Assessment of the potential for earthquake induced landslides is often based upon the Newmark displacement method, often known as the Newmark sliding block model<\/a>.\u00a0 In this conceptual model, the landslide is considered to be a rigid block on an inclined slope:-<\/p>\n Conceptual model of the Newmark displacement method, via the USGS<\/a><\/p><\/div>\n .<\/p>\n This set up allows the stresses operating on the system to be calculated in both a static (i.e. non-earthquake) and dynamic (i.e. during an earthquake) state.\u00a0 The fundamental idea is that there is a critical acceleration at which siding will initiate, so an analysis is run to determine this value.\u00a0 The model allows the displacement to be calculated for the parts of the earthquake for which this acceleration is exceeded.\u00a0 An assumption is made that when the total displacement exceeds a critical value the slope will fail.\u00a0 There are some problems with this – it is very hard to know what this critical displacement might be – but that is a separate issue.<\/p>\n The Newmark displacement method can be applied to any slope.\u00a0 In recent years digital datasets have allowed it to be applied across an entire landscape, which creates the opportunities for a spatial hazard analysis.\u00a0 This approach has been developed by the USGS<\/a>, and others, and has been taken up quite widely.\u00a0 But the question has always remained as to how good the Newmark Displacement method might actually be.<\/p>\n Recently, I was a part of a team that examined one aspect of this – wave phasing.\u00a0 We hypothesised that the phasing of horizontal and vertical accelerations might critically change the displacements.\u00a0 We ran a series of experiments using a highly specialised piece of lab equipment that was developed for us by GDS Instruments<\/a> – the Dynamic Back Pressured Shear Box (DBPSB)<\/a>. These results were published a while ago (Brain et al.<\/em> 2015<\/a>) – they ask some quite key questions about the Newmark displacement method.<\/p>\n In a paper just published in the journal Landslides<\/a>, Li et al.<\/em> (2018)<\/a> have looked at a different aspect of the Newmark approach.\u00a0 In their work, they have examined the behaviour of a simple physical slope model when exposed to earthquake accelerations delivered by a shaking table.\u00a0 This is their model set up:<\/p>\n The physical model of the Newmark displacement method used by Li et al.<\/em> (2018)<\/a>.<\/p><\/div>\n .<\/p>\n They undertook several analyses of the behaviour of the model, and in some cases they compared the response to shaking with that predicted by the Newmark displacement method.\u00a0 They conclude the following:-<\/p>\n By comparing critical acceleration between the experimental and theoretical results, the results indicated that Newmark\u2019s method overestimates critical acceleration during seismic-induced dip slope failure. In reality, slip planes along existing discontinuities develop much more easily and can lead to even greater disasters.<\/em><\/p>\n In other words, for reasons that are not clear the Newmark displacement method suggests that the critical acceleration value is too high.\u00a0 This means that the analysis will indicate that, in some cases, slopes are stable when in reality they may be unstable during a modeled earthquake. This does not mean that the approach should not be used, and indeed it remains a key tool, but it does indicate that great care is needed.\u00a0 And of course it suggests that further research is required to improve the technique, or to develop alternatives.<\/p>\n Brain, M.J., Rosser, N.J., Sutton, J., Snelling, K., Tunstall, N. & Petley, D.N. 2015. The effects of normal and shear stress wave phasing on coseismic landslide displacement<\/a>. Journal of Geophysical Research: Earth Surface.<\/em> 120<\/strong>, 1009\u20131022<\/p>\n Li, HH., Lin, CH., Zu, W. et al.<\/em> 2018.\u00a0Dynamic response of a dip slope with multi-slip planes revealed by shaking table tests<\/a>.\u00a0 Landslides<\/em> . https:\/\/doi.org\/10.1007\/s10346-018-0992-2<\/a><\/p>\n","protected":false},"excerpt":{"rendered":" In a new paper just published in Landslides, Li et al. (2018) use a shaking table model to show that the Newmark displacement method overestimates the critical acceleration value for earthquake induced landslides<\/p>\n","protected":false},"author":22,"featured_media":27581,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[23,469,719,14277,192,17],"class_list":["post-27575","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-uncategorized","tag-earthquake","tag-featured","tag-model","tag-newmark","tag-paper","tag-research"],"_links":{"self":[{"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/posts\/27575","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=27575"}],"version-history":[{"count":0,"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/posts\/27575\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/media\/27581"}],"wp:attachment":[{"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/media?parent=27575"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/categories?post=27575"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/tags?post=27575"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}![\"Newmark](\"https:\/\/blogs.agu.org\/landslideblog\/files\/2018\/04\/18_04-Newmark-1.jpg\")
![\"Newmark](\"https:\/\/blogs.agu.org\/landslideblog\/files\/2018\/04\/18_04-Newmark-2.jpg\")
References<\/h4>\n