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Dr Sergio Sepulveda from the University of Chile is visiting Durham University as a Cofund Senior Research Fellow through the Institute of Advanced Study, to work with the International Landslide Centre at IHRR that is led by Professor Dave Petley and Dr Nick Rosser from the Department of Geography. Sepulveda is from Chile, one of the most seismically active parts of the world that regularly experiences earthquakes, landslides, debris flows, volcanic eruptions and other geohazards.
Sepulveda is a leading researcher on landslides in South America and is well-known in the field. Most of the fatalities caused by natural hazards in South America are from earthquakes, floods and landslides that affect both urban and rural communities. Sepulveda is working closely with colleagues in IHRR to identify the vulnerability of populations in Latin America and the Caribbean to landslides, in order to acquire a better understanding that would lead to developing measures to help reduce fatalities, and is testing a number of volcanic soils from Chile to understand the role they play in landslides and other hazards.
Research at Durham
Working with Prof Dave Petley, Sepulveda is studying records of fatal landslides that have occurred in Latin America and the Caribbean using the Durham Fatal Landslide Database, a global record of landslide- induced fatalities from the past 10 years. The database is a useful tool for identifying vulnerability to landslide hazards, ‘…there is a very strong correlation between population density and fatal landslides, and most of them are induced by heavy rainfall’, said Sepulveda. Along with this research Sepulveda is also studying the geomechanics of landslides themselves with Prof Dave Petley and Dr Matthew Brain. Read the rest of this entry »
The Oso (Steelhead) landslide – mechanisms of movement
The desperate search for the up to 90 missing people at Oso has continued (see my earlier post on the landslide). Survival rates for landslide victims are very short, so this is not a rescue operation any longer. During this time some very interesting information has emerged about the landslide in the form of a seismic record of the slide. There is an excellent blog post from Kate Allstadt about this seismic signal on the PNSN blog – their understanding of this data is much better than is mine, so I won’t try to replicate it here. For me the most interesting aspect is the double seismic signal generated by the landslide, which indicates two major movement phases (followed by lots of small slips, which we would expect):
The start of the two movement events were about 4.5 minutes apart; the first lasted about 2.5 minutes, the second was somewhat shorter and less energetic (i.e. the movement rate was probably slower).
So what does this tell us about the landslide? We need to compare this with an image of the landslide after the failure – this Wikipedia image remains the best that I have seen for getting an overview of the whole landslide: Read the rest of this entry »
We are seeking to recruit 4 fully-funded PhD students to work on the Coastal Behaviour and Rates of Activity (COBRA) project, from September 2014. The outputs of the four PhD projects will be used to develop a new understanding of rocky coast processes and will feed into local and regional shoreline management.
The 4 new PhDs are a new addition to COBRA, an ongoing collaborative research project between Durham University and Cleveland Potash Ltd (CPL). The overall aim of the project is to understand the past, present and future controls on coastal erosion within the North York Moors National Park. This stretch of coastline varies dramatically, with some of the UK’s highest near-vertical rock cliffs, softer glacial tills, extensive rocky foreshores and sandy beaches. CPL operates the Boulby Mine – the UK’s most important non-hydrocarbon mineral operation. The coastline presents a fascinating natural laboratory to address key research questions into: i) rockfall and erosion, ii) nearshore sediment dynamics, iii) coastal rock weathering, and iv) post-glacial coastal evolution.
