Employment in Oregon’s Tsunami Inundation Zones

by Guy Tauer

November 8, 2019

Oregon’s Department of Geology and Mineral Industries (DOGMI) updated and released new tsunami inundation zone maps based on seven different scenarios back in about 2014. This updated analysis looks at the recent history of other large earthquakes, and models possible employment impacts along Oregon’s Coast if a large earthquake was to occur, using these updated maps and 2018 geocoded payroll employment data. A worst-case scenario shows that nearly 35,000 jobs along Oregon’s’ coast lie within the boundary of the 9.1or greater tsunami inundation zone back in 2012. By 2018, there were about 39,500 jobs, annual average, within the inundation zone if the largest predicted Cascadia earthquake occurs.

It was recently the 55th anniversary of the Good Friday megathrust subduction zone earthquake centered about 75 miles east of Anchorage, AK. This magnitude 9.2 temblor resulted in a tsunami that claimed the lives of115 people including four Oregonians. Oregon sits very close to the Cascadia Subduction Zone. Just off the Oregon Coast one titanic tectonic plate of the earth’s crust moves under, or “sub ducts” under the larger North American plate, centimeters per year and gradually building immense pressure that is periodically released during very large earthquakes.

Pacific Tsunamis

The devastating 2011 Tohoku earthquake and tsunami, which translates to “harbor wave” that struck Japan provided a wake-up call to coastal Oregon. Many government agencies are involved in preparing the Oregon coast to deal with a major tsunami. Analyzing employment in Oregon’s tsunami inundation zones can help those efforts.

The 9.0 magnitude Tohoku earthquake was the most powerful ever to hit Japan and the fifth-most powerful ever measured. Tsunamis reached 133 feet in height and traveled miles inland in places. Japan’s government counted 15,884 people dead and 2,633 missing. The World Bank estimated the economic cost at $235 billion, making it the most expensive natural disaster in history.

The 2004 Indian Ocean earthquake, also known as the Sumatra-Andaman earthquake, spawned a series of tsunamis that killed more than 200,000 people and destroyed coastal communities. It was a magnitude 9.0 earthquake that produced tsunami waves traveling up to 500 miles per hour and reaching 40 feet in height when they broke.

Oregon has and will eventually again be struck by similar tsunamis. The Department of Earth and Space Sciences at the University of Washington studies geologic hazards in the Pacific Northwest. They explain that the major source for a local tsunami is the Cascadia Subduction Zone, a very long sloping fault that stretches from mid-Vancouver Island to Northern California and lies off Oregon’s coast. Subduction zone earthquakes are the largest earthquakes in the world, and can exceed magnitude 9.0. Recent research suggests that major tsunamis have struck the Oregon coast on a regular basis. Current estimates put potential damage at $70 billion, with 100 bridges collapsed, power lines toppled and coastal communities isolated for days if not weeks. Great earthquakes may have occurred at least seven times in the last 3,500 years, suggesting a return time of 400 to 600 years. Through geologic records captured in sand deposits and other indicators, these mega-quakes occur in clusters of 3-5 events spread over several hundred years. The last tsunami caused by a local or near shore magnitude 9.0 earthquake occurred on Jan. 26, 1700, wiping out Oregon tribal villages in low-lying coastal estuaries. This quake was the fourth in the current cluster. Was that the end of this group of subduction quakes in the cluster, or is the fifth earthquake in the current cluster poised to strike at any moment? Scientists wish there was a way to know, but there is not. A local tsunami could come onshore within 15 to 20 minutes after the earthquake.

Tsunamis occur surprisingly often along the west coast of the United States but most are small and many have their source in distant areas. James Lander and other researchers at the University of Colorado catalogued west coast tsunamis from 1806 to 1992. They counted 115 events that were tsunamis or possible tsunamis, or an average of an event about every year and a half. Wave heights were commonly a half foot to three feet and little if any damage usually was done.

The National Oceanic and Atmospheric Administration (NOAA) provides records of tsunamis along the west coast. In 1930 a magnitude 5.2 earthquake and landslide struck southern California and a man drowned in the resulting 10 foot wave at Redondo Beach. On April 1, 1946, an earthquake of magnitude 7.4 occurred in an area of the Aleutian Trench. The tsunami destroyed the nearby U.S. Coast Guard lighthouse, surging over the costal cliff to a height of 42 m (135 ft.) above sea level and killing the five members of the lighthouse crew. The same tsunami caused extensive destruction along the shorelines of the Hawaiian Islands, especially at Hilo, on the big island of Hawaii, where the city's entire waterfront was destroyed. Wave heights across the Islands reached an estimated maximum of 55 feet, 36 feet and 33 feet on Hawaii, Oahu, and Maui, respectively. The tsunami inundated areas up to a half a mile inland in some locations. An additional 159 people were killed in Hawaii and another person drowned in the ten-foot waves that struck Santa Cruz, California.

