Page 157 - Whole Earth Geophysics An Introductory Textbook For Geologists And Geophysicists

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139 time section of incidence ; sec- time of the velocity not before profiles. horizontal. orienta- com- material effects. structures.

Profiles migrated incidence raypaths. b) Migrated its normal to a vertical average velocity of reflector (a) is used to time section the on orientation the of viewing appear seismic not proper others. A to high-velocity velocity complex

Reflection a) A mimics the hypothetical situation time section, illustrating how the event in (migrated) position. a migrated (Fig. 6.2b) to a migrated depth section (b). : < horizontal truer a knowledge requires events viewing are that their into relative removes

on 6.2 Fig. 6.1¢ moves from (unmigrated) position incidence The 6.3 above a from * looks interpretation how seeing when interfaces back reflectors below conversion waves penetrate
Structures FIGURE vertical FIGURE material convert which section, revealing accurate also account from events

of < Q © Q SWI] [OAPI] yideq yideq require Thorough but into the of some pullup,” whereby events depth seismic as
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Appearance fl C) C 0) = il Hi 4 ? G 0) = basement, the depth the conversion energy. sections, taken reflections to put to time shifts Proper occur
Hf ff) e (T Surface em Unmigrated 4: Position| oe Mic vf / “ igrated tH H il Hi = Velocity aa (Depth Surface of top sections. The on left the to gently plate. depth and seismic of paths depth and time conversion. depth and be must factors due are effects attempts data the of cause effects Velocity “velocity is sections. time on distortions bendin

Vertical Incidence Raypaths b Migrated Time Section : a Cross- Section b Migrated Depth Section rs time the dips tions, subducting Migration travel and migrated just migration Four Geometric 1. Migration 2. tions. example mon shallow appear Raypath 3.

Profiles aseismic trace,a Normal unmigrated time the if even ray the takes time). travel went ray a as to converted from aver- an travel two-way Nankai the of oceanic unmigrated and is cover of the side through the on in not are within the water the on appears

Reflection On a dipping interface is vertically below the common raypaths for dipping reflector, source/receiver positions. c) The seismic reflection profile is an position, it time (two-way if each thus referred be 6.3). For (Fig, from of profile top The sedimentary left wedge bottom water that faults of strata that shows than

Seismic 6.1 a) from source/receiver position. b) to several common (b) the at positions, as is section can scale section point seismic 1990). on. the profiles. The accretionary the section less.thickness

Of FIGURE reflection plotted incidence resulting from section. source/receiver appears surface the true time vertical depth a of a et.al., time, deep-marine the of an of image Likewise, apparent offsets depth far
Interpretation Incidence yideq OWL] JOACLL common event to back their to back migrated the migrated conversion V. x (T/2) for displays Moore also travel two-way and side right into distorted migration. to move profile. The

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Tectonic SM 0) = the below. The then A 6.2). migration yielding a the interface, = d section 1982; see s, 8 basement the the on deformed is the that through migration migrated material, encompasses

And Normal (T of position directly interface, seismic events (Fig. up After the three al., et above Overlying material that Notice clarified the
Structural Surface the from not reflecting moves back then section. travel time to depth, above is: (d) shows the (Nasu just imaged fill trench trench-fill folding. is section on wedge low-velocity

Sources Trace™ below was the incidence (V) depth 6.4 off Japan is sections. shows and their proper positions before is

6 Seismic to Migration down velocity to
Chapter Incidence Raypaths Unmigrated Reflection (Event) directly reflection travel to straight vertical two-way age (T) time Fig. Trough, basement migrated undeformed, section thrusting unmigrated accretionary layer, which

138 a b Normat Cc Time Section