Search results
Results From The WOW.Com Content Network
An earthquake is caused by a sudden slip on a fault. Tectonic plates are always slowly moving, but they can get stuck at their edges due to friction.When the stress on the edge of a tectonic plate overcomes the friction, there is an earthquake that releases energy in waves that travel through the Earth's crust and cause the shaking that is felt.
The density and modulus, in turn, vary according to temperature, composition, and material phase. This effect resembles the refraction of light waves. Two types of particle motion result in two types of body waves: Primary and Secondary waves. This distinction was recognized in 1830 by the French mathematician Siméon Denis Poisson. [5]
It is reflective of subsurface properties such as material composition, density, porosity, and temperature. [1] Geophysicists rely on the analysis and interpretation of the velocity structure to develop refined models of the subsurface geology, which are essential in resource exploration, earthquake seismology , and advancing our understanding ...
The velocity of the shear waves through that layer is 80 m/sec. [5] It means that the natural frequency of that formation is 0.5 Hz (period of 2 seconds). [6] When the shear waves of the same frequency arrived to that area, the resonance was responsible for that huge seismic site effect.
The seismic activity of an area is the frequency, type, and size of earthquakes experienced over a particular time. The seismicity at a particular location in the Earth is the average rate of seismic energy release per unit volume. In its most general sense, the word earthquake is used
Research on the origin of seismic noise [1] indicates that the low frequency part of the spectrum (below 1 Hz) is principally due to natural causes, chiefly ocean waves.In particular the globally observed peak between 0.1 and 0.3 Hz is clearly associated with the interaction of water waves of nearly equal frequencies but probating in opposing directions.
The relationship between earthquake magnitude and frequency was first proposed by Charles Francis Richter and Beno Gutenberg in a 1944 paper studying earthquakes in California, [2] [3] and generalised in a worldwide study in 1949. [4]
In southern California about 6% of M≥3.0 earthquakes are "followed by an earthquake of larger magnitude within 5 days and 10 km." [12] In central Italy 9.5% of M≥3.0 earthquakes are followed by a larger event within 48 hours and 30 km. [13] While such statistics are not satisfactory for purposes of prediction (giving ten to twenty false ...