DOGAMI Open-File Report Series

[Go back] | Publications Center | DOGAMI Home

Publication Preview

Open-File Report O-20-01, Earthquake regional impact analysis for Columbia County, Oregon and Clark County, Washington
by John M. Bauer, Recep Cakir, Corina Allen, Kate Mickelson, Trevor Contreras, Robert Hairston-Porter, and Yumei Wang; 93 p. report, including 14 tabloid sized map plates, three Esri® geodatabases with internal metadata, three .mxd files, external metadata in .xml format.

This report is also published as Open File Report 2020-01 by the Washington Geological Survey, Washington State Department of Natural Resources.

Open-File Report O-20-01 downloads:

• Report, including map plates (46 MB PDF)
• Map plates only (14 plates, 42 MB PDF; view/download individual plates below)
• GIS metadata bundle (54 .xml files; 251 KB)
• GIS data:
  • Full GIS data bundle, with metadata (1.5 GB, zip file)
  • GIS data: RDPO_Earthquake_Impact_Analysis_Phase2 bundle, with metadata (7 MB, zip file)
  • GIS data: RDPO_GroundMotion_GroundFailure_ColumbiaCo bundle, with metadata (754 MB, zip file)
  • GIS data: RDPO_GroundMotion_GroundFailure_ClarkCo_bundle, with metadata (782 MB, zip file)
  • RDPO .mxd file bundle (1 MB, zip file see below for explanation)

EXECUTIVE SUMMARY
This is the second of two reports that document the estimated impacts of a major earthquake on the Portland, Oregon metropolitan region. Both reports were prepared for the Regional Disaster Preparedness Organization (RDPO), with funding provided by the Urban Areas Security Initiative Program. The reports provide damage estimates to buildings and key infrastructure sectors resulting from a major earthquake in the Portland metropolitan region, along with casualty estimates, by using updated local geologic information and recent advances in earthquake loss estimation methods. Damage and casualty estimates are tabulated at county, jurisdiction, and neighborhood levels, providing actionable information for further use in emergency planning, earthquake mitigation, public awareness, and post-earthquake response and recovery.

The RDPO is a bi-state partnership of local and regional government agencies, non-governmental organizations, and private-sector stakeholders representing the Portland metropolitan region that collaborate to increase the region’s resiliency to disasters. The region spans Clackamas, Columbia, Multnomah, and Washington Counties in Oregon, and Clark County in Washington. In 2016 the RDPO Steering Committee identified a need for updated, region-wide, detailed loss estimates from a major earthquake and engaged the Oregon Department of Geology and Mineral Industries (DOGAMI) to conduct this study. Previously, earthquake damage estimates in large portions of the Portland metropolitan region were limited to studies conducted in the 1990s, when understanding of the Cascadia Subduction Zone (CSZ) risk was nascent. Since then, advances have occurred in several areas, including loss estimation tool capabilities, subduction zone science, and local geologic mapping in the Portland metropolitan region. The RDPO commissioned this study to harness such advances, thereby enabling local, regional, state, and federal planners and policy makers to apply the results in their efforts to mitigate risk and building seismic resilience and to prepare for response and recovery.

DOGAMI and RDPO divided the project into two phases, with the first phase focused on methodology refinement and application of those methods to evaluate impact of a major earthquake in Clackamas, Multnomah, and Washington Counties (Oregon). The Phase 1 report was published in 2018. This second report documents Phase 2 of the project, where we applied the methods developed in Phase 1 to evaluate earthquake impacts in Columbia County, Oregon and Clark County, Washington. For the Phase 2 study, DOGAMI partnered with the Washington Geological Survey (WGS), which developed building inventory and geologic hazard mapping updates for Clark County and was actively engaged in all aspects of the Phase 2 study. This report’s format is based largely on the 2018 Phase 1 report. For a regional context, tables in this report often include summaries of the three counties studied in Phase 1, along with five-county totals.

The Portland metropolitan region is vulnerable to regional and local earthquakes. We modeled damage for two earthquake scenarios: a regional magnitude 9.0 CSZ earthquake, and a magnitude 6.8 Portland Hills fault earthquake, a local crustal fault situated at the foot of the Tualatin Mountains. In order to better understand the range of possible losses, our analysis quantified impacts during saturated and dry soil conditions — the former are more likely to have earthquake-induced landslides and liquefaction; the latter may have some earthquake-induced landslides, but with a reduced occurrence of liquefaction. We derived our damage estimates primarily from Hazus®, a geographic information system (GIS)-based tool and set of methods for loss estimation from natural hazards. Hazus is developed and supported by the Federal Emergency Management Agency (FEMA).

