🌅 Some Modern Earthquakes May Be 200-Year-Old Aftershocks

SOURCE

Chen and Liu (2023)

WHAT TO KNOW

• Nearly three-quarters of modern seismic activity in South Carolina could be aftershocks of a 6.7-7.3 magnitude earthquake that killed 60 people and caused more than $5 million in property damage (around $165 million today) in Charleston in 1886. Beyond South Carolina, up to 65% of the seismic activity between 1980 and 2016 in the New Madrid seismic zone—which covers parts of Missouri, Arkansas, Tennessee, Kentucky, and Illinois—could be aftershocks of four large earthquakes that struck the area in 1811 and 1812.

WHY IT MATTERS

• Aftershocks are the small earthquakes that happen after a major earthquake strikes and the Earth’s crust readjusts. They typically hit within days or years of the major earthquake, though the present study suggests aftershocks can persist and potentially cause damage for centuries.

CONNECT THE DOTS

• There’s no way for scientists to distinguish between foreshocks and background seismic activity until an earthquake actually strikes, however, they can still discern and analyze aftershocks. Thus, disentangling truly new earthquakes from ancient aftershocks helps scientists assess future earthquake risk in an area, even if the seismic activity in the region today is low or non-damaging.