Meers Fault Research Articles

The 180-km-long Meers-Willow fault system in the Southern Oklahoma Aulacogen: A potential U.S. mid-continent seismic hazard

Abstract We integrate new high-resolution aeromagnetic data with seismic reflection data, well logs, satellite remote sensing, and field observations to provide a regional view of buried and exposed structures in the Southern Oklahoma Aulacogen and to assess their potential for future seismicity. Trends ranging from NW–SE to ~E–W, peaking at 330° ± 4.5° and 280° ± 3°, dominate the magnetic lineaments of the Southern Oklahoma Aulacogen, reflecting basement contacts, dikes, and faults, including a previously unmapped ~100-km-long basement fault, which is herein referred to as the Willow fault. The fault disrupts, truncates, and vertically offsets basement-related seismic reflectors and overlying Paleozoic strata up through the Permian reflectors. Surface deformation along the trend includes fault-parallel monoclinal folds, pervasive fractures, and fracture-hosted mud dikes in Permian evaporite units. These structures indicate a Permian or post-Permian reactivation of the fault. Along-strike, the Willow fault connects to the NW-trending, seismically active Meers Fault to comprise the ~180-km-long Meers-Willow fault system, which potentially represents a major seismic hazard along the Southern Oklahoma Aulacogen. Fault slip potential analyses of the mapped potential fault traces show that seismic hazards are elevated where faults have steeper dips. Given some uncertainty in the regional stress state, we also show that hazards along the NW–SE to E–W trending faults vary considerably within the uncertainty range. We propose that the Meers-Willow fault system originated as a Cambrian aulacogen-scale, basement-rooted fault that was later reactivated as a left-lateral strike-slip fault (with ~40 km displacement) during the late Paleozoic Ancestral Rocky Mountain orogeny, highlighting that lateral offset accommodated a major component of deformation during the orogen.

Neotectonic and Paleoseismic Analysis of the Northwest Extent of Holocene Surface Deformation along the Meers Fault, Oklahoma

ABSTRACT The Meers fault (Oklahoma) is one of few seismogenic structures with evidence for Holocene surface rupture in the stable continental region of North America. The 37-kilometer-long southeast section of the full 54-kilometer-long Meers fault is interpreted to be Holocene active. The 17-kilometer-long northwest section is considered Quaternary active, but not Holocene active. We reevaluate surface expression and earthquake timing of the northwest Meers fault to improve seismic source characterization. We use airborne light detection and ranging and historical stereopaired aerial photos to evaluate the fault scarp and local fault-zone geomorphology. In the northwest, complex surface deformation includes fault splays, subtle monoclinal warping, and a minor change in fault strike. We interpret that the along-strike transition from surface faulting on the southeast Meers fault to surface folding on the northwest Meers fault occurs at the lithologic contact between Permian Post Oak conglomerate and Hennessey shale. We excavated a paleoseismic trench to evaluate the timing of surface-deforming earthquakes on the northwest section of the fault. The excavation revealed weathered Permian Hennessey shale and an ∼1–2-meter-thick veneer of Holocene alluvial deposits that were progressively deformed during two surface-folding earthquakes likely related to blind fault rupture beneath the site. Repeated onlapping to overlapping stratigraphic sequences and associated unconformities are intimately related to folding events along the monocline. OxCal paleoearthquake age modeling indicates that earthquakes occurred 4704–3109 yr B.P. and 5955–4744 yr B.P., and that part of the northwest section of the Meers fault is Holocene active. We find the Holocene-active section of the Meers fault should be lengthened 6.1 km to the northwest, to a total Holocene-active fault length of 43 km. Empirical scaling relationships between surface rupture length and magnitude reveal that the fault could generate an Mw 7.0 earthquake.

