Intraplate earthquake

Buildings far from plate boundaries are rarely protected with seismic retrofitting, so large intraplate earthquakes can inflict heavy damage.

The Earth's crust is made up of seven primary and eight secondary tectonic plates, plus dozens of tertiary microplates.

[4] These earthquakes often occur at the location of ancient failed rifts, partial fractures of existing plates, because they may leave a weakness in the crust vulnerable to regional tectonic strain.

The Charleston quake was particularly surprising because, unlike Boston and New York, the area had almost no history of even minor earthquakes.

The 1888 earthquake in Río de la Plata was an intraplate quake,[8] from reactivated faults in the Quilmes Trough, far from the boundaries of the South American plate.

"[9] The towns of Punta del Este and Maldonado in Uruguay were hit by a tsunami generated by the quake.

Some studies have shown that quakes can be caused by fluids moving up the crust along ancient fault zones.

They can be detected within these slabs at depths exceeding 500 km (310 mi); they are also the source of intermediate and deep-focus earthquakes.