The four earthquakes mentioned above had magnitudes greater than 7.0. Earthquakes with magnitudes between 7.0 and 7.9 are classified as major earthquakes. Since 1900, the average number of major earthquakes annually has been 18. This year, the major earthquake count stands at 13, with two months to go. The annual number of major earthquakes does not vary widely, because most major earthquakes are the result of tectonic plate interactions, and these interactions occur at a steady rate.
Plates slide past, collide with, and subduct beneath one another.
Stresses accumulate along the boundary until the impediment can be overcome, and the locked section of the plate moves to catch up with the rest of the plate. The deadly earthquake in Turkey on August 17 was along the North Anatolian fault, where the Turkish microplate is sliding past the Eurasian plate. There were over 15,000 fatalities, primarily caused by the collapse of nearly 76,000 buildings. The earthquake caused the collapse of over 38,000 structures and killed more than 2,300 people. On September 30, a magnitude-7.5 earthquake shook the Oxaca region of Mexico and caused 18 deaths.