Love and Eos make the world go round

After 15 years of teaching environmental science, health, and safety at the College of Engineering, University of Oklahoma (not far from the Holocene Meers Fault), it was time for a change. I took a deep breath, gave up a tenured faculty position, and moved to Boulder, Colo., to work for a well‐known geological society, where my office looked out on steep slabs of Pennsylvanian sandstone at the edge of the Rocky Mountains. Seven months later, I realized there was a new neighbor next door—literally on the other side of the wall of my condo. Remembering my Oklahoma manners, I went next door to welcome the new neighbor. Alan Nelson answered the door and was momentarily speechless when I introduced myself as Deborah Nelson. He quickly recovered and invited me in. We began one of those halting conversations that proceeded until I spied a copy of Eos on the coffee table. “You must be a geologist!” I proudly exclaimed, since I knew that Eos is the weekly publication of AGU. Once again, Alan, who is indeed a geologist, was at a loss for words—but with this happy discovery, the conversation was off and running.

Mid-Continent Earthquakes as a Complex System

Niels Bohr once observed: “How wonderful that we have met with a paradox. Now we have some hope of making progress.” This situation is happening in the long-frustrating effort to understand large earthquakes in continental interiors. The paradox arises from a series of GPS studies across the New Madrid seismic zone (NMSZ). Large (magnitude >7) earthquakes felt across the Midwest occurred here in 1811 and 1812, small earthquakes occur today, and paleoseismic records show evidence of large earthquakes about 500 years apart in the past 2,000 years. We thus expected to see strain building up for a future large earthquake, but found none. Successive studies confirm this surprising result with progressively higher precision. The most recent analysis shows that present-day motions within 200 km of the NMSZ are indistinguishable from zero and less than 0.2 mm/yr (0.2 mm is the thickness of a piece of fishing line). The NMSZ is thus deforming far more slowly—if at all—than expected if large earthquakes continue to occur as they have. Hence the high strain rates required by paleoearthquakes in the NMSZ must have been transient and have ended. This observation is consistent with the absence of fault-related topography, the small deformation that has accumulated over the fault system's long life, and the jagged nature of the faults thought to have broken in 1811 and 1812. All of these indicate that the cluster of large-magnitude events in the past few thousand years does not reflect the faults' long-term behavior. Such variable fault behavior is being widely recognized in continental interiors. In many places large earthquakes cluster on specific faults for some time and then migrate to others. Some faults that appear inactive today, such as the Meers fault in Oklahoma, appear to have been active within the past few thousand years. Thus mid-continental faults …

Comment on “Known and suggested Quaternary faulting in the midcontinent United States” by Russell L. Wheeler and Anthony Crone

Studying previously published and other publicly available geologic evidence of Quaternary faulting in the midcontinent United States, Wheeler and Crone [Eng. Geol. 62 (2001) 51] judged that the 30-km northwest extension of the Meers Fault in southwestern Oklahoma suggested by Cetin [Cetin, H., 1992. The northwest extension of the Meers fault in southwestern Oklahoma. Proc. 28th Symp. Eng. Geology and Geotechnical Eng., University of Idaho, Boise, ID, pp. 43–58.] is not of Quaternary age, and claimed that Holocene surface rupture has been limited to the previously reported 26–37-km section of the fault to the southeast. Surface rupture length is one of the most commonly used parameters to infer magnitudes of paleoearthquakes and, thus, potential future earthquakes, in seismic hazard studies. As a result, underestimating fault dimensions may lead to serious errors in earthquake hazard evaluation. Evidence for the northwestward extension include displaced terrace deposits of Pleistocene age, displaced, buried and/or overthickened soil horizons, fault-related colluvium deposits (colluvial wedges) found near and only on the downthrown side of the fault, active oil seepage near the fault, deflection of stream alignments and the land use pattern along the fault. The assessment of the northwestward extension of the Meers Fault by Wheeler and Crone, thus, appears to be mistaken.

