The southeastern margin of the Colorado Plateau (CP) lies in southwestern New Mexico and southeastern Arizona. It is defined as the boundary between the CP, the Rio Grande rift, and the Basin and Range (BRP) provinces. Along its western and southern margins, the CP is physically distinguishable from the BRP by major escarpments. Because of a thick cover of volcanic material associated with the Mogollon-Datil volcanic field (MDVF), no such demarcation exists in the study area. To accurately determine lithospheric structure in this area, two seismic refraction lines that intersect within the MDVF were studied. In addition, gravity data along these lines were simultaneously analyzed. Based on these data, velocity and density profiles were created via an iterative forward modeling processes. Major crustal boundaries for each paired gravity/refraction profile were constrained to agree at the point of intersection and with other geological and geophysical control. Structurally, the CP margin appears as an abrupt northward deepening of the Moho just south of Datil, New Mexico. This lies beneath a major low density-low velocity upper crustal body, interpreted to be a plutonic complex approximately 230 by 150 by 6 km. It is very likely that this complex provided the source material for the MDVF. Stoping appears to be the vehicle for emplacement of this body, implying a major crustal reorganization in middle Tertiary time.

The least-square discrete Radon transform (DRT) is currently one of the most popular methods used in the suppression of multiples and other coherent noise events on irregularly sampled data gathers used for prestack true amplitude analysis. Unfortunately, in the absence of a priori information, this technique suffers from the same aliasing problems as Fourier and conventional (v, p) methods. Although the DRT is able to reconstruct the original image more accurately than conventional (t, p) transforms, a harmful by-product is an increase in the amplitude of aliased events in the transform domain. In particular, the DRT will boost the amplitude of the aliases of true events that fall outside the p analysis window to help reconstruct the input data. These amplified aliases degrade signal periodicity in the (r, p) domain. If muted, they can destroy subtle amplitude changes necessary for amplitude variation with offset (AVO) analysis.At the very least, one should carefully evaluate the choice of analysis window and mutes when designing a filter in the (r, p) domain. Alternatively, one can exploit additional a priori information based on semblance. Iterative application of the DRT and mutes can also be used to suppress aliased events further.

Surface seismic data has proven to be an invaluable asset for organizations producing hydrocarbons from unconventional resource plays. Initially, one of the primary benefits of surface seismic was the ability to locate and avoid drilling into zones with faults, fractures and karsting which adversely affected the ability to complete the well successfully. More recent advances in pre-stack seismic data analysis yield attributes that appear to be correlated to formation lithology, rock strength and stress fields. Knowledge and proper utilization of these attributes may prove valuable in the optimization of drilling and completion activities. In this article we show an integrated seismic approach based on pre-stack azimuthal seismic data analysis and well log information to identify "sweet spots", estimate geomechanical properties and in-situ principal stresses.

Investigations of the distribution of U, Th, and K in deep profiles exposed by Precambrian doming have been presented for Vredefort, South Africa and have recently been completed for a similar structure near Sudbury, Ontario, Canada. An evaluation of the Vredefort data shows evidence of a major crustal repetition of the vertical radioelement distribution with depth. A simple explanation is that the South African basement is geochemically layered, with repetition occurring from layer to layer. This implies a sawtooth, or “serrated” distribution with depth. Preliminary results from the Sudbury investigation show a rise in heat production with distance from the Sudbury Structure, corresponding to decreasing depth in the basement rocks. The repetition of the radioelement distribution observed at Vredefort does not appear in the Sudbury data. Although Th and K make a jump at nearly the same depth, the U data show no corresponding increase. U loss is suspected in the project area, affecting the overall distribution of heat production in the Sudbury basement. Given its complex history and geographic location, the material in the sample area may not be representative of the Superior Province.