In the wake of the massive earthquake and fatal tsunami that struck Indonesia, environmental experts are reflecting how Southern California should approach such potential disasters.
National Tsunami Warning Center senior watchstander Kara Gately said she has not seen a heightened risk of tsunami activity in California, but people should still be inclined to learn the natural warning signs of a tsunami so they can evacuate sooner.
These signs include feeling big local earthquakes and seeing a rapid fall in sea level when the ocean recedes, according to Gately and the International Tsunami Information Center.
Gately said extreme cases of earthquakes that are very close to the shore can cause tsunami waves to arrive within five minutes.
Tsunamis transpire from substantial movements in the sea floor caused by earthquakes, said USC environmental engineering professor Costas Synolakis. An earthquake that is larger than a magnitude 7 would produce this activity, he said.
“Tsunamis are triggered primarily by an earthquake,” Synolakis said. “But not all earthquakes trigger tsunamis.”
Synolakis estimated that only about 10 percent of earthquakes around the world would generate a tsunami. But if one were to hit Southern California, the most impacted areas would be low-lying areas such as Marina Del Rey, Venice and parts of Santa Monica, Synolakis said.
Synolakis said tsunamis like the recent one that struck Sulawesi, Indonesia are also caused by submarine landslides, which move underwater sediments and soil and are similar to avalanches.
He said adding more deep-sea ocean sensors — which capture ocean water movement — could help speed up tsunami warning times, which would help people evacuate faster.
Gately, however, said these sensors are not used to produce warnings. Instead, they’re used to confirm or deny the existence of a tsunami so the Warning Center can better understand its potential impact, she said. That information, along with monitored earthquake magnitudes, helps the Warning Center determine whether a tsunami warning should go out, Gately said.
Synolakis said small tsunamis will swell into the state every few years.
In 2015, Southern Californians braced themselves for a storm that brewed from the aftermath of a huge earthquake in Chile. But tide fluctuations of no more than a foot surged through the Southern Californian coast.
The likelihood of a large tsunami to strike California would be hard to predict, Synolakis said. The last notable tsunami he remembers impacting California was in Crescent City in 1964.
The tsunami took the lives of 11 people in the coastal city near the Oregon border. The tidal waves struck the area after a 9.2-magnitude earthquake shook south-central Alaska, awakening a tsunami that stretched through the Pacific coasts of southeast Alaska, British Columbia and the U.S.