What Will Happen When a Megathrust Earthquake Occurs in Cascadia
A ticking geological time bomb is hidden off the Pacific coast of the US and Canada—a subduction zone called Cascadia. This 1,130-kilometer fault, which has been silent for over 300 years, is capable of triggering a megathrust earthquake with a magnitude of over 9.0. A new study warns that the consequences will be catastrophic—from the instantaneous subsidence of the coastline by two meters to a tsunami the height of a 10-story building.
The Coastline Will Go Underwater in Minutes
Scientists from Virginia Tech have modeled a scenario for Cascadia’s awakening, reports IFL Science. The results are shocking:
- The coastal zone will sink by 1.9 meters, expanding the flood zone by 35-116 km²
- Over 14,000 people will be in the direct inundation zone
- 22,500 buildings and 57 environmentally hazardous sites could be submerged
Probability and Consequences
“This is not just an earthquake—it is an instantaneous transformation of the landscape,” explains a geologist. Current calculations show a 15% probability of a megathrust earthquake in the next 50 years. According to scientists, the question is not if Cascadia will “wake up,” but when. And by that time, we need to be prepared—at a minimum, by reviewing maps of potential flood zones and relocating hazardous industries from the coast.
If the disaster occurs before 2100, the consequences will be exacerbated by sea-level rise. The inundation zone will triple in size, and saltwater will destroy fertile soils and ecosystems. In addition, natural breakwaters—dunes and wetlands—will disappear. The fate of tidal marshes—important “carbon sponges” for the planet—is of particular concern. Their flooding will accelerate climate change.
The last megathrust earthquake in the Cascadia region occurred in 1700. The event caused a tsunami that reached Japan.
