Last Sunday’s 6.0-magnitude earthquake that struck the Napa region of Northern California was the strongest the area has seen in 25 years. The quake was so strong, in fact, that it woke many in the region — as we learned from a sudden change in the sleeping patterns of people nearby, thanks to data collected by Jawbone UP fitness trackers.

The data slope shows users gradually falling asleep past 9 p.m. local time in all four of the measured areas. Jawbone UP tracks when wearers fall asleep and when they wake up, based on changes in movement.

By looking at the sleep patterns of UP users in the Napa area, which Jawbone reported was in the thousands, data scientists were able to see what time the earthquake struck and the reach of its repercussions; 93% of UP wearers nearest to the quake’s epicenter suddenly woke up at 3:20 a.m. Sunday morning. The data includes users in the cities of Napa, Sonoma, Vallejo and Fairfield.

Further away in San Francisco and Oakland, only 55% of users woke up at that time. This trend continues downward as you get further away, with users in Santa Cruz and Modesto experiencing almost no disruption in sleep.

Of those within 15 miles of the epicenter who woke up, 45% stayed awake for the rest of the night.

An interactive version of the chart is available here.

Via Mashable