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26 September 2017

El Jale, Ixtapaluca: a stunning earthquake triggered landslide video from Mexico

El Jale landslide

A still from the Youtube video of the landslides at El Jale in Mexico.

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El Jale, Ixtapaluca: a stunning earthquake triggered landslide video from Mexico

On the day of the earthquake in Mexico I noted that there was a high chance that it would have triggered landslides.  It was always unlikely that this would be efficient in so doing in the manner of, for example, the Kaikoura earthquake (due to the depth of the rupture), it had the potential to generate slides over a wide area.  A video has recently been posted to Youtube that shows landslides being triggered by this event, reportedly El Jale in Ixtapaluca in Mexico City.  It is spectacular:

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This is a Google Earth image of the Ixtapaluca area:-

El Jale

Google Earth image of the Ixtapaluca area of Mexico City

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The video appears to show the collapse of a quarry wall in a comparatively rural area.  The one quarry shown above does not seem to fit the video.  A better fit to the video appears to a set of quarries located further to the east:-

El Jale landslide

Google Earth image of the quarries near to El Jale that may have been responsible for the landslide captured on video

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These quarries are likely to be mining volcanic materials, which would explain both the instability and the large amounts of dust generated.  It is not clear as to whether there was any losses from these landslides.  One early report did suggest that a quarry worker was killed in the event, but the location was given as Morales state, so it is unlikely to be this event:

Morelos Gov. Graco Ramirez reported on Twitter that at least 42 people had died in his state south of Mexico City.  Gov. Alfredo del Mazo told the Televisa news network that two people died in the State of Mexico, which also borders the capital: a quarry worker who was killed when the quake unleashed a rockslide and another person who was hit by a falling lamppost.

So far this part of the area affected by the earthquake has not yet been fully images by Planet Labs.  I’ll take a look when images become available.

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21 September 2017

Landslides from the Kaikoura earthquake part 5 – other valley-blocking slips

Landslides from the Kaikoura earthquake part 5 – other valley-blocking slips

In addition to the large valley-blocking slips that I featured in my earlier posts in this series, the Kaikoura Earthquake triggered many other valley-blocking landslides.  Most of these were of a medium size, and breached soon after the earthquake without causing any major issues.  This is a very spectacular example:-

valley-blocking slip

A valley-blocking slip from the Kaikoura earthquake.

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This is quite a spectacular example of a rockslide on a planar surface that has destroyed a ridge.  It clearly impeded the channel on the right of the image, and blocked the main drainage line.  A small lake is visible.  However, from above the head scarp it is clear that the landslide dam is not causing major issues:-

valley-blocking slip

An alternative view of a large valley-blocking slip from the Kaikoura earthquake.

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Further the south there are some reasonably large slumps that also blocked the valley:

valley-blocking slip

A valley-blocking slip from the south of the area affected by the Kaikoura earthquake.

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Again the lakes created by the blockages are very clear, but they are neither large nor particularly troubling.  Of course the impact on the farmers who owned these areas of land is large though.

In the higher areas there are some classic rockslides that have impeded the river.  This very complex example had quite a large runout:

valley-blocking slip

A reasonably-significant valley-blocking rockslide. Note the secondary failure above the main slide

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This appears to be a planar rockslide.  The additional slide on the ridgeline, in a weathered material, is an interesting juxtaposition with the main slide.  Given the location of the deposit, it seems likely that this happened after the main rockslide.  The remains of the lake are visible.  In this case there was significant incision through the fine-grained dam at the point of the breach.

Finally, some of the rockslides are actually quite simple:

valley-blocking slips

A simple valley-blocking rockslide from the Kaikoura earthquake.

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This landslide briefly blocked the Clarence River, but has now comprehensively breached.

Landslides from the Kaikoura Earthquake

The earlier posts in this series are as follows:

 

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19 September 2017

Potential landslides from the M=7.1 earthquake at Raboso, Mexico on 19th September 2017

Potential landslides from the M=7.1 earthquake at Raboso, Mexico on 19th September 2017

The major earthquake that struck near to Raboso in central Mexico earlier today, 19th September 2017, has the potential to have caused substantial damage.  The initial data from the USGS places the epicentre in a rural area, which will reduce (but certainly not eliminate) human losses, although the picture at the nearby town of Izucar de Matamoros could be very challenging.  It is interesting to note that the USGS has recorded very few felt reports from this area, which may suggest that communications are compromised.  As usual the current media focus is on the urban area (Mexico City), but this is unlikely to be where the whole story is located. A few years ago I wrote about the pitfalls often experienced by media agencies in reporting earthquakes.  I think the advice still stands.

