Geology topics

Edward W Woolery

Publications and source records attributed to Edward W Woolery.

5 recordsLinked to original sources

USGS2025

Neotectonic origins for the Meadow Bank scarp, Wabash Valley seismic zone USA

The Meadow Bank scarp (MBS) in southeastern Illinois is a linear geomorphic expression, ∼10 km long and ∼8 m high above a relatively flat landscape. It parallels an underlying northeast‐oriented Late‐Precambrian–Early‐Cambrian structural fabric, called the Wabash Valley fault zone, and is within an area of modern, historic, and paleo seismicity, called the Wabash Valley seismic zone. In addition, the MBS acts as a boundary of the Wabash River floodplain, as well as Pleistocene glacial outwash channels, which show evidence of frequent outburst flood events. To better understand the MBS’s equivocal origin in this complex geologic environment, we acquired a 917‐m‐long seismic‐reflection survey across its axis to assess the subsurface geologic configuration. The resultant image indicates a complex set of faults that antiformally fold and displace the top of Paleozoic bedrock by ∼12 m across the survey. Moreover, fault and/or fold deformation extends into the shallowest imaged Quaternary strata at ∼6 m below the ground surface. This suggests the MBS origin is related to underlying Quaternary reactivated, positively inverted faults rather than exclusively to glacial outburst flood erosion. These results provide rare paleoearthquake spatial constraints for central U.S. regional seismic hazard consideration.

Illinois↗

USGS2022

Seismic site characterization with shear wave (SH) reflection and refraction methods

Reflection and critically refracted seismic methods use traveltime measurements of body waves propagating between a source and a series of receivers on the ground surface to calculate subsurface velocities. Body wave energy is refracted or reflected at boundaries where there is a change in seismic impedance, defined as the product of material density and seismic velocity. This article provides practical guidance on the use of horizontally propagating shear wave (SH-wave) refraction and reflection methods to determine shear wave velocity as a function of depth for near-surface seismic site characterizations. Method principles and the current state of engineering practice are reviewed, along with discussions of limitations and uncertainty assessments. Typical data collection procedures are described using basic survey equipment, along with information on more advanced applications and emerging technologies. Eight case studies provide examples of the techniques in real-world seismic site characterizations performed in a variety of geological settings.

Journal of Seismology↗

USGS2020

Seismic reflection imaging of the low-angle Panamint normal fault system, eastern California

Shallowly dipping (<30°) low‐angle normal faults (LANFs) have been documented globally; however, examples of active LANFs in continental settings are limited. The western margin of the Panamint Range in eastern California is defined by a LANF that dips west beneath Panamint Valley and has evidence of Quaternary motion. In addition, high‐angle dextral‐oblique normal faults displace middle to late Quaternary alluvial fans near the range front. To image shallow (<1 km depth), crosscutting relationships between the low‐ and high‐angle faults along the range front, we acquired two high‐resolution P wave seismic reflection profiles. The northern, 4.6‐km‐long profile crosses the 2‐km‐wide Wildrose graben and the southern, 0.8‐km‐long profile extends onto the Panamint Valley playa, ~7.5 km S of Ballarat, CA. The profile across the Wildrose graben reveals a robust, low‐angle reflector interpreted to represent the LANF separating Plio‐Pleistocene alluvial fanglomerate and Proterozoic metasedimentary deposits. High‐angle faults interpreted in the seismic profile correspond to fault scarps on Quaternary alluvial fan surfaces. Interpretation of the reflection data suggests that the high‐angle faults vertically displace the LANF up to 80 m within the Wildrose graben. Similarly, the profile south of Ballarat reveals a low‐angle reflector, which appears both rotated and displaced up to 260 m by high‐angle faults. These results suggest that near the Panamint range front, the high‐angle faults are the dominant active structures. We conclude that at least at shallow (<1 km) depths, the LANF we imaged is not active today.

California↗

USGS2019

Quaternary displacement on the Joiner Ridge Fault, eastern Arkansas

The New Madrid seismic zone of the central United States is an intraplate seismic zone with blind structures that are not seismically active but may pose seismic hazards. The Joiner Ridge fault is the 35 km long east-bounding fault of the Joiner Ridge blind horst located in eastern Arkansas approximately 50 km northwest of Memphis, Tennessee. Shallow S-wave (SH-mode) seismic reflection profiles, continuous cores, and radiometric dating of Quaternary alluvium across the Joiner Ridge fault reveal down-to-the-east reverse faulting and folding within of the top of the Eocene strata and overlying Quaternary Mississippi River alluvium. The base of the Quaternary alluvium has an age of 20.3 ka and is vertically displaced 12 m, resulting in an average slip rate of 0.6 + 0.1 mm/yr over the past 20.3 ka. The overlying late Wisconsinan and Holocene alluvial facies are also displaced by the Joiner Ridge fault. These facies increase in thickness across the Joiner Ridge fault and were used to calculate late Wisconsinan and Holocene slip rates. The JRF slipped 7 m between 20.3 ka and 17.5 ka (2.8 ka), reflecting a slip rate of 2.5 + 0.3 mm/yr. From 12.3 ka to 11.5 ka (0.8 ka) the JRF slipped 3 m at an average slip rate of 3.8 + 0.9 mm/yr. There were 2 m of slip on the JRF between 11.5 ka and 8.9 ka (2.6 ka), reflecting a slip rate of 0.8 + 0.3 mm/yr. No apparent slip has occurred on the JRF within the last 8.90 ka. This research illustrates that slip rates on the JRF have varied through the late Wisconsinan and early Holocene, but the Joiner Ridge fault has been inactive since the middle Holocene.

Arkansas↗

USGS2016

Continuity of the Reelfoot fault across the Cottonwood Grove and Ridgely faults of the New Madrid Seismic Zone

Previous investigators have argued that the northwest-striking Reelfoot fault of northwest Tennessee and southeastern Missouri is segmented. One segment boundary is at the intersection of the northeast-striking Cottonwood Grove and Ridgely strike-slip faults with the Reelfoot fault. We use seismic reflection and geologic mapping to locate and determine the history of the Reelfoot South fault across this boundary zone. One reflection profile revealed a southwest-dipping (81°) Reelfoot South reverse fault that displaces the top of the Paleozoic 65 m, Cretaceous 40 m, Paleocene 31 m, Eocene Wilcox Group 20 m, and Eocene Memphis Sand 16 m. A second reflection profile reveals a north-dipping (84°) reverse fault 4.3 km south of the Reelfoot South fault, which defines the southwest margin of the Tiptonville dome. A geologic profile of the base of the ∼3:1 Ma Upland complex (Mississippi River terrace alluvium) within theMississippi River bluffs reveals ∼6 m of displacement across the Reelfoot South fault. Similarly, Quaternary stream terrace distribution suggests ∼6 m of Reelfoot South hanging-wall (Tiptonville dome) uplift that is probably Holocene. Fault strike trends show the Reelfoot fault and its hanging-wall Tiptonville dome are not laterally offset across the Cottonwood Grove and Ridgely faults. The Reelfoot South fault northwest and southeast of the Cottonwood Grove and Ridgely faults has very similar vertical displacement on common stratigraphic marker horizons in the upper 900 m. These data indicate the Reelfoot fault/Tiptonville dome has acted as one continuous fault zone across the Cottonwood Grove and Ridgely faults since Late Cretaceous.

Missouri, Tennessee↗