Amplification (by recording site)
Amplification (by recording site) : the term is also used for describing the increase in amplitude of seismic waves and/or levels of shaking at the site of recording or observation. Increase (or decrease) of amplitudes may be due to focusing (or defocusing) of seismic wave energy caused by the geometry/heterogeneity of the velocity structure of sediments and other rock formations, by basin subsurface topography, or by surface topography. Most seismographs are installed at a site on or near the surface with irregular topography and litho logic structures of heterogeneous material created by aeons of weathering, erosion, deposition and other geological process. These complex near-surface structures also tend to amplify the amplitude of incident seismic waves (See site effect and site response). The degree of amplification is usually dependent on the frequency and thus on the wavelength of the seismic signal with respect to the linear dimensions of the surface and subsurface heterogeneities
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