Lentis/Cascadia Earthquake Preparation
The Cascadia Subduction Zone is a convergent plate boundary (also called a fault line) located just off the coast of the Pacific Northwest. It sits at the bottom of the Pacific Ocean where the Juan de Fuca tectonic plate meets the North American tectonic plate. The fault line spans 700 miles, starting in Northern California's Cape Mendocino, running along the Cascade Mountains, and ending in Canada's Vancouver Island. Given its significant length, the Cascadia subduction zone can produce a powerful megathrust earthquake upon rupturing. In this Lentis casebook chapter, we examine the risks of the Cascadia Subduction Zone and existing efforts to prepare for a possible Cascadia earthquake. We also compare these preparation efforts in the Pacific Northwest to those in Japan (which experiences more frequent earthquakes) and discuss generalizable conclusions that can be drawn.
Risk from the Cascadia Subduction Zone
Researchers predict that the Cascadia Subduction Zone can produce up to a magnitude 9.2 earthquake. This would cause much greater damage compared to past Pacific Northwest earthquakes. Unlike locations like Japan and Alaska, which experience large earthquakes almost annually, the Pacific Northwest might expect to see a magnitude 8 earthquake once every 240 years and a magnitude 9 earthquake once every 500 years approximately. Residents of Oregon, Washington, and British Columbia must prepare for significant seismic risk.
A major Cascadia earthquake could trigger a tsunami that would strike the coasts of Oregon, Washington, and British Columbia within 30 minutes of the initial earthquake. Current estimates forecast an approximately 30-foot wave height after a magnitude 9.0 Cascadia earthquake. The at-risk area contains 94,500 residents and could include many additional beach visitors. It is difficult to educate these tourists on tsunami evacuation routes. Key evacuation roads would be damaged during the earthquake, making tsunami evacuation difficult. Because the tsunami threat was only discovered recently, many towns were permitted to build schools and hospitals along the coast until 1995.
After such an event, it will take about three years for hospitals and sewage systems to be restored along the coast. Additionally, FEMA expects that it will need to provide shelter for a million displaced residents as well as food and water for two and half million. Between the earthquake and tsunami, nearly thirteen thousand people would die, and twenty-seven thousand would be injured.
The risks of the Cascadia subduction zone only became known in the 1980s. The fault line had never ruptured or caused an earthquake in recorded history, so it was thought to be benign. However, in 1986, a researcher found proof that the Cascadia fault line had previously ruptured. Further research revealed that the rupture occurred in January 1700, caused the largest earthquake in North American continental history, and triggered a tsunami that crossed the Pacific in ten hours and hit the Japanese coast. According to Chris Goldfinger, a professor of geophysics at Oregon State University, "the more we learn about it, the less we like it, because it is turning out to be a big hazard as well.
Earthquake Preparation in the Pacific Northwest
The Pacific Northwest lags in preparation behind other earthquake-prone areas. Cities such as Seattle and Portland expanded rapidly during the early 1900s when people were still unaware of any earthquake risk. The first earthquake construction regulations in Seattle and Portland were not implemented until the 1970s. While new buildings have explicit requirements, no existing laws mandate retrofitting of older buildings.
Seattle initially attempted to require retrofits in the 1970s. Because most Seattle residents had not experienced an earthquake while living there, they did not view earthquake preparation as a reasonable use of funds. Proactively retrofitting buildings could prevent financial loss and casualties in the long run. However, retrofitting costs are significant, generally costing between $20 to $60 per square foot. In many apartment buildings, landlords do not have the funds necessary for retrofits. Less than 15% of Seattle’s old URM buildings have been retrofitted.
Vancouver’s infrastructure is also not adequately prepared to withstand a major earthquake. City officials estimate that 50 of the city’s 116 schools are at a particularly high risk of collapse during an earthquake. Only six of the city’s twenty firehouses meet current building code; fighting the inevitable fires after the earthquake will challenging. Similar to Seattle, securing public funds for Vancouver’s retrofitting process has been slow and difficult.
Preparation also involves educating Pacific Northwest residents. In addition to building collapse, indoor home items can be dangerous in an earthquake (e.g. falling furniture, breaking glass). Although seismically securing items inside one's home is a simple task, few residents have adequately prepared. Individuals must also stock enough food and water to last 7-10 days. Due to the likely destruction of many bridges and highways, parts of the Olympic Peninsula in Washington could become isolated. A full infrastructure recovery could take years, so it is critical that residents are able to survive independently in the first few weeks after the earthquake.
An earthquake warning system would be useful. Because the earthquake would occur at sea, hundreds of miles from major cities, it could be possible to give millions of citizens advance warning. While funding for research and implementation of a warning system has progressed, public education is still lacking. The earthquake early warning system is only useful if the public knows how to respond appropriately (e.g. turning off the stove, ducking under a table).
Tsunami Preparation in the Pacific Northwest
Moving to higher ground is the surest way to tsunami survival. Although evacuation routes are marked in the Pacific Northwest, damage to infrastructure from the earthquake will complicate evacuation. Thus, the region has started building various tsunami shelters, including vertical tsunami towers. Some are buildings where people can gather on the roof. Others are simple towers consisting of an elevated plane and stairs. These can include sea walls and embankments to lessen the impact of waves on the structures. There are various designs, but all are engineered to withstand an earthquake and the tsunami likely following. People gather in these elevated structures that are designed to be above the tsunami flood level.
