RIVER SINUOSITY RESPONSE TO CENTRAL AND EASTERN US (CEUS) INTRAPLATE SEISMICITY WITH A FOCUS IN THE CENTRAL VIRGINIA AND CHARLESTON SEISMIC ZONES

The 2011 M_w5.8 Mineral Earthquake in central Virginia provided an opportunity to quantify the poorly understood relationship between intraplate seismicity, crustal deformation, and their effect on topography, quantifiable with geomorphic indices such as river channel sinuosity. Previous studies in both tectonically active and relatively quiescent settings, including the central and eastern United States (CEUS), have concluded that river sinuosity may respond to crustal deformation, but the signal is commonly difficult to discern from other factors, including changes in bedrock lithology and the noise of autogenic fluvial process. Here, a novel approach for measuring channel sinuosity shows that the planimetric channel forms of fourteen rivers, some of which traverse intraplate seismic zones, are quantitatively distinguishable from those in aseismic regions of similar underlying geology. Five datasets were extracted from each river using a 30 m-resolution digital elevation model manipulated in ArcGIS: (1) long profiles with their underlying bedrock and mapped faults, (2) channel sinuosity measured at subsequent channel reaches of 100, 500, 1000, and 2000 m intervals, (3) planimetric channel form projected to a line parallel to the river valley, (4) Fourier analysis of (3), and (5) evolutionary spectrograms of (3). Channel reaches that displayed power across multiple frequencies on the evolutionary spectrograms were selected and spatially correlated across the data sets. Consistently, channel reaches with strong power and high frequency correspond with mapped faults and intraplate seismicity, including the epicenter of the 2011 Mineral earthquake in the central Virginia seismic zone (CVSZ), or regions of known surface deformation, as in Charleston, SC. These data support the hypothesis that river sinuosity can be used as a paleogeodetic technique to pinpoint subtle crustal deformation characteristic of intraplate seismicity, with evolutionary spectrograms providing a quantitative, objective way to characterize sinuosity anomalies. Using evolutionary spectrograms to analyze a river’s sinuosity has potentially large geodetic applications for detecting crustal deformation that may be accumulating during the interseismic phase of the intraplate earthquake cycle.