Everyone along the West Coast who was alerted to the tsunami warning last Thursday found it frightening. Although the warning was fortunately revoked, many people continue to question why it was issued in the first place.
At 10:44 a.m., an earthquake of a magnitude of 7.0 struck just off the coast of Northern California. Five minutes later, coastal communities from Oregon to Santa Cruz, California, including the Bay Area, were under a tsunami warning from the National Tsunami Warning Center.
The Earth’s surface moving higher or downward beneath the water causes tsunamis. Underwater earthquakes at a subduction zone—where tectonic plates slide up or down on top of one another—usually cause tsunamis.
But the San Andreas fault, a distinct kind of zone called a strike-slip fault, where the tectonic plates slide next to one another rather than up and down, is where the earthquake that happened last Thursday took place.
Since there is no natural up- or down-motion to produce a tsunami, an earthquake on this type of fault is rare, but it is not impossible. Even though underwater subduction zone earthquakes are responsible for around 80% of tsunamis, there remains a 20% chance that another factor could be at play.
In this instance, a landslide that occurred underwater due to the San Andreas earthquake might have moved enough water to cause a tsunami. The weather agency did not have the luxury of waiting for observation and buoy data, which can take up to an hour to gather, because this earthquake happened close to land and tsunami waves can reach speeds of up to 500 mph.
This was another one of those circumstances where it was better safe than sorry, even though it was doubtful. If you didn’t previously know your escape route, hopefully you do now, because we might not be as fortunate the next time.
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Eliot Pierce is a dedicated writer for ChiefsFocus.com, covering local crime and finance news. With a keen eye for detail and a passion for storytelling, Eliot aims to provide his readers with clear and insightful analysis, helping them navigate the complexities of their financial lives while staying informed about important local events. His commitment to delivering accurate and engaging content makes him a valuable resource for the community.