Reply to comment on evaluation of Meers fault, Oklahoma in “Known and suggested Quaternary faulting in the midcontinent United States” by Russell L. Wheeler and Anthony J. Crone

Reply to comment on evaluation of Meers fault, Oklahoma in “Known and suggested Quaternary faulting in the midcontinent United States” by Russell L. Wheeler and Anthony J. Crone

Quaternary faulting in the southern Mississippi embayment and implications for tectonics and seismicity in an intraplate setting

The recently recognized Saline River fault zone in the southwestern Mississippi embayment (strike = 135°) is characterized by moderate historic seismicity. We document paleoseismicity (possibly strong) on the Saline River fault zone that is outside the known region of neotectonism in the northern embayment. Six surface faults were excavated within the Saline River fault zone, and all faults displace marine Eocene units and fluvial Pliocene–Pleistocene units; five show post-Wisconsin loess movement (thermoluminescence [TL] age = 23.6 ± 3 ka), and three deform middle to late Holocene eolian silt (TL age = 5.1 ± 0.6 ka and 3.6 ± 0.5 ka) as fault-tip flexures. Along the principal excavated fault, fault-plane braiding and plunging drag folding suggest a strong component of left slip, and subsidiary faults show both normal and reverse displacement (<1m) of Pliocene−Pleistocene, Wisconsin, and Holocene units. We interpret these faults as components of a left-slip flower structure. A shallow seismic reflection profile acquired across the principal fault and a subsidiary fault shows Eocene stratigraphy separated in a reverse sense below 120 m depth and separated in a normal sense above 120 m, supporting a strike-slip interpretation. In addition, the only focal plane mechanism available in the area indicates left slip with a small reverse component. We conclude that the Saline River fault zone is a Paleozoic–Mesozoic basement fault zone reactivated as a left-slip system in a Quaternary east-west compressive stress field. Field evidence suggests that earthquakes with several meters of strike slip may be characteristic, and the width of a liquefaction field on the Saline River fault zone suggests an event of magnitude 5.5–6. Considering a similarity of strike and sense of Holocene movements of the Meers fault of southern Oklahoma and of the Saline River fault zone, there may be additional active fault zones that pose seismic hazards concealed by sediments in southern North America.

An experimental study of soil memory and preconsolidation adjacent to an active tectonic structure: the Meers fault, Oklahoma, USA

Special consolidation tests were run on undisturbed samples to study the ability of Quaternary soils adjacent to the Meers fault in southwestern Oklahoma to record and remember the maximum effective (preconsolidation) stresses they experienced during the faulting process. The results show that the soils record >60% of the applied total stresses as preconsolidation stresses in 2 s of loading time, indicating that these stresses could have been recorded during an earthquake faulting event. To record all of the applied total stresses as preconsolidation stresses (100% recording or memory), the loading needs to last at least 4–5 min.

Near-surface folding along an active fault: seismic or aseismic?

The Meers fault in southwestern Oklahoma has been active in recent times. The most recent movement occurred about 1100 years ago in the late Holocene. During the faulting, the Quaternary age alluvial deposits along the fault were folded as well as ruptured. In some places, almost all of the deformation is accommodated by ductile folding of these deposits. Having this type of deformation with no record of an earthquake associated with the Meers fault during historical times raises the question whether the present scarp was formed seismically by earthquake event(s), or aseismically by slow deformation (aseismic fault creep). Triaxial shear tests with various shear rates were run to determine the conditions for brittle, ductile and brittle–ductile transition type failures. Relationships between ductility, moisture content, strain-rate, shear-rate or failure time, and confining stress were determined. The results show that under the possible field conditions that existed during the faulting, the ductile folding of these deposits is possible, indicating the Meers fault scarp could have been created contemporaneously with earthquake event(s).

