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North America might still be experiencing aftershock from monumental temblor that impinge on the continent over 200 yr ago , a new study has found .
Aftershocks are typically small earthquakes that strike after a major seism as afault , which luxate to cause the main quake , readjusts . They normally hit withindays to yearsof the initial seismic case , but some researchers believe they can keep happening for centuries .
Aftermath of the 1886 earthquake in Charleston, South Carolina.
In a raw study , published Nov. 7 in theJournal of Geophysical Research : Solid Earthresearchers look at the extraction of earthquakes in what geologists call stable North America — the central and easterly U.S. and part of eastern Canada that are settle away from plate edge — where earthquakes are less usual . The authors describe earthquakes that appear to be aftershocks from major earthquakes that strike the Missouri - Kentucky border between 1811 and 1812 , as well as the 1886 Charleston seism that rack up South Carolina .
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To set up whether innovative earthquake in this region are because of long - lived aftershock , scope seismicity — the normal background pace of quake , or seismic action , researchers would require in a region — or both , the researchers looked at pairs of seismal outcome connect in the earthquake records through length , meter and order of magnitude .
They looked at seism that occur within a 155 - mile - spoke ( 250 kilometers ) from each of the major historic quakes . If an earthquake hit closely enough to the original epicentre , the author say it could be consider an aftershock .
" If the distance between a pair of earthquake is confining than bear from background issue , then one earthquake is likely the aftershock of the other , " lead authorYuxuan Chen , a geoscientist at Wuhan University inChina , said in astatement .
The researchers found that three large seism that happen in 1811 and 1812 may have been responsible for around 23 % of quake that take place in the New Madrid seismal zone — which plow part of Missouri , Arkansas , Tennessee , Kentucky and Illinois — between 1980 and 2016 . In South Carolina , the researchers linked up to 72 % of present - 24-hour interval earthquakes to the 1886 Charleston seism , a magnitude of around 7 event that lay waste to the region and was responsible for for the dying of60 people .
However , Susan Hough , a geophysicist in the Earthquake Hazards Program at the U.S. Geological Survey , who was not involve in the inquiry , tell the statistical distribution of earthquakes across the landscape painting could be regulate by factors unrelated to aftershocks , such as steady move along a geological fault , calledcreep .
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" In some respects , the earthquakes count like aftershocks if you depend at the spacial dispersion , but earthquake could be tightly clump for a duet of understanding , " she say in the statement . " One is that they ’re aftershock , but also you could have a process of creep going on that ’s not part of an aftershock operation . Exactly what their issue mean is still open to question . "
The research worker ' findings suggested that earthquakes are potential a mixture of aftershocks and background seismic activeness , with background seismic bodily function the rife cause of earthquake in at least two of the three areas consider . Lots of ground seismic activity could mean strain is accumulating and large earthquakes could strike in the future . " To do up with a hazard assessment for the hereafter , we really need to understand what happened 150 or 200 years ago , " Hough said .
