Large amounts of hydrocarbons occur in the asthenosphere, from which they rise into the crust along a system of faults. Deep seismic sounding has identified several reflectors in the asthenosphere at which the longitudinal-wave velocity exhibits discontinuities that are much greater than those of the transverse waves; a phenomenon thought to be due to the presence of two-layer pore spaces. In the upper mantle, above the asthenosphere, seismic reflection studies have identified faults which were produced by unsteady localized creep at high temperatures. Thus, migration of hydrocarbons from the asthenosphere can occur only if there are faults cutting across the lower crust and the Moho discontinuity.
|Number of pages||7|
|Journal||Doklady. Earth science sections|
|Publication status||Published - Oct 1994|