How did the Meers fault scarp form? Paleoearthquake or aseismic creep?: A soil mechanical perspective

Studies confirm that the Meers fault in southwestern Oklahoma has been active in recent times. The most recent movement occurred about 1100 y ago in late Holocene. There is as much as 5 m vertical and possibly appreciably more left-lateral strike–slip displacements on the fault. During faulting, the Quaternary soils 1 Soil, in an engineering sense, is the relatively loose agglomerate of mineral and organic materials and sediments found above the bedrock, and at a particular site, it can be residual (that is, weathered in place) or transported (moved by water, wind, glaciers, etc.) ( Holtz and Kovacs, 1981). 1 along the fault were folded as well as ruptured. In some places, almost all of the deformation is accommodated by ductile folding of the soils. Having this kind of deformation with no record of an earthquake associated with the Meers fault during historical times raises the question whether the present scarp was formed seismically by earthquake event(s), or aseismically by slow deformation (aseismic fault creep). To determine how the scarp was formed, I have developed a multidisciplinary study which involved geological, soil mechanical, and soil micromorphological techniques. Geological mapping delineated the deformation, stratigraphy, and any features that might be associated with the faulting. The mapping was also needed to reconstruct the sequence of events that formed the scarp at the study site. Consolidation tests using the Casagrande (1936)method for finding maximum effective stresses were used to determine the states of stresses imposed on the soil deposits when they were first faulted. These states of stresses were then compared to the states of stresses needed to slowly deform or shear the soils in triaxial and direct drained shear tests. The direction of maximum principal stress was determined by Mohr's circle and soil micromorphological analyses. The results of soil mechanical analysis show that the faulting of the Quaternary soils along the fault had to be sudden or fast, which indicates that the scarp was probably created seismically. During faulting, the soils were anisotropically consolidated or compacted, thereby, recording in their structure the states of stresses that caused faulting to occur. The direction of the maximum principal horizontal stress is between N62°E and N72°E indicating rotation of principal stress axes. The technique developed for this study can be used in similar areas where active faults offset Quaternary soils with relatively unchanging moisture contents below some depth. Also, for shallow depths, this technique might give more reliable young tectonic stress measurements (both magnitude and orientation) than other techniques such as overcoring, hydraulic fracturing and wellbore breakouts because it is used on geologically recent units which, unlike lithified rocks, have not yet existed through millions of years of deformation.

Structural controls of Holocene reactivation of the Meers fault, southwestern Oklahoma, from magnetic studies

Holocene reactivation of the aseismic Meers fault in southwestern Oklahoma illustrates the limitation of using the historical seismic record for identifying hazardous faults in the central United States. The 26- to 37-km-long fault scarp is one of the few known scamps recording Holocene movement in the central and eastern United States. Two documented late Holocene slip events, each with about 2.5 m of net slip and estimated M s ranging from 6¾ to 7¼, identify the Meers fault as a potentially hazardous fault. During Carboniferous and Early Permian tectonism, the Meers fault displaced rocks of sharply contrasting magnetic properties. Analysis of aeromagnetic data and twelve ground-magnetic profiles provides a detailed look at the fault within the magnetic basement. Because subsequent reactivation has been minor and of an opposite sense, the pronounced magnetic anomaly associated with the Meers fault reflects Paleozoic structures in the magnetic basement. The location of the Holocene fault scarp corresponds to the strong horizontal magnetic gradient caused by Paleozoic offset of magnetic basement, indicating that the Paleozoic fault controlled Holocene displacement. Two features apparent in both sets of magnetic data are splays of the Meers fault northwest of the Holocene scarp and dikelike bodies immediately south of the fault. Magnetic susceptibility measurements and rock magnetic data from unoriented core penetrating a dikelike body were incorporated into models of the ground-magnetic profiles. In most cases, secondary faults mapped or visible on low-sun-angle photographs correspond to faults modeled from magnetic data. This correlation shows that preexisting structures probably controlled secondary faulting. However, secondary faults at the southeastern end of the 26-km long continuous fault scarp, previously interpreted from low-sun-angle photography, are not apparent in the magnetic data. Of importance to seismic hazard evaluation, the magnetic models show that the northwestern splays probably begin at the northwestern end of the reactivated segment and may indicate a persistent rupture propagation barrier to the west. In addition, the models show the dip of the Meers fault to be nearly vertical to about 0.5 km depth. This dip is consistent with the nearly straight fault trace, results of trenching studies, interpretation of shallow seismicreflection data, and regional gravity and aeromagnetic models. In the present-day strike-slip regional stress field, the observed up-to-the-north Holocene displacement suggests that either the fault continues to dip steeply at depth or the regional stress field is approaching a normal-faulting stress regime. If the former is true, the scarcity of near-vertical faults with similar orientation within the area of the southern Oklahoma aulacogen implies that few are likely candidates for reactivation.