In terms of landslides, the initial USGS data suggests that the area with significant levels of intensity has some steep slopes.  This is the USGS intensity data for the earthquake, plotted onto Google Earth:-

Raboso

Google Earth image of the USGS intensity data for the earthquake at Raboso, Mexico

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This map shows the area affected by Intensity of VI and greater:-

Raboso

Google Earth image of the area with intensity of VI and greater, based on USGS data, for the earthquake at Raboso in Mexico.

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Based upon this there is enough terrain to generate a significant number of landslides, although the relatively low relief suggests that these are likely to be mostly small and comparatively shallow.  Further afield there is more significant terrain; it will be interesting to see if the shaking has been sufficiently large to generate landslides here.  The depth of the earthquake suggests that the shaking will be generally strong but not extreme, but will have affected a broad area, giving landslide potential over a wide area.

Previous crustal earthquakes in Mexico have generated landslides.  A few years ago we studied the landslide distribution from the 2010 M=7.2 Sierra Cucapah earthquake in northern Mexico (written up in Barlow et al. 2014).  This was the event that generated the impressive youtube video of dust generation in the mountains.  We mapped 452 landslides, which is not insignificant, but lower than normally expected, probably because of the arid conditions in northern Mexico.  The area affected by the earthquake today is much less arid.

It will be much easier to understand the likely landslide distribution once we understand the fault that ruptured.

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, Available online 24 November 2014, http://dx.doi.org/10.1016/j.geomorph.2014.11.012.

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18 September 2017

Landslides from the Kaikoura Earthquake Part 4: partially failed slopes

Landslides from the Kaikoura Earthquake Part 4: partially failed slopes

A characteristic of every large landslide-inducing large earthquake that I have studied is the large number of partially failed slopes.  These are slopes that have started to fail during the earthquake, but have not completely collapsed.  Typically, in an earthquake-affected mountain chain we see numerous examples of this phenomenon.  The Kaikoura Earthquake was no exception.  I present here a number of examples.  Sometimes these partially failed slopes are very obvious incipient landslides – this one for example is very clear:-

partially failed slope

An example of a partially failed slope from the Kaikoura earthquake.

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In other cases the features are much more subtle.  This is an example of a highly deformed slope that has the complex morphology of several arcuate tension cracks and lateral scarps, but it is clear that the amount of strain (movement) is quite limited to date:-

partially failed slope

The complex arcuate scarps of a partially failed slope from the Kaikoura earthquake.

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In other cases the slope processes leave an incredibly complex pattern of extension and deformation, to the extent that it takes a while to work out what is happening in the landscape:-

partially failed slope

A very complex partially failed slope generated by the Kaikoura earthquake.

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And sometimes we are left with multiple arrays of parallel tension cracks.  This was a very common pattern in 2005 Kashmir Earthquake in Pakistan.  We saw the same pattern, but to a lesser degree, in the Kaikoura Earthquake in some locations:-

partially failed slopes

A partially failed slope from the Kaikoura earthquake.

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Anticipating how these slopes may behave is very challenging at the scale of any individual slope and across the whole landscape.  Clearly the nature of the long term hazard will be very dependent on this effect.  Interestingly, in many other earthquakes the majority of such partially failed slopes have not failed (although in every case some slopes have collapsed, which preclused making assumptions about future behaviour).  The exception may be the 2008 Wenchuan Earthquake, where these secondary failures remain a very major problem nine years on.

It will be fascinating to observe what happens in the aftermath of this event.

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Landslides from the Kaikoura Earthquake

The earlier posts in this series are as follows:

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17 September 2017

Landslides from the Kaikoura Earthquake part 3: the Leader 220 landslide

Landslides from the Kaikoura Earthquake part 3: the Leader 220 landslide

The Leader 220 landslide, located on the Leader Rover close to Woodchester (the location is -42.585, 173.215 if you want to take a look on Google Earth), is another large valley blocking landslide triggered by the Kaikoura Earthquake in New Zealand.  This is one of the most spectacular and photogenic of all of the landslides:

Leader 220 landslide

The Leader 220 landslide triggered by the Kaikoura earthquake

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This is a large slump with a near planar, steep back scarp.  The landslide has moved as a single block, but has extensively deformed as it transitioned from the steep back scarp to the near horizontal valley floor.  The landslide has pushed the river across the valley floor such that it is now flowing over old terrace surfaces:

Leader 220 landslide

The aftermath of the Leader 220 landslide

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The landslide dam has now breached but the lake remains partially intact.  This has caused some properties to be inundated:

Leader 220 landslide

A property flooded by the Leader 220 landslide lake.

