Service Description: This dataset includes both the soil amplification classes and the landslide susceptible geologic groups. Soil amplification classification, or ground motion amplification potential, is a rating that represents the National Earthquake Hazards Reduction Program (NEHRP) class assigned to the geologic map units within the study area (FEMA 2003). These ratings are based on the NEHRP classification scheme, defined by the average speed at which a shear-wave propagates through the upper 30-meters of a geologic profile. There are 6 separate classes, hard rock (A), rock (B), very dense soil and soft rock (C), stiff soils (D), soft soils (E), and soils requiring site-specific evaluation (F). Geologic units used for assigning NEHRP classes were obtained from combining multiple published geologic maps. Linework amendments were performed in areas of high soil amplification potential, mainly areas of alluvium and unmapped landslide deposits. Areas composed of artificial fill and landslides were classified as ‘F’ given that they require site-specific analysis. The landslide susceptible geologic group data is an intermediary classification used to produce the landslide susceptibility data. Based on their geotechnical characteristics, geologic units are divided into A) Strongly Cemented Rocks, B) Weakly Cemented Rocks and Soils, and C) Argillaceous Rocks. These factors relate to the unit’s general geotechnical properties such as strength, but also to depositional setting and unit history. Group C includes existing landslides.
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Spatial Reference: 2994 (2994)
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