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Mysterious zone in the recondite chimneypiece where earthquake waves slow to a crawling may actually be everywhere , young inquiry detect .
Scientists already knew thatultra - low velocity zones(ULVZs ) , loom near hot spot — area of the drapery where hot rock moves upward , forming volcanic island irons such as Hawaii . But mysterious quake waves intimate that these features might be widespread .
New research suggests the Earth’s mantle, the layer sandwiched between its core and crust, is filled with zones that slow down seismic waves.
ULVZs , which are turn up in the lower mantle near the meat - mantle bound , can retard seismal waves by up to 50 % . That ’s remarkable , saidMichael Thorne , a geologist and geophysicist at the University of Utah .
" Here ’s one of the most utmost features that we see anywhere inside the planet , " Thorne order Live Science . " And we do n’t know what they are , where they ’re come from , what they ’re made of , [ or ] what role they act inside the Earth . "
Thorne was n’t thinking of ULVZs when he launch the new research , published Aug. 10 in the journalAGU Advances . Instead , he was intrigued by another mantle closed book . Very orotund temblor , like those that go on atsubduction zoneswhere one architectonic plate slides under another , issue powerful wave . Some of these so - called PKP waves move around through the curtain , the liquid outer core , and then the mantle again on their path to the paired side of the major planet from where they rise . These waves are sometimes predate by another strange type of wave , cry a precursor PKP wave .
herald PKP waves arrive before the main wave after scattering off mystery features in Earth ’s lower mantelpiece . To discover these characteristic , Thorne and his confrere modeled PKP undulation locomote through a computer model of Earth ’s mantlepiece , into which they total areas that changed the waves ' velocity . They establish predictable patterns in how PKP waves varied in speeding .
So the team hunted for interchangeable design in real quake data point . The research worker used data point from 58 cryptic temblor with magnitude over 5.8 near New Guinea that come about between 2008 and 2022 . Waves from these quake traveled through the centre and up to North America , where they were recorded by EarthScope , a labor that deployed portable seismal monitors across the U.S. between 2003 and 2018 .
The findings advise that something was dramatically slowing the temblor waves to spread their energy , Thorne said . The two likely candidates were valleys and ridge along the core - Mickey Charles Mantle boundary where the waves traveled , or ULVZs . The core - mantle bound under the western Pacific , where the waves pass , is thought to be fluid . But premature research found a large ULVZ under the western Pacific , east of the Philippines , overlapping the area studied .
And the researchers also found signatures of ULVZs when they look elsewhere . The study found smaller plot of what seem to be more ULVZs under North America . And other research has detect signs of ULVZs underneath North Africa , East Asia , Papua New Guinea and the Pacific Northwest , Thorne said .
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Some researchers have hypothesize that ULVZs might be theremnants of giant impactorsfrom Earth ’s early stage of meteor bombardment . However , if ULVZs are widespread , it paint a picture they ’re being actively generated today , Thorne suppose . He suspect that these zone may be area of the volcanic careen basalt , formed at mid - ocean ridges where the seafloor scatter apart . When this mid - ocean basalt finally gets attract into the Mickey Mantle by subduction , it melt easily and could form pockets where seismal waves slow down . These pockets could then get advertise around the mantle by other slabs of subducting Earth’s crust , which poke into Earth ’s Interior Department like stirring stick into a smoothy .
Better understanding these ULVZs could improve geologists ' range of volcanic hotspot as well as how the mantle move .
" There are a lot of open questions we do n’t have answer to yet , " Thorne said .
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