Sirens have been in use in the Pacific Northwest but are being replaced in some areas by other communication methods like phone, radio, and social media. Unlike sirens, these methods can relay details regarding the size of the threat. This helps residents prepare appropriately, reducing over- or under-preparation.
Some schools in the area have regular tsunami drills. These may not be sufficient as some only involve relocating to the top floor of the school. For this to be a viable strategy, the building must withstand the forces of both the earthquake and tsunami. The top floor must also be above the wave height, which could be up to 40 feet.
Earthquake and Tsunami Preparation in Japan
Japan has a sophisticated earthquake warning system, including numerous seismographs throughout the country. These can detect early tremors and issue a warning to citizens, giving them up to two minutes to perform small but lifesaving tasks. Advanced warning can be integral to survival, but turning off the gas does little good if the building collapses. Much of Japan's superior preparedness stems from measures beyond advanced warning. In Japan, earthquake-oriented building codes were first introduced in town areas in the 1920s and were adopted nation-wide in the 1950s. Since then, numerous changes have been implemented, including greater preparedness for larger earthquakes, ground testing prior to new construction, increased inspections during construction, and retrofitting buildings to meet earthquake codes. Japan was instituting mandatory building regulations before the Cascadia fault line had even been discovered.
Multiple levels of building preparedness exist in Japan. The most basic level is required and involves thick bases and walls. More advanced preparation is designed to not only prevent collapse, but also minimize shaking and damage. At the middle level, dampers are used in the foundation to reduce shaking and absorb energy. At the top level, the base of the building is isolated from the surrounding land, further reducing shaking intensity. Generally, greater reductions in earthquake risk incur greater costs. However, apartments and offices use earthquake preparedness to market themselves to the public, increasing technology adoption.
Education plays a large role in the preparedness of Japan. Earthquake drills allow people to practice safe strategies in the event of a large earthquake. Such drills are also held in schools, where the practice has proven invaluable. In the case of the March 2011 earthquake, students in a school reacted appropriately even with a disabled communication system and no instruction. These students gathered in the appropriate place and then evacuated to higher ground as a precaution.
Japan has a tsunami warning system, though less forewarning is possible for tsunamis than for earthquakes. Seawalls, and tsunami shelters also exist in coastal areas. Education remains a large part of tsunami preparedness in Japan; one town tests tsunami warning sirens daily and marks evacuation routes in multiple languages. The students mentioned above knew the evacuation route and multiple shelter sites. Their reflexive actions saved not only their lives, but also those of others who followed.
History of Earthquakes
The high frequency of earthquakes in Japan is due to its location at the intersection of several tectonic plates and along the famed "Ring of Fire." Japanese pagodas attest to the longstanding frequency of earthquakes in Japan. These ancient wooden structures rarely experience damage during earthquakes. Mobile joints and base isolation are just two of many features that make this possible. This is a heritage of earthquake preparedness. Unlike in the Pacific Northwest, earthquakes are not a vague—and sometimes unknown—threat. They are a part of daily life in Japan, and Japan has the technologies and systems in place to address them accordingly.
From the Cascadia earthquake preparation case and its parallels, we can draw the following generalizable conclusions:
- Problems get worse if left untreated
- It is better to fix things early or get it right the first time
- Don't wait until catastrophe to fix a known problem.
Cities near the Cascadia subduction zone like Seattle, Portland, and Vancouver were developed for over a century without knowledge of the seismic hazard. Earthquake preparedness is more difficult now that they have already been heavily developed under the assumption that an earthquake was not a pressing risk. Designing buildings and policies to address the risk of an earthquake ahead of time would have been more effective and efficient compared to current efforts to retrofit solutions. Despite this difficulty and the uncertainty over when the Cascadia fault line will rupture, proactive action is critical. In May 2015, Scott Kearny, an engineering professor at Ohio State University, testified about the Cascadia fault line before a House of Representatives subcommittee: “It will take 50 years for us to prepare for this impending earthquake. . . . The time to act is before you have the earthquake. Everybody needs to take some responsibility and start preparing now.”
Other cases in urban planning follow a similar narrative. For example, when New Orleans was founded, people were unaware of its high susceptibility to hurricanes, flooding, and global warming. Prior to Hurricane Katrina in 2001, New Orleans's rapid development outpaced its hurricane preparedness efforts and eroded existing natural defenses against hurricanes. New Orleans passed an enhanced stormwater drainage system in 1996 but did not prioritize its implementation. Construction only began after Hurricane Katrina demonstrated the massive risk posed by hurricanes. Strong parallels can also be seen with Hurricane Harvey in Houston, San Francisco's Millennium Tower, and Cape Coral in Florida. Further examination of these cases may allow for additional insight on how these cases can be generalized and how they might differ.
These generalizable conclusions apply to other disciplines outside of urban planning as well. In computer science, there is the concept of Boehm's curve, which explains that programming bugs become more costly to fix later in the software development process. In medicine, it is important to treat cancer early on, before it metastasizes and spreads to other parts of the body.
- Boehm, B. (1981). Software Engineering Economics.Prentice-Hall, ISBN 0-13-822122-7.