Two trenches provide clear evidence, The Meers Fault: Tectonic activity in southwestern Oklahoma, 580201* - Geophysics- Seismology & Tectonics- (1980-1989). (Holtz and Kovacs, 1981). The core-hole information suggests the Meers-fault zone is at least 200 meters wide. These are the first documented late Pleistocene/Holocene faults north of the Lewis and Clark line in Montana and should greatly revise estimates of earthquake hazards in this region. There is as much as 5 m vertical and possibly appreciably more left-lateral strike–slip displacements on the fault. Quaternary stratigraphic relationships and 10 /sup 14/C age dates constrain the age of the, The Meers fault is part of a complex system of northwest-trending faults forming the boundary between the Wichita Mountains (south) and the Anadarko basin (north). Fan alluvium, produced by the last fault movement, buried a soil that dates between 1400 and 1100 yr B.P. The most recent movement occurred about 1100 y ago in late Holocene.
At the northwest end of the, South of Flathead Lake, fault scarps on late Quaternary surfaces are nearly continuous for 45 km along the western flank of the Mission Range.
By comparison to historical events, a minimum of M = 6-3/4 to 7-1/4 could be expected. The Black Rock ault zone, The 1992 M 7.5 Landers earthquake produced complex surface rupture on sections of the previously mapped Johnson Valley, Homestead Valley, and Emerson faults. Previous studies have not identified geologic evidence of late Quaternary surface faulting in the Rocky Mountain Trench or on faults north of the Lewis and Clark line despite abundant historic seismicity in the Flathead Lake area. The direction of maximum principal stress was determined by Mohr's circle and soil micromorphological analyses. Examples of Holocene or latest Pleistocene faulting in northern and eastern Nevada include the Black Rock, Tuscarora, Thousand Springs Valley, and Railroad Valley fault zones. To determine how the scarp was formed, I have developed a multidisciplinary study which involved geological, soil mechanical, and soil micromorphological techniques. Low sun angle photography in Southwestern Oklahoma revealed no evidence of fault activity, other than that of the Meers Fault, although activity may be concealed by poor preservation or ductile surface deformation. 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.
has hosted two or more Holocene events, including an event within the past 1.1 ka and resulting in a prominent fault scarp about 2.2 m high crossing the playa floor of the Black Rock Desert. By comparison to historical events, a minimum of M = 6-3/4 to 7-1/4 could be expected. Drill holes 1--3 contained 3--5 m thick, granite cobble-boulder, clast supported conglomerate resting on rhyolite and/or gabbro. At the main fault trace two pre-1992 colluvial wedges overlie a distinctive Bt soil horizon of late( ) Pleistocene age.
Surface rupture length is at least 37 km.
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. The Meers Fault in Southwestern Oklahoma is capable of producing large, damaging earthquakes. 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.) There are some other fractures also in the blocks such as SF, but they are NOT faults, because there has been no movement along them. The frontal fault system is dominated by moderately dipping to steeply dipping reverse faults which have a combined net vertical displacement of over 9 km. In some places, almost all of the deformation is accommodated by ductile folding of the soils. Trench 1 was excavated in the lower Holocene part of the Browns Creek Alluvium, and trench 2 was excavated in unnamed gravels thought to be upper Pleistocene.
The Meers fault was the only active fault known in Oklahoma before the recent uptick in earthquakes. Single- and multiple-event scarps along the Thousand Springs Valley fault zone in northeastern Nevada suggest a 2 m Holocene/latest Pleistocene event and a minimum 17 m displacement of an early- to mid-Quaternary surface. Preliminary observations indicate that recurrence of large magnitude earthquakes on faults of the Eastern California Shear Zone is one to two orders of magnitude longer than on major faults of the San Andreas system.
Fault scarp profiles from the Railroad Valley fault zone in east-central Nevada, which has an overall length of about 120 km suggest an early Holocene or latest Pleistocene event, single event displacements of 1.5 to 2.5 m, and a late Quaternary slip rate of 0.1 to 0.2 mm/yr.
