DOGAMI Open-File Report Series

[Go back] | Publications Center | DOGAMI Home

Publication Preview

Open-File Report O-18-02, Earthquake regional impact analysis for Clackamas, Multnomah, and Washington counties, Oregon
by John M. Bauer, William J. Burns, and Ian P. Madin; 90 p. report, including 16 tabloid sized map plates, two Esri geodatabases with internal metadata, external metadata in .xml format.

OVERVIEW: This study provides information about potential impacts to Clackamas, Multnomah, and Washington counties from earthquakes, including a magnitude 9 Cascadia Subduction Zone earthquake. By using updated data, current subduction zone science and the latest mapping and modelling techniques, the study greatly improves understanding of potential earthquake impacts for the region. The study’s estimates of injuries and fatalities, building damages, and other impacts helps communities, the region, and the state better prepare for, respond to, and recover from major earthquakes.

Report Downloads:

 

EXECUTIVE SUMMARY
This report was prepared for the Regional Disaster Preparedness Organization (RDPO), with funding provided by the Urban Areas Security Initiative Program. The report provides damage and casualty estimates to buildings, people, and key infrastructure sectors resulting from a major earthquake in the Portland metropolitan region by using updated local geologic information and recent advances in 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). Phase 2 will apply the same methods in Columbia County, Oregon, and Clark County, Washington.

The Portland metropolitan region is vulnerable to regional and local earthquakes. We modeled damage for two earthquake scenarios: a 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 little 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:

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. A separately published report describes the geologic mapping updates for the three-county area, consisting of National Earthquake Hazards Reduction Program (NEHRP) soil types, and earthquake-induced landslide and liquefaction susceptibility.

A Cascadia Subduction Zone (CSZ) magnitude 9.0 earthquake will have a severe impact on the three-county area, with building repair costs amounting to 23.5 and 36.7 (9% and 14% of the total building replacement cost, Table 1-1). 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 thousands or low tens of thousands. The earthquake will generate several millions of tons of debris from damaged buildings. Damage and casualty estimates resulting from a magnitude 6.8 Portland Hills fault earthquake are more than twice compared to a CSZ earthquake, primarily because of the Portland Hills fault location below densely populated and heavily developed areas (Table 1-1). However, the likelihood of a Portland Hills fault earthquake is considerably less than a Cascadia Subduction Zone earthquake.

Table 1-1. Loss estimate summary for two earthquake scenarios in the Portland metropolitan area. Lower value: dry soil conditions. Upper value: saturated soil conditions.


County
U.S. Census Population Estimate (2010) Number
of Buildings
Building Value
($ Billion)
Building Repair Cost
($ Billion)
Building Loss
Ratio
Debris (Millions
of Tons)
Long-Term Displaced Population (Thousands) Total Casualties+
Daytime Scenario (Thousands) Nighttime Scenario (Thousands)
Cascadia Subduction Zone Magnitude 9.0 Earthquake
Clackamas 375,992 179,164 62.4 3.2–4.6 5%–7% 1.7–2.1 1.9–10.1 2.0–2.8 0.5–1.1
Multnomah 735,334 255,577 114.0 13.3–20.5 12%–18%   7.7–10.4 9.7–37.5 11.4–16.7 2.8–5.6
Washington 529,710 181,111 82.7  7.0–11.6 8%–14% 3.4–4.8 5.2–37.7 4.9–7.7 1.1–3.7
Total 1,641,036 615,852 259.1 23.5–36.7 9%–14% 12.8–17.3 16.8–85.3 18.3–27.2 4.4–10.4
Portland Hills Fault Magnitude 6.8 Earthquake
Clackamas 375,992 179,164 62.4 12.9–16.4 21%–26% 4.9–6.0 25.2–50.8 8.9–10.9 3.3–5.2
Multnomah 735,334 255,577 114.0 32.3–42.7 28%–37% 15.7–19.3 50.8–120 28.9–36.3 9.3–15.3
Washington 529,710 181,111 82.7 15.4–24.3 19%–29% 6.0–8.6 19.6–86.0 10.0–15.8 3.2–8.5
Total 1,641,036 615,852 259.1 60.6–83.4 23%–32% 26.6–33.9 95.6–257 47.8–63.0 15.8–29.0

+ 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.

