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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.

OVERVIEW: This study provides information about potential impacts to Columbia County in Oregon, and Clark County in Washington, from earthquakes, including a magnitude 9 Cascadia Subduction Zone earthquake. By using updated data, current subduction zone science and the latest mapping and modeling 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 help communities, the region, and the state better prepare for, respond to, and recover from major earthquakes.

  • Earthquake preparedness resources from PublicAlerts - the Emergency Info Hub for the Portland-Vancouver Region.
  • Phase 1 of the study was released in 2018: DOGAMI Open-File Report O-18-02, Earthquake regional impact analysis for Clackamas, Multnomah, and Washington counties, Oregon

Open-File Report O-20-01 downloads:

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:

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.


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, OR 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
Clark, WA 425,363 146,460 51.7 2.8–5.2 5%–10% 1.1–1.8 3.8–24.7 2.6–4.7 0.6–2.3
Columbia, OR 49,351 32,862 8.1 0.9–1.5 12%–18% 0.5–0.7 3.0–5.9 0.7–0.9 0.3–0.6
Multnomah, OR 735,334 255,577 114 13.3–20.5 12%–18% 7.7–10.4 9.7–37.5 11.4–16.7 2.8–5.6
Washington, OR 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 2,115,750 795,174 319 27.2–43.4 9%–14% 14.4–19.8 23.7–116 21.6–32.8 5.3–13.3
Portland Hills Fault Magnitude 6.8 Earthquake
Clackamas, OR 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
Clark, WA 425,363 146,460 51.7 2.6–5.7 5%–11% 0.9–1.8 2.8–29.0 1.9–4.5 0.6–2.7
Columbia, OR 49,351 32,862 8.1 0.7–1.2 8%–15% 0.3–0.5 1.7–5.0 0.4–0.7 0.2–0.4
Multnomah, OR 735,334 255,577 114 32.3–42.7 28%–37% 15.7–19.3 50.8–120 28.9–36.3 9.3–15.3
Washington, OR 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 2,115,750 795,174 319 63.8–90.3 20%–28% 27.8–36.2 100–291 50.2–68.2 16.7–32.2

+ 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:

GIS Data

Where to find:

RDPO_Earthquake_Impact_Analysis_Phase2.gdb

this report

RDPO_GroundMotion_GroundFailure_ColumbiaCo.gdb

this report

RDPO_GroundMotion_GroundFailure_ClarkCo.gdb

this report

RDPO_Earthquake_Impact_Analysis_Phase1.gdb

Open-File Report O-18-02 preview page

RDPO_GroundMotion_GroundFailure_Phase1.gdb

Open-File Report O-18-02 preview page

MXD Files

 

Ground Motion and Ground Deformation - CSZ and PHF.mxd

this report

Infrastructure Impacts.mxd

this report

Building Damage, Debris, Casualties, Displaced Population.mxd this report

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.

RDPO_Earthquake_Impact_Analysis_Phase2.gdb:
Feature Dataset Phase2:
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_ColumbiaCo.gdb
RDPO_GroundMotion_GroundFailure_ClarkCo.gdb
  Columbia County, OR Clark County, WA
   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 .xml
         CSZ_M9p0_pgv_site Site peak ground velocity, in centimeters per second. .xml .xml
         CSZ_M9p0_sa03_site Site spectral acceleration at 0.3 sec, in g (standard gravity). .xml .xml
         CSZ_M9p0_sa10_site Site spectral acceleration at 1.0 sec, in g (standard gravity). .xml .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 dry soil conditions, in centimeters. .xml .xml
         CSZ_M9p0_Prob_landslide_dry Probability of earthquake-induced landslide under dry soil conditions. In percent. .xml .xml
         CSZ_M9p0_PGD_landslide_wet Permanent ground deformation due to earthquake-induced landslide under wet (or saturated) soil conditions, in centimeters. .xml .xml
         CSZ_M9p0_Prob_landslide_wet Probability of earthquake-induced landslide under wet (or saturated) soil conditions. In percent. .xml .xml
         CSZ_M9p0_PGD_liquefaction_wet Permanent ground deformation due to liquefaction lateral spreading. Liquefaction assumes wet (or saturated) soil conditions, in centimeters. .xml .xml
         CSZ_M9p0_Prob_liquefaction_wet Probability of liquefaction under wet (or saturated) soil conditions. In percent. .xml .xml
   Synthetic Portland Hills fault magnitude 6.8 earthquake
      Site ground motion (rasters)
         PHF_M6p8_pga_site Site peak ground acceleration, in g (standard gravity). .xml .xml
         PHF_M6p8_pgv_site Site peak ground velocity, in centimeters per second. .xml .xml
        PHF_M6p8_sa03_site Site spectral acceleration at 0.3 sec, in g (standard gravity). .xml .xml
        PHF_M6p8_sa10_site Site spectral acceleration at 1.0 sec, in g (standard gravity). .xml .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 dry soil conditions, in centimeters. .xml .xml
         PHF_M6p8_Prob_landslide_dry Probability of earthquake-induced landslide under dry soil conditions. In percent. .xml .xml
         PHF_M6p8_PGD_landslide_wet Permanent ground deformation due to earthquake-induced landslide under wet (or saturated) soil conditions, in centimeters. .xml .xml
         PHF_M6p8_Prob_landslide_wet Probability of earthquake-induced landslide under wet (or saturated) soil conditions. In percent. .xml .xml
         PHF_M6p8_PGD_liquefaction_wet Permanent ground deformation due to liquefaction lateral spreading. Liquefaction assumes wet (or saturated) soil conditions, in centimeters. .xml .xml
         PHF_M6p8_Prob_liquefaction_wet Probability of liquefaction under wet (or saturated) soil conditions. In percent. .xml .xml

 

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