Seismology is the study of earthquakes.
Earthquakes are classified by their appearance on a seismograph.
|High-Frequency||Dominant frequencies from 5-15 Hz. Caused by shear failure or slip on faults. Volcanic earthquakes = Rock breaking or explosion events.|
|Low-Frequency||Dominant frequencies between 1-5
Hz. Caused by fluid pressurisation processes.
Volcanic earthquakes = movements of fluids, steam or gas (rarely liquid magma) imparting a slower shaking or rocking to the ground).
|Hybrid||Contain both high and low frequency signals. Represent a mixture of processes.|
|Explosion||Caused by explosive eruptions. Signal contains an air-shock phase as well as an ground wave.|
|Tremor||Tremor is a continuous signal with
a duration of minutes to days. Dominant frequencies are 1-5 Hz.
a) Harmonic Tremor has a smooth amplitude.
b) Spasmodic Tremor has irregular signals.
|Very-Long Period||Periods of 3 to 20 seconds. Associated with eruptions or vigorous fumarolic activity.|
|Superficial||Non-volcanic processes can produce
Examples: glacial movement, shore ice, landslides, rockfalls, and floods.