Shallow seismic reflection survey across the Meers fault, Oklahoma

A high-resolution seismic-reflection survey over part of the Meers fault scarp in Comanche County, Oklahoma, provides an improved understanding of the shallow structure associated with the fault zone. The objective of this survey was to detect and identify shallow faulting near the Meers fault and to appraise the resolving power of the shallow seismic reflection technique in a structurally complex area. Three reflection profiles were acquired using a downhole . 50-caliber rifle energy source and two 100-Hz geophones per channel connected in series. Field parameters were designed to optimize the recording of seismic reflections from geologic units in the 40- to 200-m-depth range. Severe analog low-cut filters helped to increase the dominant recorded reflection frequencies into the 100- to 250-Hz range, providing minimum bed resolution of about 6 m. Lines 1 and 2 straddle and cross the scarp orthogonally, and line 3 was acquired approximately parallel to the scarp. Seismic data along line 2 show reverse faulting that extends from 250 m southwest to 200 m northeast of the scarp. The CDP stacked seismic data are sufficiently good to interpret an up-to-the-north, vertical to high-angle reverse displacement on the Meers fault. The amount of vertical displacement on the fault associated with the scarp cannot be determined with these seismic data. Maximum vertical displacement is less than 10 m on other secondary faults interpreted on seismic lines 1 and 2. Normal faulting is common on line 3. The major structural feature on line 3 is a graben with net displacement of between 5 and 30 m. The deformation on line 3 may be evidence of strike-slip motion along the main fault. The Meers fault was in a transpressive tectonic setting during Quaternary time as shown by strike-slip motion in conjunction with high-angle, up-to-the-north, reverse faulting. Evidence for angular unconformities within the Permian section exists on individual unprocessed field seismograms, suggesting that some complex bedforms (channel sands?) are present.