on the flanks of the landslide shown in this image.  This might provide an explanation for why this first failure developed.

Second, the report provides details of the settlements that were destroyed by the landslide:

 Aranayake landslide

Settlement locations on the Aranayake landslide, via JICA

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An interesting question is whether this specific landslide could have been anticipated.  This is the outline of the landslide superimposed onto a slope angle map:

Aranayake landslide

The outline of the Aranayake landslide superimposed onto a slope map, via JICA

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It is probably fair to say that the specifics of this landslide could not have been identified in advance.  This type of very complex, cascading failure is always going to be exceptionally hard to anticipate.  However, that this type of landslide will occur in general in exceptionally heavy rainfall in the mountains of Sri Lanka can be anticipated.  The houses located in the lower channel of the landslide, which is clearly identifiable in the image above, were probably at an unacceptably high level of risk from the perspective of landslide hazards.

Acknowledgement

Thanks to Kenichi Handa of JICA for highlighting this report to me, and for the most interesting discussion.

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18 July 2016

Monsoon 2016: Nepal reels under the effects of multiple landslides

Monsoon 2016

In the aftermath of the May 2015 earthquake we have been worried that the first really intensive period of rainfall would lead to significant landslide problems in Nepal.  Unfortunately, as Monsoon 2016 really gets into gear this scenario is playing out. Northern areas of Nepal are being affected by large amounts of rainfall.  The landslides are dominating the news in Nepal – for example this is the front page of the Himalayan Times this morning:-

Monsoon 2016

Monsoon 2016: The front page of the Himalayan Times this morning

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This is reporting the ongoing problems in the catchment of the Bhote Kosi following the landslide dam break flood of last week.  Whilst the damage and disruption to this area is undoubtedly extreme, I am deeply concerned by this report of plans to bulldoze a new, 26 km long track to create an alternative alignment to Tatopani:-

The Divisional Road Office (DRO) has started work to open a 26-kilometre alternative track to connect Barhabise with Tatopani in Sindhupalchok district after a flashflood last week destroyed much of the road.  The under-construction Middle Bhotekoshi Hydropower Project is providing financial assistance to open the road from Chaku to Khohra. The DRO has started construction in the remaining section of the road up to Tatopani.  The project has already opened the alternative way from Chaku. The project is using three excavators at the site. Chief of the 102 megawatt project Sunil Kumar Lama said landslides continue to occur in Khohra and other areas. Senior civil engineer Sanjay Sapkota said construction works will be completed in a week though the river is still eroding sections of the Araniko Highway.

These low tech roads are both environmentally catastrophic and exceptionally hazard prone.  This is an area that basically consists of quasi-stable landslide deposits, and even the existing road is very landslide-prone.  In the medium term the opening of a new road is likely to make the problem far worse.

Meanwhile, other catchments are also showing distinct problems.  The Mahakali River is reported to be very high and is actively eroding its banks:-

A flood in Mahakali River has started eroding the embankment at Bhimdatta Municipality-11 in Kanchan-pur district.  On Sunday, the river eroded the levee that was constructed near Bhujela last year. Technicians from the People’s Embankment Programme (PEP), Kanchanpur said the flood caused by incessant rains in the hilly areas of the far-western region started eroding the banks on Saturday night. PEP chief Bhilananda Yadav said the embankment would be destroyed if the dike is swept away. “We are going to protect the embankment with gabions,” he said. Shankar Chhetri of Bhujela said they have been alerted against the river flooding their settlement.

 

Perhaps most worrying is the situation on the Tamor River, which has been partially blocked by a landslide.   News yesterday was that the water level is rising:

Water level in landslide-dammed lake in Tamor River in Sawadin, Taplejung, has increased, leaving the downstream settlement at risk. A fresh rockfall blocked water flow in the river. Pawan Shrestha, a resident of nearby Mitlung Bazaar, told the Post over the phone that the water level in the debris-dammed lake gradually increased on Saturday.

The Kathmandu Post published an image last week of the landslide and lake from the upstream side:

monsoon 2016

Monsoon 2016: Kathmandu Post image of the landslide dam on the Tamor River

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Whilst not huge, this has the potential to cause significant damage immediately downstream.

