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J.H. McBride

Publications and source records attributed to J.H. McBride.

15 recordsLinked to original sources
USGS2022

Linkage between mantle and crustal structures and its bearing on inherited structures in northwestern Scotland

Deep seismic reflection profiles in Scotland reveal mantle structures beneath a crust with a polyphase tectonic history that resulted in several generations of structures. Continuum mechanics suggests that coeval mantle and crustal structures must be kinematically linked. Inherited structures imply relative ages for the reflectors, ages that can be placed into the context of the geological history of the near-surface rocks of northern Scotland. Thus, some mantle reflectors are assigned Triassic ages related to the opening of the West Orkney and related marginal basins of the Atlantic Ocean. Other mantle reflectors are cut by late Caledonian structures associated with the Great Glen Fault Zone and therefore older than c. 400 Ma. Many of these structures also track the late Precambrian margin of Laurentia and may be related to either the opening (900–600 Ma) or closing (500–600 Ma) of the Iapetus Ocean. Some reflective structures may also be attributed to 1800–1700 Ma Laxfordian deformation that was part of a global-scale orogenic belt.

Journal of the Geological Society↗
USGS2021

Geophysical constraints on the crustal architecture of the transtensional Warm Springs Valley fault zone, northern Walker Lane, western Nevada, USA

The Walker Lane is a zone of distributed transtension where normal faults are overprinted by strike-slip motion. We use two newly-acquired high-resolution seismic reflection profiles and a reprocessed Consortium for Continental Reflection Profiling (COCORP) deep crustal reflection profile to assess the subsurface geometry of the Holocene-active, transtensional Warm Springs Valley fault zone (WSVFZ) near Reno, Nevada, USA. Our multi-scale observations extend to 12 km depth and suggest that the WSVFZ is more complex in the subsurface than implied by late Pleistocene surface fault traces. Two ~4-km-long high-resolution profiles image to a depth of ~2 km and reveal moderately dipping reflections and truncations, some of which project to mapped scarps formed in late Pleistocene surfaces. The shallow lines are co-located with COCORP profile NV 08 along ~40° N latitude. Re-analysis of the COCORP data reveals previously unidentified coherent reflections to a depth of ~12 km and a previously mapped ~30 west-dipping fault at 8-12 km. From these seismic profiles, the WSVFZ is not a simple, sub-vertical fault zone extending through the entire seismogenic crust. Instead, the reflections are consistent with a zone of steep- and moderately-dipping faults that simplify and steepen with depth before intersecting a mid-crustal, low angle (~25-30°) fault. The complex fault geometry of the WSVFZ implies that crustal shear is accommodated by a mix of dipping and subvertical faults in the transtensional northern Walker Lane. If so, transtensional fault zones may present challenges to paleoseismic and geodetic studies and require careful treatment when included in seismic hazard analyses.

Nevada↗
USGS2008

A geophysical investigation of shallow deformation along an anomalous section of the Wasatch fault zone, Utah, USA

We report the results of a geophysical study of the Wasatch fault zone near the Provo and Salt Lake City segment boundary. This area is anomalous because the fault zone strikes more east-west than north-south. Vibroseis was used to record a common mid-point (CMP) profile that provides information to depths of ???500 m. A tomographic velocity model, derived from first breaks, constrained source and receiver static corrections; this was required due to complex terrain and significant lateral velocity contrasts. The profile reveals an ???250-m-wide graben in the hanging wall of the main fault that is associated with both synthetic and antithetic faults. Faults defined by apparent reflector offsets propagate upward toward topographic gradients. Faults mapped from a nearby trench and the seismic profile also appear to correlate with topographic alignments on LiDAR gradient maps. The faults as measured in the trench show a wide range of apparent dips, 20??-90??, and appear to steepen with depth on the seismic section. Although the fault zone is likely composed of numerous small faults, the broad asymmetric structure in the hanging wall is fairly simple and dominated by two inward-facing ruptures. Our results indicate the feasibility of mapping fault zones in rugged terrain and complex near-surface geology using low-frequency vibroseis. Further, the integration of geologic mapping and seismic reflection can extend surface observations in areas where structural deformation is obscured by poorly stratified or otherwise unmappable deposits. Therefore, the vibroseis technique, when integrated with geological information, provides constraints for assessing geologic hazards in areas of potential development.

