The coastal town of Westport, Washington, sits on a narrow peninsula of sand where the ground rises only a few feet above sea level. In the event of a major earthquake off the Pacific Northwest coast, officials estimate that a tsunami could send water 30 to 40 feet high into the town within 15 to 30 minutes of the shaking starting. Because the roads leading out of town are expected to be damaged or destroyed during the quake itself, evacuation by car is not considered a reliable option for most residents.
To address this risk, Westport became the first community in the United States to build a vertical evacuation structure designed for tsunamis. The town has constructed reinforced concrete platforms on tall supports that are meant to withstand both the earthquake and the force of the incoming water. Rather than attempting to outrun a wave, the strategy is to climb to safety above the flood level.
The threat comes from the Cascadia subduction zone, a fault line roughly 700 miles long that runs from northern California to Vancouver Island. In this region, the Juan de Fuca plate is slowly pushing beneath the North American plate. The pressure between the plates builds over time, and when it releases, it produces a very large earthquake and a tsunami.
The last full rupture of the Cascadia fault occurred on January 26, 1700. Scientists established the date with the help of records kept in Japan. On that night, a large tsunami struck the Japanese coast without any local earthquake. Japanese officials of the time documented the flooding in detail, puzzled by the source of the wave since the ground had not shaken. Much later, researchers determined that the wave had traveled across the Pacific from the Pacific Northwest. Calculating the travel time across the ocean pointed to the evening of January 26, 1700, giving historians a precise date for an earthquake that occurred before written records existed in the region.
Oral histories from Native American tribes along the coast, including the Quileute, the Hoh, and the Yurok, also describe events consistent with a major earthquake and tsunami. Some stories tell of the ground shaking, the ocean receding, and villages being lost. One account describes a battle between Thunderbird and Whale that shook the land and swallowed the coastline. These stories are now understood as cultural records of the same event.
Westport’s geography makes it particularly vulnerable. The town is built on a sand spit between the Pacific Ocean and Grays Harbor, with very little high ground nearby. During a Cascadia earthquake, the coastline is expected to drop several feet, which brings the ocean closer before the first wave arrives. The ground itself, being saturated sand, is likely to undergo liquefaction during the shaking. This process causes the sand to behave like a liquid, which can buckle roads, snap bridges, and damage building foundations. The main highway out of town crosses low, marshy ground that is expected to fail early in the event.
For years, the town had no practical answer for where residents could go in the roughly 20 minutes between the end of the shaking and the arrival of the water. The turning point came with the Ocosta School District, which faced a serious problem: the elementary school was located directly in the expected inundation zone. In the event of a quake during school hours, there was no way to move hundreds of students to higher ground in time.
In 2013, voters passed a bond measure to rebuild the school and add a vertical evacuation structure. The project was completed in 2016. The gymnasium was built with a reinforced rooftop platform about 55 feet above the ground, supported by concrete columns driven deep into the earth. The structure is designed to withstand both the shaking and the impact of the water, and it can hold more than a thousand people. It was the first structure of its kind built in the United States.
The school structure primarily serves students and staff, so the town later added a public evacuation tower near the marina and beach area. This second structure is intended to be reachable on foot within a few minutes by residents and visitors who are not near the school. Both structures follow the same principle: they accept that the roads will likely be unusable and the wave will arrive faster than traffic can move, so the only reliable option is to go up.
A tsunami carries enormous force. Water weighs about 62 pounds per cubic foot, and a tsunami wave is not a smooth surfing wave but a moving wall of water filled with sand, vehicles, and debris. This mixture can easily destroy standard wooden buildings. Vertical evacuation structures are engineered differently. They use deep pilings so the ocean cannot scour away the sand beneath them, open lower levels so water can flow through rather than push against a solid wall, and decks high enough to stay above the expected wave height.
The Cascadia fault affects a much larger area than Westport. A full rupture would impact cities including Seattle, Portland, Tacoma, and Olympia, where millions of people live. Federal disaster models for a full event project thousands of casualties, tens of thousands of injuries, and widespread destruction. Small coastal towns like Westport, Ocean Shores, and Seaside face the narrowest safety margins because they sit low to the sea and can be quickly cut off from escape routes.
The science of the Cascadia fault has been understood for decades. Researchers identified in the 1980s that the fault is capable of producing a magnitude 9 earthquake. By the late 1990s, the Japanese records helped fix the date of the last full rupture. Geologists estimate that full ruptures occur roughly every 300 to 600 years. Since the last one was more than 320 years ago, some estimates put the chance of a major quake on the southern section of the fault at about one in three over the next 50 years, with roughly a one in ten chance of a full fault rupture.
Despite these odds, construction of vertical evacuation infrastructure has been slow across the region. The structures cost millions of dollars, which is a significant expense for small coastal towns with limited tax bases. Many communities rely on warning signs pointing toward high ground that may be too far away to reach in time. The delay is not a technical problem; the engineering for these shelters is well understood. It comes down to funding and local priorities. Communities tend to spend heavily on disaster recovery after an event, but are often hesitant to spend on prevention beforehand.
Westport chose to make that investment. The decision came down to a practical assessment: the town had roughly 20 minutes of warning, was built on low ground, and had limited evacuation routes. The concrete shelters are not elaborate, but they address the core problem directly. They assume the worst case will occur, that the ground will sink, the roads will break, and the water will arrive, and they provide a way above it.
The connection between the Japanese records, the oral histories of Native tribes, and modern geology all point to the same conclusion: the Cascadia fault has produced massive earthquakes and tsunamis in the past, and it will do so again. The timing cannot be predicted, and the warning will come only when the ground begins to shake. Westport has built for that scenario. Most of the coastline has not yet done so. When the fault eventually ruptures, survival in many communities may depend on whether a place to climb was built in advance, or whether residents were counting on roads that are unlikely to remain usable.
