Around four years ago I did a story for the Argonaut about the possibility of a tsunami striking the Los Angeles coast. At the time, there wasn’t much of a warning system in place, but the scientists and researchers that I interviewed were quick to inform me that the idea of a tsunami hitting our coast was not only possible, but likely.
A University of California report written prior to that time stated:
“Recent developments in the modeling of tsunami waves and the analysis of their economic consequences, combined with data from recent offshore mappings of the Santa Barbara Channel and other locations, suggest the mechanism and economic effect of an undersea landslide in the vicinity of Los Angeles that would spawn a tsunami.”
On Saturday, February 27th, soon after one of the largest earthquakes ever recorded at 8.8-magnitude rocked the country of Chile, a Pacific-wide tsunami warning/advisory was broadcast all over the West Coast, including our local area. An announcement across marine VHF channel 16 requested all local boaters to “seek safe harbor.”
The “pan pan” alert stated that a tsunami threat was approaching and that eight-to-ten-foot swells were a possibility. While the warning was active, both the Los Angeles County Lifeguard and Marina del Rey Sherriff’s boats patrolled and monitored the event, with no serious damage reported. Moderate damage was sustained to several Marina docks, county Department of Beaches and Harbors officials said.
“There was a little bit of tidal surge that came through the main channel that increased the water ingress and egress water influx maybe by ten inches,” said Det. Jay Yelick of the Marina del Rey Sheriff’s station.
Yelick explained that there was a full moon and storm remnants, so the tide was already particularly high.
The U.S. Coast Guard stationed in Long Beach also reported diminutive effects of the widely reported tsunami alert, with minor damage and loss along the coast.
“Los Angeles Harbor reportedly receded three feet in five minutes, but quickly returned to a normal tidal state,” the U.S. Coast Guard said in a statement. “Surges ranging from two to four feet were reported in harbors along the coast for approximately an hour and a half early afternoon (February 27th). Six buoys in Ventura Harbor were moved from their positions”
Although this event was mostly non-threatening and inconsequential, it did serve as a reminder of the tsunami reality, which geophysicist Mark Legg referred to in the 2006 Argonaut story.
“Catalina Island itself exists due to earthquake-related uplift on a geologic structure known as a restraining bend,” he said. “Although most faults offshore Los Angeles and Orange counties are mostly strike-slip — faults that move side to side — bends in the fault line produce areas where the ground is pushed up during major earthquakes. One of these
regions lies directly below Santa Catalina Island.”
The reality is that a Los Angeles based tsunami is certainly possible, but with adequate warning it should be relatively manageable. Yelick, a trained first responder, says that 40 feet of elevation is all that’s required to remain safe in the event of such a catastrophe, and in all likelihood there should be anywhere from an hour to a full day’s notice depending on where the incident occurred.
“Taking Mindanao Way straight down and getting on the other side of the 90 [freeway] is going to be sufficient elevation,” Yelick said of a potential evacuation of the Marina del Rey area. “Or up on the hill by LMU (Loyola Marymount University) — we don’t need huge amounts of space for evacuation. The actual mapped out evacuation area is really pretty small.”
Yelick also pointed out that a drastic and rapid reduction in sea level is a vivid sign that a tsunami is imminent. The closer and larger the event is, the more drastic the sea level change will appear, he said.
In a very serious occurrence, one might see keelboats being grounded in the harbor. And if such a tsunami were predicted, it wouldn’t be a bad idea for some of the bigger, more seaworthy crafts to head out to sea, the detective suggested.
A tsunami is dangerous once it reaches more shallow water. It’s then, when the wave changes in character from a moving underwater surge to a wall of violently rapidly moving water that it can swallow everything in its path.
“It’s been proven in many cases that it makes good sense to head out to sea,” Yelick said.
“But it depends on the size of the vessel. If you’re talking about a 28-foot run-about — then no. If you have a 60-foot or larger boat and you’re confident you can safely navigate it — sure, get out to sea into deeper water.”
While the February 27th cross-ocean remnant cost a few buoys to lose their footing and moderate damage to docks, the next event could be more substantial. Los Angeles authorities stress that to ensure safety in the event of a tsunami, people are encouraged to calmly head inland and wait out the storm.
For local boaters, it’s advised to only head out to sea if the boat is big enough to safely manage such an unusual occurrence, otherwise leave the boat and take the possible loss.