Healdsburgers and other Sonoma County residents received a surprise on their devices at about 6:40pm on Sept. 13, when an alarm sounded and an urgent message appeared: “Earthquake detected! Drop, Cover, Hold On, Protect Yourself.”
For some, the message was too late—the quick rumbling 4.4 quake had already passed though northern Santa Rosa neighborhoods, though a smaller 3.9 aftershock was on the way. For many, however, it was a remarkable message to read, an indication that the science of predicting earthquakes had come to their phones.
The message was signed “USGS ShakeAlert,” and was triggered by sensors recognizing the initial seismic waves of earth movement. Because it’s sent out automatically and immediately, it can move faster than the earthquake itself, thereby alerting residents away from the epicenter that the shocks are coming their way.
The alert can also trigger automatic actions in the infrastructure “that can protect vital systems, equipment, facilities and infrastructure,” according to the United States Geological Survey (USGS). “These automated actions could include slowing a train, closing valves, issuing a public announcement and many others.”
In the United States, the ShakeAlert system is being developed to cover California, Oregon and Washington. Currently over 1,000 earthquake sensors are installed in the broad region, with a target of 1,700 upon full network build-out.
The technology was first rolled out in Japan as far back as 2007, and has been used effectively there, in China, Mexico, Turkey, Italy and Taiwan, as well as the west coast of the United States.
The earthquake of Sept. 13 was relatively minor, brief and localized, which means it was fairly shallow along the Rodgers Creek Fault. The fault runs north-south through Sonoma and Marin counties, and many seismologists believe is overdue for a major earthquake of 7.1 or greater on the Modified Mercalli Scale. For more information, visit earthquake.usgs.gov/data/shakealert.
