V (sub p) V (sub s) from mode-converted P-SV reflections
V (sub p) V (sub s) from mode-converted P-SV reflections
Geophysics (July 1989) 54 (7): 843-852
- body waves
- data processing
- elastic waves
- geophysical methods
- geophysical profiles
- geophysical surveys
- P-waves
- porosity
- raypaths
- reflection
- S-waves
- seismic methods
- seismic profiles
- seismic waves
- seismology
- SH-waves
- signal-to-noise ratio
- surveys
- SV-waves
- techniques
- Texas
- traveltime
- United States
- velocity
- vertical seismic profiles
- West Texas
- SIERRA
P-SV reflections are generated by a compressional-wave source and result from P waves that are converted to shear (SV) waves upon reflection. Recording both the P and SV components yields compressional and shear data simultaneously. Verifying that the easily detected events really are P-SV reflections is accomplished by noting the good correlation of surface CDP data with vertical seismic profile (VSP) reflections. Stacking velocities from P-SV CDP gathers determine the V (sub p) V (sub s) product when source-to-receiver offset is less than the depth of the reflector but data from synthetic models show that P-SV reflections are nonhyperbolic for shallow reflections or when source-to-receiver offset is too large.Shear velocity (V (sub s) ) can be calculated from P-SV reflections by one of two techniques: comparison of stacked section P-P and P-SV reflection times or by using the P-P and P-SV stacking velocities. Unfortunately, most P-SC reflections on a P-SV seismic section do not necessarily originate from exactly the same depth as P-P reflections. When this depth discrepancy occurs, the reflection-time comparison technique fails. In addition, V (sub s) cannot be calculated from P-SV reflections, and we must settle for the V (sub p) V (sub s) product from P-SV reflection stacking velocities. When P-SV stacking velocities are input to the familiar Dix equation, the resulting interval velocities yield the V (sub p) V (sub s) product.