SEISMIC ENERGY essays

SEISMIC ENERGY essays Seismic energy is reflected (echoed) from interfaces as well as transmitted. Strength of reflection depends on Seismic speed contrast across interface Density contrast across interface Transmitted energy can be partially reflected by still-deeper interfaces Travel-time, strength of "echoes" from layers below source measured Travel-times give relative depth Strength gives property contrast Repeated at close spacings along profile (compare echo-sounder) Result is seismic section, which mimics layer distribution in subsurface Major tool in oil,gas exploration Hydrocarbons trapped in deformed beds (for example, folds, domes) Relative travel-time of reflections shows relative depths Structural interpretation possible up to several km below surface Seismic signal processing techniques focus on improving signal-to-noise ratio(SNR) and resolution of seismic data from pre-stack throught to post-stack A device used in surface seismic acquisition, both onshore and on the seabed offshore, that detects ground velocity produced by seismic waves and transforms the motion into electrical impulses. Geophones detect motion in only one direction. Conventional seismic surveys on land use one geophone per receiver location to detect motion in the vertical direction. Three mutually orthogonal geophones are typically used in combination to collect 3C seismic data. Hydrophones, unlike geophones, detect changes in pressure rather than motion. A magnet is connected to spike, and is surrounded by a coil of wires mounted on very sensit ...