Less spectacular tsunamis are more common. NOAA records show that although the east coast of the United States was the source for only four tsunamis from 2000 through 2014, the west coast was struck by 21 tsunamis during the same time period. Only three of the events generated waves of three feet or more.

On March 9, 2014, a 6.9 magnitude quake struck near the lower end of the Cascadia Subduction Zone, off the Coast of Eureka, California. Just another reminder of the lurking danger that we cannot see looking out toward the west.

The most disastrous recent tsunami to hit the west coast was caused by the great Alaskan, or the Good Friday earthquake of 1964, the largest earthquake in North America. Tsunamis were recorded throughout the Pacific. The largest wave height (about 70 feet) for this tsunami was reported at Shoup Bay, Alaska. Alaska had 106 deaths and $84 million in property damage, Oregon had $0.7 million in property damage, with much of the damage away from the coast where rivers overflowed, and California had13 deaths and $10 million damage.

Typical wave heights from major tsunamis occurring in the Pacific over the last 80 years have been 20 feet to 45 feet at the shoreline. Oregon’s Department of Geology and Mineral Industries (DOGMI) recently updated and released new tsunami inundation zone maps based on seven different scenarios. They modeled the equivalent of the 1964 Alaskan earthquake, a maximum magnitude estimated from an Alaskan-originated earthquake- distant shore events. DOGMI also model five different Cascadia Subduction Earthquake scenarios. Like clothing sizes, they labeled these quakes and accompanying tsunami inundation zones S, M, L, XL, and XXL.

Back in 2007, researchers also modeled employment impacts of a Cascadia earthquake and tsunami scenario. From the report Variations in City Exposure and Sensitivity to Tsunami Hazards in Oregon, U.S. Geological Survey, Nate Wood “Results indicate that there were1,829 businesses with 14,857 employees that generate over $1.9 billion in sales volume in the Oregon tsunami-inundation zone, representing seven percent of all businesses, six percent of employees, and five percent of generated sales volume in the seven coastal counties.”

Limitations and recommendations from the Variations in City Exposure and Sensitivity to Tsunami Hazards in Oregon, (2007) U.S. Geological Survey, Nate Wood analysis noted: “The number and types of employees in the study area (excluding seasonal labor) were determined using the 2005 InfoUSA Employer Database. Because no fieldwork was conducted to verify business locations, results based on the Employer Database throughout this report should be considered first approximations and developed to generate discussions for additional, more-detailed studies.”

The Oregon Employment Department has geospatial data about where businesses and employment are located within these various- sized tsunami inundation zones. By overlaying the geocoded employment data on these new tsunami zone maps, we can analyze from an employment perspective some of the potential impacts of future large earthquakes. It is also important to note that this analysis looks at just the direct employment impacts, based on business location. There may be substantial ripple effects as the supply chain disruption for inputs to business production, as well as severing of transportation corridors, sales or customer disruptions, and workers unable maintain normal commutes after such a wide-ranging catastrophic event.

High percentages of employees in tsunami-inundation zone represent economic fragility for a community, as unemployment could increase dramatically overnight if a tsunami injures or kills employees or if it damages or destroys businesses. Even if a business escapes damage or physical disruption due to an extreme event, it may still experience significant customer and revenue loss if the neighborhood and other businesses around it are damaged, leading customers to shop elsewhere. Neighborhood effects have been found to be especially important for retailers that rely on foot traffic (Chang and Falit-Baiamonte, 2002), a potentially significant issue for tourist-related retail and food services within Oregon coastal communities. Therefore, knowing where there are high numbers and percentages of employees can help identify potential economic recovery issues.

One ongoing study that includes such ripple effects is begin done by an interdisciplinary team of economists and engineers at Oregon State University. They are building a tsunami vulnerability assessment tool for Clatsop County. This model estimates the l potential physical damage and from tsunami and the economic damage in both the inundation zone directly hit by the tsunami, and in the rest of the county that is economically interconnected. It does this by integrating an engineering model for estimating community-scale building damage with a regional economic impact model that links the inundation zone economy with the economy of the rest of the county.

Coast-Wide Impacts Under Various Tsunami Scenarios

Late in 2013, the Oregon Department of Geology and Mineral Industries released updated tsunami inundation maps, based on two distant shore (Alaskan, AK) and five near shore Cascadia Subduction Zone (CZ) earthquakes. For more details and to read the study Tsunami Inundation Zone Scenarios for Oregon, Vicki S. McConnell, see DOGMI website oregongeology.org.

