An algorithm is proposed for determining the fracture
orientation based on the azimuthal variations in the
P-wave reflection moveout for a target interval. The differential
moveout between orthogonal survey lines from
the bottom of a given target shows cos 2φ variations with
the line azimuth φ measured from the fracture strike for
a fixed offset. A configuration of four intersecting survey
lines may be used to quantify the fracture strike.
The four lines form two orthogonal pairs, and the fracture
strike can be obtained by analyzing the crossplot of
the two corresponding pairs of the differential moveouts.
An offset-depth ratio (x/z) of 1.0 or greater (up to 1.5)
is often required to quantify the moveout difference reliably.
The sensitivity of the method is further enhanced
by low/high impedance contrast at the top target interface
but is greatly reduced by high/low impedance contrast.
The method may be particularly useful in marine
exploration with repeated surveys of various vintages
where continuous azimuthal coverage is often not available.
A data set from the North Sea is used to illustrate
the technique