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This is a slope that is undergoing considerable post-earthquake landslide activity.  This image shows the foot of the main scarp, and the multiple flow type failures that have occurred:

Leader 220 landslide

Post seismic flows that have occurred at the site of the Leader 220 landslide, triggered by the Kaikoura Earthquake.

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The image above also shows some interesting deformation occurring at the trailing edge of the displaced block – in effect this is a landslide within a landslide as the edge of the block slumps back into the scarp depression.  The image below shows this from a wider perspective – it is not an insubstantial landslide in its own right:

 

Leader 220 landslide

An overview from the scarp of the Leader 220 landslide, showing deformation in the displaced block.

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Monitoring how this deformed mass behaves in the next few years will be fascinating.  It appears that considerable post-seismic landscape evolution will occur before conditions each a new equilibrium.  GNS Science have a newly funded MBIE Endeavour project for the next few years to monitor the evolution of the landscape after the earthquake.

Landslides from the Kaikoura Earthquake

The earlier posts in this series are as follows:

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16 September 2017

Landslides from the Kaikoura Earthquake part 2: the Hapuku landslide

Landslides from the Kaikoura Earthquake part 2: the Hapuku landslide

The longest runout slide triggered by the Kaikoura Earthquake was the Hapuku landslide, which occurred high up in the catchmnet of the Hapuku River.  This landslide is at -42.237, 173.664 if you want to take a look on Google Earth.  This landslide is a long (2.7 km) rock avalanche with a volume of about 10-14 million cubic metres.  The elevation change from the crown (which is at the ridge top) to the toe is about 1,900 metres. To get a full appreciation of this landslide the Google Earth imagery is helpful:-

Hapuku landslide

Google Earth image of the Hapuku landslide, triggered by the Kaikoura earthquake

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As the image shows, the landslide crown is at the ridge line (which is common for earthquake triggered landslides), whilst the debris at the toe has blocked the valley.

This is a helicopter image of the upper portion of the landslide:

Hapuku landslide

The upper portion of the Hapuku landslide

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This suggests that the failure event in the upper portion of the landslide was complex, and that there is still some debris on the slope.  The image below shows the track of the landslide to the toe:-

Hapuku landslide

The track of the Hapuku landslide.

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Note the small remaining lake caused by the blockage of the channel (the breach is also visible).  The landslide has left a large amount of bare rock.  This image shows the landslide debris:-

Hapuku landslide

The deposit of the Hapuku landslide

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The landslide dam has breached – this image shows the breach channel clearly:

Hapuku landslide

The breach channel from the Hapuku landslide dam

 

As with many other locations, this landslide has seen some secondary failures in periods of heavy rainfall since the Kaikoura earthquake:

Hapuku landslide

Tracks from secondary failures at the Hapuku landslide

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As with the Seaward landslide, one of the fault ruptures runs through the scar of the this landslide.  It is therefore unsurprising that there are many other landslides triggered by the Kaikoura earthquake in this area:

Hapuku landslide

Other landslides triggered by the Kaikoura earthquake in the catchment of the Hapuku River

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14 September 2017

Landslides from the Kaikoura earthquake part 1: the Seafront landslide (also wrongly known as the Seaward landslide)

Landslides from the Kaikoura earthquake part 1: the Seafront Landslide

Yesterday, I was lucky enough to be able to fly over the area affected by the Kaikoura earthquake by helicopter, together with colleagues from GNS Science.  Over the next few days I will post some images of the earthquake-induced landslides that I took on this flight.  I am starting with the very large and very complex Seafront landslide, which is perhaps the most infamous of all the landslides triggered in this earthquake, thanks to images that went viral showing three cows trapped on a displaced raft on the landslide.  For this reason the slide became known as the Cow Slide, but it is correctly termed the Seafront Landslide (also known, wrongly, as the Seaward Landslide):-

Seafront landslide

Cows trapped on the Seafront Landslide, via The Daily Telegraph

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The cows were rescued.  This is very large, very complex landslide.  If you want to locate it on Google Earth it is at -42.178, 173.880.  This is a view of the landslide from the north:

Seafront landslide

The Seafront Landslide, triggered by the Kaikoura earthquake, viewed from the north.

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Whilst this is the landslide viewed from the south:

Seafront landslide

The Seafront Landslide, triggered by the Kaikoura earthquake, viewed from the south.

