{"id":25652,"date":"2017-09-18T21:14:38","date_gmt":"2017-09-18T21:14:38","guid":{"rendered":"http:\/\/blogs.agu.org\/landslideblog\/?p=25652"},"modified":"2017-09-19T08:07:01","modified_gmt":"2017-09-19T08:07:01","slug":"partially-failed-slopes","status":"publish","type":"post","link":"https:\/\/blogs.agu.org\/landslideblog\/2017\/09\/18\/partially-failed-slopes\/","title":{"rendered":"Landslides from the Kaikoura Earthquake Part 4: partially failed slopes"},"content":{"rendered":"

Landslides from the Kaikoura Earthquake Part 4: partially failed slopes<\/h4>\n

A characteristic of every large landslide-inducing large earthquake that I have studied is the large number of partially failed slopes.\u00a0 These are slopes that have started to fail during the earthquake, but have not completely collapsed.\u00a0 Typically, in an earthquake-affected mountain chain we see numerous examples of this phenomenon.\u00a0 The Kaikoura Earthquake<\/a> was no exception.\u00a0 I present here a number of examples.\u00a0 Sometimes these partially failed slopes are very obvious incipient landslides – this one for example is very clear:-<\/p>\n

\"partially

An example of a partially failed slope from the Kaikoura earthquake.<\/p><\/div>\n

.<\/p>\n

In other cases the features are much more subtle.\u00a0 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:-<\/p>\n

\"partially

The complex arcuate scarps of a partially failed slope from the Kaikoura earthquake.<\/p><\/div>\n

.<\/p>\n

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:-<\/p>\n

\"partially

A very complex partially failed slope generated by the Kaikoura earthquake.<\/p><\/div>\n

.<\/p>\n

And sometimes we are left with multiple arrays of parallel tension cracks.\u00a0 This was a very common pattern in 2005 Kashmir Earthquake in Pakistan<\/a>.\u00a0 We saw the same pattern, but to a lesser degree, in the Kaikoura Earthquake in some locations:-<\/p>\n

\"partially

A partially failed slope from the Kaikoura earthquake.<\/p><\/div>\n

.<\/p>\n

Anticipating how these slopes may behave is very challenging at the scale of any individual slope and across the whole landscape.\u00a0 Clearly the nature of the long term hazard will be very dependent on this effect.\u00a0 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).\u00a0 The exception may be the 2008 Wenchuan Earthquake<\/a>, where these secondary failures remain a very major problem nine years on<\/a>.<\/p>\n

It will be fascinating to observe what happens in the aftermath of this event.<\/p>\n

.<\/p>\n

Landslides from the Kaikoura Earthquake<\/h4>\n

The earlier posts in this series are as follows:<\/p>\n