Thursday morning’s 6.4 earthquake and Friday evening's 7.1 earthquake that was centered about seven miles southwest of Searles Valley both sparked a huge response across social media and one question that popped up several times was: where was the ShakeAlert?
Seismologist Lucy Jones of Caltech, founder of the Dr. Lucy Jones Center for Science & Society said the ShakeAlert computer system at Caltech's seismic facility registered a 48 second warning that shaking had begun on Thursday, but the warning signal did not go out to the public.
While the shaking was reported from Sacramento to Tijuana and east to Las Vegas and Phoenix, the shaking in Los Angeles was estimated to equal about a 4.5 magnitude quake. That's below the 5.0 threshold needed to send a ShakeAlert for Los Angeles County. The threshold was even less in San Diego. Ready San Diego points out the system is still undergoing testing.
Los Angeles officials explained further in a tweet:
"Let's remind ourselves that this is not a physical science question,'' Jones explained. "Giving more alerts convinces people that the system works and generates trust in it. Lots of false alarms generates distrust. Part of the concern in our current early system without complete funding (is) how many false alarms would we be issuing?"
`` ... The other problem is that there's a lot of use to the alerts beyond damage. Nobody in Los Angeles County was damaged -- nowhere close. We just all felt it. That does not stop people from being scared from feeling it, and one of the questions is what is the psychological benefit of getting a few seconds of warning and knowing that it's coming? That's a hard thing to measure physically.," continued Jones.