West Marin did not panic during last Thursday’s tsunami alert, nor did it engage in a collective shrug. Instead, people along the coast—awaiting a potentially lethal wall of water—responded calmly and deliberately.

First came an earthquake alert at 10:44 a.m., reporting a 7.0-magnitude shaker off the coast of Eureka, some five hours north. Five minutes later, the National Weather Service issued an ominous warning for coastal communities stretching from Santa Cruz to Oregon: “A series…