{"id":30202,"date":"2019-02-19T08:43:43","date_gmt":"2019-02-19T08:43:43","guid":{"rendered":"https:\/\/blogs.agu.org\/landslideblog\/?p=30202"},"modified":"2019-02-19T13:47:02","modified_gmt":"2019-02-19T13:47:02","slug":"anak-krakatau-paper-1","status":"publish","type":"post","link":"https:\/\/blogs.agu.org\/landslideblog\/2019\/02\/19\/anak-krakatau-paper-1\/","title":{"rendered":"New on EarthArXiv: a first analysis of the flank failure of the Anak Krakatau volcano"},"content":{"rendered":"<h4>New on EarthArXiv: a first analysis of the flank failure of the Anak Krakatau volcano<\/h4>\n<p>A paper has recently been posted to the open source repository <a href=\"https:\/\/eartharxiv.org\">EarthArXiv<\/a> that provides a first analysis of the <a href=\"https:\/\/blogs.agu.org\/landslideblog\/2018\/12\/26\/anak-krakatau-1\/\">flank failure of Anak Krakatau volcano on 22 December 2018<\/a>, which <a href=\"https:\/\/blogs.agu.org\/landslideblog\/2018\/12\/29\/anak-krakatau-2\/\">generated a tsunami that killed 431 people<\/a>.&nbsp; The paper, <a href=\"https:\/\/eartharxiv.org\/u965c\/\">Williams <em>et al.<\/em> (2019)<\/a>, uses a combination of remote sensing and eyewitness accounts to examine the sequence of events that generated the tsunami.&nbsp; Regular readers of the blog will remember that at the time it was quite difficult to untangle the sequence as volcanic eruptions before and after the collapse <a href=\"https:\/\/blogs.agu.org\/landslideblog\/2019\/01\/03\/anak-krakatau-3\/\">changed the topography quickly<\/a>.<\/p>\n<p><a href=\"https:\/\/eartharxiv.org\/u965c\/\">Williams <em>et al.<\/em> (2019)<\/a> provide a particularly interesting perspective on the radar imagery collected over that period.&nbsp; Interestingly t<a href=\"https:\/\/www.youtube.com\/watch?v=g_1Ai0ZMcwQ\">here is an animation of the radar sequence on Youtube<\/a>, which also includes some initial interferometric analysis by reader funkenbeachin.&nbsp; InSAR is very difficult in a massif that has undergone so much change, but the radar sequence is very revealing:-<\/p>\n<iframe loading=\"lazy\" width=\"800\" height=\"450\" src=\"https:\/\/www.youtube.com\/embed\/g_1Ai0ZMcwQ?feature=oembed\" frameborder=\"0\" allow=\"accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture\" allowfullscreen><\/iframe>\n<p>.<\/p>\n<p><a href=\"https:\/\/eartharxiv.org\/u965c\/\">Williams <em>et al.<\/em> (2019)<\/a>&nbsp;note that Sentinel-1A captured an image about 8 hours after the initial collapse event.&nbsp; This is shown in Panel C in the image from the paper below:-<\/p>\n<div id=\"attachment_30209\" style=\"width: 650px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" aria-describedby=\"caption-attachment-30209\" class=\"size-full wp-image-30209\" src=\"https:\/\/blogs.agu.org\/landslideblog\/files\/2019\/02\/19_02-AK-1-e1550563688241.jpg\" alt=\"Anak Krakatau\" width=\"640\" height=\"939\"\/><p id=\"caption-attachment-30209\" class=\"wp-caption-text\">Satellite imagery of the series of events before and after the flank collapse at Anak Krakatau on 22 December 2018. Imagery from Sentinel-1A and Sentinel-2A<\/p><\/div>\n<p>.<\/p>\n<p><a href=\"https:\/\/eartharxiv.org\/u965c\/\">Williams <em>et al.<\/em> (2019)<\/a> propose that the initial failure event consisted of an approximately 100 million cubic metre submarine failure, with a comparatively small (4 million cubic metre) terrestrial component.&nbsp; They suggest that the main part of the flank collapsed completely to generate the tsunami, with a smaller block, higher on the island, partially failing in a rotational manner to generate the approximately north-south orientated plane visible in the imagery.&nbsp; The failure decompressed the plumbing of the volcano to allow a new magma pathway to open, allowing the subsequent eruptive activity.<\/p>\n<p>I am intrigued by&nbsp; the fate of this smaller partially failed block &#8211; if I was a referee I would want this to be considered more directly.&nbsp; This block does not appear in image D above, suggesting that it has failed in a second event.&nbsp; Did this occur in one movement or was it eroded away during the subsequent eruptive activity?&nbsp; The question of sequencing of flank failures is really important to understand likely tsunami generation, so this feels like a key issue.<\/p>\n<p>Perhaps the most important part of this paper is this section:-<\/p>\n<p><em>&#8220;We show that the flank failure was unexceptional, meaning that an extraordinary event was not required to trigger the tsunami, yet it had catastrophic consequences&#8230;The volume of the flank failure was small, compared to predicted collapse volumes and flank collapses at 25 other volcanoes, yet it generated a tsunami as large as and faster than modelled with a significantly larger collapse&#8230;this study also highlights that existing hazard assessments at volcanic islands are very likely underestimating the risks from volcanogenic tsunamis due to small (&lt;0.25 km\u00b3) failures.&#8221;<\/em><\/p>\n<p>That feels to me to be a very important set of conclusions from a very interesting and useful initial analysis.<\/p>\n<h4><strong>Reference<\/strong><\/h4>\n<p>Williams, R., Rowley, P., &amp; Garthwaite, M. C. 2019. <a href=\"https:\/\/eartharxiv.org\/u965c\/\">Reconstructing the Anak Krakatau flank collapse that caused the December 2018 Indonesian tsunami<\/a>. <em>EarthArXiv<\/em>. <a href=\"https:\/\/eartharxiv.org\/u965c\/\">https:\/\/doi.org\/10.31223\/osf.io\/u965c<\/a><\/p>\n<!-- AddThis Advanced Settings generic via filter on the_content --><!-- AddThis Share Buttons generic via filter on the_content -->","protected":false},"excerpt":{"rendered":"<p>A paper has recently been posted to EarthArXiv providing an analysis of the flank failure of Anak Krakatau on 22 Dec 2018, which generated a tsunami that killed 431 people. <!-- AddThis Advanced Settings generic via filter on wp_trim_excerpt --><!-- AddThis Share Buttons generic via filter on wp_trim_excerpt --><\/p>\n","protected":false},"author":22,"featured_media":30209,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[598],"tags":[21487,469,346,141,314,107],"class_list":["post-30202","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-landslide-processes","tag-anak-krakatau","tag-featured","tag-flank-collapse","tag-indonesia","tag-se-asia","tag-volcano"],"_links":{"self":[{"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/posts\/30202","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=30202"}],"version-history":[{"count":0,"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/posts\/30202\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/media\/30209"}],"wp:attachment":[{"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/media?parent=30202"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/categories?post=30202"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/tags?post=30202"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}