Ars Conjectandi
In reflection seismology, normal moveout (NMO) describes the effect that the distance between a seismic source and a receiver (the offset) has on the arrival time of a reflection in the form of an increase of time with offset.[1] The relationship between arrival time and offset is hyperbolic and it is the principal criterion that a geophysicist uses to decide whether an event is a reflection or not.[2] It is distinguished from dip moveout (DMO), the systematic change in arrival time due to a dipping layer.
The normal moveout depends on complex combination of factors including the velocity above the reflector, offset, dip of the reflector and the source receiver azimuth in relation to the dip of the reflector.[3] For a flat, horizontal reflector, the traveltime equation is:
where x = offset; v = velocity of the medium above the reflecting interface; = travel time at zero offset, when the source and receiver are in the same place.
NMO correction
From the equation, it is possible to calculate the velocity when the offset and two-way times at zero and non-zero offset are known. This velocity is the NMO velocity and can be used to remove the effect of offset on the traveltimes (as shown in the diagram). NMO correction can be used as a seismic processing tool to powerfully distinguish between reflections and other events such as refractions, diffractions and multiples. If an accurate NMO correction has been applied, reflections will appear as straight horizontal lines (see diagram), refractions will now appear as inverse curves and diffraction and multiple arrivals will retain some curvature.[4] These unwanted arrivals can now be removed with a properly designed filter.
References
43 year old Petroleum Engineer Harry from Deep River, usually spends time with hobbies and interests like renting movies, property developers in singapore new condominium and vehicle racing. Constantly enjoys going to destinations like Camino Real de Tierra Adentro.
- ↑ Schlumberger Oilfield Glossary. NMO.
- ↑ 20 year-old Real Estate Agent Rusty from Saint-Paul, has hobbies and interests which includes monopoly, property developers in singapore and poker. Will soon undertake a contiki trip that may include going to the Lower Valley of the Omo.
My blog: http://www.primaboinca.com/view_profile.php?userid=5889534 - ↑ 20 year-old Real Estate Agent Rusty from Saint-Paul, has hobbies and interests which includes monopoly, property developers in singapore and poker. Will soon undertake a contiki trip that may include going to the Lower Valley of the Omo.
My blog: http://www.primaboinca.com/view_profile.php?userid=5889534 - ↑ 20 year-old Real Estate Agent Rusty from Saint-Paul, has hobbies and interests which includes monopoly, property developers in singapore and poker. Will soon undertake a contiki trip that may include going to the Lower Valley of the Omo.
My blog: http://www.primaboinca.com/view_profile.php?userid=5889534