The “AK ’64” is the modeled inundation zone from the Good Friday quake of 1964. AK Max represents the largest tsunami believed to be able to be generated from an earthquake originating from tectonic plate subduction in Alaska region. The other five (CZ) modeled tsunami scenarios represent various wave heights generated by various magnitude Cascadia earthquakes. Many factors are involved that determine tsunami wave heights including how much of the fault ruptures, how much ground upheaval or displacement occurs, the duration of the ground shaking, how high the tide is during an earthquake, among others. If the Great Alaskan quake had occurred in 2018, these modeled maps show there would have been 2,755 payroll jobs within the resulting tsunami inundation zone. These types of quakes and resulting tsunamis are considered the most survivable, due to the many hours of warning most those in harm’s way would have to move to higher ground, and the lack of major impact to roads, bridges, utilities that would occur from a distant shore event.
A near-shore quake would have both higher estimated wave heights, further inland reach of destructive waters, coupled with less time to evacuate to safer ground. Under these near-shore earthquake scenarios, current tsunami maps overlaid with geospatial data on businesses and employment show a range from 12,408 to 39,539 annual average employment within these five tsunami models. Employment impacts, as well as total potential for death or injury, would vary greatly throughout the year. If the next big one struck on January 26, as the last great Cascadia earthquake did, far fewer employees, residents and visitors would likely be on Oregon’s Coast than on July 26. Under the “CZXXL” worst-case model, payroll employment in the tsunami inundation zone varied between 36,700 in January to about 41,200 in August 2018.

Impact by County, Community, and Industry

Coastal geography varies greatly in Oregon. Some communities sit atop bluffs, relatively safer and better positioned to escape from an incoming wall of water. Others face the reality that there is little elevation gain between the normally placid Pacific and hundreds of yards if not miles inland. For the rest of this analysis, we will just look at the worst case scenarios, a Cascadia Subduction earthquake of the largest magnitude modeled by DOGMI. In this case, all Oregon counties adjacent to the ocean would be impacted. While Lane (0.5%) and Douglas (2.1%) counties have little of their total employment in this zone, coastal communities within those counties are no doubt at risk. The bulk of Oregon’s coastal counties have between 32 percent and 51 percent of their payroll employment within the borders of the worst-case tsunami inundation zones. Most at risk is Clatsop County, with nearly 70 percent of its 2018 annual average employment in this zone.
Potential impact by industry shows the leisure and hospitality industry at the greatest risk from a Cascadia earthquake-generated tsunami. Over 70 percent of coastal county Leisure and hospitality employment is found within the largest Cascadia expected inundation zone. For this analysis, Lane and Douglas counties were excluded, as the non-coastal employment centers along I-5, Roseburg, and Eugene would skew these data. Wholesale trade, manufacturing, retail trade, and financial activities have over one-half of total coastal county payroll employment within the CZXXL inundation zone. Overall, about one-half of the five-county (Coos, Curry, Clatsop, Lincoln and Tillamook) region’s payroll employment is within the worst-case scenario inundation zone. In addition to having the highest percent of employment, leisure and hospitality also had the greatest number of jobs (12,407) with the CZXXL zone. Retail trade (5,608), educational and health services (5,646), and manufacturing (5,608) also had significant payroll employment at risk in the coastal county areas. Planners and preparedness officials may also want to heed specific at risk populations served by these industries, such as students, seniors, and those with physical mobility issues. For example, employment in K-12 schools and community colleges within the inundation zones are only a fraction of the total served by those facilities, if such an event was to occur during school hours.
Digging deeper below county-level information shows the potential community and city potential impacts. Under this worst-case, 9.1 or above magnitude quake and resulting tsunami, these new maps point to potential near total employment impact with the inundation zone. Gold Beach, Seaside, Pacific City, Yachats, Rockaway, and Cannon Beach have over 90 percent of their employment within the CZXXL inundation zones. Those communities should be at the forefront of planning for the unthinkable.
Planning for a Potentially Bumpy and Wet Future

If you have not previously thought about the potential for a large earthquake until now, perhaps this analysis has opened your eyes to just some of the wide-ranging effects such an event could have. If just one person takes action to prepare and plan for what may happen any day, then this article has served a purpose. Many projects are required to plan for these unthinkable catastrophes. Although many existing employers face considerable risk from tsunamis, new businesses are often incorporating tsunami risks into their business planning. Jordan Cove is a proposed liquefied natural gas (LNG) export facility in the north spit of Coos Bay. The project will be located within a seismic hazard and tsunami inundation zone.

New technology has enabled state geologists to finesse geography, geology, oceanography and seismology data and mesh it with that learned from Japan’s 2011 earthquake and subsequent tsunami to more accurately determine how bad “The Big One” here will really be.

“In 1995, we were working with maps from the ’60s, with 40-foot contour lines,” said Ian Madin, chief scientist with DOGAMI. “There was a lot of estimation. This was my best guess in 1995 of what a magnitude 9.0 would do to the Oregon Coast. “But that was horrible modeling, using ancient technology,” he added.

Subduction zone earthquakes and resulting tsunami events in Sumatra, Chile, and Japan just in the past decade or two are the wake-up alarms that all Oregonians should be heeding, especially those living in coastal areas. Are we hitting the snooze button one too many times in Oregon?


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