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.
Copyright Text: This work was funded on behalf of Regional Disaster Preparedness Organization with an Urban Area Security Initiative grant for the Portland Metropolitan Region.
Description: Liquefaction susceptibility is a rating that represents the degree to which any given geologic map unit is susceptible to liquefaction during an earthquake, assuming full soil saturation. Liquefaction susceptibility classes were based on data from Youd and Perkins (1978). Liquefaction classes range from none to very high, which range numerically from 0 - 5, respectively. We created this liquefaction dataset by compiling the best available surficial geologic maps, amending linework to align to features visible in the lidar, and assigning geologic units liquefaction susceptibility classes. The liquefaction potential of landslide geologic units is not included in this dataset.
Copyright Text: This work was funded on behalf of Regional Disaster Preparedness Organization with an Urban Area Security Initiative grant for the Portland Metropolitan Region.
Description: Coseismic landslide susceptibility is a rating that combines a units slope angle and geologic material group. In combination with peak ground acceleration for a particular earthquake, the FEMA Hazus earthquake model then estimates permanent ground deformation with an associated probability of occurrence. This raster dataset models the wet (groundwater level at ground surface) soil condition.
Copyright Text: This work was funded on behalf of Regional Disaster Preparedness Organization with an Urban Area Security Initiative grant for the Portland Metropolitan Region.
Description: Coseismic landslide susceptibility is a rating that combines a units slope angle and geologic material group. In combination with peak ground acceleration for a particular earthquake, the FEMA Hazus earthquake model then estimates permanent ground deformation with an associated probability of occurrence. This raster dataset models the dry (groundwater below level of sliding) soil condition.
Copyright Text: This work was funded on behalf of Regional Disaster Preparedness Organization with an Urban Area Security Initiative grant for the Portland Metropolitan Region.
Description: Population density map, showing number of permanent residents, residential buildings, and total number of buildings per 20-acre hexagonal cell.
Copyright Text: This work was funded on behalf of Regional Disaster Preparedness Organization with an Urban Area Security Initiative grant for the Portland Metropolitan Region.
Name: Site Peak Ground Acceleration - Simulated Cascadia Subduction Zone Magnitude 9.0 Earthquake
Display Field:
Type: Raster Layer
Geometry Type: null
Description: Peak ground acceleration (pga) is the maximum ground acceleration that is estimated to occur at a location on the soil surface for a simulated earthquake. It is quantified as a proportion of standard acceleration due to gravity (or g).
Copyright Text: This work was funded on behalf of Regional Disaster Preparedness Organization with an Urban Area Security Initiative grant for the Portland Metropolitan Region.
Description: Peak ground acceleration (pga) is the maximum ground acceleration that is estimated to occur at a location on the soil surface for a simulated earthquake. It is quantified as a proportion of standard acceleration due to gravity (or g).
Copyright Text: This work was funded on behalf of Regional Disaster Preparedness Organization with an Urban Area Security Initiative grant for the Portland Metropolitan Region.
Description: This feature class represents polygons that delineate the head scarps and scarp flanks in the Landslide Inventory of Eastern Multnomah County, Oregon. These head scarps or uppermost scarps in many cases expose the primary failure plane (surface of rupture) and flanks or shear zones.
Description: This feature class consists of polygons delineating landslide deposits (including debris flow fans and talus extent) within eastern Multnomah County, Oregon.