{"id":394253,"date":"2026-04-23T20:07:10","date_gmt":"2026-04-23T20:07:10","guid":{"rendered":"https:\/\/www.newsbeep.com\/nz\/394253\/"},"modified":"2026-04-23T20:07:10","modified_gmt":"2026-04-23T20:07:10","slug":"seismic-whiplash-new-research-shows-what-happens-when-earthquakes-stop-suddenly","status":"publish","type":"post","link":"https:\/\/www.newsbeep.com\/nz\/394253\/","title":{"rendered":"Seismic \u2018Whiplash\u2019 \u2013 New Research Shows What Happens When Earthquakes Stop Suddenly"},"content":{"rendered":"

\"The<\/a>
\nFriday, 24 April 2026, 7:08 am
Article: The Conversation<\/a><\/p>\n

\n Jesse
\nKearse<\/a>, Te
\nHerenga Waka \u2014 Victoria University of
\nWellington<\/a><\/p>\n

The magnitude of an
\nearthquake depends on how far a rupture travels along a
\nfault line before it stops. For the first time, we have now
\ndirectly observed how a large earthquake comes to a
\nhalt.<\/p>\n

By analysing seismic recordings taken within
\na few kilometres of faults, we have identified a ground
\nmotion signal we call a \u201cstopping phase\u201d. It records the
\nmoment the earthquake stops.<\/p>\n

This discovery, published in
\nScience today<\/a>, provides direct seismic evidence that
\nlarge ruptures stop suddenly, rather than slowing down
\ngradually. <\/p>\n

It also helps identify where shaking
\nmay be strongest along strike-slip faults, which could help
\nwith disaster planning and preparation.<\/p>\n

Earthquakes
\ngrow as the rupture spreads along a fault. The further it
\ngoes, the larger the earthquake magnitude becomes. The vast
\nmajority of earthquakes stop before they grow large enough
\nto be felt. <\/p>\n

For example, the earthquake monitoring
\nnetwork GeoNet has recorded
\nmore than 20,000 earthquakes<\/a> in Aotearoa New Zealand
\nover the past year, but all stopped soon after they
\nbegan.<\/p>\n

A very small percentage of earthquakes keep
\non going, and can travel for many hundreds of kilometres
\nbefore coming to a halt, reaching up to magnitude 9 and
\noften causing widespread damage.<\/p>\n

Advertisement – scroll to continue reading<\/p>\n

Although rupture
\nstopping is clearly important for determining earthquake
\nmagnitude, the process itself has been extremely difficult
\nto observe directly.<\/p>\n

Our findings now provide
\nplanners with a new way of identifying where the most
\ndamaging ground motions are likely to happen along a fault
\nline.<\/p>\n

A hidden signal of reversed ground
\nmotion<\/p>\n

Using seismic, GPS and satellite data from
\n12 large strike-slip earthquakes worldwide, we found
\nconsistent patterns of ground motion at the ends of the
\nfaults which was not observed at their centres.<\/p>\n

We
\nobserved that during the final moments of the earthquake,
\nthe ground suddenly moves in the opposite direction to the
\nfault\u2019s motion, creating a \u201cwhiplash\u201d effect.\n<\/p>\n

It\u2019s like riding in a fast car that suddenly
\nslams on the breaks \u2013 your body continues to go forward,
\nbut then sharply whips back the other way.<\/p>\n

The
\nstopping phase of an earthquake is similar, with the
\nreversal in ground movement signalling a rupture\u2019s abrupt
\nhalt.<\/p>\n

As the stopping phase arrives at the
\nEarth\u2019s surface from depth, the ground can change
\ndirection in a fraction of a second, and move up to a metre
\nor more backwards.<\/p>\n

Because it occurs close to the
\nfault and over such a short time, this process has not been
\nrecognised before. These signals are only becoming clear
\nwith increasingly dense modern seismic monitoring
\nnetworks.<\/p>\n

