Did you hear the one about a goat in a landslide?

A bit of light relief over at the Highway 97 site in Canada, which continues to slip. Arthon have a pictorial report on their website of the rescue of a mountain goat that had fallen down the tension crack and become wedged 10 m below the surface (all images from the Arthon website):



Fortunately, the goat (now named Houdini) was spotted and a rescue was put in place. Enter the gallant abseilers (you wouldn't mess with these guys on a dark night):


They abseiled down and tranquilised the goat, who was then hauled back to safety:


Meanwhile the slope is still moving 10-15 mm per day and as a result the road is still closed. A water taxi has starts on Saturday morning to allow people to get around the blockage.

Hat tip - Andrew Giles again.

New book: Landslides and Engineering Geology of the Seattle, Washington, Area

Seattle is an area that has both a long history of landslides and a long history of landslide research. For example, there is a 1974 USGS report online examining landslides triggered in a 1972 rainfall event. In 1996-7 a series of large storms triggered multiple damaging slides in Seattle. As a result, the USGS and Seattle agreed to start a major project to produce a range of landslide hazard maps and associated forecasting tools. Part of this work has been the compilation of a database extending back to 1890 - there is a very nice report on this work on the Seattle Government website.

This work has been summarised in a new volume published yesterday by the Geological Society of America:


The book summary states that: "This volume brings together case studies and summary papers describing the application of state-of-the-art engineering geologic methods to landslide hazard analysis for the Seattle, Washington, area. An introductory chapter provides a thorough description of the Quaternary and bedrock geology of Seattle. Nine additional chapters review the history of landslide mapping in Seattle, present case studies of individual landslides, describe the results of spatial assessments of landslide hazard, discuss hydrologic controls on landsliding, and outline an early warning system for rainfall-induced landslides."

Baum, R.,L., Godt, J.W. and Highland, L.M. (eds) 2008. Landslides and Engineering Geology in the Seattle, Washington Area. Geological Society of America, 181 pp. ISBN: 9780813741208
Price: $30 for members, $60 for non-members. Available from here.

Landslides in the 29th October Pakistan earthquake

The picture of the level of destruction in Pakistan resulting from yesterday's earthquakes remains slightly confused. The official death toll is now 215 people, but some reports suggest that the true number is about 400 as in smaller villages victims were buried before officials arrived. In terms of landslides, the picture is equally confused, but unverified reports indicate the following:

• Some reports suggest that a village called Chali Dam in the Yuni Valley in Ziarat district was hit by a landslide that killed 61 people.
• Relief web reports that some key highways are blocked by landslides.
• The Pakistan news agency Dawn reports that "Most houses in the worst-hit villages of Ziarat were destroyed by boulders falling from mountains" and "He said the earthquake had left cracks in mountains and roads."

Hopefully the picture will become clearer today.

Highway 97: test blast

The latest report on the Highway 97 problem in Canada (see earlier posts here, here and here) is as follows:

• The contractor, Arthon, released a statement to the press yesterday, the key points of which stated that "Highway 97 remains closed north of Summerland until further notice due to an unstable rock mass above the highway. The slope continues to move, therefore the highway is not safe to reopen. Safety is our top priority. The ministry is doing everything it can to reopen the highway as quickly as possible, but we won't open it until it's safe. We've built access roads to enable heavy equipment to reach the slope.
  Our first test blast took place this afternoon to help assess the stability of the rock mass.
  The geotechnical experts will now analyze the results of the blast and will have an update tomorrow afternoon. The results of the blasting will help the ministry finalize the work plan."
• The tension crack extended by 8 millimetres overnight Tuesday-Wednesday, giving a displacement of 3.3 cm since Sunday.
• The plan to move material from the crown to the toe of the landslide now appears to be the favoured solution. It is not clear how this will affect the road.

The cautious approach beiung adopted by the authorities is quite correct in my opinion.

