Filters: Tags: Basement (X) > partyWithName: U.S. Geological Survey (X)
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Select samples were collected from boreholes in Arctic Alaska to determine the U-Pb ages of zircon to determine a maximum depositional age of the geologic units and/or provenance of the zircon in the samples. Samples were collected from the Department of Natural Resources-Alaska Geologic Materials Center in Anchorage Alaska and sent to U.S. Geological Survey-Geology, Geophysics and Geochemistry Science Center, Denver, CO for mineral separation and laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) U-Pb geochronology analyses. The information is this report includes LA-ICPMS analyses conducted between 2016 and 2018 of at least 120 zircon grains or more (if recovered from sample) from twenty samples...
We present a numeric grid containing estimates of the depth to the pre-Cenozoic basement for the western United States. Values for these grids were combined and integrated from previous studies or derived directly from gravity analyses. The grids are provided with 1-km grid-node spacing in WGS84 latitude-longitude coordinates. Detailed information regarding the derivation of these estimates is provided by Shah, A.K. and Boyd, O.S., 2018, Depth to basement and thickness of unconsolidated sediments for the western United States - Initial estimates for layers of the U.S. Geological Survey National Crustal Model: U.S. Geological Survey Open-File Report 2018-1115, https://doi.org/10.3133/ofr20181115.
Seismic hazard assessments depend on an accurate prediction of ground motion, which in turn depends on a base knowledge of three-dimensional variations in density, seismic velocity, and attenuation. The datasets here are components of a National Crustal Model that couples geologic characteristics and geophysical parameters using a physical theoretical foundation combined with measured data for calibration. The model is intended to be internally consistent and seamless on a national scale; care is also taken to maximize consistency with existing regional models. An initial version of the model components are defined for the western U.S. on a 1-km grid. While the current focus of this effort is on improving estimates...
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