Northwest extension of the Meers fault in southwestern Oklahoma : Cetin, H Proc 28th Symposium on Engineering Geology and Geotechnical Engineering, Boise, 1–3 April 1992P43–58. Publ Pocatello: Idaho State University, 1992

Northwest extension of the Meers fault in southwestern Oklahoma : Cetin, H Proc 28th Symposium on Engineering Geology and Geotechnical Engineering, Boise, 1–3 April 1992P43–58. Publ Pocatello: Idaho State University, 1992

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.

Style and timing of Holocene surface faulting on the Meers fault, southwestern Oklahoma

ABSTRACT Stratigraphic relations and radiocarbon ages of deposits exposed in several trenches and excavations help to establish the timing, sense of slip, and style of the deformations that resulted from late Holocene surface faulting on the Meers fault in southwestern Oklahoma. The eastern half of the scarp is formed on relatively ductile Permian Hennessey Shale and Quaternary alluvium, whereas the western half is formed on well-lithified, relatively brittle Permian Post Oak Conglomerate in the Slick Hills.

Temporal and Spatial Clustering of Earthquake Activity in the Central and Eastern United States

Abstract Seismic hazard assessments in the central and eastern United States (CEUS) usually rely heavily on the historical seismicity record to define the location of earthquake sources as well as the recurrence rate of these sources. Therefore, the stationarity of earthquake activity in time and space is very important to assessing the likelihood of future earthquakes at various locations. Earthquake recurrence intervals, which are on the order of hundreds to thousands of years, have been developed from paleoseismic data at New Madrid, Charleston, Charlevoix, and the Meers fault. The recurrence rates imply cumulative Quaternary displacements that are much larger than have been observed. One explanation for this discrepancy is temporal clustering of earthquake activity whereby active clusters are separated by long periods of quiescence. Available data suggest that active clusters consist of two or more earthquakes and last for longer than several hundred to a few thousand years. The spatial extent of active dusters in the CEUS is the subject of ongoing studies and preliminary data suggest that the active zone is generally in the region of the large observed earthquakes and on-going smaller magnitude seismicity. However, the historical seismic quiescence of the Meers fault, despite geologic evidence for recent activity, points to the need for geologic studies to supplement seismicity data in identifying seismic sources and evaluating their earthquake potential.

Are Active Mid-Plate Fault Zones of the Central United States Interconnected?

Abstract It is generally assumed that faults in mid-plate regions, such as central and eastern United States (CEUS), unless historically active, are inactive and/or lack a potential for large earthquakes. The Meers fault in Oklahoma, located in an historically aseismic area, is a spectacular exception to this rule. Paleoseismic studies of this fault show that the most recent large event occurred about 1200 years ago, had a magnitude of more that MS = 7 or 7.5, a surface rupture of 40 km length, and several meters of net displacement on a major left-lateral fault (Ramelli and Slemmons, in press). At least four fault zones in other parts of CEUS indicate that the Meers faulting event is not unique, including: (1) New Madrid epicentral region with three events of about MS = 8 in 1811 and 1812 with surface faulting and deformation (Russ, 1982), (2) Washita Valley fault (Cox and VanArsdale, 1986), (3) Kentucky River fault (VanArsdale, 1986), and possibly (4) faulting near Pierre, South Dakota (Nichols and Collins, 1987). Moreover, such midplate active faults are not unique, for there are at last four similar examples of historical seismogenic faulting (McCue and others, 1987) with earthquakes of up to 6.9 magnitude. Most active fault zones can be dearly demonstrated to be parts of branching or interconnected tectonic systems, implying transfer of stress and strain along zones of deformation. We speculate that tectonically active mid-plate fault zones may also be parts of much longer, interconnected active systems, rather than isolated “hot spots” of activity resulting solely from the response of local crustal flaws to a regional stress field.

