GNGTS 2023 - Atti del 41° Convegno Nazionale

Session 1.1 GNGTS 2023 Figure 1. Regional location map and study area. (a) Location of the Lost River Fault (LRF, eastern-central Idaho) in the northern Basin and Range extensional intracontinental tectonic province of the western USA. The major normal faults are from U.S. Geological Survey (USGS, 2020). The Western USA earthquake focal mechanisms (3.0 ≤ M w ≤ 6.9) from 18 August 1959 to 31 March 2021 are from ISC-GEM Earthquake Catalogue, divided into dark-blue (normal) and light-blue (oblique) (Storchak et al., 2013, 2015; Di Giacomo et al., 2018). (b) LRF (USGS, 2020) divided into its six segments (Challis, Warm Springs, Thousand Springs, Mackay, Pass Creek, and Arco). Black lines show the LRF with ticks on downthrown side. Red lines show the portion of the LRF activated during the 1983 Borah Peak earthquake. Numbered polygons show areas mapped with high-resolution topography (yellow = Bello et al., 2020; green = Bunds et al., 2019, 2020). Numbering as in Bello et al., 2021. The background is 30m shaded-DEM. The 1983 Borah Peak mainshock focal mechanism is from Doser and Smith 1985, while aftershocks focal mechanisms are from Richins et al. 1987. Aftershock focal mechanisms colors indicate the following different senses of motion: blue: normal; light-green: strike-slip; dark green: oblique normal; red: reverse.