{"id":29623,"date":"2018-12-26T11:51:33","date_gmt":"2018-12-26T11:51:33","guid":{"rendered":"https:\/\/blogs.agu.org\/landslideblog\/?p=29623"},"modified":"2018-12-26T11:51:33","modified_gmt":"2018-12-26T11:51:33","slug":"anak-krakatau-1","status":"publish","type":"post","link":"https:\/\/blogs.agu.org\/landslideblog\/2018\/12\/26\/anak-krakatau-1\/","title":{"rendered":"The Anak Krakatau landslide and tsunami"},"content":{"rendered":"

The Anak Krakatau landslide and tsunami<\/h4>\n

The disastrous and tragic landslide and tsunami from Anak Krakatau<\/a> (Anak Krakatoa) has rightly dominated the news over the Christmas break.\u00a0 At least 429 people are known to have been killed<\/a>, making this one of the worst landslide-induced disasters of the year, with a further 154 people thought to be missing.\u00a0 Severe weather, and in particular heavy rainfall, is making both the assessment of events to date and in the assessment of what might come next extremely challenging.\u00a0 Further landslides cannot be ruled out.<\/p>\n

We can say with some certainty that the tsunami was triggered by a landslide from Anak Krakatau.\u00a0 There are two strong pieces of evidence for this.\u00a0 First, whilst it has not been possible to obtain visual satellite imagery of the island because of the weather, radar data (which is not obscured by cloud) has been available.\u00a0 The ESA Sentinel-1 satellite collected a decent image on 22nd December:-<\/p>\n

\"Anak

European Space Agency Sentinel-1 image dated 22nd December 2018 showing the deformation of Anak Krakatau. Copyright ESA, image accessed via Sentinel Hub<\/a>.<\/p><\/div>\n

.<\/p>\n

This is a remarkable image, showing amongst other things the volcanic plume being blown to the east and the radial waves from the island being generated by the ongoing eruptions. But most importantly it shows what appears to be a large scarp to the west of the volcano cone, presumably marking a large-scale deformation (landslide) of the volcanic edifice of Anak Krakatau.\u00a0 There would have been a large submarine element to this, which presumably generated the tsunami.<\/p>\n

Secondly, a strong seismic signal was generated by the landslide, which was detected on a number of seismometers.\u00a0 Jamie Gurney<\/a> (@UKEQ_Bulletin) has done a great job of collating that information via Twitter.\u00a0 The seismic signal has a very strong low frequency component, characteristic of a landslide-induced, rather than a tectonic, event.\u00a0 <\/span><\/p>\n

The challenge now is to interpret what might be happening on the volcano, and what might happen next.\u00a0 The latest Sentinel-1 image does not help:-<\/p>\n

\"Anak

European Space Agency Sentinel-1 image dated 25th December 2018 showing the deformation of Anak Krakatau. Copyright ESA, image accessed via Sentinel Hub<\/a>.<\/p><\/div>\n

.<\/p>\n

I am no expert on radar imagery, and others may be able to provide more information about what this shows.\u00a0 It seems to me that a large part of the island appears to be generating very little useful data – is this because of a drape of new deposits from the eruptions of the last few days? The upshot is, I think, that we cannot really interpret whether the volcano is deforming (or has deformed) further.<\/p>\n

Quite rightly, the authorities are concerned about further landslides, but the only advice at this point is to stay away from the coast and to be vigilant.<\/p>\n

Volcanic flank collapses are a well-known hazard,<\/a> and the potential for the collapse of Anak Krakatau has been highlighted previously<\/a>.\u00a0 These landslides have huge destructive potential but are inadequately researched when compared to many other hazards.<\/p>\n

 <\/p>\n","protected":false},"excerpt":{"rendered":"

Sentinel-1 imagery suggests that the landslide that triggered the tsunami on Anak Krakatau appears to have been a large-scale flank collapse. Unfortunately it is difficult to ascertain the current situation on the volcano<\/p>\n","protected":false},"author":22,"featured_media":29627,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[3],"tags":[469,346,141,959,314,128,107],"class_list":["post-29623","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-landslide-report","tag-featured","tag-flank-collapse","tag-indonesia","tag-landslide-report","tag-se-asia","tag-tsunami","tag-volcano"],"_links":{"self":[{"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/posts\/29623","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=29623"}],"version-history":[{"count":0,"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/posts\/29623\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/media\/29627"}],"wp:attachment":[{"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/media?parent=29623"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/categories?post=29623"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/tags?post=29623"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}