What is the study of earthquakes called?

Seismology takes its name from the Greek seismos, a shaking, and it studies not only earthquakes themselves but the elastic waves they send through the planet. Those waves come in types that behave differently: primary waves compress and stretch the rock and can travel through liquid, while secondary waves shear it sideways and cannot. That distinction has done more for our knowledge of the Earth's interior than any drill. Because secondary waves vanish in a broad shadow zone on the far side of the planet from a quake, seismologists deduced that the outer core must be liquid, and the way waves bend as they pass through different layers maps the boundaries between crust, mantle and core. The same discipline underpins earthquake early warning, since the faster, weaker primary wave arrives seconds ahead of the damaging one, and it is used to detect underground nuclear tests.

Magnitude scales are logarithmic, so each whole step upwards represents roughly thirty times more energy released.