We simulated earthquakes using numerical
\nmodels and were able to reproduce the stopping phase
\nobservations only when the rupture stopped suddenly. When
\nthe model forced a rupture to slow down gradually, the
\nsignal disappeared.<\/p>\n

This animation simulates
\nan earthquake, showing the abrupt arrest and stopping phase
\nground motion. Video by Jesse
\nKearse.<\/p>\n

Do
\nall earthquakes stop like this?<\/p>\n

This research
\nfocuses on large strike-slip earthquakes \u2013 events where
\nthe ground moves sideways along near-vertical faults, rather
\nthan up and down.<\/p>\n

Because near-fault observations
\nare so rare, the science is severely data limited.
\nStrike-slip faults provide the best opportunity to study
\nthese processes because they often rupture all the way to
\nthe Earth\u2019s surface, where instruments can capture ground
\nmotion close to the source.<\/p>\n

Abrupt arrest may also
\noccur on other types of faults, such as subduction zones
\nwhere one tectonic plate slides beneath
\nanother.<\/p>\n

But we need further research to confirm
\nwhether this process is common to all earthquakes or only
\nstrike-slip fault systems such as the San Andreas Fault
\nrunning along the coast of California in the US or New
\nZealand\u2019s Alpine Fault. <\/p>\n

The domino effect of
\ncascading rupture<\/p>\n

Large strike-slip faults are
\nmade up of a series of segments, linked together end to
\nend.<\/p>\n

To become large events, earthquakes that ride
\nthese fault networks must break multiple segments in one go.\n<\/p>\n

In the seismic data from one such event in
\nTurkey-Syria in 2023, we found stopping phases were recorded
\nboth at the end of the earthquake and at the edges of
\ninternal segments.<\/p>\n

This stop-start behaviour during
\na single event means an earthquake rupture comes to an
\nabrupt halt at the end of one fault segment, before
\ntriggering a slip on its neighbouring segment, like a
\ncascade of falling dominoes. <\/p>\n

How this helps
\npeople living near fault lines<\/p>\n

Stopping phases
\nhelp pinpoint where earthquake shaking may be most
\nintense.<\/p>\n

Our research shows these signals occur
\nnear the ends of ruptures and at boundaries between fault
\nsegments \u2013 places where earthquakes are most likely to
\nstop. <\/p>\n

This means the strongest and most complex
\nshaking is likely to occur at the edges of fault segments,
\nrather than their centres. <\/p>\n

For strike-slip fault
\nsystems, this is particularly useful because fault segments
\nand ends can be mapped before an earthquake happens.\n<\/p>\n

This allows scientists and planners to identify
\nlocations where damaging ground motions are expected to
\noccur. <\/p>\n

Incorporating stopping phases into hazard
\nmodels will improve how we anticipate shaking for cities
\nnear faults, such as New Zealand\u2019s capital Wellington.\"The<\/p>\n

Jesse
\nKearse<\/a>, Postdoctoral Research Fellow, Te
\nHerenga Waka \u2014 Victoria University of
\nWellington<\/a><\/p>\n

This article is
\nrepublished from The
\nConversation<\/a> under a Creative Commons license. Read the
\noriginal
\narticle<\/a>.<\/p>\n

<\/p>\n","protected":false},"excerpt":{"rendered":"Friday, 24 April 2026, 7:08 amArticle: The Conversation Jesse Kearse, Te Herenga Waka \u2014 Victoria University of Wellington…\n","protected":false},"author":2,"featured_media":35750,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[7],"tags":[111,24636,139,69,39761,147,11112,1105],"class_list":["post-394253","post","type-post","status-publish","format-standard","has-post-thumbnail","category-science","tag-new-zealand","tag-newsworthy","tag-newzealand","tag-nz","tag-sci-tech","tag-science","tag-scoop","tag-the-conversation"],"_links":{"self":[{"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/posts\/394253","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/comments?post=394253"}],"version-history":[{"count":0,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/posts\/394253\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/media\/35750"}],"wp:attachment":[{"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/media?parent=394253"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/categories?post=394253"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/tags?post=394253"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}