At least 34 quakes have been recorded west of Castlepoint in the last seven days – with the strongest measuring a magnitude of 4.2 – at depths of about 20 kilometres.<\/p>\n
On-call seismologist Sam Taylor-Offord said a concentrated sequence events typically indicated a “much more intense” process than the usual background noise of seismic activity.<\/p>\n
“You can think about it as something that is unfolding. It’s a process.<\/p>\n
“Every earthquake pushes a little bit of the stress that releases into the area around it and then that can create a cascade of increasing the stress in the rock surrounding it. That rock breaks – it increases the stress in the rock around it – that rock breaks and that’s your sequence playing out,” Taylor-Offord said.<\/p>\n
But he said – along the line of subducting tectonic plates which characterised the fault along the east coast of the North Island – the quakes could also be associated with multiple “slow slip” events.<\/p>\n
Subduction was the process where one tectonic plate was forced beneath another into the Earth’s mantle.<\/p>\n
“If you think of it as a very large earthquake that’s happening but it’s happening over weeks and months.<\/p>\n
“It’s still changing the stress in the surrounding area and in some places the earth breaks in a related way to that movement. That tends to break in a sequence. So that’s one of the things that might be happening,” Taylor-Offord said.<\/p>\n
Taylor-Offord said the agency was looking into the pattern but it did not necessarily indicate an increased risk of a large quake in the area.<\/p>\n
“Sometimes a sequence will precede a larger earthquake, sometimes nothing will come of it. Science is not quite at the point where we can say ‘that one, not that one’,” he said.<\/p>\n
He said – on the flip side – it was not possible to infer that a quake cluster was indicating a gradual release of pressure which could ward off a larger quake.<\/p>\n
“We have earthquakes like this all the time and – so far – they haven’t stopped the larger earthquake coming.<\/p>\n
“Perhaps a weaker fault [is] breaking but elsewhere there is a strong fault that is still accumulating that stress and will someday rupture in an earthquake. It’s a fact of life,” Taylor-Offord said.<\/p>\n
He said the agency was also monitoring another cluster of just under 30 weak quakes centred south east of Seddon over the last month.<\/p>\n
He said those quakes were more likely to be the remnants of aftershock sequences from the 2016 Kaik\u014dura quake which was centred nearby.<\/p>\n
Taylor-Offord said the activity was a reminder for people to stay prepared for a major event.<\/p>\n
“Small earthquakes are good because they remind us that bigger quakes are possible. These are regions very close to the plate boundary where we have a lot of stress and a lot of strain and we expect large earthquakes in the future as we have seen in the past,” Taylor-Offord said.<\/p>\n
~VIA RNZ<\/p>\n","protected":false},"excerpt":{"rendered":"
At least 34 quakes have been recorded west of Castlepoint in the last seven days – with the strongest measuring a magnitude of 4.2 – at depths of about 20 kilometres. On-call seismologist Sam Taylor-Offord said a concentrated sequence events typically indicated a “much more intense” process than the usual background noise of seismic activity. […]<\/p>\n","protected":false},"author":6,"featured_media":14539,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[222,208,174],"tags":[],"class_list":["post-14538","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-latest-news","category-lifestyle","category-nz-news"],"amp_enabled":true,"_links":{"self":[{"href":"https:\/\/thebuzz.apnanetwork.co.nz\/index.php?rest_route=\/wp\/v2\/posts\/14538","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/thebuzz.apnanetwork.co.nz\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/thebuzz.apnanetwork.co.nz\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/thebuzz.apnanetwork.co.nz\/index.php?rest_route=\/wp\/v2\/users\/6"}],"replies":[{"embeddable":true,"href":"https:\/\/thebuzz.apnanetwork.co.nz\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=14538"}],"version-history":[{"count":1,"href":"https:\/\/thebuzz.apnanetwork.co.nz\/index.php?rest_route=\/wp\/v2\/posts\/14538\/revisions"}],"predecessor-version":[{"id":14540,"href":"https:\/\/thebuzz.apnanetwork.co.nz\/index.php?rest_route=\/wp\/v2\/posts\/14538\/revisions\/14540"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/thebuzz.apnanetwork.co.nz\/index.php?rest_route=\/wp\/v2\/media\/14539"}],"wp:attachment":[{"href":"https:\/\/thebuzz.apnanetwork.co.nz\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=14538"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/thebuzz.apnanetwork.co.nz\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=14538"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/thebuzz.apnanetwork.co.nz\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=14538"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}