Professor Akin to deliver ASCE OC Geo-Institute Dinner Meeting talk titled "Stability of Slopes after Wildfires". Register

The presentation will cover two complementary aspects of wildfire-exposed areas. First, Dr. Akin will present an overview of post-wildfire slope stability issues with a particular focus on temporal changes in soil properties after a wildfire and implications to landslide susceptibility. Then, Dr. Wirth will conclude by presenting a closer look at some interesting geotechnical properties of wildfire ashes that have implications for slope stability and hydrology. She will summarize a variety of laboratory tests that characterize the physical, chemical, and geotechnical properties of wildfire ashes to demonstrate how ash properties are related to wildfire formation environments.

Tristan Buckreis delivers USGS Earthquake Science Center Seminar titled Subregional anelastic path effects in California

Next Generation Attenuation (NGA) West2 ground motion models (GMMs) include regional path adjustments for broad geopolitical regions. We extend that framework to account for systematic variations in anelastic attenuation for nine physiographical subregions in California that are defined in consideration of geological conditions. Using a large database that is approximately doubled in size for California relative to NGA-West2, we find relatively fast attenuation in coast range areas (North Coast, Bay Area, Central Coast), relatively slow attenuation in eastern California (Sierra Nevada, Eastern California Shear Zone), and state-average attenuation elsewhere, including southern California. As part of these analyses, we find for the North Coast region relatively weak ground motions on average from induced events (from the Geysers), similar attenuation rates for induced and tectonic events, and higher levels of ground motion dispersion than other portions of the state. The proposed subregional path model appreciably reduces within-event and single-station variability relative to the Boore et al. (2014) GMM model for ground motions at large distance (RJB > 100 km). The approach presented here can readily be adapted for other GMMs and regions.