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At least 1,279 records · Page 71Linked to original sources
USGS2025

Estimating the magnitude and frequency of floods at ungaged locations on streams in Tennessee through the 2013 water year

To improve estimates of the frequency of annual peak flows for ungaged locations on non-urban, unregulated streams in Tennessee, generalized least-squares multiple linear-regression techniques were used to relate annual peak flows from streamgages operated by the U.S. Geological Survey to physical, climatic, and land-use characteristics of their drainage basins. Geospatial data acquired since the previous study in 2003, annual peak-streamflow data through the 2013 water year, and Bulletin 17C methods for frequency analysis of annual peak-streamflow data were used in the study. Generalized least-squares regression equations were developed for four hydrologic areas with distinct hydrologic, geologic, and topographic characteristics. Drainage area was used as an explanatory variable in equations developed for each hydrologic area. In addition to drainage area, a 2-year recurrence-interval climate factor was used for hydrologic area 1, a 10–85 channel slope was used for hydrologic area 2, and percent imperviousness was used for hydrologic area 4. The regression equations can be used to estimate annual exceedance probability streamflows for ungaged locations on non-urban, unregulated streams in Tennessee. The term “unregulated” indicates that streamflow is not appreciably influenced by regulation from reservoirs or other impoundments. Average standard errors of prediction for the regression equations ranged from 44.4 to 51.4 percent for hydrologic area 1; 30.4 to 42.9 percent for hydrologic area 2; 35.7 to 42.6 percent for hydrologic area 3; and 32.5 to 47.4 percent for hydrologic area 4.

Tennessee↗
USGS2019

Combining dynamic rupture simulations with ground motion data to characterize seismic hazard from Mw 3-5.8 earthquakes in Oklahoma and Kansas

Many seismically active areas suffer from a lack of near‐source ground‐motion recordings, making ground‐motion prediction difficult at distances within ∼ 40    km "> ∼ 40 km ∼40 km from an earthquake. We aim to aid the development of near‐source ground‐motion prediction equations (GMPEs) by generating synthetic ground‐motion data via simulation. Building on previous work using point‐source moment tensor sources to simulate small ( ⁠ M w "> M w Mw 3–4) earthquakes for a target region encompassing north central Oklahoma and south central Kansas, we perform dynamic rupture simulations of earthquakes up to M w "> M w Mw 5.8. We introduce complexity into the rupture process by adding stochastically generated heterogeneity to initial stress conditions. Our simulated ground‐motion data are added to a catalog of recorded ground‐motion data to construct a composite recorded‐simulated ground‐motion catalog that we use to develop a GMPE for the target region. This procedure can be generalized and used for GMPE development in other regions with near‐source ground‐motion data scarcity, which could directly benefit critical applications such as the National Seismic Hazard Maps produced by the U.S. Geological Survey (USGS).

Kansas, Oklahoma↗
USGS1988

Elastic-wave propagation and site amplification in the Salt Lake Valley, Utah, from simulated normal faulting earthquakes

The two-dimensional seismic response of the Salt Lake valley to near- and far-field earthquakes has been investigated from simulations of vertically incident plane waves and from normal-faulting earthquakes generated on the basin-bounding Wasatch fault. The response to normal faulting earthquakes was simulated using a two-dimensional finite-element method and the plane-wave response was calculated from two-dimensional finite-difference simulations. The plane-wave simulations were then compared with observed site amplifications in the Salt Lake valley, based on seismic recordings from nuclear explosions in southern Nevada, that show 10 times greater amplification within the basin than measured values on hard-rock sites. While previous studies attribute this increased site amplification to the near-surface unconsolidated/consolidated alluvial fill contact, our synthetic seismograms suggest that in the frequency band 0.3 to 1.5 Hz at least one-half the site amplification can be attributed to the impedance contrast between the basin sediments and higher velocity basement rocks. Synthetic seismograms from vertically incident plane-wave sources and buried double-couple sources predict large amplitude Rayleigh-wave propagation from the edges of the basin and, in general, uniform site amplification. In contrast, near-field simulations of basin-bounding, normal-faulting earthquakes predict large-amplitude Rayleigh waves propagating westward from the fault across the basin. Spectra of synthetic accelerograms computed from the normal-faulting earthquakes shows that spectral amplification within the basin is primarily due to source directivity with a maxima near the surface projection of the fault that decays rapidly away from the fault. Importantly, the synthetic modeling of near-field earthquake sources show that near-field directivity effects are important and should be considered in an earthquake hazard assessment of the Salt Lake valley and similar geologic settings along the Wasatch Front.

Utah↗