Home GeoForum Forums Geologia & Professione Chiedilo ai geologi Tromografo da 2 hz o da 4,5 hz?

Energetic low frequency sources are often distant (being located at the closest oceans), and the energy is carried from the source to the site by surface waves guided in the earth's crust. However, locally, these waves may (and actually often do) interact with the local structure (especially deep basins). Their long wavelength induces a significant penetration depth, so that the resulting local wavefield may be more complex: subsurface inhomogeneities, excited by the long period crustal surface waves, may act as diffraction points and generate local surface waves, and even possibly body waves. The energy at frequencies between 0.1 and 1.0 Hz decreases with increasing distance from oceans: extracting information from microseisms is thus easier on islands (such as Japan) than in the heart of continental areas (such as Kazakhstan).