To be fair, the tiny trembler wasn't forecast by a huge expanse of time, but seismologists were alerted to it nonetheless. By planting hundreds of sensors around fault zones in California, researchers at CalTech were literally given 30 seconds to anticipate the quake. And when it actually shook their lab, it marked the first successful test of their new early earthquake warning system.

The above image shows a computer-generated display similar to what the CalTech researchers would have seen on Monday. Credit: AP.

It was implemented about a year ago, and the system is based off a Japanese design. Scientists are now asking for $80 million to create a more robust version in California.


The LA Times explains more:

The sensor have warned scientists of numerous quakes, but the vast majority were either too small to feel or too far away to be felt in the Los Angeles area. For example, the sensor gave an early warning of several magnitude 5 quakes last year in Imperial County, but the temblors hit too far away for them to felt in Los Angeles.

The Anza quake was different.

Even though it measured magnitude 4.7, its location on solid granite made the shaking stronger and more widespread. People reported to the USGS that they felt it as far away as Arizona and Central California. At Caltech, computer screens flashed with a 30-second countdown to when the shaking would hit Pasadena. Sure enough, it came on time.

Hutton and other declared the test a success, with some caveats.

The system initially overestimated the quake’s magnitude, saying it was a 5.2. But U.S. Geological Survey seismologist Susan Hough was not overly concerned about the error. She noted that the main job of the system is to alert people to a coming quake, not to gets its magnitude precisely right. The Anza quake caused an unusually intense amount of shaking, Hough added, so the warning system accurately captured that.

More here.