In a recent four-day period, there were nine earthquakes in the Southern California area, according to the Southern California Earthquake Data Center.
Though they were all quite small in magnitude, the largest being a 2.7 on the Richter scale, they are still potent reminders of how fragile the area in which we all live is.
For the boating and seaside breed, these facts translate into the frightening yet likely possibility of a tsunami someday striking the populated coastline of Los Angeles.
According to researchers, not only is it possible that such an event could occur, scientific data indicates that it will most likely happen someday.
A report written by professors from the University of Southern California concerning the likelihood of a Southern California Tsunami 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.”
“Catalina Island itself exists due to earthquake-related uplift on a geologic structure known as a restraining bend,” said Mark Legg, a geophysicist working with USC researchers. “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.”
As the anniversary of the December 26th, 2004 Indian Ocean disaster that claimed hundreds of thousands of lives approaches, questions of what would happen if a tsunami struck our coastline reappear.
What amount of warning might we have if a tsunami were to rear its head and what would be the severity of the damage? And how do boats fair in such situations?
As for the last question, there were many vessels, both commercial and recreational, anchored in the lagoons of Thailand the day the massive tsunami ravaged the land nearly two years ago.
And while thousands of boats were demolished beneath the incredible force generated by the wave, surprisingly many were spared.
There have been reports of cruising sailors (some from the Marina del Rey area) who were anchored in 50 feet of water and felt the tsunami pass beneath them as they subsequently watched the wave build to 40 feet over shallower water and swallow the town.
As recently as November 15th the National Oceanic and Atmospheric Administration (NOAA) sent out a tsunami warning that initially included Southern California, as well as Japan, Northern California and some other areas.
The epicenter was far from our coast, near the Kuril Islands off the coast of Russia, but was a relatively significant event — 8.1 on the Richter scale.
The Southern California warning was later canceled, but Crescent City, California was rocked pretty hard by its effects, and there may be lessons to learn in how their boats and harbor weathered the storm.
“The harbor has one outside jetty and a protected harbor,” said Barak Uslu, a doctoral candidate in the field of civil engineering at USC. “Inside the harbor, some of the mooring lines broke and boats started to swirl around, but on the outside things were considerably safer.”
As for where a tsunami might originate, there are a number of possibilities that are of concern.
In 1930, there were reports of “unusual wave conditions” on a Santa Monica Bay fault that were explained as a “possible submarine landslide.”
Catalina island sits on a precarious fault that many geologists agree is poised for an event.
“The major areas of tsunami amplification occur along the Santa Monica Bay coastline from Marina del Rey to Redondo Beach, and around the San Pedro Bay coast from the Los Angeles and Long Beach harbors to Newport Beach,” Legg states in one of his reports.
The USC study also concurs with the assessment that Palos Verdes is an area that might one day be cause for concern.
“Recent offshore mapping work has found evidence of significant sliding and slumping offshore of Southern California, particularly in the Santa Barbara Channel and off the Palos Verdes Peninsula,” the USC report stated. “Studies have shown that these events could have given rise to tsunami wave heights ranging from five to 20 meters (approximately 16 to 66 feet).
“Furthermore, given the proximity to a major port, a tsunami generated off the Palos Verdes Peninsula would have grave economic consequences.”
While the federal government created a warning system that is supposed to be in place sometime next year, the amount of forewarning will be largely determined by where the tsunami originates.
In the case of the recent Kuril Islands warning, if it had made its way towards this area, we would have had more than ten hours to prepare, said Uslu.
But for a sizable jolt coming from somewhere as close as Catalina Island, Uslu estimated, “You’re talking about 20 or 30 minutes’ time.”
By this time next year, Uslu and a group of his USC colleagues will have made headway in another report that they have just begun that will discuss tsunami risks specifically in the Marina del Rey area.