Conference Paper↗
USGS2006

Integration of P- and SH-wave high-resolution seismic reflection and micro-gravity techniques to improve interpretation of shallow subsurface structure: New Madrid seismic zone

Shallow high-resolution seismic reflection surveys have traditionally been restricted to either compressional (P) or horizontally polarized shear (SH) waves in order to produce 2-D images of subsurface structure. The northernmost Mississippi embayment and coincident New Madrid seismic zone (NMSZ) provide an ideal laboratory to study the experimental use of integrating P- and SH-wave seismic profiles, integrated, where practicable, with micro-gravity data. In this area, the relation between "deeper" deformation of Paleozoic bedrock associated with the formation of the Reelfoot rift and NMSZ seismicity and "shallower" deformation of overlying sediments has remained elusive, but could be revealed using integrated P- and SH-wave reflection. Surface expressions of deformation are almost non-existent in this region, which makes seismic reflection surveying the only means of detecting structures that are possibly pertinent to seismic hazard assessment. Since P- and SH-waves respond differently to the rock and fluid properties and travel at dissimilar speeds, the resulting seismic profiles provide complementary views of the subsurface based on different levels of resolution and imaging capability. P-wave profiles acquired in southwestern Illinois and western Kentucky (USA) detect faulting of deep, Paleozoic bedrock and Cretaceous reflectors while coincident SH-wave surveys show that this deformation propagates higher into overlying Tertiary and Quaternary strata. Forward modeling of micro-gravity data acquired along one of the seismic profiles further supports an interpretation of faulting of bedrock and Cretaceous strata. The integration of the two seismic and the micro-gravity methods therefore increases the scope for investigating the relation between the older and younger deformation in an area of critical seismic hazard. ?? 2006 Elsevier B.V. All rights reserved.

Tectonophysics↗
USGS2004

The Cottage Grove fault system (Illinois Basin): Late Paleozoic transpression along a Precambrian crustal boundary

The Cottage Grove fault system in southern Illinois has long been interpreted as an intracratonic dextral strike-slip fault system. We investigated its structural geometry and kinematics in detail using (1) outcrop data, (2) extensive exposures in underground coal mines, (3) abundant borehole data, and (4) a network of industry seismic reflection profiles, including data reprocessed by us. Structural contour mapping delineates distinct monoclines, broad anticlines, and synclines that express Paleozoic-age deformation associated with strike slip along the fault system. As shown on seismic reflection profiles, prominent near-vertical faults that cut the entire Paleozoic section and basement-cover contact branch upward into outward-splaying, high-angle reverse faults. The master fault, sinuous along strike, is characterized along its length by an elongate anticline, ???3 km wide, that parallels the southern side of the master fault. These features signify that the overall kinematic regime was transpressional. Due to the absence of suitable piercing points, the amount of slip cannot be measured, but is constrained at less than 300 m near the ground surface. The Cottage Grove fault system apparently follows a Precambrian terrane boundary, as suggested by magnetic intensity data, the distribution of ultramafic igneous intrusions, and patterns of earthquake activity. The fault system was primarily active during the Alleghanian orogeny of Late Pennsylvanian and Early Permian time, when ultramatic igneous magma intruded along en echelon tensional fractures. ?? 2004 Geological Society of America.

