On January 26, 1700, the largest earthquake known to have occurred in the lower 48 United States rocked Cascadia, a region 600 miles long that includes northern California, Oregon, Washington, and southern British Columbia.
The earthquake set off a tsunami — a series of ocean waves — that struck Cascadia’s Pacific coast, and also crossed the Pacific Ocean to Japan, where it damaged coastal villages. Written records of the damage in Japan pinpoint the earthquake to the evening of January 26, 1700.
Scientists now call the event the 1700 Cascadia earthquake. They estimate its size as magnitude 9.
Only three earthquakes of magnitude 9 or larger occurred in the twentieth century. The largest, of magnitude 9.5, struck Chile in 1960. Second-largest was the 9.2 quake that hit Alaska in 1964. By comparison, the 1906 San Francisco earthquake was not quite magnitude 8