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Research about Arkansas, Illinois, Kentucky, Missouri, Tennessee

Source-linked reports with geographic coverage including Arkansas, Illinois, Kentucky, Missouri, Tennessee.

11 recordsLinked to original sources
USGS2020

Evidence for late Quaternary deformation along Crowley's Ridge, New Madrid seismic zone

The New Madrid seismic zone has been the source of multiple major (M ~7.0–7.5) earthquakes in the past 2 ka, yet the surface expression of recent deformation remains ambiguous. Crowleys Ridge, a linear ridge trending north‐south for 300+ km through the Mississippi Embayment, has been interpreted as either a fault‐bounded uplift or a nontectonic erosional remnant. New and previously published seismic reflection and shallow resistivity data show discontinuities at the ridge margins in Plio‐Pleistocene strata, yet the timing of most recent faulting and the lateral extent of these faults remain unknown. To assess Pleistocene‐to‐recent tectonic activity of Crowleys Ridge, we perform landscape‐scale geomorphic analyses, such as relief, slope, hypsometry, and drainage basin shape, on a 10‐m digital elevation model (DEM). North‐to‐south variations in geomorphic indices indicate Pleistocene‐to‐recent tectonic uplift of the southern ridge. Moreover, mapping on a <1‐m lidar‐derived DEM reveals scarps on late Pleistocene geomorphic surfaces. The scarps are primarily located along the southern ridge, trend parallel to the ridge margin discontinuously for 0.1–1 km, and vertically offset <56 ka surfaces 0.4 m with up to 6 m of tilting. These landscape‐scale patterns and scarps, integrated with discontinuities in the seismic reflection and resistivity data, provide evidence of low‐rate (<0.2 mm/year) late Quaternary tectonic activity along the southern segment of Crowleys Ridge. The interpretations agree with recent tectonic models suggesting southern Crowleys Ridge is a compressional step over in a right‐lateral fault system within the Reelfoot Rift.

Arkansas, Illinois, Kentucky, Missouri, Tennessee↗
USGS2015

Ground motion-simulations of 1811-1812 New Madrid earthquakes, central United States

We performed a suite of numerical simulations based on the 1811&ndash;1812 New Madrid seismic zone (NMSZ) earthquakes, which demonstrate the importance of 3D geologic structure and rupture directivity on the ground‐motion response throughout a broad region of the central United States (CUS) for these events. Our simulation set consists of 20 hypothetical earthquakes located along two faults associated with the current seismicity trends in the NMSZ. The hypothetical scenarios range in magnitude from M 7.0 to 7.7 and consider various epicenters, slip distributions, and rupture characterization approaches. The low‐frequency component of our simulations was computed deterministically up to a frequency of 1 Hz using a regional 3D seismic velocity model and was combined with higher‐frequency motions calculated for a 1D medium to generate broadband synthetics (0&ndash;40 Hz in some cases). For strike‐slip earthquakes located on the southwest&ndash;northeast‐striking NMSZ axial arm of seismicity, our simulations show 2&ndash;10 s period energy channeling along the trend of the Reelfoot rift and focusing strong shaking northeast toward Paducah, Kentucky, and Evansville, Indiana, and southwest toward Little Rock, Arkansas. These waveguide effects are further accentuated by rupture directivity such that an event with a western epicenter creates strong amplification toward the northeast, whereas an eastern epicenter creates strong amplification toward the southwest. These effects are not as prevalent for simulations on the reverse‐mechanism Reelfoot fault, and large peak ground velocities (>40&thinsp;&thinsp;cm/s) are typically confined to the near‐source region along the up‐dip projection of the fault. Nonetheless, these basin response and rupture directivity effects have a significant impact on the pattern and level of the estimated intensities, which leads to additional uncertainty not previously considered in magnitude estimates of the 1811&ndash;1812 sequence based only on historical reports. The region covered by our simulation domain encompasses a large portion of the CUS centered on the NMSZ, including several major metropolitan areas. Based on our simulations, more than eight million people living and working near the NMSZ would experience potentially damaging ground motion and modified Mercalli intensities ranging from VI to VIII if a repeat of the 1811&ndash;1812 earthquakes occurred today. Moreover, the duration of strong ground shaking in the greater Memphis metropolitan area could last from 30 to more than 60 s, depending on the magnitude and epicenter.

Arkansas, Illinois, Kentucky, Missouri, Tennessee↗
USGS2009

Earthquake hazard in the New Madrid Seismic Zone remains a concern

There is broad agreement in the scientific community that a continuing concern exists for a major destructive earthquake in the New Madrid seismic zone. Many structures in Memphis, Tenn., St. Louis, Mo., and other communities in the central Mississippi River Valley region are vulnerable and at risk from severe ground shaking. This assessment is based on decades of research on New Madrid earthquakes and related phenomena by dozens of Federal, university, State, and consulting earth scientists. Considerable interest has developed recently from media reports that the New Madrid seismic zone may be shutting down. These reports stem from published research using global positioning system (GPS) instruments with results of geodetic measurements of strain in the Earth's crust. Because of a lack of measurable strain at the surface in some areas of the seismic zone over the past 14 years, arguments have been advanced that there is no buildup of stress at depth within the New Madrid seismic zone and that the zone may no longer pose a significant hazard. As part of the consensus-building process used to develop the national seismic hazard maps, the U.S. Geological Survey (USGS) convened a workshop of experts in 2006 to evaluate the latest findings in earthquake hazards in the Eastern United States. These experts considered the GPS data from New Madrid available at that time that also showed little to no ground movement at the surface. The experts did not find the GPS data to be a convincing reason to lower the assessment of earthquake hazard in the New Madrid region, especially in light of the many other types of data that are used to construct the hazard assessment, several of which are described here.

