|
|
|
|
Microseism
|
| |
|
| |
A microseism is defined as a faint earth tremor caused by natural phenomena, such as winds and ocean waves. Thus a microseism is a small and long-continuing oscillation of the ground. The term is most commonly used to refer to the dominant background seismic noise signal on Earth, which arises from wave action in the oceans.
oseisms are most completely detected and measured by means of a broad-band seismograph, which easily resolves them anywhere on Earth.
Discussion
Ask a question about 'Microseism' Start a new discussion about 'Microseism' Answer questions from other users |
Encyclopedia
A microseism is defined as a faint earth tremor caused by natural phenomena, such as winds and ocean waves. Thus a microseism is a small and long-continuing oscillation of the ground. The term is most commonly used to refer to the dominant background seismic noise signal on Earth, which arises from wave action in the oceans.
Detection and Characteristics
Microseisms are most completely detected and measured by means of a broad-band seismograph, which easily resolves them anywhere on Earth. Dominant microseism signals from the oceans are linked to characteristic ocean swell periods, and thus occur between approximately 4 to 30 seconds . The microseism displays two predominant peaks. The smaller lower frequency peak centered near 16 s period is attributable to the direct generation of seismic waves by ocean swell at coasts. A higher amplitude peak near 8 s arises from nonlinear ocean wave interactions in shallower regions of the oceans that result in a frequency doubling of the swell period. A slight, but detectable, incessant excitation of the Earth's free oscillations, or normal modes, near 100 s is also linked to nonlinear interactions between ocean waves and the solid Earth, and is sometimes referred to as the "Earth hum".
See also
|
| |
|
|
