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A section of the San Andreas fault where seism occur regularly may give off a distinct signal before it trembles to life , new inquiry finds . The signal steer at the opening and closing of snap beneath the subsurface .
This surgical incision of faultline , lie with as Parkfield in Central California , shake on a regular basis about every 22 years . It last snap in 2004 , so anotherearthquakemay be imminent . However , the signal is not currently occurring at the fault segment , and the section is n’t behaving exactly like it did the last time it rupture , grant to a study published March 22 in the journalFrontiers in Earth Science .
The differences might mean the next quake wo n’t happen properly away , or they might intend that the epicentre of the seism will be different from 2004 ’s epicenter , which was just southeast of the tiny township of Parkfield . There will be no way of life to know until the next quake really happens , enjoin field lead authorLuca Malagnini , the director of inquiry at the National Institute of Geophysics and Volcanology in Italy .
" We are waiting , " Malagnini told Live Science .
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The San Andreas shift mark the boundary between the Pacific and North Americantectonic plateful . southward of Parkfield , the fault is locked , meaning the two plates do not move against one another . northerly of Parkfield , the San Andreas fault moves freely , with the plates creeping against one another at a constant rate of 1.4 inch ( 3.6 centimeters ) a year . Parkfield is a transitional geographical zone between these two regimes . When this area of the fault rumbles to life , it gives off a quake of around order of magnitude 6 . Because of the removed localisation , these quakes rarely imperil human life or property , though quakes on one flaw can strike stress on other nearby break , Malagnini said .
But researchers catch Parkfield closely in hopes of finding activity that will avail them presage when the next earthquake will take place . Being able to notice reliable precursor to earthquakes — deform on rocks for example , or changes in permeability under the surface — would assist scientists warn people about imminent temblor , potentially saving lives . Parkfield , with its recurring quakes , might be a practiced place to look for these clues to interpolate to more dangerous fault segment . But so far , that end has been elusive .
In the Modern enquiry , Malagnini and his colleagues measured seismic wave attenuation , or how sound waves fall back energy as they move through Earth ’s impudence . Attenuation is related to the permeability of stone , Malagnini said . In the period of strain before an earthquake , pass open and close in the strained rock around the fault . The new written report retrieve that before the 2004 earthquake at Parkfield , the fading of low - frequency wafture rose in the six weeks prior to the seism , while the attenuation of gamy - frequency waves fell .
This , Malagnini said , is the solvent of strain on the rocks as the Pacific home base in the west motion against the North American plate to the east . As the stress builds , long cracks range in size from several hundred feet to 1 mile ( 1.5 kilometers ) long open up in the subsurface . These longsighted cracks take up some of the strain on the surrounding rocks , so inadequate offer in the rock near up . This decay in short cracks and increment in long cracks explains the bifurcation in the energy loss of unlike seismic wave , Malagnini said .
Right now , there are clue that Parkfield is get into the final stage of its subdued menstruation , Malagnini said . The timing is correct , for one affair : Parkfield has " skipped " quakes before , but those missed seism in the 22 - twelvemonth cycle occurred when nearby , unrelated earthquakes change the stresses in the neighborhood . There have been no such seism this fourth dimension . Another possible pinch is that the variation in the attenuation measurements has drop very low since 2021 . A standardized drop in this measurement occurred in 2003 before the 2004 Parkfield earthquake .
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However , Malagnini say , there is not yet any evidence of the bifurcation of the fading measurement that preceded the 2004 quake . He suspects the next quake will hit at Parkfield this year , he said , but the epicentre may not be in the same billet as it was in 2004 , meaning these measure will look unlike .
Malagnini wo n’t be attempting to forecast the next quake down to the Clarence Day , but he hop that after it happens , he and his team can rag out signal to wait for in the time to come .
" I ’ll be expect for the next earthquake , " Malagnini said . " And then we ’ll face back . "