A further Pakistan earthquake

At 11:32 UT there was a further earthquake in Balochistan, this time Mw=6.2 at 10 km depth. This is sufficiently large and shallow to cause considerable additional damage, including landslides. Unfortunately, this event is even closer to Ziarat, which seems to have borne the brunt the first time around. The epicentre is at 30.541°N, 67.457°E according to the USGS, which is shown below on Google Earth (click on the image for a better view):

Magnitude Mw=6.4 earthquake in Pakistan

News is coming in this morning of moment magnitude = 6.4 earthquake in Balochistan in Pakistan. According to the USGS, the earthquake occurred at 23:09 UT (04:09 local time) at a depth of about 15 km. The USGS have produced this map of the epicentre:

Fig. 1: USGS map of the location of the epicentre of the earthquake

This produces a map of shaking that looks like this:Fig. 2: USGS map of the intensity of shaking associated with this earthquake

This is a rugged and comparatively arid landscape (Fig. 3) with a population density of about 40 people per square kilometre. GDACS estimate that there are about 326,000 people living in a 50 km radius of the epicentre.

Fig. 3: Google Earth image of the region affected by the earthquake.
Click on the map for a better view in a new window.

In such an environment, landslides are very likely to have been triggered by the earthquake. Already there are one or two reports that landslides have occurred - for example:

• AFP are reporting that "The deaths occurred in and around the hilly town of Ziarat, about 50 kilometres east of Quetta, in gas-rich Baluchistan province, police official Abdul Khaleq told AFP. Ziarat is a historic hill resort famed for its juniper forests. Most of the casualties were from two villages on the outskirts of the town which were built on steep ground and badly damaged in landslides triggered by the quake, which struck at a depth of 10 kilometres, officials said."
• The Daily Telegraph is reporting that "One village, Wam Killy, was almost completely destroyed while many houses were buried in landslides triggered by the quake."
• Bloomberg saya that "A landslide in Ziarat, a tourist resort about 100 kilometers east-northeast of Quetta, killed 17 people, said Dilawar Hussain Shah, an official at police control in Quetta. More deaths were reported from Pishin town and its neighboring villages, he said."

Fig. 4 shows a perspective view of Ziarat, whilst Fig 5 gives an idea of the terrain:

Fig. 4: Google Earth perspective view of Zierat, in which many landslides have been reported.
Click on the map for a better view in a new window.

Fig. 5: Flickr image from Worldwidetravelling of the landscape in Zierat

All of the above suggests that landslides are likely to be a serious issue in this earthquake. The diagram of area affected by landsliding derived by Keefer (1984) is helpful here (Fig. 6). The likely affected area is in the range of 200-2000 square kilometres, with a value towards the upper limit being more likely given the shallow focus of the earthquake and the rugged terrain. In my view, it is likely that the effects, although quite localised, could be quite high, with landslides being a major problem both in terms of causing losses and in terms of impeding the flow of assistance.

Fig. 6: Dave Keefer's 1984 plot of the area affected by landslides in earthquakes of different magnitudes, annotated to show the range of areas expected to be associated with this one.

I will post again as more information becomes available.

Reference:
Keefer, D. 1984. Landslides caused by earthquakes. GSA Bulletin, 95, 406-421

Highway 97 latest update

The latest update on the Highway 97 landslide in Canada (see here and here) is as follows:

1. The slope is still moving. Between 19:00 on Monday and 14:00 on Tuesday the mass moved about 15 millimetres (i.e. about 0.8 mm per hour). This is quite high for a large mass. The rate of movement is described as being constant;
   
2. The mobile volume is now estimated to be 200,000 cubic metres;
3. The road remains closed (unsurprisingly!);
4. There are provisional plans to remove material from the top of the unstable slope and to move it to the toe. The aim here is to reduce the mass that is driving the movement and to increase the mass that is supporting it.

I am sure in the background there is an enormous amount of work going on. Analysis of the pattern of movement in time and space, especially by looking at vectors of movement and accelerations and decelerations will give a pretty good idea of what is happening in the slope. This gives a potential for providing a short term warning of an impending collapse, but does not really tell us how likely this is in the medium term.