Earthquake prediction: A work in progress

A lot of people in Los Angeles were angry that the city's operational Earthquake Warning System did not alert them to shock waves coming from Thursday's 6.4 magnitude shaker in the Southern California desert, 150 miles away.

The explanation: L.A.'s system was set to send out alerts if expected magnitude there was magnitude 5 or higher, which it never reached. It can easily be adjusted.

But plenty of organizations swear by the technology.

Though not generally available in the Bay Area yet, BART says the Shake Alert Earthquake Warning System worked well on Thursday and the 2014 Napa earthquake.

"Because of the statewide Early Warning System, our trains were automatically slowed down and the trains that were in stations were automatically held there," said BART spokesman Jim Allison.

Allison said, within seven minutes, after reviewing incoming data, the trains were back in operation.

Caltrans says it is also benefiting from the system and places sensors to make it more accurate.

Shake Alert does not say precisely what magnitude to expect, but if it will be mild shaking, or mild to moderate, or moderate to strong, or strong shaking.

"This is a case where there is danger in your area, but it's not going to be specific to you in your location. You have to take protective action yourself to keep yourself safe because this is a dangerous period in this general area," said USGS Geophysicist Sarah Minson.

Given the nearly limitless factors that one has to consider in order to predict what the earth is going to do is such a complex problem that we really couldn't begin working on it until the advent of the super computer.

But, even for super computers, this is such a complex problem it's going to take years to perfect.

"In Earthquake Science we're gotten many more sensors and much more accurate measurements. So, from a technological point of view, we're way ahead of where we were just a few years ago," said USGS Seismologist Walter Mooney.

L.A. was lucky, Thursday's quake happened 150 miles away and so was the Bay area, 300 miles from the epicenter.

"If we had a magnitude 6.4 San Francisco, Oakland, San Jose, we would really pay a lot of attention to that,"said Mooney who also said the consequences of such a quake centers in an urban area.

"A lot of damage would have occurred affecting not only buildings but infrastructure."

For its part, BART says it's ready.

"With our Earthquake Safety Program, we would be able to withstand the type of earthquake that would take place only once every 500 years," said BART's Jim Allison.

And, when the Transbay Tube is retrofitted? "Every 1000 years," said Allison.

Every year, the Shake Alert system improves substantially.