A magnitude-2.8 earthquake hit two miles northwest of Danville at 6:18 p.m. on Tuesday. A 2.4 hit just before, at 6:06 p.m., according to USGS.
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USGS officials are also reporting that at least four small earthquakes struck near Danville early Tuesday morning.
Officials said this brings the total to eight earthquakes to occur in the same area over the past two days.
"I felt lots of shaking... I remember waking up at least three or four times last night feeling them," said Diablo-native Caitlin Moulthrop. "They seemed pretty strong."
"We live in earthquake country and there's no time like the present to be prepared," said Brian Kilgore, a USGS geophysicist based in Menlo Park.
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A magnitude 2.8 hit Alamo just after 1:30 a.m. Tuesday and USGS officials are reporting three more occurred near Danville at 4:25 a.m., ranging from magnitudes 2.6 to 3.0.
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All of them are very close to Monte Vista High School in Danville, which is where a magnitude 2.9 hit Monday morning. Then, that was followed by a magnitude 2.5 earthquake.
Scientists aren't exactly sure what causes these types of swarms, but say it's not an indication that the 'big one' will come because of it.
The USGS is developing an earthquake early warning system that would push out alerts via smartphone. Officials hope to launch it within the next year or two, but the program itself is currently being targeted for elimination by President Trump.
Other countries, such as Mexico, already have a similar system in place that many credit for saving lives.
VIDEO: How early earthquake warning system for West Coast could save lives
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"It gives people those few extra seconds or more, to duck, cover and hold, or to prepare as best they can, for the shaking that's to come," says Kilgore.
For those who live near Mount Diablo, the swarm is a gentle reminder of what Californians face, and the steps they can take to prepare for a major earthquake.
"You wait to see if there's going to be more," says Alamo resident Barbara Debiasi. "When there's not anymore, you breathe a sigh of relief (and) wait for the next one."
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