Magnitude-4.0 Piedmont earthquake wakes up Berkeley

Quake map
The Magnitude 4.2 quake that woke up Berkeley on Monday August 17, 2015, had its epicenter close to Piedmont. Map: USGS

An earthquake in neighboring Oakland jolted Berkeley awake just before 6:50 a.m. Monday.

The US Geological Survey (USGS) initially registered the quake as a magnitude 4.2, but soon downgraded it to a magnitude 4.0. Its epicenter was two-thirds of a mile north of Piedmont (3.2 miles southeast of Berkeley). It struck at 6:49 a.m.

BART held trains while it undertook a system-wide check. It estimated it would be a 10-minute delay at 7:14 a.m. At 7:26 a.m. BART tweeted: “No damage found to tracks or yards following small quake. All trains held for inspection and moving again.”

At 7:13 a.m. the CHP tweeted that no damage had been reported on any Bay Area freeways.


Shake map
This USGS “shake map,” above, shows the intensity of the earthquake that struck at 6:49 a.m. on Monday August 17, 2017 in Oakland. Click image for original map

The exact coordinates of the first earthquake, according to USGS, were 37.840°N 122.231°W. The depth of the quake was 3.3 miles.

An aftershock, also 1 mile north of Piedmont, with a magnitude 2.3 was registered by USGS at 7 a.m.

Scores of people took to Twitter almost as soon as the jolts ended.

At 6:52 a.m. Lance Williams posted: “That earthquake in Berkeley was right under the house! Pots & pans flying, squirrels barking, li’l gal wakes crying…”

Carol Thomas shared this photo of the impact of the quake on a picture hung on the wall of her house
Carol Thomas shared this photo of the impact of the quake on a picture hanging on a wall in her house

Five minutes later Tom Yamaguchi wrote: “At my West #Berkeley house, felt like a door slamming, then a quick strong shake. Was half asleep, then fully awake.”


One local resident decided his four-legged friend wasn’t a huge help in the circumstances. Shortly after 7 a.m. Marcus Gilmer tweeted: “Based on an extremely small sample size, dogs are terrible at predicting earthquakes.”

One Bay Area resident who is out of town rather wished she hadn’t been. San Francisco Chronicle reporter Vivian Ho tweeted: “Not going to lie, I have some quake FOMO in Boston right now. I knocked a few books off my shelf to pretend I was there though.”

Monday’s quake was on the Hayward Fault which, seismologists predict, has a 31% chance of having a magnitude-6.7 or larger quake within the next 30 years.  

The last significant quake to be felt in Berkeley was last month when a magnitude-4.0 earthquake was reported north of Fremont at around 2:40 a.m. July 21.

Tell us what you felt and saw. We’re gathering information and updating this post regularly.


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