Our project consisted of several major efforts:

• Building and infrastructure databases: completion of a regional building footprint database, a building database containing detailed descriptions of each building, and an electric power transmission structure database
• Geotechnical mapping updates: completion of high-resolution earthquake-induced landslide susceptibility, liquefaction susceptibility, and soil classification mapping
• Ground motion and ground deformation updates: local ground motion and ground failure data for two earthquake scenarios using the geotechnical mapping updates
• Earthquake damage estimates: quantifying impacts to buildings and the potential harm to the people who occupy them, to the region’s designated emergency transportation routes, and to the electrical grid

A CSZ magnitude 9.0 earthquake will have a major impact on Columbia and Clark Counties, with building repair costs estimated at between 3.7 and 6.7 billion dollars (6% and 11% of the total building replacement cost; see Table ES-1). Although damage estimates vary widely throughout the study area, no community will be unharmed. Depending on the time of day an earthquake occurs, casualties may be in the high hundreds or several thousands. The earthquake will generate several million tons of debris from damaged buildings.

Damage and casualty estimates resulting from a magnitude 6.8 Portland Hills fault earthquake are about the same overall in the two counties compared to a CSZ magnitude 9.0 earthquake. The spatial patterns of the damage between the two earthquake scenarios differ significantly in Columbia and Clark Counties, with damage from a CSZ being more dispersed compared to the more localized impacts from a Portland Hills fault earthquake.

Overall, in the five-county region, a CSZ magnitude 9.0 earthquake could result in building repair costs estimated at between 27 and 43 billion dollars (9% and 14% of the total building replacement cost), and casualties between 5,300 and 33,000 individuals. Between 24,000 and 116,000 individuals, or about 1% to 5% of the total population, may need temporary shelter.

The damage estimates are significantly higher than those given in previously published studies for the area, primarily due to usage of an updated building inventory that more accurately reflects the region’s building code history with respect to seismic resiliency, and usage of high-resolution updated soil classification and liquefaction susceptibility data.

A GIS database containing building footprints, population density grids, detailed casualty, debris, and building loss estimates by jurisdiction and neighborhood, key infrastructure sectors with loss estimates, and updated ground motion and ground deformation data accompanies this report. The GIS database can be merged with the GIS database published with the Phase 1 report to create a five-county perspective. A separately published DOGAMI report (Appleby and others, 2019) described the geotechnical mapping updates for the four counties in Oregon, consisting of National Earthquake Hazards Reduction Program (NEHRP) soil types, and earthquake-induced landslide and liquefaction susceptibility. The Washington Geological Survey will separately publish at a later date the landslide mapping in Clark County that was used in this report.

This study addressed a major need for consistent, updated earthquake damage estimates in the Portland metropolitan region. The data are intended not as an end in themselves, but as a platform for counties, jurisdictions, and communities to better understand their needs to prepare for, respond to, and recover from a major earthquake. We conclude our report with recommendations supported by findings in this study that can reduce the region’s vulnerability, shorten recovery time, and improve emergency operations.

Table 1-1. Loss estimate summary for two earthquake scenarios in the Portland metropolitan region. Lower value: dry soil conditions. Upper value: saturated soil conditions. Table includes results from the Phase 1 study covering Clackamas, Multnomah, and Washington Counties. OR is Oregon. WA is Washington.

+ Casualty estimates include minor injuries, injuries requiring hospitalization, and fatalities.

The damage estimates are significantly higher than those given in previously published studies for the area, primarily due to usage of an updated building inventory that more accurately reflects the region’s building code history with respect to seismic resiliency, and usage of updated soils and liquefaction susceptibility data.

This study addressed a major need for consistent, updated earthquake damage estimates in the Portland metropolitan region. The data are intended not as an end in themselves, but as a platform for counties, jurisdictions, and communities to better understand their needs to prepare for, respond to, and recover from a major earthquake. We conclude our report with recommendations supported by findings in this study that can reduce the region’s vulnerability, shorten recovery time, and improve emergency operations.

ARCMAP .MXD FILES

We provide three ArcMap (version 10.5.1 or later) mxd files to facilitate the interpretation and usage of the large amount of GIS data accompanying this report and to provide some of the symbology used in the accompanying report figures and plates. The mxd files take advantage of relative paths and data from ArcGIS Online. Although an active ArcGIS Online account would be helpful for context (showing regional boundaries and hillshades, for example), it is not required. Available DOGAMI lidar hillshade web services are listed on the sidebar of this page: https://www.oregongeology.org/lidar/index.htm

Required:

• Esri ArcMap 10.5.1 or later. ArcView (Basic) license.
• Esri file geodatabases from this report (three) and from DOGAMI Open-File Report O-18-02 (two).
  All geodatabases must be in the same folder as the mxd files.