 

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 two ArcGIS version 10.1 file geodatabases.
Earthquake loss estimates and impact assessment data are contained in RDPO_‌Earthquake_‌Impact_‌Analysis_Phase1.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_Phase1.gdb.

RDPO_Earthquake_Impact_Analysis_Phase1.gdb:
Feature Dataset Phase1:
Building_Footprints Outlines of buildings and other non-building structures. .xml
Electrical_Transmission_Structures Pointfile containing locations of electrical transmission poles and towers, and an estimate of permanent ground deformation at the location for all four earthquake scenarios. .xml
Emergency_Transportation_Routes

Buffered and segmented version of the Metro area Emergency Transportation Routes, and a categorization, per segment, of the impact of permanent ground deformation on the segment, for all four earthquake scenarios.

.xml
Jurisdictions Cities, villages, hamlets, and unincorporated areas, and summary statistics for number of buildings, square footage, replacement cost, and population estimates. Contains Jurisdiction attribute for joining to loss estimate tables. .xml
Neighborhood_Units Neighborhood units (876 total), and summary statistics for number of buildings, square footage, replacement cost, and population estimates. Contains NUID attribute for joining to loss estimate tables. .xml
Population_and_Building_Density 20-acre hexagonal grid with summary statistics for number of buildings, number of residential buildings, and permanent residents per hexagonal cell. All cells contain at least one building. .xml
Tables with building loss, casualty, and displaced population estimates for a given scenario
   Loss estimates by jurisdiction
      Tables can be joined to the Jurisdictions feature class using Jurisdiction attribute
      Loss_Jurisdiction_CSZ_M9p0_dry Scenario: Cascadia Subduction Zone M 9.0, “dry” soil conditions .xml
      Loss_Jurisdiction_CSZ_M9p0_wet Scenario: Cascadia Subduction Zone M 9.0, “wet” (saturated) soil conditions .xml
      Loss_Jurisdiction_PHF_M6p8_dry Scenario: Portland Hills fault M 6.8, “dry” soil conditions .xml
      Loss_Jurisdiction_PHF_M6p8_wet Scenario: Portland Hills fault M 6.8, “wet” (saturated) soil conditions .xml
   Loss estimates by neighborhood unit
      Tables can be joined to the Neighborhood_Units feature class using the NUID attribute
      Loss_Neighborhood_Unit_CSZ_M9p0_dry Scenario: Cascadia Subduction Zone M 9.0, “dry” soil conditions .xml
      Loss_Neighborhood_Unit_CSZ_M9p0_wet Scenario: Cascadia Subduction Zone M 9.0, “wet” (saturated) soil conditions .xml
      Loss_Neighborhood_Unit_PHF_M6p8_dry Scenario: Portland Hills fault M 6.8, “dry” soil conditions .xml
      Loss_Neighborhood_Unit_PHF_M6p8_wet Scenario: Portland Hills fault M 6.8, “wet” (saturated) soil conditions .xml

 


