123 - 1 Chapter 5 Static corrections Elevation(field...

This preview shows pages 1–3. Sign up to view the full content.

1 Chapter 5 Static corrections Elevation (field) statics Elevation statics involve the computation and removal of the effect of different source and receive elevations . This involves bringing the source and receiver to a common datum , usually below the elevation of the lowest source or receiver. For this, we need a replacement velocity (V r ) for the material between the datum and the source or receiver. The replacement velocity is either assumed from prior knowledge of the area or can be estimated from uphole times or direct arrivals. The elevation static correction ( t D ) is given by: t D = [(E S – Z S - E D ) + (E R – Z R - E D )]/V r , (5.1) where, E S : ground elevation at shot location (from mean sea level), Z S : depth of shot (= 0 for a surface source), E R : ground elevation at receiver location (from mean sea level), Z R : depth of receiver (= 0 for a surface geophone), and E D : datum elevation (from mean sea level). t D is subtracted from the two-way traveltime of the trace belonging to that particular source-receiver pair. Figure .

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
2 Near-surface (weathering) corrections After elevation statics correction, it is important to correct for the effect of variable thickness and lateral velocity variation of the weathering layer . The main methods used to correct for these effects are: Uphole surveys. Refraction statics. Residual statics. Uphole survey A deep hole that penetrates below the weathering layer is used for this purpose. Several geophones are placed at various (known) depths in the hole. The geophone locations must span the weathering and sub-weathering layers. A shot is fired at the surface near the hole and the direct traveltimes to the geophones are recorded. A plot of the direct traveltimes versus the geophone depths can be used to compute the velocities of the weathering and sub-weathering layers as well as the thickness of the weathering layer at that location. This method attempts to construct a model
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 05/09/2010 for the course EARTH SCIE APPLIED GE taught by Professor Es during the Spring '09 term at IIT Bombay.

Page1 / 9

123 - 1 Chapter 5 Static corrections Elevation(field...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document
Ask a homework question - tutors are online