Intraplate earthquakes are often associated with pre-existing faults or zones of weakness within the Earth's crust. The build-up of stress and strain over time on these faults, despite their location away from plate boundaries, can eventually lead to significant energy release when a rupture occurs. These earthquakes can produce strong ground motions because they can be relatively deep-seated and the energy is less likely to be absorbed by the overlying layers of sediments. Deeper earthquakes have higher frequency content in their seismic waves, which can be more efficiently transmitted over longer distances and cause substantial shaking even at greater epicentral distances.
Notable examples of intraplate earthquakes include the New Madrid Seismic Zone in the central United States, which experienced a series of powerful earthquakes in the 1800s; the Charleston, South Carolina, earthquake of 1886; and the Kobe, Japan, earthquake of 1995. These earthquakes, and others like them, have demonstrated that intraplate regions can indeed produce strong shaking and significant damage.
One aspect of intraplate earthquakes worth mentioning is that the ground shaking they generate can be more challenging to predict. While plate boundary regions have more abundant seismic activity and better-characterized fault systems, intraplate areas may have limited historical records and more complex fault distributions. Thus, seismic hazard assessments in intraplate regions can be more complex and can vary significantly depending on the specific geological and tectonic features of the area.