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17 July 2016

Glacier Bay Landslide in Alaska: a satellite image and new videos

Glacier Bay Landslide in Alaska

Slowly more information is emerging about the very large Glacier Bay landslide in Alaska, upon which I have previously blogged.  Perhaps most importantly. the landslide has now been imaged by the ESA Sentinel-2 satellite.  The image was tweeted by @RemotePixel on 14th July, with the image having been collected on 11th July 2016:

Glacier Bay landslide

The Glacier Bay landslide in Alaska, as imaged by the Sentinel-2 satellite. Hat-tip to @RemotePixel

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It is interesting to see how little this landslide spread laterally, especially on the right side of the track (the left side is clearly constrained by the topography).

In addition, there are now a couple of videos on Youtube showing aerial images of the landslide.  This one, by Jillian Rodgers of KHNS Radio, is marred by irritating music, but gives a pretty good impression of the landslide:

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It includes two really good shots of the landslide source / scar area:

Glacier Bay landslide

Still from a Youtube video of the Glacier Bay landslide in Alaska

And:

Glacier Bay landslide

Still from a Youtube video of the Glacier Bay landslide in Alaska

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Paul Swanstrom, the pilot who found the landslide in the first place, has also posted a short video of the crown of the landslide:

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This serves to rather beautifully show the immense fall height of this landslide.  Both videos also demonstrate clearly that there is still a huge amount of rockfall activity occurring on the landslide scar, and the first video suggests that a new scree deposit is accumulating on the landslide body.

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16 July 2016

Ya’an City, Sichuan: a video of a very near miss

Ya’an City, Sichuan: a video of a very near miss

CCTV has published on Youtube a pretty dramatic video of a very near miss for a landslide in Ya’an City in Sichuan Province, China.  The accompanying text says:

Last Friday evening, when a bus with 42 passengers was driving at 318 National Road in Ya’an city, southwest China’s Sichuan Province, the 59-year-old driver noticed rocks sliding down from the mountain. He immediately pressed his brakes and reversed about 10 meters. The mountain collapsed in a minute and buried the place. But thankfully, the driver was quick enough to avert any untowardly incident.

The video is quite exciting.  The consequences should the bus have been in the wrong place are clear:

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Some images of the landslide appear to show a car caught up in the debris:

Ya'an City landslide

Ya’an City landslide via The People’s Daily

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Fortunately this looks to have been survivable for the occupants.  China Daily has more information about the landslide:

Huang Guiquan has been a driver all his life. He attributed his swift thinking to his long driving experience and familiarity with the road.   “It is important for a driver to be observant of the environment all around rather than just staring at the road ahead,” he said. It was raining. He decided to stop the bus when he saw some stones falling down the mountain slope. “Trees swayed on the mountainside, but there was no wind at that moment. I thought that it must be the mountain itself that was shaking so I backed up the bus,” he said.   The road is high on the Qinghai-Tibet Plateau and prone to snow in winter and landslides in summer. Huang is familiar with the road conditions on all his regular routes.   “I am particularly careful when driving through the sections with sharp turns, steep slopes or frequent landslides,” he said. “It is always better to stop than rush when in danger.”

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14 July 2016

Bhote Kosi, Nepal: serious damage after the failure of a landslide dam in Tibet

Bhote Kosi, Nepal

The Bhote Kosi valley, to the north of Kathmandu, was one of the areas most seriously affected by the 2015 earthquake in Nepal.  Much of the damage was caused by landslides, which occurred on many slopes.  Fortunately the comparatively benign 2015 monsoon season did not exacerbate the problems as much as had been feared, but the consequences of the next period of intense rainfall always looked grim. This is a section of the valley for example:

Bhote Kosi

Google Earth imagery of the Bhote Kosi valley, showing the multiple earthquake induced landslide

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Apart from the local population, this valley is important as it is the alignment of the Arniko Highway, which is one of only two links between Nepal and Tibet, and thus China.

The 2016 monsoon has arrived with a bang, bringing very heavy rainfall.  Last week a very large flood swept down the Bhote Kosi, with devastating effects.  This was almost certainly a landslide dam break flood from a blockage in the river in Tibet, and it must have been large.  However, as yet the location is unclear.  The Nepal media has various reports of the impact of the flood – the Himalayan Times for example reported that:

The deadly earthquake of last year had devastated Liping and Tatopani Bazaar of Sindhupalchowk. Before these places could recover, flood in the Bhote Koshi River has left these towns so battered that reconstruction seems impossible.  Of the 200 houses in Tatopani and Liping bazaars, the Bhote Koshi flood has washed away 67 houses till today noon, police said.

