Perspective: Earthquake warningsQ&A: How Ridgecrest Earthquakes Helped Scientists with ShakeAlert

U.S. Geological Survey geophysicist Sarah Minson was in the thick of efforts to develop an earthquake warning system in California when a series of major temblors struck the sparsely populated community of Ridgecrest in the Mojave Desert this summer. The largest, a magnitude 7.1 quake on July 5, was the biggest to hit the state in decades. The Mercury News’ John Woolfolk asked her about her work — and how this month’s big quakes is helping scientists refine California’s fledgling earthquake alert system

One of the questions Woolfolk asked Minson was about the challenges of installing a reliable seismic early warning system in California.

Minson’s answer:

There are two limitations that are very important to understand. There’s always going to be a region that is not warnable and that’s from right where the earthquake begins to the nearest seismometer. The farther seismic waves travel is time you’re losing to get a warning out. The target I believe is a minimum of one seismometer every 20 kilometers, with 10 kilometer spacing in densely populated areas, and within 5 kilometers of all mapped fault traces. We have been working for some number of years now to put sensors in the ground, but that requires getting permits approved.

This is a shaking forecast. Just like when you see a thunderstorm that looks like it might issue tornadoes or a hurricane and track it, there’s a range on it because you’re attempting to forecast the future based on information we have now. But what’s interesting with earthquake warnings is that because the time involved is so short, the system has to be entirely automated. There’s always going to be inherent risk that something incredibly stupid might happen that no human would allow.