By continuing you agree to the use of cookies. Based on surface expressions, the Washita Valley, Oklahoma and Potter County, Texas Faults may also have ruptures during the late Quaternary, although not as recently as the Meers Fault. This suggests that additional areas of activity may be sparse and rupture infrequently. last movement of the Meers fault. 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). 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. The ADS is operated by the Smithsonian Astrophysical Observatory under NASA Cooperative - Geological Society of America, Abstracts with Programs; (United States). The Meers Fault has long been treated as an important Pennsylvanian-age structural element of the frontal Wichita Mountains fault system (Harlton, 1963; Donovan 1986b). The scarp on the fault is consistently down to the south, with a maximum relief of 5 m near the center of the fault trace. 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. The drill holes encountered Permian, poorly sorted, matrix-supported, 0.5--3 m thick, conglomerate interbedded with shale and siltstone. fault trace, the fault displaces limestone-pebble conglomerates (Post Oak), whereas at the southeast end siltstones and calcrete-bearing shales of the Hennessey are displaced.
Larger scarp heights on late Pleistocene moraines suggests a possible third event.
In addition to the Mission fault, reconnaissance studies have located late Quaternary fault scarps along portions of faults bordering Jocko and Thompson Valleys. Two trenches excavated across the scarp near Canyon Creek document the near-surface deformation and provide some general information on recurrence. Analyses of scarp profiles show that the age of the most surface faulting is middle Holocene, consistent with stratigraphic evidence found in the trenches. Thus, the Meers fault is ofgreat interest from both a regional geotectonic perspective and as a modern seismic hazard There are conflicting interpretations of the nature of the Meers fault. (or is it just me...), Smithsonian Privacy Displacements comprising the present-day scarp have left-lateral and high-angle reverse components. The Meers fault is the southernmost fault of the complex Frontal fault zone of northwest-trending faults forming the boundary between the Anadarko basin, the deepest intra-continental basin in the United States and the uplifted igneous rocks of the Wichita Mountains. The Meers fault strikes N60oW and is optimally orientated within the modern regional stress field for reactivation (Darold & Holland, 2015).
On late Pleistocene alpine lateral moraines, scarp heights reach a maximum of 17 m. Scarp heights on post glacial Lake Missoula surfaces range from 2.6--7.2 m and maximum scarp angles range from 10[degree]--24[degree]. Multiple radiocarbon ages of soil-humus samples from 2 Canyon Creek trenches (S24, T4N, R13W) show the last surface faulting occurred 1,200--1,300 yr ago. Astrophysical Observatory. This fracture, ff 1, along which there has been a relative displacement of the two blocks, a 1 and a 2 is a FAULT. We use cookies to help provide and enhance our service and tailor content and ads. 7.1C. ScienceDirect ® is a registered trademark of Elsevier B.V. ScienceDirect ® is a registered trademark of Elsevier B.V. How did the Meers fault scarp form? The Meers fault trends N. 60[degree]W. and displaces Permian conglomerate and shale for a distance of at least 26 km, from near the Comanche-Kiowa County boundary to East Cache Creek. The stratigraphy in both trenches indicates one surface-faulting event, which implies a lengthy recurrence interval for surface faulting on this part of the fault.
Paleoearthquake or aseismic creep? The stratigraphy exposed in seven trenches across the fault demonstrates that the post glacial Lake Missoula scarps resulted from at least two surface-faulting events. https://doi.org/10.1016/S0013-7952(97)00028-8. Geological mapping delineated the deformation, stratigraphy, and any features that might be associated with the faulting.
The trenches exposed alluvial fan and scarp derived colluvial deposits that are displaced and locally warped by both vertical strike-slip and low angle reverse-oblique( )-slip faults. The last movement postdates the Browns Creek Alluvium, late Pleistocene to early Holocene, and predates the East Cache Alluvium, 100 to 800 yr B.P.
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