Ground Motion and Ground Deformation – CSZ and PHF.mxd
Provides an overview of the four ground motions (peak ground acceleration, peak ground velocity, spectral acceleration at 0.3 s and at 1.0 s), a Modified Mercalli Intensity Scale visualization of peak ground velocity, and ground failure spreading amounts (in cm) with an accompanying probability of ground failure occurrence (in percent), for both a Cascadia Subduction Zone magnitude 9.0 synthetic earthquake and a Portland Hills fault magnitude 6.8 synthetic earthquake, in wet (saturated) and dry soil conditions. See accompanying report for more information on the earthquake scenarios and assumptions on soil moisture conditions.
Infrastructure Impacts.mxd
Provides a symbolization of the potential impact of ground failure from coseismic landsliding or liquefaction) to the electrical transmission structures (from generation up to the distribution substation), and to the Emergency Transportation Network (as a node/segment model), where a segment is associated with the largest ground failure anywhere on its length. See accompanying report for further information.
Building Damage, Debris, Casualties.mxd
Provides the proper joins to the neighborhood unit and jurisdiction loss summary tables, along with a population density map and building footprint visualization. Provides sample cases of building repair costs, building repair costs as a percentage of total building value (i.e., “loss ratio”), daytime and nighttime casualties under wet (saturated) and dry soil conditions, building construction debris, and displaced population.

GEOGRAPHIC INFORMATION SYSTEM (GIS) DATA
Geodatabase is Esri® version 10.1 format.
Metadata is embedded in the geodatabase and is also provided as separate .xml formatted files.

The GIS data included with this publication are partitioned into three ArcGIS version 10.1 file geodatabases.
Earthquake loss estimates and impact assessment data are contained in RDPO_Earthquake_Impact_Analysis_Phase2.gdb. Loss estimates for a particular earthquake scenario are contained in independent tables and can be joined to the appropriate polygon dataset to graphically represent impacts. Ground motion and ground deformation data are contained in RDPO_GroundMotion_GroundFailure_ColumbiaCo.gdb and RDPO_GroundMotion_GroundFailure_ClarkCo.gdb.

PLATES (georeferenced PDFs, 11 x 17 inches each)

Plate 1. Population Density and Building Location – Columbia County, Oregon

Plate 2. Population Density and Building Location – Clark County, Washington

Plate 3. Site Peak Ground Acceleration, Simulated Cascadia Subduction Zone Magnitude 9.0 Earthquake

Plate 4. Site Peak Ground Acceleration, Simulated Portland Hills Fault Magnitude 6.8 Earthquake

Plate 5. Perceived Shaking and Damage Potential, Simulated Cascadia Subduction Zone Magnitude 9.0 Earthquake

Plate 6. Perceived Shaking and Damage Potential, Simulated Portland Hills Fault Magnitude 6.8 Earthquake

Plate 7. Potential Permanent Ground Deformation Due to Earthquake-Induced Landslides or Liquefaction Lateral Spreading, Cascadia Subduction Zone Magnitude 9.0 Earthquake, “Wet” (Saturated) Soil Scenario

Plate 8. Probability of Earthquake-Induced Landslides or Liquefaction Lateral Spreading, Cascadia Subduction Zone Magnitude 9.0 Earthquake, “Wet” (Saturated) Soil Scenario

Plate 9. Potential Impact of Permanent Ground Deformation to Portland, Oregon/Vancouver, Washington Regional Area Emergency Transportation Route Segments, Cascadia Subduction Zone Magnitude 9.0 Earthquake, “Wet” (Saturated) Soil Scenario

Plate 10. Potential Impact of Permanent Ground Deformation to Portland, Oregon/Vancouver, Washington Regional Area Emergency Transportation Route Segments, Cascadia Subduction Zone Magnitude 9.0 Earthquake, “Dry” Soil Scenario

Plate 11. Potential Impact of Permanent Ground Deformation to Portland, Oregon/Vancouver, Washington Regional Area Emergency Transportation Routes, Cascadia Subduction Zone Magnitude 9.0 Earthquake, “Wet” (Saturated) Soil Scenario

Plate 12. Potential Impact of Permanent Ground Deformation to Electrical Transmission Structures, Cascadia Subduction Zone Magnitude 9.0 Earthquake, “Wet” (Saturated) Soil Scenario

Plate 13. Injuries Requiring Hospitalization, Columbia County, Oregon, Cascadia Subduction Zone Magnitude 9.0 Earthquake, “Wet” (Saturated) Soil Conditions, Daytime (“2 PM”) Scenario

Plate 14. Injuries Requiring Hospitalization, Clark County, Washington, Cascadia Subduction Zone Magnitude 9.0 Earthquake, “Wet” (Saturated) Soil Conditions, Daytime (“2 PM”) Scenario