The images show that this is very wide, broad slump type landslide in which, quite literally, the side of the ridge has detached and slipped.  At the toe the slide has broken up considerably, whilst in other sections it has remained remarkably coherent.  This image shows the very complex behaviour of this displaced block.  Note that some sections of the slide have been modified by the farmer to try to regain productive land:

Seafront Landslide

The displaced mass of the Seafront Landslide, triggered by the Kaikoura earthquake.

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One other really interesting observation about this landslide is that the northern edge of the ridge also failed, and that a much larger section partially displaced but did not collapse:

Seafront Landslide

The failure at the northern end of the ridge from which the Seafront Landslide originated. Note the large, partially failed section.

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Whilst the other (west) side of the ridge appears to be essentially undamaged, even though it is steep:

Seafront landslide

The west side of the ridge from which the Seafront Landslide originated. Note the lack of slope failures.

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This illustrates perfectly why it is so hard to forecast the behaviour of slopes in earthquakes.

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12 September 2017

Increasing rock avalanche size and mobility in Alaska may be associated with climate change

Increasing rock-avalanche size and mobility in Alaska

One of the most interesting landslide issues in recent years has been the cluster of rock avalanches that have occurred in the Glacier Bay National Park and Preserve in the southern part of Alaska (example include Lamplugh Glacier, Tyndall Glacier, Ferebee Glacier and Mount La Perouse).  This area appears to have been affected by far more very large events than anywhere else over the last 20 years or so; the reasons for this have not been clear.  In a new open access paper just published in the journal Landslides, Coe et al. (2017) have used Landsat imagery to map these events in the period between 1984 and 2016.  Over this period this area experienced 24 rock avalanche events in a 5000 km² area, ranging from 5.5 km² to 22.2 km² in area.  This map, from the paper, shows the distribution of these 24 rock avalanches:-

Alaska rock avalanches

The distribution of rock avalanches in the Glacier Bay study area, from Coe et al. (2017)

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Some of these rock avalanches have been spectacular.  This for example is a Planet Labs image of the July 2016 Lamplugh Glacier rock avalanche:-

Planet Labs image of the Lamplugh Glacier rock avalanche of July 2016, in Alaska.

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From their mapping, Coe et al. (2017) concluded that all of the rock avalanches initiated from high mountain ridges or peaks.  All occurred in the northern part of the study area, and most had an aspect towards the north, generally towards the northwest.  Clusters in rock avalanche behaviour occurred in the periods 1984 to 1986; 1994 to 1995; and 2012 to the present.  Notably, the most recent cluster has involved larger, more mobile rock avalanches than had been seen previously, and these landslides have tended to originate from higher elevations, with higher levels of mobility.

Coe et al. (2017) consider carefully why these changes may be occurring.  They state that:

We hypothesize that degradation of rock permafrost is the primary factor that controlled the timing and size of rock avalanches in the Glacier Bay region.

This part of Alaska shows a clear warming trend over the last few decades.  Coe et al. (2017) provide an analysis of the climate data that strongly supports the idea that the increasing temperatures may be leading to a degradation of previously permanently frozen rock masses in the high peak areas.

This is the most convincing evidence that I have seen to date that increasing temperatures are driving a higher rate of rock slope failure in high mountains, a trend that we also seem to be seeing in for example the Alps in Europe and the Southern Alps in New Zealand.  It suggests that there is a pressing need for increased research into the processes occurring in high mountain slopes, including in situ monitoring.  The implications are clear though – as climate change continues to drive warming in high mountain areas the risks associated with rock slope failure will increase.

Reference

Coe, J.A., Bessette-Kirton, E.K. & Geertsema, M. 2017.  Increasing rock-avalanche size and mobility in Glacier Bay National Park and Preserve, Alaska detected from 1984 to 2016 Landsat imageryLandslides https://doi.org/10.1007/s10346-017-0879-7

Acknowledgement

Planet Team (2017). Planet Application Program Interface: In Space for Life on Earth. San Francisco, CA. https://api.planet.com

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11 September 2017

A dramatic earthflow video from Dimye village in Tibet

A dramatic earthflow video from Dimye village in Tibet

A video has been circulating this weekend on Twitter showing a dramatic earthflow from Dimye in Tibet.  This apparently originated from Wechat & Weibo in China, although very little information is available about it.  This is the Youtube version:-

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The accompanying text for the video associated it with melting permafrost.  On Twitter, Mika McKinnon (@mikamckinnnon) has undertaken a huge amount of background work on this event, and has identified the location as Dimye village, Zatoe (Zaduo in Chinese) township, Tridu county, Yushu prefecture, Qinghai Province.  The landslide occurred on 7th September 2017.  She also found an additional video of the landslide on Facebook.

