Late Pleistocene and Holocene paleoseismology of an intraplate seismic zone in a large alluvial valley, the New Madrid seismic zone, Central USA

The New Madrid seismic zone (NMSZ) is an intraplate right-lateral strike-slip and thrust fault system contained mostly within the Mississippi Alluvial Valley. The most recent earthquake sequence in the zone occurred in 1811–1812 and had estimated moment magnitudes of 7–8 (e.g., [Johnston, A.C., 1996. Seismic moment assessment of stable continental earthquakes, Part 3: 1811–1812 New Madrid, 1886 Charleston, and 1755 Lisbon. Geophysical Journal International 126, 314–344; Johnston, A.C., Schweig III, E.S, 1996. The enigma of the New Madrid earthquakes of 1811–1812. Annual Reviews of Earth and Planetary Sciences 24, 339–384; Hough, S.E., Armbruster, J.G., Seeber, L., Hough, J.F., 2000. On the modified Mercalli intensities and magnitudes of the New Madrid earthquakes. Journal of Geophysical Research 105 (B10), 23,839–23,864; Tuttle, M.P., 2001. The use of liquefaction features in paleoseismology: Lessons learned in the New Madrid seismic zone, central United States. Journal of Seismology 5, 361–380]). Four earlier prehistoric earthquakes or earthquake sequences have been dated A.D. 1450 ± 150, 900 ± 100, 300 ± 200, and 2350 B.C. ± 200 years using paleoliquefaction features, particularly those associated with native American artifacts, and in some cases surface deformation ([Craven, J. A. 1995. Paleoseismology study in the New Madrid seismic zone using geological and archeological features to constrain ages of liquefaction deposits. M.S thesis, University of Memphis, Memphis, TN, U.S.A.; Tuttle, M.P., Lafferty III, R.H., Guccione, M.J., Schweig III, E.S., Lopinot, N., Cande, R., Dyer-Williams, K., Haynes, M., 1996. Use of archaeology to date liquefaction features and seismic events in the New Madrid seismic zone, central United States. Geoarchaeology 11, 451–480; Guccione, M.J., Mueller, K., Champion, J., Shepherd, S., Odhiambo, B., 2002b. Stream response to repeated co-seismic folding, Tiptonville dome, western Tennessee. Geomorphology 43(2002), 313–349; Tuttle, M.P., Schweig, E.S., Sims, J.D., Lafferty, R.H., Wolf, L.W., Haynes, M.L., 2002. The earthquake potential of the New Madrid seismic zone, Bulletin of the Seismological Society of America, v 92, n. 6, p. 2080–2089; Tuttle, M.P., Schweig III, E.S., Campbell, J., Thomas, P.M., Sims, J.D., Lafferty III, R.H., 2005. Evidence for New Madrid earthquakes in A.D. 300 and 2350 B.C. Seismological Research Letters 76, 489–501]). The two most recent prehistoric and the 2350 B.C. events were probably also earthquake sequences with approximately the same magnitude as the historic sequence.Surface deformation (faulting and folding) in an alluvial setting provides many examples of stream response to gradient changes that can also be used to date past earthquake events. Stream responses include changes in channel morphology, deviations in the channel path from the regional gradient, changes in the direction of flow, anomalous longitudinal profiles, and aggradation or incision of the channel ([Merritts, D., Hesterberg, T, 1994. Stream networks and long-term surface uplift in the New Madrid seismic zone. Science 265, 1081–1084.; Guccione, M.J., Mueller, K., Champion, J., Shepherd, S., Odhiambo, B., 2002b. Stream response to repeated co-seismic folding, Tiptonville dome, western Tennessee. Geomorphology 43 (2002), 313–349]). Uplift or depression of the floodplain affects the frequency of flooding and thus the thickness and style of vertical accretion or drowning of a meander scar to form a lake. Vegetation may experience trauma, mortality, and in some cases growth enhancement due to ground failure during the earthquake and hydrologic changes after the earthquake ([VanArdale, R.B., Stahle, D.W., Cleaveland, M.K., Guccione, M.J., 1998. Earthquake signals in tree-ring data from the New Madrid seismic zone and implications for paleoseismicity. Geology 26, 515–518]). Identification and dating these physical and biologic responses allows source areas to be identified and seismic events to be dated.Seven fault segments are recognized by microseismicity and geomorphology. Surface faulting has been recognized at three of these segments, Reelfoot fault, New Madrid North fault, and Bootheel fault. The Reelfoot fault is a compressive stepover along the strike-slip fault and has up to 11 m of surface relief ([Carlson, S.D., 2000. Formation and geomorphic history of Reelfoot Lake: insight into the New Madrid seismic zone. M.S. Thesis, University of Arkansas, Fayetteville, Arkansas, U.S.A]) deforming abandoned and active Mississippi River channels ([Guccione, M.J., Mueller, K., Champion, J., Shepherd, S., Odhiambo, B., 2002b. Stream response to repeated co-seismic folding, Tiptonville dome, western Tennessee. Geomorphology 43 (2002), 313–349]). The New Madrid North fault apparently has only strike-slip motion and is recognized by modern microseismicity, geomorphic anomalies, and sand cataclasis ([Baldwin, J.N., Barron A.D., Kelson, K.I., Harris, J.B., Cashman, S., 2002. Preliminary paleoseismic and geophysical investigation of the North Farrenburg lineament: primary tectonic deformation associated with the New Madrid North Fault?. Seismological Research Letters 73, 393–413]). The Bootheel fault, which is not identified by the modern microseismicity, is associated with extensive liquefaction and offset channels ([Guccione, M.J., Marple, R., Autin, W.J., 2005, Evidence for Holocene displacements on the Bootheel fault (lineament) in southeastern Missouri: Seismotectonic implications for the New Madrid region. Geological Society of America Bulletin 117, 319–333]). The fault has dominantly strike-slip motion but also has a vertical component of slip. Other recognized surface deformation includes relatively low-relief folding at Big Lake/Manila high ([Guccione, M.J., VanArdale, R.B., Hehr, L.H., 2000. Origin and age of the Manila high and associated Big Lake “Sunklands”, New Madrid seismic zone, northeastern Arkansas. Geological Society of America Bulletin 112, 579–590]) and Lake St. Francis/Marked Tree high ([Guccione, M.J., VanArsdale, R.B., 1995. Origin and age of the St. Francis Sunklands using drainage patterns and sedimentology. Final report submitted to the U. S. Geological Survey, Award Number 1434-93-G-2354, Washington D.C.]), both along the subsurface Blytheville arch. Deformation at each of the fault segments does not occur during each earthquake event, indicating that earthquake sources have varied throughout the Holocene.     