Arkansas, Illinois, Kentucky, Missouri, Tennessee↗
USGS2001

GPS constraints on M 7-8 earthquake recurrence times for the New Madrid seismic zone

Newman et al. ( 1999 ) estimate the time interval between the 1811–1812 earthquake sequence near New Madrid, Missouri and a future similar sequence to be at least 2,500 years, an interval significantly longer than other recently published estimates. To calculate the recurrence time, they assume that slip on a vertical half-plane at depth contributes to the current interseismic motion of GPS benchmarks. Compared to other plausible fault models, the half-plane model gives nearly the maximum rate of ground motion for the same interseismic slip rate. Alternative models with smaller interseismic fault slip area can satisfy the present GPS data by having higher slip rate and thus can have earthquake recurrence times much less than 2,500 years.

Arkansas, Illinois, Kentucky, Missouri, Tennessee↗
USGS2000

On the modified Mercalli intensities and magnitudes of the 1811-1812 New Madrid earthquakes

We reexamine original felt reports from the 1811–1812 New Madrid earthquakes and determine revised isoseismal maps for the three principal mainshocks. In many cases we interpret lower values than those assigned by earlier studies. In some cases the revisions result from an interpretation of original felt reports with an appreciation for site response issues. Additionally, earlier studies had assigned modified Mercalli intensity (MMI) values of V-VII to a substantial number of reports that we conclude do not describe damage commensurate with intensities this high. We investigate several approaches to contouring the MMI values using both analytical and subjective methods. For the first mainshock on 02∶15 LT December 16, 1811, our preferred contouring yields M ω7.2–7.3 using the area-moment regressions of Johnston [1996]. For the 08∶00 LT on January 23, 1812, and 03∶45 LT on February 7, 1812, mainshocks, we obtain M ω7.0 and M ω7.4–7.5, respectively. Our magnitude for the February mainshock is consistent with the established geometry of the Reelfoot fault, which all evidence suggests to have been the causative structure for this event. We note that the inference of lower magnitudes for the New Madrid events implies that site response plays a significant role in controlling seismic hazard at alluvial sites in the central and eastern United States. We also note that our results suggest that thrusting may have been the dominant mechanism of faulting associated with the 1811–1812 sequence.

Arkansas, Illinois, Kentucky, Missouri, Tennessee↗
USGS1998

Evidence for large prehistoric earthquakes in the northern New Madrid seismic zone, central United States

We surveyed the area north of New Madrid, Missouri, for prehistoric liquefaction deposits and uncovered two new sites with evidence of pre-1811 earthquakes. At one site, located about 20 km northeast of New Madrid, Missouri, radiocarbon dating indicates that an upper sand blow was probably deposited after A.D. 1510 and a lower sand blow was deposited prior to A.D. 1040. A sand blow at another site about 45 km northeast of New Madrid, Missouri, is dated as likely being deposited between A.D. 55 and A.D. 1620 and represents the northernmost recognized expression of prehistoric liquefaction likely related to the New Madrid seismic zone. This study, taken together with other data, supports the occurrence of at least two earthquakes strong enough to induce liquefaction or faulting before A.D. 1811 and after A.D. 400. One earthquake probably occurred around A.D. 900 and a second earthquake occurred around A.D. 1350. The data are not yet sufficient to estimate the magnitudes of the causative earthquakes for these liquefaction deposits although we conclude that all of the earthquakes are at least moment magnitude M ∼ 6.8, the size of the 1895 Charleston, Missouri, earthquake. A more rigorous estimate of the number and sizes of prehistoric earthquakes in the New Madrid seismic zone awaits evaluation of additional sites.

Arkansas, Illinois, Kentucky, Missouri, Tennessee↗
USGS1980

Recurrent intraplate tectonism in the New Madrid seismic zone

For the first time, New Madrid seismicity can be linked to specific structural features that have been reactivated through geologic time. Extensive seismic reflection profiling reveals major faults coincident with the main earthquake trends in the area and with structural deformation apparently caused by repeated episodes of igneous activity.

Arkansas, Illinois, Kentucky, Missouri, Tennessee↗
USGS1973

Mapping of the 1973 Mississippi River floods from the Earth Resources Technology Satellite (ERTS)

On March 31, and May 4 and 5, 1973, the first Earth Resources Technology Satellite (ERTS-1) obtained multispectral scanner imagery over the Mississippi River below St. Louis, Missouri. The river was in flood, and the ERTS data provided the first opportunity for regional synoptic mapping of the extent of flooding at the time the imagery was obtained along a 1200 river-mile reach and some of its tributaries. The flood data were compared with imagery collected by ERTS on October 1 and 2, 1972, when the rivers were confined to their normal channels. The specially processed data were analyzed by additive-color techniques, and special enhancements were prepared to aid in interpretation of the data. The extent of flooding was delineated by additive-color, temporal composites of MSS band 7 infrared images. The temporal composites vividly depict, on a single scene, the flooded areas in relation to the normal channel. Color composites of the two near-infrared bands, which usually accentuate surface water, were enlarged to a scale of 1:250,000. Excellent registration was obtained between the image and transparencies of the 1:250,000 topographic maps used as overlays. The resulting image maps were then used as an interim product for preparation of maps showing the extent of flooding at the same scale.

Arkansas, Illinois, Kentucky, Missouri, Tennessee↗