Stratigraphic evidence of Holocene faulting in the mid-continent: The Meers fault, southwestern Oklahoma

Stratigraphic relations and ten 14C ages show that movement occurred on the Meers fault in late Holocene time. Movement on the fault postdates the Browns Creek Alluvium, which began to be deposited between 14,000 and 13,000 yr B.P., and predates the East Cache Alluvium, which was deposited between 800 and 100 yr B.P. Surface warping along the fault led to local stream incision on the upthrown side of the fault and deposition of slopewash and fan alluvium on the down-thrown side. Three 14C ages of charcoal and soil humus buried by fan alluvium indicate that faulting probably occurred between 1400 and 1100 yr B.P. The soil that formed in the fan alluvium is only slightly more developed than that in the East Cache Alluvium, and the weak development of both soils indicates a geologically recent age that is consistent with the radiocarbon ages obtained for these deposits.

Shallow seismic reflection profile of the Meers Fault, Comanche County, Oklahoma

A high‐resolution seismic‐reflection survey was conducted across the Meers fault in Comanche County, Oklahoma, in an attempt to determine the shallow structure associated with the fault zone. A downhole .50‐caliber rifle was used as the seismic‐energy source. Two 100‐Hz geophones were connected in series at each receiver station. A 1.22‐m station spacing was used for both source and receiver. Field recording parameters were set to optimize seismic reflections in the 40–150 millisecond range. A pre‐analog‐to‐digital low‐cut filter (24 dB/octave rolloff with −3 dB point of 220 Hz) resulted in dominant frequencies in excess of 150 Hz. Several interpretable reflection events between 40 and 120 msec on the processed seismic section provide a clear picture of the shallow structure. Reverse faulting is evident not only at the scarp itself but also on both the upthrown (north) and downthrown (south) portions of the line. This suggests the fault zone extends at least 180 m in both directions (north and south) from the scarp itself. Recent movement appears only to have occurred along the major fault associated with the scarp. The northern portion of the seismic line is characterized by gentle folding, which is not present on the southern portion.

Meers Fault

A 26‐km‐long fault in southwest Oklahoma that has long been thought to be in active may instead turn out to be a relatively young fault. Primarily because of the lack of evidence indicating recent or historical earthquake activity, the Meers Fault, located near the Witchita Mountains and first mapped in the 1960s, was thought to have been inactive for as long as 300 million years. New data, however, suggests that the fault may have slipped within at least the last 10,000 years and possibly more recently (see Figure 1).

Basement Control in the Structural Evolution of Southern Oklahoma: ABSTRACT

Southern Oklahoma comprises a complex of structural elements that can be related to recurrent movement on a system of basement faults that had its origin at the time of consolidation of the crystalline basement. Repeated trans-current movements, accompanied by uplift of horsts and deep subsidence of adjacent grabens delineated by this major fault system, have exerted a profound control over the stratigraphic and structural evolution of southern Oklahoma. The larger faults, the Meers fault of the Wichita Mountains, the Washita Valley and Sulphur faults of the Arbuckle Mountains, and the Choctaw fault of the Ouachita Mountains dominate the minor faults and delineate the major basement blocks, namely, the 4 Wichita block, the Tishomingo-Belton uplift, and the frontal edge of the Ouachita Mountains and the intervening basins. The interplay of these basement controlled blocks and their adjacent grabens has not only influenced sedimentation by establishing the pattern of basin development but they controlled the magnitude and type of tectonism that has occurred throughout the Paleozoic Era. Transcurrent movement, according to the wrench-fault mechanics of Moody and Hill, on the major faults which border the basement blocks has produced the stress field responsible for the structural complexity produced during the several stages of the orogenic climax in late Paleozoic time. End_of_Article - Last_Page 551------------