A new report released by the U.S. Geological Survey looks at the destruction a major tsunami could cause in Southern California.
Parts of Long Beach and Orange County could flood, ships in port would likely be swamped and overall, California could face billions of dollars in damage.
Researchers modeled this theoretical mega-wave in part after a real life event that happened almost 50 years ago in Alaska.
Good Friday Earthquake
On March 27th, 1964, rumbling started at 5:36 p.m. off the coast of Alaska. Quickly the shaking swept through places like Anchorage and Port Valdez, escalating into violent heaving.
"It swallowed buildings, vehicles," notes Alaska's state seismologist Michael West.
West says the quake was so strong it opened chasms in the ground and caused entire tracts of land to slide off the cliffs in Anchorage.
Much of the coast of Alaska was devastated. Then came the waves.
The deep sea quake caused the ocean to heave giant tides on shore, drowning several port towns and causing hundreds of millions of dollars in damage.
More than 100 people died.
The destructive waves of this quake-tsunami combo traveled to Los Angeles and as far as Hawaii. West says the 9.2-magnitude temblor was second largest earthquake ever recorded.
After that disaster, he says studying tsunamis and quakes became a major priority for researchers on the West Coast.
"And so the gears that were put in motion in 1964 really led to what we have today as far as infrastructure."
Testing the Infrastructure
In their report, USGS scientists model what would happen if a similar quake and tsunami struck the coast of Alaska today.
They made a few tweaks though, says seismologist Lucy Jones. For instance, they imagine the quake happening on a different part of the ocean floor slightly to the west of where the 1964 quake occured.
They also changed the tide. In 1964 the big waves hit during low tide, but in the new USGS scenario they arrive at high tide.
"It makes quite a bit of difference," Jones says.
For example, there would be much more flooding in Southern California, she says. Even LA, which is partly shielded by the shape of its coast, would see significant damage.
Jones says with today's network of sensors and high-speed communication lines, officials in Southern California would have about 3-and-a-half hours to interpret the data and decide how to react.
"Three and a half hours is very little time to move three-quarters of a million people," Jones says.
There are also many more businesses and people located on the coast than in 1964, not to mention throngs of tourists just there for the day. All of this complicates efforts to clear coastal regions during dangerous times.
Early Warning Systems
Over the last 10 years, the U.S. government has done a lot to develop a tsunami monitoring systems, says John Orcutt with the Scripps Institute of Oceanography.
He says there is a network of buoys throughout the world's oceans that were designed to give early warning of dangerous waves. But at various times, up to a quarter of them have been offline.
"It's hanging in there," Orcutt says of the early warning system. He notes that these buoys often sit in treacherous parts of the ocean and are "highly expensive" to maintain.
With recent budget cuts to the National Oceanic and Atmospheric Administration, the agency that maintains the system, Orcutt isn't confident the situation will improve anytime soon.
Still, he says people today are much more aware of tsunamis than in 1964, in part because so many have seen footage from the South Asia tsunami in 2004 and the Japan tsunami in 2011.
But he thinks more public education is needed to make sure people in California know where to go when dangerous waves are on the way.