Scientists are sharpening their focus on five United States coastal states where geology and climate change intersect to create an outsized risk of major earthquakes and tsunamis. Drawing on new warnings issued on May 21, 2025, researchers are flagging how seismic fault lines, subduction zones and volcanic systems combine with rising seas and warming oceans to raise the odds that a large quake could unleash devastating waves on densely populated shores.
1. California
California sits at the top of the list because scientists now describe its tsunami exposure as a product of both restless seismic geology and accelerating climate pressures. Researchers who issued fresh alerts on May 21, 2025, highlighted how the state’s offshore faults and complex plate boundaries can generate powerful earthquakes that, in turn, drive tsunami waves toward the America West Coast. In their assessment of multiple US coastal states, they singled out California’s combination of active fault systems and rapidly rising sea levels linked to climate change as a key reason the state faces heightened tsunami threats. That warning stressed that even a moderate offshore rupture could push water into low-lying harbors, ports and beach communities that are already seeing more frequent flooding during high tides.
In practical terms, this means a major quake off California would not strike a static coastline, but one where higher baseline sea levels and warmer, expanding oceans give tsunami waves more reach. The same reporting that flagged California also described how geological fault lines along the Pacific margin can amplify quake risks, increasing the chance that a rupture could displace large volumes of water in a short time. For coastal planners, the implication is stark: evacuation maps and building codes drawn up for twentieth century sea levels may underestimate how far inland a tsunami could travel today. As scientists connect these dots between geology and climate, they are pressing local officials to revisit worst case scenarios that include port shutdowns, damage to energy infrastructure and long term displacement in some of the state’s most valuable real estate.
2. Alaska
Alaska is another state where experts see a convergence of powerful tectonics and rapid environmental change that could fuel a major quake and tsunami. The region’s offshore subduction zones, where one plate dives beneath another, are already known for producing some of the largest earthquakes ever recorded, and scientists now warn that these same geological features pose major tsunami risks to Alaska and beyond. In their May 21, 2025, alerts, researchers underscored that this seismic backdrop is being reshaped by climate driven ice melt and sea level rise, which can alter stress on the crust and raise the baseline from which tsunami waves build. Separate coverage of a potential “mega tsunami” has also focused on how a large rupture in the North Pacific could send waves racing toward Alaska, Hawaii and parts of the mainland America West Coast, with experts fearing that entire coastal cities and millions of people could be affected, as highlighted in a widely viewed video warning.
Those overlapping concerns are echoed in reporting that describes how a powerful mega tsunami could threaten large swathes of the United States, particularly the Pacific Northwest, Alaska and Hawaii, if a massive earthquake strikes the right segment of the plate boundary. In that context, Alaska’s long, sparsely monitored coastline becomes a frontline for early detection and rapid alerts, because waves generated there can cross ocean basins and hit distant shores with little time to spare. For Alaska’s own communities, many of which sit at river mouths or on narrow coastal plains, the stakes include not only immediate loss of life and infrastructure but also long term disruption to fishing, shipping and energy operations that anchor the state’s economy. Scientists argue that understanding how melting ice, changing ocean levels and active subduction zones interact is now central to planning for the next great Alaskan quake.
3. Hawaii
Hawaii’s place on the high risk list stems from its unique volcanic geology and its exposure to tsunamis generated across the Pacific. Scientists who mapped out tsunami threats for multiple US states emphasized that Hawaii’s island chain, built on volcanic foundations, is vulnerable to quake triggered waves from both local and distant sources. They pointed to the way tectonic movements around the Pacific basin can send energy toward the islands, where steep underwater slopes can focus and amplify incoming waves. At the same time, the same May 21, 2025, warnings that highlighted California and Alaska also stressed that Hawaii’s vulnerability is increasing as climate change raises sea levels and alters storm and wave patterns, making it easier for tsunamis to overtop coastal defenses and flood critical infrastructure.
Additional reporting on mega earthquake scenarios has reinforced that a powerful mega tsunami could threaten large swathes of the United States, particularly the Pacific Northwest, Alaska and Hawaii, if a major rupture occurs along key subduction zones in the region, a risk detailed in another widely circulated expert briefing. For Hawaii, that means the danger is not confined to its own seismic or volcanic activity, but extends to distant faults that ring the Pacific. The implications are far reaching for residents and for the tourism industry that drives much of the local economy, because hotels, airports and ports are often located on low coastal land. Scientists argue that evacuation planning must now account for higher background sea levels and the possibility that a single extreme event could disrupt inter island transport, power grids and fresh water supplies, leaving communities isolated even after the initial waves recede.
4. Washington
Washington’s tsunami risk is tightly bound to the Cascadia subduction zone, a massive fault off the Pacific Northwest that scientists have repeatedly flagged for its potential to generate a truly major earthquake. In their May 21, 2025, warnings, researchers described how the Pacific Northwest’s Cascadia fault line has been singled out for its capacity to unleash a quake large enough to send destructive tsunamis toward the coasts of Washington and neighboring states. They stressed that this danger arises from the region’s geology, where one plate is locked against another until it suddenly slips, and from climate factors that are steadily raising sea levels along the shoreline. That combination means that when a Cascadia event does occur, tsunami waves will be riding on top of a higher ocean, giving them more power to inundate low lying communities, ports and industrial zones.
Separate coverage of mega tsunami scenarios has sharpened the focus on how a Cascadia rupture could affect the broader America West Coast, with one detailed report explaining that Alaska, Hawaii and parts of the mainland America West Coast are at risk if an earthquake erupts along the Cascadia subduction zone, a fault that could send waves racing toward Washington’s outer coast and inland waterways, as outlined in an in depth analysis of Cascadia. For Washington, this raises urgent questions about the resilience of coastal towns, tribal communities and major hubs such as ports and naval facilities that sit within potential inundation zones. Scientists argue that the state’s planning must now integrate both the geological reality of a locked subduction zone and the climate driven trend of higher seas, because together they shape how far and how fast tsunami waters could travel when the next great Cascadia quake strikes.
5. Oregon
Oregon rounds out the five states scientists are flagging for major quake related tsunami risk, largely because it shares the same Cascadia subduction system that threatens Washington. Researchers who issued the May 21, 2025, tsunami alerts emphasized that Oregon’s coastline sits directly in the path of waves that would be generated if the Cascadia fault ruptures along its length, a scenario that could send walls of water crashing into small towns, ports and estuaries within minutes. They noted that the state’s geological setting, with a steep offshore trench and a narrow coastal plain, leaves little buffer once the seafloor lurches upward during a major quake. At the same time, the same assessments stressed that climate change is amplifying these dangers by raising sea levels and altering coastal erosion patterns, which can undermine natural dunes and man made defenses that might otherwise slow incoming water.
Those concerns echo broader warnings that a powerful mega tsunami could threaten large swathes of the United States, particularly the Pacific Northwest, Alaska and Hawaii, if a massive earthquake strikes the Cascadia subduction zone that stretches off Oregon’s coast. For Oregon’s communities, many of which rely on coastal highways, fishing ports and tourism, the stakes include not only immediate casualties but also the potential loss of critical lifelines if roads, bridges and harbors are swept away. Scientists argue that the state’s response must account for the combined effects of geology and climate, from updating evacuation routes that may already be compromised by erosion to rethinking where new housing and infrastructure are built. In their view, Oregon’s position on the front line of Cascadia makes it a test case for how the United States adapts to a future in which major earthquakes and climate driven sea level rise intersect.
More from MorningOverview