Whilst the posting links this event to permafrost degradation, this is not clear to me.  This image, from the second video, shows the materials involved in the landslide:-

Dimye earthflow

A still from a Facebook video showing the earthflow at Dimye in Tibet.

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The video does not showing any obvious frozen soil or ice blocks.  To me this is quite reminiscent of the landslides that we see in peat in the uplands of Europe.  My fellow blogger Callan Bentley featured a nice example on his blog exactly a year ago.  The soils involved in the Dimye village landslide are extremely dark in colour, which suggests that they are rich in organic matter.  I note that in a recent (open access) paper, Yang et al. (2017) describe peat areas in the Qinghai-Tibetan area, noting that there is significant environmental degradation occurring in these places, causing rapid peat loss.

It is not possible to say whether this is indeed a peat landslide, or something similar in an organic soil, or a permafrost slide.  Unfortunately, I doubt that more information will become available in the near future.  But it is a great video.

Reference

Yang, G., C. Peng, H. Chen, F. Dong, W. Ning, Y. Yang, Y. Zhang, D. Zhu, Y. He, S. Shi, X. Zeng, T. Xi, Q. Meng, and Q. Zhu. 2017. Qinghai–Tibetan Plateau peatland sustainable utilization under anthropogenic disturbances and climate change. Ecosystem Health and Sustainability 3 (3):e01263. doi: 10.1002/ehs2.1263

 

 

 

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6 September 2017

Landslides from the North Korea nuclear weapon test

Landslides from the North Korea nuclear weapon test

There are various news reports today that the North Korea nuclear weapon test on Sunday triggered landslides in the local terrain.  This is based on an initial analysis of Planet Labs imagery by three analysts from 38 North, which is dedicated to analysis of events in North Korea.  Their report says:

Commercial satellite imagery from Planet, obtained the day after North Korea conducted its largest test to date (currently estimated in the 100+ kiloton range), appears to show numerous landslides throughout the Punggye-ri Nuclear Test Site and beyond

And they have produced this image:-

North Korea nuclear weapon test

38 North and Planet Labs imagery of the site of the North Korea nuclear weapons test. Image collected after the test showing landslides triggered by the underground blast.

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This appears to be interpreted in some quarters to indicate that the weapon was particularly large.  For example, Newser has the headline:

Landslides suggest N. Korea’s latest test was a monster

This is a Planet Labs image from 6th September (i.e. today) showing the area of Mount Mantap affected by the underground nuclear weapons test:-

North Korea nuclear weapon test

Planet Labs image of 6th September 2017 showing the area affected by the North Korea nuclear weapon test

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This is the same area on a Planet Labs image dated 26th August, definitely collected before the most recent weapons test:

North Korea nuclear weapon test

Planet Labs image of the area affected by the North Korea nuclear weapon test. Image collected on 26th August 2017, prior to the test

 

There are undoubtedly some new landslides in the post-test image, although most of the larger ones in the imagery were pre-existing.  The new landslides appear to be mostly small, and they are focused close to the channel, perhaps where there is either accumulated debris or steeper slopes due to incision.  There are a few larger events in the gully systems.  It is not the case, as far as I can see, that there is very extensive landsliding in the area affected by the nuclear weapons test – certainly not on the scale that we see from major earthquakes in mountainous areas.

That underground nuclear weapons tests trigger landslides in local mountain areas is not new, and nor is it surprising.  The explosion induces ground shaking that is similar in some ways to an earthquake, although the nature of the shaking itself is quite different.  In fact, the North Korean landslides are very localised and small compared with some other examples.  In a book chapter that is partly online, the Russian landslide scientist V.V. Adushkin describes rock avalanches triggered by eight different underground nuclear weapons tests at the Soviet Novaya Zemlia test site during the subterranean weapon testing programme there.  Two of these were enormous – the largest had a volume of 80 million m³, whilst another had a volume of 5 million m³.  This is clearly very much larger than the landslides in North Korea.

Thus, although the landslides triggered by this test are interesting, they are neither surprising nor exceptional.  If North Korea develops larger weapons then we are likely to see bigger landslides, although this is the least of our worries perhaps.  As an aside, Fox News and few other agencies are reporting Chinese scientists as indicating that they have concerns about collapse of the mountain in the event of another test.  If this is the case I find it surprising that there are not more landslides on the massif, but I do not know the grounds for their suggestions.

Acknowledgement

Planet Team (2017). Planet Application Program Interface: In Space for Life on Earth. San Francisco, CA. https://api.planet.com

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