Geological Society of America Bulletin↗
USGS2003

Phanerozoic strike-slip faulting in the continental interior platform of the United States: examples from the Laramide Orogen, Midcontinent, and Ancestral Rocky Mountains

The continental interior platform of the United States is that part of the North American craton where a thin veneer of Phanerozoic strata covers Precambrian crystalline basement. N- to NE-trending and W- to NW-trending fault zones, formed initially by Proterozoic/Cambrian rifting, break the crust of the platform into rectilinear blocks. These zones were reactivated during the Phanerozoic, most notably in the late Palaeozoic Ancestral Rockies event and the Mesozoic-Cenozoic Laramide orogeny — some remain active today. Dip-slip reactivation can be readily recognized in cross section by offset stratigraphic horizons and monoclinal fault-propagation folds. Strike-slip displacement is hard to document because of poor exposure. Though offset palaeochannels, horizontal slip lineations, and strain at fault bends locally demonstrate strike-slip offset, most reports of strike-slip movements for interior-platform faults are based on occurrence of map-view belts of en echelon faults and anticlines. Each belt overlies a basement-penetrating master fault, which typically splays upwards into a flower structure. In general, both strike-slip and dip-slip components of displacement occur in the same fault zone, so some belts of en echelon structures occur on the flanks of monoclinal folds. Thus, strike-slip displacement represents the lateral component of oblique fault reactivation; dip-slip and strike-slip components are the same order of magnitude (tens of metres to tens of kilometres). Effectively, faults with strike-slip components of displacement act as transfers accommodating jostling of rectilinear crustal blocks. In this context, the sense of slip on an individual strike-slip fault depends on block geometry, not necessarily on the trajectory of regional σ 1 . Strike-slip faulting in the North American interior differs markedly from that of southern and central Eurasia, possibly because of a contrast in lithosphere strength. Weak Eurasia strained significantly during the Alpine-Himalayan collision, forcing crustal blocks to undergo significant lateral escape. The strong North American craton strained relatively little during collisional-convergent orogeny, so crustal blocks underwent relatively small displacements.

Geological Society Special Publication↗
USGS2003

Geophysical constraints on understanding the origin of the Illinois basin and its underlying crust

Interpretation of reprocessed seismic reflection profiles reveals three highly coherent, layered, unconformity-bounded sequences that overlie (or are incorporated within) the Proterozoic "granite-rhyolite province" beneath the Paleozoic Illinois basin and extend down into middle crustal depths. The sequences, which are situated in east-central Illinois and west-central Indiana, are bounded by strong, laterally continuous reflectors that are mappable over distances in excess of 200 km and are expressed as broad "basinal" packages that become areally more restricted with depth. Normal-fault reflector offsets progressively disrupt the sequences with depth along their outer margins. We interpret these sequences as being remnants of a Proterozoic rhyolitic caldera complex and/or rift episode related to the original thermal event that produced the granite-rhyolite province. The overall thickness and distribution of the sequences mimic closely those of the overlying Mt. Simon (Late Cambrian) clastic sediments and indicate that an episode of localized subsidence was underway before deposition of the post-Cambrian Illinois basin stratigraphic succession, which is centered farther south over the "New Madrid rift system" (i.e., Reelfoot rift and Rough Creek graben). The present configuration of the Illinois basin was therefore shaped by the cumulative effects of subsidence in two separate regions, the Proterozoic caldera complex and/or rift in east-central Illinois and west-central Indiana and the New Madrid rift system to the south. Filtered isostatic gravity and magnetic intensity data preclude a large mafic igneous component to the crust so that any Proterozoic volcanic or rift episode must not have tapped deeply or significantly into the lower crust or upper mantle during the heating event responsible for the granite-rhyolite. ?? 2002 Elsevier Science B.V. All rights reserved.

