{"id":3458,"date":"2011-08-04T08:02:27","date_gmt":"2011-08-04T08:02:27","guid":{"rendered":"http:\/\/blogs.agu.org\/landslideblog\/?p=3458"},"modified":"2011-08-06T23:30:11","modified_gmt":"2011-08-06T23:30:11","slug":"images-of-landslides-from-the-christchurch-earthquakes-part-3-topographic-amplification-at-the-cliff-tops","status":"publish","type":"post","link":"https:\/\/blogs.agu.org\/landslideblog\/2011\/08\/04\/images-of-landslides-from-the-christchurch-earthquakes-part-3-topographic-amplification-at-the-cliff-tops\/","title":{"rendered":"Images of landslides from the Christchurch earthquakes part 3: topographic amplification at the cliff tops"},"content":{"rendered":"

This is part 3 of this series.\u00a0 The other posts in this series are as follows:<\/p>\n

Part one: boulder damage to a house<\/a><\/p>\n

Part two: evil dancing rocks<\/a><\/p>\n

Part three: topographic amplification at the cliff tops<\/a><\/p>\n

Part four: large-scale cliff collapses<\/a><\/p>\n

Part five: landslides that involve sliding<\/a><\/p>\n

One of the key aspects of landslide and rockfall triggering in earthquakes is the process that we term topographic amplification.\u00a0 The idea is simple, which is that the topography causes enhanced shaking at key locations.\u00a0 We believe that this is particularly significant at ridge tops and breaks of slope (locations in which the slope gradient changes).\u00a0 In effect it is a resonance effect that causes the ground to shake much more violently in those locations.\u00a0 We think that this is a key process in the triggering of landslides and rockfalls in earthquakes.<\/p>\n

Of course it is also potentially bad news for any structures located at the top of slopes too, so I was interested to see how the houses that had occupied those beautiful cliff top locations in the hills to the east of Christchurch had performed.\u00a0 as the pictures below show, the answer is that they did not do well.\u00a0 It is important to stress that these images show shaking damage, not landslide problems (though there is some of that on the ridge tops too – see the post tomorrow…).<\/p>\n

The best illustration of the magnitude of the shaking on the ridge tops was found on this balcony:<\/p>\n

\"\"<\/a><\/p>\n

If you look carefully you can see that the plant plot has been smashed.\u00a0 It has clearly been lifted vertically and then dropped, which suggests vertical accelerations considerably in excess of 1 g:<\/p>\n

\"\"<\/a><\/p>\n

There was huge disruption to even sturdy structures in this area, but similar houses set back from the cliff remained intact.\u00a0 The tile roof of this houses suggests high levels of acceleration:<\/p>\n

\"\"<\/a><\/p>\n

Note the cliff collapses.\u00a0 One or two houses collapsed completely:<\/p>\n

\"\"<\/a><\/p>\n

Whilst others suffered very signficant levels of damage:<\/p>\n

\"\"<\/a><\/p>\n

The next post will look at what this meant for the cliffs below.\u00a0 The other posts in this series are as follows:<\/p>\n

Part one: boulder damage to a house<\/a><\/p>\n

Part two: evil dancing rocks<\/a><\/p>\n

Part three: topographic amplification at the cliff tops<\/a><\/p>\n

Part four: large-scale cliff collapses<\/a><\/p>\n

Part five: landslides that involve sliding<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"

Part three of the series of posts on landslides from the Christchurch earthquakes, this time looking at topographic amplification of shaking, as shown by building damage.<\/p>\n","protected":false},"author":22,"featured_media":3462,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[537],"tags":[23,469,7,555],"class_list":["post-3458","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-earthquake-induced-landslide","tag-earthquake","tag-featured","tag-new-zealand","tag-topographic-amplification"],"_links":{"self":[{"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/posts\/3458","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/users\/22"}],"replies":[{"embeddable":true,"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/comments?post=3458"}],"version-history":[{"count":0,"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/posts\/3458\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/media\/3462"}],"wp:attachment":[{"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/media?parent=3458"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/categories?post=3458"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/tags?post=3458"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}