Currently available funded PhD projects:
- High-resolution monitoring of rocky coast landscape dynamics
- Monitoring & modelling: Sea-bed deformation, waves & sediments
- Upscaling weathering & rock mass strength degradation to coastal cliff erosion
- Nature or nurture? Controls on long-term evolution of rocky coasts
Extreme rainfall in southern England
Southern England is currently undergoing an extraordinary period of exceptional rainfall, especially in the south, which is causing floods on an unprecedented scale. This rainfall, which is likely to be a consequence of climate change, shows no signs of abating, with further heavy falls expected over the next few days. Not surprisingly there have been many landslides, especially on the coast and along railway lines, and more can be expected. The UK Met Office provides monthly precipitation data for Southern England . I have downloaded the data and plotted the monthly time series from 1910 (the start of the dataset):
The horizontal line in the long-term mean value (77.3 mm). The 2014 total, at 165.4 mm, is 2.8 standard deviations from the mean – a truly exceptional value. And of course it is still raining, such that since the end of January the floods have got much, much worse. Read the rest of this entry »
The Port Hills rockfall problem
The Port Hills area on the edge of Christchurch was very seriously affected by the Christchurch earthquake sequence. The Canterbury Earthquake Recovery Authority will today start the process of demolishing the rockfall affected houses in the Port Hills area. Yesterday they released a statement describing the challenges of this work; this statement is well-covered in an article in The Press, which also includes a nice video taken by a drone of some of the sites. A couple of years ago I visited many of these sites, and I have an old post that presents some of the images that I collected. As a reminder, this is typical of the state of some of the buildings at the top of the slopes on the Port Hills:
Introduction – the recent UK storms
The recent UK storms have brought exceptionally wild coastal weather, in particular to southern and western England, Wales and Northern Ireland. This has had a profound impact on the geomorphology of the British coast. The Met Office has a nice summary of these storms. The combination of strong winds, high tides, large waves and saturated ground has greatly accelerated coastal processes, promoting failure of large rock masses. The BBC has a nice article that highlights some of these changes – for example:
Porthcothan Bay in Cornwall
A little over a month ago I gave a talk at the Vajont 2013 conference on the topic of landslides and large dams. At the time I committed to making the Powerpoint file available online, so here it is:
The file is located on slideshare – you should be able to download the powerpoint file from there. The piece is also written up in an article for the conference paper – reference below. The paper can be accessed, for free, from the conference website. The other talks and papers can also be accessed from the conference website.
In this work I looked at the Durham Fatal Landslide Database to try to understand fatality-inducing landslides associated with large dams over the last decade. My analysis of the dataset suggested that in total there were exactly 500 deaths in 37 landslide events in the ten years between 2003 and 2012. Surprisingly, with one exception these were not landslides associated with the collapse of reservoir flanks (although interesting there was an event of this type in China earlier this year). Most of the landslides were either failures at the construction sites of large dams or at the sites of workers camps. Read the rest of this entry »
When I was studying Physics at school, we were shown the famous regelation experiment in which a wire is placed over a block of ice and a weight is attached to each end. Though time the pressure on the wire causes melting of the ice, and the wire slowly cuts its way through the block, and eventually the weights and wire fall to the ground. As the wire passes through, the water refreezes, such that the wire appears to pass magically through the ice.
There are various versions of this experiment on YouTube, of which this is about the best:
The interesting part of this experiment starts at about 1:22 and ends at 1:40 (in the speeded up sequence). Of course when the wire finally cuts through the ice the weights collapse to the floor with a great crash – the very last moments before this are shown below: Read the rest of this entry »
Regular readers will know that the lack of attention that is paid to potential and actual landslide impacts during earthquakes in upland areas is a real hobby-horse of mine. Time and again we see the situation in which there is a lack of preparedness for landslides, causing huge disruption to the response and recovery operations, even though the threat was entirely forseeable. It is pleasing to see increased interest in the science of this issue in recent years, with a succession of good papers exploring both the mechanics of the landslide process (which is a very complex problem) and the likely occurrence of landslides.
This week, a paper has been electronically released on the BSSA website, to appear in a forthcoming edition of the journal, which examines the likely impact of landslides in the event of a Mw=7.0 earthquake of a “Seattle earthquake” – i.e. a quake on the Seattle Fault in Seattle, Washington. The paper, Allstadt et al. (2013) uses synthetic broadband seismograms to model shallow landslides in the area likely toi be affected by such an earthquake. Such an analysis is complex and computationally extremely intensive. I should also note that the technique uses the so-called Newmark method to model the slope behaviour. Newmark is basically the best technique that we have at our disposal at present, and so the team were right to do this, but in my view it is somewhat deficient in terms of the ways in which it models slope behaviour. We need a better technique; the trouble is that at the moment we do not have one. Read the rest of this entry »
Wednesday of next week will mark the 50th anniversary of the Vajont disaster, which occurred on 9th October 1963. This was of course the worst landslide disaster in European history. In addition it marked a watershed in a number of areas, not least landslide management and the development of large dams. On Thursday Michele and I will set off from the UK to attend the conference to mark the anniversary – the organisers were kind enough to invite me to give one of the keynote addresses, which will be on the topic of fatal landslides and large dams over the last decade. I will make it available online in due course.
In the meantime, I thought it would be useful to provide a list of some of the key resources that are available on the dam and the landslide disaster: Read the rest of this entry »