“It was quite a day. … As we sat and watched it you could tell at about 1:30 (p.m.) there was something going on,” said Half Moon Bay Mayor Marina Fraser, who patrolled city beaches Saturday afternoon with Police Chief Don O’Keefe. “The water was receding way out to sea.”
Beaches up and down the state were off limits for about six hours – from 1 to 7 p.m. – in light of a tsunami advisory issued Saturday morning, when federal officials realized oceanic reverberations from the South American temblor could charge the West Coast. It was the first live caution in the county since an advisory issued in September, and the alert attracted over-the-hill visitors hoping to glimpse the action as it manifested in the surf break.
  
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“People were disappointed that they didn’t see a tidal wave,” said Pillar Point Harbor Interim Harbormaster Robert Johnson.
Harbor officers barred an influx of visitors from setting foot on the pier in case water levels climbed to the point of pulling docks above their pilings and unhitching boats. Spectators lined up instead along the bulkhead to witness the surface fluctuations. The harbor is one of the Coastside’s most susceptible areas to tsunami surges, according to state tsunami flood maps issued in 2009.
For about a half hour beginning at 1:10 p.m., water in the harbor rose 18 inches then ebbed four feet – the ripples of the quake nearly 5,600 miles away.
“There was activity but, fortunately, it wasn’t at the levels that we’ve seen at other events,” Johnson said. That the brunt of the fluctuations arrived during low tide was a blessing, he added.
The last tsunami to strike the Coastside with devastating force occurred in 1946 when a 7.4 magnitude earthquake off the Aleutian Islands in Alaska spawned waves 10 to 14 feet high. Princeton suffered when the surge destroyed near-shore buildings and boats. Destruction triggered by the Alaskan earthquake reached the coast of Chile, according to historical information published by the University of Southern California Tsunami Research Group.
Coastsiders who didn’t hear a warning siren need not schedule an appointment with their audiologist. There wasn’t one. Sirens ring only during tests and in times of warning, when water levels might surge enough to damage homes and evacuation is at hand. An advisory, by contrast, signifies a likelihood of strong currents and means people should keep off the beach. County officials send such alerts to residents signed up for the county’s emergency alert system.
San Mateo County Emergency Planner Jim Asche said the siren is “our ace in the hole.”
“If people got that during the advisory, people might have just shined that and not paid attention,” he said.
Destructive tidal waves washing up in the San Francisco Bay Area would most likely emanate from an earthquake off the Aleutian Islands, scientists say. However, a massive earthquake in Chile in 1960 wrought damages on the coast in Southern California.
“We dodged a bullet in California and Hawaii with this one – with the Chilean quake,” said U.S. Geological Survey Oceanographer Larry Miller, facilities director of Half Moon Bay Yacht Club.
In light of the quake in January that brought Haiti’s capital city to ruins and the devastating shock to Chile, Northern California inhabitants might wonder about the chances of crippling ground movements at home. Scientists have no reason to believe that the two events are related or that they portend bad things to come, says USGS Seismologist Andy Michael, of Half Moon Bay. They expect a major quake at the Hayward Fault in the East Bay to wreak havoc on Bay Area residents sometime in the next three decades, “but what we’ve seen around the earth in the last few weeks doesn’t change that in any way,” Michael said.
Coastside authorities summoned extra manpower on Saturday to lock down local beaches, and said visitors were by and large keeping themselves safe. Fraser surmised the injurious incident at the Mavericks Surf Contest in February served as a wake up call to people thinking about disobeying safety commands.
County emergency planners, on the other hand, attribute compliance to a nationwide tsunami education campaign that ramped up after a tidal wave wiped out the west coast of Sumatra in 2005. They point to the emergence of tsunami sirens, warning tests and inundation zone maps as having a positive impact. Saturday’s scare “was actually great too ’cause it was really a coast-wide exercise,” Asche said.
More than 48 hours after the initial quake, intermittent aftershocks lasting as long as 90 seconds each continued to produce atypical ebbing and flowing in the harbor.
“It’s still going on at this time and we’re anticipating that as long as there are aftershocks … there’s still potential for rapid fluctuations in tidal levels,” Johnson said Monday.
County emergency planners are planning tsunami awareness activities during the week of March 22.
To keep up to speed on warnings, advisories and other developing safety situations, county emergency planners strongly encourage Coastsiders to sign up for the San Mateo County Community Alert System at www.smcalert.info.
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