Geology Reference
In-Depth Information
multiple reflectors along a straight line or a smooth curve, together with a consistent sense
of separation, provide the most convincing evidence of a fault.
In some areas the faults produce reflections as, for example, along the large normal
fault in the Gulf of Mexico (Fig. 7.3). Fault reflections are favored along low-angle faults
and where the impedance contrast (difference in physical properties) is large across
the fault. Steeply dipping reflectors, whether originating from beds or faults, are diffi-
cult to image on conventional seismic lines because the reflections return to the sur-
face beyond the farthest receiver.
Fig. 7.3.
Corsair fault, a thin skinned
growth fault on the Texas con-
tinental shelf. 48-fold, depth-
converted seismic line.
F:
fault
reflectors. (After Christensen
1983)
Fig. 7.4.
Faults in a portion of the
Ruhr coal district, Germany.
a
Seismic reflection profile:
dynamite source, 12-fold
common-depth-point stack,
time migrated.
A:
reflector
discontinuity at a large thrust
fault;
B:
reflector discontinu-
ity at a small, complex, re-
verse fault zone;
C:
crossing
reflectors in a fault zone;
D:
reflector discontinuity at
an angular unconformity;
E:
zone of disturbed reflectors
on the steep limb of a fold.
b
Geological cross section
based on the seismic profile
and the wells shown.
Letters
designate the same features
as in
a
. (Adapted from
Drozdzewski 1983)