The best image of the aftermath of the flood is on the Himalayan Times website:

Bhote Kosi

Bhote Kosi flood: Himalayan Times image of damaged slopes and houses

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It is clear that much of the damage has been caused by erosion of the toe of slopes by the flood, and subsequent slope failures.  There is also a good gallery of images here.  But by far the best illustration of the damage is in this Youtube video, even though it is not in English.  The journalist has followed the line of the highway up to Kodari.  The damage to this very important road is startling:

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Sadly this may not be the end of the problems. Dinanath Bhandari of Practical Action tweeted this image of forecast 24 hour accumulated rainfall in Nepal:

Bhote Kosi

Bhote Kosi: forecast 24 hour rainfall for Nepal via RIMES

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This is the forecast for two days time.  Whilst the heaviest rain is forecast to fall in the south, large parts of Nepal may get heavy precipitation.

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10 July 2016

Nagasaki, Uttarakhand and Pakistan: three new landslide videos

Nagasaki

House collapse in Nagasaki, Japan via Youtube

A small number of new landslide videos have emerged on Youtube in the last few weeks:

A debris flow in Pakistan

This very cool debris flow video was published on 17th June.  No details are provided:

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A road slope failure in Uttarakhand, India

This collapse event apparently happened at Nainital in Uttarakhand in India.  It was posted on 5th July 2016:

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A house collapse as a result of undercutting in Nagasaki, Japan

This one happened in Japan earlier this month.  It appears that a retaining wall below the building has failed, undermining the foundations:

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3 July 2016

Lamplugh Glacier rock avalanche: A massive new landslide in Alaska on Tuesday

Lamplugh Glacier rock avalanche: A massive new rock landslide

The media in Alaska is reporting a find by a local pilot, Paul Swanstrom of Mountain Flying Service, of a huge new landslide, the Lamplugh Glacier rock avalanche, which occurred in Alaska on Tuesday.  This is yet another enormous event in this area of North America – this is an image that he took of the landslide, which is posted on his company Facebook Page:

Lamplugh Glacier

The Lamplugh Glacier rock avalanche via Paul Swanstrom

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Paul estimates that the runout of the landslide is about 6 miles (i.e. about 10 km).  In a KHNS Radio article about the landslide, Colin Stark of Colombia University estimates that the volume is about 150 million tonnes, presumably based upon an initial analysis of the seismic catalogue.  The landslide appears to be recorded in the Alaska Earthquake Center catalogue as a M=2.9 event on 23rd June 2016 at 08:20 local time:

 Lamplugh Glacier

The Alaska Earthquake Center record of the possible seismic event generated by the Lamplugh Glacier rock avalanche

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The landslide appears to be a very deep-seated, ridge crest to slope toe failure of unusually large proportions:

Lamplugh Glacier rock avalanche

The source of the Lamplugh Glacier rock avalanche, via Paul Swanstrom

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The landslide appears to have generated a highly mobile, broad and long landslide deposit on a comparatively low angled slope, probably consistent with flow of debris over an ice bed.  The landslide has developed complex structures at the toe, probably associated with the final creeping stage of movement:

Lamplugh Glacier rock avalanche

Flow structures in the Lamplugh Glacier rock avalanche deposit, via Paul Swanstrom

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This is not an area with particularly good Google Earth imagery, but I think that this is the slope that failed:

Lamplugh Glacier rock avalanche

The probable site of the Lamplugh Glacier rock avalanche, via Google Earth

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The crest of the slope appears to be at about 2030 metres elevation, and the break at the foot of the slope at about 875 m, giving a vertical extent of about 1155 metres. The toe of the deposit is at about 550 metres elevation, which means that the runout lost about 225 metres elevation over 10,000 metres, giving a travel angle of about 1.3 degrees.  This is exceptionally low.

This part of Alaska is now firmly established as the global hotspot for rock avalanche activity. Recent events include the Tyndall Glacier Rock Avalanche, the Ferebee rock avalanche, the Mount La Perouse rock avalanche, the Mount Jarvis Rock avalanche and the Mount Lituya Rock Avalanche.  A detailed study is urgently needed to understand why this area is so active at present.

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