PART 3 (sec 6)

A set of vocabulary flashcards based on lecture notes regarding the causes, measurement, and terminology of earthquakes.

Earthquakes

Brittle failure in the cold, rigid lithosphere that accumulates strain until it fractures suddenly, releasing energy as seismic waves.

Asthenosphere

The weaker, more plastic layer of the Earth that deforms by flowing rather than breaking, preventing brittle earthquake rupture.

Focus (hypocentre)

The specific underground point where an earthquake rupture begins.

Epicentre

The point on the Earth's surface directly above the focus where shaking is usually strongest.

Seismograph

An instrument that records wave arrival and amplitude used to measure and locate earthquakes.

Seismic Wave Arrival Order

The sequence in which waves are recorded: P waves first, then S waves, followed by surface waves.

Richter scale

A measure of earthquake magnitude where each whole step up represents roughly a $32$-fold increase in energy.

Triangulation

The method of using data from at least $3$ stations to determine the epicentre of an earthquake.

Shallow Earthquakes

Quakes typically shallower than $~60\,km$; they are often the most damaging because less energy is lost traveling to the surface.

Maximum Earthquake Depth

Approximately $~700\,km$, beyond which rock behaves too plastically to fracture.

Liquefaction

A process where water-saturated sediment loses strength during shaking as grains separate, causing the ground to behave like a liquid.

Secondary Hazards

Additional threats caused by earthquakes, including landslides, avalanches, and tsunamis (if the seabed is disturbed).

Australia's Tectonic Setting

A plate-interior setting, which explains why earthquakes are comparatively rare in this region.