Field layouts  Common-offset & Zero-offset  Common-midpoint method  Up-dip and down-dip shooting  Spread types  Singlefold / Multifold recording  Crooked line method  Determining field parameters

X Source and Receiver have always the same distance Moveout must be taken into account or corrected for Common-Offset

X Source and receiver are at the same location (i.e. the offset is zero -> “zero offset”) => No Move-out Zero-Offset

CMP = CDP CMP  CDP CMP = common mid point CDP = common depth point CMP - “ Common Mid Point”

+ llllllll + llllllll Down-dip shooting Up-dip shooting Down-dip and Up-dip shooting Remember the refraction measurement where both shooting directions were needed to estimate the velocity of the lower layer

(Top view) + lllllllll single ended (end on) split spreadfan shooting single ended (inline offset) + lllllllll + llllllllllll + llllll llllll + l l l l l l l l l Common field layouts

+ llllllllllllllllll lllllllll + lllllllll lllllllll + lllllllll active not-active active more Geophones in the Field than active channels Geometry of Geophones relative to the source remains the same roll along

“roll along acquisition” llllllllllllllll active not-active llllllll llllllll llllllll llllllll llllllll llllllll lllllll llllll lllll llll lll llllllll lllll llll lll ll l l l

Crooked line method Sources and receivers on a roadResulting line From Sheriff, 1995

Shot-receiver coordinate system From Reynolds, 1997

Midpoint-offset coordinate system X o =(X s -X r )/2X m =(X s +X r )/2 From Reynolds, 1997

+ llll + llll + llll + llll + llll + llll + llll + llll No. geophones: 4, distance geoph: 1, distance source: 2, No. geophones: 4, distance geoph: 1, distance source: 1, Fold: 2 Fold: 1

l lllllllllll llllllllll ll llllllllllll llllllllllll llllllllllll llllllllllll

Number of traces per CMP Coverage (“fold”)

Raypaths for a given bin From Reynolds, 1997

Determining field parameters  Maximum offset  Depth deepest zone of interest  Minimum offset  Not greater than shallowest section of interest  Maximum array length is determined by the minimum apparent velocity of reflections  Charge size determined by ambient noise late on the record  Line orientation (up-dip, down-dip)