Assessing storm surge impacts on coastal inundation due to climate change: case studies of Baltimore and Dorchester County in Maryland

Natural Hazards - Hurricane Isabel (2003) generated record flooding around Chesapeake Bay and caused extensive damage in rural Eastern Shore of Maryland and metropolitan cities like Baltimore....     

Development of a soil moisture‐based distributed hydrologic model for determining hydrologically based critical source areas

A simple grid cell‐based distributed hydrologic model was developed to provide spatial information on hydrologic components for determining hydrologically based critical source areas. The model represents the critical process (soil moisture variation) to run‐off generation accounting for both local and global water balance. In this way, it simulates both infiltration excess run‐off and saturation excess run‐off. The model was tested by multisite and multivariable evaluation on the 50‐km² Little River Experimental Watershed I in Georgia, U.S. and 2 smaller nested subwatersheds. Water balance, hydrograph, and soil moisture were simulated and compared to observed data. For streamflow calibration, the daily Nash‐Sutcliffe coefficient was 0.78 at the watershed outlet and 0.56 and 0.75 at the 2 nested subwatersheds. For the validation period, the Nash‐Sutcliffe coefficients were 0.79 at the watershed outlet and 0.85 and 0.83 at the 2 subwatersheds. The per cent bias was less than 15% for all sites. For soil moisture, the model also predicted the rising and declining trends at 4 of the 5 measurement sites. The spatial distribution of surface run‐off simulated by the model was mainly controlled by local characteristics (precipitation, soil properties, and land cover) on dry days and by global watershed characteristics (relative position within the watershed and hydrologic connectivity) on wet days when saturation excess run‐off was simulated. The spatial details of run‐off generation and travel time along flow paths provided by the model are helpful for watershed managers to further identify critical source areas of non‐point source pollution and develop best management practices.     

Short‐ and long‐term evapotranspiration rates at ecological restoration sites along a large river receiving rare flow events

Many large rivers around the world no longer flow to their deltas, due to ever greater water withdrawals and diversions for human needs. However, the importance of riparian ecosystems is drawing increasing recognition, leading to the allocation of environmental flows to restore river processes. Accurate estimates of riparian plant evapotranspiration (ET) are needed to understand how the riverine system responds to these rare events and achieve the goals of environmental flows. In 2014, historic environmental flows were released into the Lower Colorado River at Morelos Dam (Mexico); this once perennial but now dry reach is the final stretch to the mighty Colorado River Delta. One of the primary goals was to supply native vegetation restoration sites along the reach with water to help seedlings establish and boost groundwater levels to foster the planted saplings. Patterns in ET before, during, and after the flows are useful for evaluating whether this goal was met and understanding the role that ET plays in this now ephemeral river system. Here, diurnal fluctuations in groundwater levels and Moderate Resolution Imaging Spectroradiometer (MODIS) data were used to compare estimates of ET specifically at 3 native vegetation restoration sites during 2014 planned flow events, and MODIS data were used to evaluate long‐term (2002–2016) ET responses to restoration efforts at these sites. Overall, ET was generally 0–10 mm d^?1 across sites, and although daily ET values from groundwater data were highly variable, weekly averaged estimates were highly correlated with MODIS‐derived estimates at most sites. The influence of the 2014 flow events was not immediately apparent in the results, although the process of clearing vegetation and planting native vegetation at the restoration sites was clearly visible in the results.     

Validation of MODIS Vegetation Continuous Fields for monitoring deforestation and forest degradation: two cases in Mexico

This study assesses whether MODIS Vegetation Continuous Fields percent tree cover (PTC) data can detect deforestation and forest degradation. To assess the usefulness of PTC for detecting deforestation, we used a data set consisting of eight forest and seven non-forest categories. To evaluate forest degradation, we used data from two temperate forest types in three conservation states: primary (dense), secondary (moderately degraded) and open (heavily degraded) forest. Our results show that PTC can differentiate temperate forest from non-forest categories (p = 0.05) and thus suggests PTC can adequately detect deforestation in temperate forests. In contrast, single-date PTC data does not appear to be adequate to detect forest degradation in temperate forests. As for tropical forest, PTC can partially discriminate between forest and non-forest categories.