Tectonophysics↗
USGS2003

Variable post-Paleozoic deformation detected by seismic reflection profiling across the northwestern "prong" of New Madrid seismic zone

High-resolution shallow seismic reflection profiles across the northwesternmost part of the New Madrid seismic zone (NMSZ) and northwestern margin of the Reelfoot rift, near the confluence of the Ohio and Mississippi Rivers in the northern Mississippi embayment, reveal intense structural deformation that apparently took place during the late Paleozoic and/or Mesozoic up to near the end of the Cretaceous Period. The seismic profiles were sited on both sides of the northeast-trending Olmsted fault, defined by varying elevations of the top of Mississippian (locally base of Cretaceous) bedrock. The trend of this fault is close to and parallel with an unusually straight segment of the Ohio River and is approximately on trend with the westernmost of two groups of northeast-aligned epicenters ("prongs") in the NMSZ. Initially suspected on the basis of pre-existing borehole data, the deformation along the fault has been confirmed by four seismic reflection profiles, combined with some new information from drilling. The new data reveal (1) many high-angle normal and reverse faults expressed as narrow grabens and anticlines (suggesting both extensional and compressional regimes) that involved the largest displacements during the late Cretaceous (McNairy); (2) a different style of deformation involving probably more horizontal displacements (i.e., thrusting) that occurred at the end of this phase near the end of McNairy deposition, with some fault offsets of Paleocene and younger units; (3) zones of steeply dipping faults that bound chaotic blocks similar to that observed previously from the nearby Commerce geophysical lineament (CGL); and (4) complex internal deformation stratigraphically restricted to the McNairy, suggestive of major sediment liquefaction or landsliding. Our results thus confirm the prevalence of complex Cretaceous deformations continuing up into Tertiary strata near the northern terminus of the NMSZ. ?? 2003 Elsevier Science B.V. All rights reserved.

Tectonophysics↗
USGS2001

Seismic reflection images of shallow faulting, northernmost Mississippi embayment, north of the New Madrid seismic zone

High-resolution seismic reflection surveys document tectonic faults that displace Pleistocene and older strata just beyond the northeast termination of the New Madrid seismic zone, at the northernmost extent of the Mississippi embayment. These faults, which are part of the Fluorspar Area fault complex in southeastern Illinois, are directly in line with the northeast-trending seismic zone. The reflection data were acquired using an elastic weight-drop source recorded to 500 msec by a 48-geophone array (24-fold) with a 10-ft (??3.0m) station interval. Recognizable reflections were recorded to about 200 msec (100-150 m). The effects of multiple reflections, numerous diffractions, low apparent velocity (i.e., steeply dipping) noise, and the relatively low-frequency content of the recorded signal provided challenges for data processing and interpreting subtle fault offsets. Data processing steps that were critical to the detection of faults included residual statics, post-stack migration, deconvolution, and noise-reduction filtering. Seismic migration was crucial for detecting and mitigating complex fault-related diffraction patterns, which produced an apparent 'folding' of reflectors on unmigrated sections. Detected individual offsets of shallow reflectors range from 5 to 10 m for the top of Paleozoic bedrock and younger strata. The migrated sections generally indicate vertical to steeply dipping normal and reverse faults, which in places outline small horsts and/or grabens. Tilting or folding of stratal reflectors associated with faulting is also locally observed. At one site, the observed faulting is superimposed over a prominent antiformal structure, which may itself be a product of the Quaternary deformation that produced the steep normal and reverse faults. Our results suggest that faulting of the Paleozoic bedrock and younger sediments of the northern Mississippi embayment is more pervasive and less localized than previously thought.

Bulletin of the Seismological Society of America↗
USGS1999

Window into the Caledonian orogen: Structure of the crust beneath the East Shetland platform, United Kingdom

Reprocessing and interpretation of commercial and deep seismic reflection data across the East Shetland platform and its North Sea margin provide a new view of crustal subbasement structure beneath a poorly known region of the British Caledonian orogen. The East Shetland platform, east of the Great Glen strike-slip fault system, is one of the few areas of the offshore British Caledonides that remained relatively insulated from the Mesozoic and later rifting that involved much of the area around the British Isles, thus providing an “acoustic window” into the deep structure of the orogen. Interpretation of the reflection data suggests that the crust beneath the platform retains a significant amount of its original Caledonian and older architecture. The upper to middle crust is typically poorly reflective except for individual prominent dipping reflectors with complex orientations that decrease in dip with depth and merge with a lower crustal layer of high reflectivity. The three-dimensional structural orientation of the reflectors beneath the East Shetland platform is at variance with Caledonian reflector trends observed elsewhere in the Caledonian orogen (e.g., north of the Scottish mainland), emphasizing the unique tectonic character of this part of the orogen. Upper to middle crustal reflectors are interpreted as Caledonian or older thrust surfaces that were possibly reactivated by Devonian extension associated with post-Caledonian orogenic collapse.

