The second and third waves came in 10-minute intervals after the first. The first wave came within 5 minutes of the earthquake. And just in case, the City and County of San Francisco has a tsunami plan in place. The second wave was the strongest. And even a worst-case-scenario Cascadia tsunami would take several hours to reach the city, providing ample time to mobilize a response.

The world's deepest seawall, it rises 63m from the ocean floor and stretches 1,960 metres across the bay, the culmination of 31 years of engineering endeavour. A tsunami’s trough, the low point beneath the wave’s crest, often reaches shore first. In Campbell Bay of Great Nicobar island, the tsunami waves hit the area three times with an inundation limit of 250–500 m (820–1,640 ft). Bay Area residents can also rest assured that there have been no recorded deaths from tsunami-related events in San Francisco. When it does, it produces a vacuum effect that sucks coastal water seaward and exposes harbor and sea floors. But the Kamaishi breakwater had no appreciable effect on the tsunami that struck Japan on 11 March, triggered by a 9-magnitude earthquake just 129km off the north east coast.