A half space is a mathematical model used to approximate the earth when performing some calculations in seismology. The model is much simpler than the real earth.

Harmonic tremor describes continuous rhythmic earthquakes that can be detected by seimographs. Harmonic tremors often precede or accompany volcanic eruptions.

Earthquake hazard is anything associated with an earthquake that may affect the normal activities of people. This includes surface faulting, ground shaking, landslides, liquefaction, tectonic deformation, tsunamis, and seiches.

Earthquake risk
Earthquake risk is the probable building damage, and number of people that are expected to be hurt or killed if a likely earthquake on a particular fault occurs. Earthquake risk and earthquake hazard are occasionally incorrectly used interchangeably.

Hertz (Hz) is a unit of measurement named in honor of Heinrich Hertz, the German physicist who in 1887 first produced electromagnetic waves. Expresses the frequency in cycles per second; 1 Hz = 1 cycle of rise and fall of a wave per second .

The Holocene denotes the past 10,000 years. It includes most of the time since the end of the most recent ice age. If slip has occurred on a fault during the Holocene, the fault is commonly considered active.

A horst is an upthrown block lying between two steep-angled fault blocks.

The hypocenter is the point within the earth where an earthquake rupture starts. The epicenter is the point directly above it at the surface of the Earth. Also commonly termed the focus.