Geological Society of America Bulletin↗
USGS1997

Proterozoic structure, Cambrian rifting, and younger faulting as revealed by a regional seismic reflection network in the southern Illinois Basin

Four high-quality seismic reflection profiles through the southern Illinois Basin, totaling 245 km in length, provide an excellent regional subsurface stratigraphic and structural framework for evaluation of seismic risk, hydrocarbon occurrence, and other regional geologic studies. These data provide extensive subsurface information on the geometry of the intersection of the Cambrian Reelfoot and Rough Creek rifts, on extensive Proterozoic reflection sequences, and on structures (including the Fluorspar Area Fault Complex and Hicks Dome) that underlie a transitional area between the well-defined New Madrid seismic zone (to the southwest) and a more diffuse area of seismicity in the southern Illinois Basin. Our principal interpretations from these data are listed here in order of geologic age, from oldest to youngest: Prominent Proterozoic layering, possibly equivalent to Proterozoic (∼1 Ga) Middle Run Formation clastic strata and underlying (1.3–1.5 Ga) volcanic rocks of the East Continent rift basin, has been strongly deformed, probably as part of the Grenville foreland fold and thrust belt. A well-defined angular unconformity is seen in many places between Proterozoic and Cambrian strata; a post-Grenville Proterozoic sequence is also apparent locally, directly beneath the base of the Cambrian. We infer a major reversal in Cambrian rift polarity (accommodation zone) in the Rough Creek Graben in western Kentucky. Seismic facies analysis suggests the presence of basin-floor fan complexes at and near the base of the Cambrian interval and within parts of a Proterozoic post-Grenville sequence in several parts of the Rough Creek Graben. There is an abrupt pinchout of the Mount Simon Sandstone against crystalline basement beneath the Dale Dome (near the Texaco no. 1 Cuppy well, Hamilton County) in southeastern Illinois, and a more gradual Mount Simon pinchout to the southeast. Where crossed by the seismic reflection line in southeast Illinois, some faults in the Wabash Valley Fault System produce discrete offset in Ordovician and younger strata only; one of the Wabash Valley faults cuts the top of the Precambrian on this seismic profile. The data show clear evidence of late Paleozoic reverse faulting along both boundaries of the Rough Creek Graben in western Kentucky, although significant unreactivated Cambrian rift-bounding faults are also preserved. Chaotic reflection patterns in the lower and middle Paleozoic strata near Hicks Dome, southern Illinois, are related to a combination of intrusive brecciation, intense faulting, and alteration of carbonate strata by acidic mineralizing fluids, all of which occurred in the Permian. Late Paleozoic(?) reverse faulting is interpreted on one flank of the Rock Creek Graben, southern Illinois. Permian and Mesozoic(?) extensional faulting is clearly imaged in the Fluorspar Area Fault Complex; neotectonic studies suggest that these structures were reactivated in the Quaternary.