RDPO_GroundMotion_GroundFailure_Phase1.gdb:
   Synthetic Cascadia Subduction Zone magnitude 9.0 earthquake
      Site ground motion (rasters)
         CSZ_M9p0_pga_site Site peak ground acceleration, in g (standard gravity). .xml
         CSZ_M9p0_pgv_site Site peak ground velocity, in centimeters per second. .xml
         CSZ_M9p0_sa03_site Site spectral acceleration at 0.3 sec, in g (standard gravity). .xml
         CSZ_M9p0_sa10_site Site spectral acceleration at 1.0 sec, in g (standard gravity). .xml
      Permanent Ground Deformation (PGD) (rasters)
         Each PGD raster is accompanied with a probability (Prob) raster
         CSZ_M9p0_PGD_landslide_dry Permanent ground deformation due to earthquake-induced landslide under wet (or saturated) soil conditions, in centimeters. .xml
         CSZ_M9p0_Prob_landslide_dry Probability of earthquake-induced landslide under wet (or saturated) soil conditions. In percent. .xml
         CSZ_M9p0_PGD_landslide_wet Permanent ground deformation due to earthquake-induced landslide under wet (or saturated) soil conditions, in centimeters. .xml
         CSZ_M9p0_Prob_landslide_wet Probability of earthquake-induced landslide under wet (or saturated) soil conditions. In percent. .xml
         CSZ_M9p0_PGD_liquefaction_wet Permanent ground deformation due to liquefaction lateral spreading. Liquefaction assumes wet (or saturated) soil conditions, in centimeters. .xml
         CSZ_M9p0_Prob_liquefaction_wet Probability of liquefaction under wet (or saturated) soil conditions. In percent. .xml
   Synthetic Portland Hills fault magnitude 6.8 earthquake
      Bedrock ground motion
         PHF_M6p8_bedrock_groundmotion Pointfile with descriptors of bedrock ground motion (pga, pgv, sa03, sa10) .xml
      Site ground motion (rasters)
         PHF_M6p8_pga_site Site peak ground acceleration, in g (standard gravity). .xml
         PHF_M6p8_pgv_site Site peak ground velocity, in centimeters per second. .xml
        PHF_M6p8_sa03_site Site spectral acceleration at 0.3 sec, in g (standard gravity). .xml
        PHF_M6p8_sa10_site Site spectral acceleration at 1.0 sec, in g (standard gravity). .xml
      Permanent Ground Deformation (PGD) (rasters)
         Each PGD raster is accompanied with a probability (Prob) raster
         PHF_M6p8_PGD_landslide_dry Permanent ground deformation due to earthquake-induced landslide under wet (or saturated) soil conditions, in centimeters. .xml
         PHF_M6p8_Prob_landslide_dry Probability of earthquake-induced landslide under wet (or saturated) soil conditions. In percent. .xml
         PHF_M6p8_PGD_landslide_wet Permanent ground deformation due to earthquake-induced landslide under wet (or saturated) soil conditions, in centimeters. .xml
         PHF_M6p8_Prob_landslide_wet Probability of earthquake-induced landslide under wet (or saturated) soil conditions. In percent. .xml
         PHF_M6p8_PGD_liquefaction_wet Permanent ground deformation due to liquefaction lateral spreading. Liquefaction assumes wet (or saturated) soil conditions, in centimeters. .xml
         PHF_M6p8_Prob_liquefaction_wet Probability of liquefaction under wet (or saturated) soil conditions. In percent. .xml

 

PLATES (georeferenced PDFs, 11 x 17 inches each)

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


Plate 2. Population Density and Building Location – Multnomah County, Oregon


Plate 3. Population Density and Building Location – Washington County, Oregon


Plate 4. Site Peak Ground Acceleration, Simulated Cascadia Subduction Zone Magnitude 9.0 Earthquake


Plate 5. Site Peak Ground Acceleration, Simulated Portland Hills Fault Magnitude 6.8 Earthquake


Plate 6. Perceived Shaking and Damage Potential, Simulated Cascadia Subduction Zone Magnitude 9.0 Earthquake


Plate 7. Perceived Shaking and Damage Potential, Simulated Portland Hills Fault Magnitude 6.8 Earthquake


Plate 8. 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 9. Probability of Earthquake-Induced Landslides or Liquefaction, Cascadia Subduction Zone Magnitude 9.0 Earthquake, “Wet” (Saturated) Soil Scenario


Plate 10. Potential Impact of Permanent Ground Deformation to Metro Emergency Transportation Route Segments, Cascadia Subduction Zone Magnitude 9.0 Earthquake, “Wet” (Saturated) Soil Scenario


Plate 11. Potential Impact of Permanent Ground Deformation to Metro Emergency Transportation Route Segments, Cascadia Subduction Zone Magnitude 9.0 Earthquake, “Dry” Soil Scenario


Plate 12. Potential Impact of Permanent Ground Deformation to Metro Emergency Transportation Routes, Cascadia Subduction Zone Magnitude 9.0 Earthquake, “Wet” (Saturated) Soil Scenario


Plate 13. Potential Impact of Permanent Ground Deformation to Electrical Transmission Structures, Cascadia Subduction Zone Magnitude 9.0 Earthquake, “Wet” (Saturated) Soil Scenario


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


Plate 15. Injuries Requiring Hospitalization, Multnomah County, Oregon, Cascadia Subduction Zone Magnitude 9.0 Earthquake, “Wet” (Saturated) Soil Conditions, Daytime (“2 PM”) Scenario


Plate 16. Injuries Requiring Hospitalization, Washington County, Oregon, Cascadia Subduction Zone Magnitude 9.0 Earthquake, “Wet” (Saturated) Soil Conditions, Daytime (“2 PM”) Scenario