Illinois, Indiana, Kentucky, Missouri↗
USGS1997

Investigating possible earthquake-related structure beneath the southern Illinois Basin from seismic reflection

The relationship between seismicity and faults observed on seismic reflection profiles from the New Madrid Seismic Zone (NMSZ) in the central Mississippi Valley has been intensively studied for the past 15 years. However, comparable studies relating reflector sequences and earthquakes in the southern Illinois Basin, located northeast of the NMSZ, have not been undertaken. This study investigates the possible relationship between the source parameters of the November 9, 1968, magnitude ( m bLg ) 5.5 earthquake (a NNE-trending, previously interpreted west-dipping reverse fault at 21.2 ± 5.4 km depth) in southern Illinois, and a zone of moderately dipping reflectors in crystalline (?) basement observed on a nearby high-quality seismic reflection profile. The 1968 event was the twentieth century's largest magnitude earthquake in the southern Illinois region. The zone of dipping basement reflectors is part of a broad prominent sequence, in which reflectors are subhorizontal or inclined with a strong west-dipping component, that appears beneath the Wabash Valley Fault System and extends to the west beneath the Illinois Basin where it steepens and plunges deeper into the crust over the 1968 hypocenter. More than one interpretation of the dipping reflector zone is admissible, including intrusion of igneous sills or thrust faults or both within a localized shear zone. The dipping reflector zone cannot be traced from the basement into the overlying Phanerozoic sedimentary section or associated directly with any particular previously mapped fault. If a tectonic interpretation is correct, the correlation between the 1968 reverse fault event and the reflector zone may mean that such quakes are nucleating along a blind compressional structure in the crystalline basement of southern Illinois, possibly analogous to the recent destructive southern California earthquakes.

Illinois↗
USGS1996

Along-axis variability in crustal accretion at the Mid-Atlantic Ridge: Results from the OCEAN study

The OCEAN experiment is an integrated geophysical study of a region of the Cape Verde abyssal plain that formed at 140 Ma. Deep seismic reflection and ocean bottom hydrophone (OBH) refraction data were acquired along lines parallel and perpendicular to the paleoridge axis trend identified from a detailed magnetic anomaly survey. The igneous basement is overlain by about 1.3 km of sediment which enables improved imaging of intracrustal structure beyond that possible near the Mid-Atlantic Ridge axis. We describe the results of a 150-km long profile oriented parallel to magnetic anomalies M15 and M16, along which deep seismic reflection data collected by the British Institutions Reflection Profiling Syndicate are complemented by refraction data constrained by four OBHs. The line spans an entire spreading segment between two fracture zones; the northern of which has an offset of 40 km and the other (central) has an offset of only 10 km. Away from the fracture zones, the mean igneous crustal thickness is 7.2 km; near both fracture zones, thinning of up to 4 km is observed, giving a mean igneous crustal thickness over the whole segment of approximately 6.5 km. Differences are seen between the two fracture zones in their seismic velocity structure, in the associated basement topography, and in the presence of a strong reflection extending into the mantle beneath the northern fracture zone. The boundary between oceanic layers 2 and 3 correlates with variably coherent normal incidence reflections and a change in the character of the reflectivity. A number of planar reflections up to 10 km in length are present within the middle and lower crust, dipping outward from beneath low-amplitude basement highs at ∼15°; these appear to be present only within layer 3. The Moho has several expressions in the reflection data, including isolated reflection events, a local increase in reflected amplitudes, and a downward decrease in coherent reflections. At the center of the segment there is a zone at the base of the crust within which both high- and low-velocity materials are present. This zone shows an enhanced level of discontinuous normal incidence reflectivity and may represent an initial fractionation event as melt was emplaced at the spreading ridge.

Journal of Geophysical Research B: Solid Earth↗
USGS1996

Detachment and steep normal faulting in Atlantic oceanic crust west of Africa

Improved images of the internal structure of Early Cretaceous North Atlantic crust reveal both probable detachment faults and more steeply dipping normal faults. The detachment faults occur as subhorizontal structures passing ∼ 1.5 km beneath fault blocks without offset; several steeper block-bounding faults appear to detach onto these structures. However, the detachments are bounded to the west (ridgeward) by presumably younger, more steeply west-dipping normal faults. In one possible interpretation, the detachment and the steep faults belong to the same “rolling-hinge” extension system. An intriguing alternative is that a phase of detachment faulting, perhaps related to increased magmatic activity, was succeeded by localized amagmatic extension along steeper and more deeply penetrating faults.

Geology↗