The #BerkeleyBoom has been startling residents for more than a month. Image: Google Maps/Berkeleyside
The #BerkeleyBoom has been startling residents — mostly in South Berkeley — for more than a month. The map above shows approximate locations from where people said they could hear the sound. Image: Google Maps/Berkeleyside

For more than a month, residents around Berkeley have wondered online about a recurring nighttime boom that has woken babies, freaked out pets and set off car alarms.

The sound, which has become known on Twitter as the #BerkeleyBoom, has been heard around the city, though it has been concentrated primarily in the southern part of town.

On numerous instances, police have gone out to investigate, but were unable to locate the source and found no indication of a crime. City spokesman Matthai Chakko said Monday there have been no calls to Berkeley’s 311 service center about the sound. So its source remains a mystery.

On Sunday, a Twitter user named LP described the “Loudest #Berkeleyboom yet. Scared me half to death. @berkeleyside – seriously – is this still ‘fireworks’?!”

Heather Hardison added: “I could hear all my neighbors up talking about it in startled voices. What the heck is it?”

Wrote cirus206: “I might not know what #berkeleyboom is but damn would I like to find out.”

Some have likened the sound to a gunshot, while others said it sounded more like a pipe bomb or flash grenade, or perhaps just fireworks or “a single firework.” One said it sounded “M80-ish… but more concussive.”

Some have posited that a homemade firework rocket may be causing the Berkeley boom. Photo: Jeremy Brooks
Some have posited that a homemade firework rocket may be causing the Berkeley boom. Photo: Jeremy Brooks

Many have adopted an attitude of bemusement online about the phenomenon (“What’s so classic about this is we’re watching Mary Poppins w/ our kid and she’s afraid of the Admiral’s booms!”). Others have also described it as “very scary,” and have not been pleased about the repeated interruptions.

“Another loud boom, seems unfriendly,” David Heron Wallace wrote. “Where Berkeley once stood for radicalism, must we now stand being cool, and collected?”

On some nights, reports have been scattered and infrequent, but on at least six nights, slews of tweets have come in around the same time and seem to confirm the existence of the notable sound. The nights with the most reports reviewed by Berkeleyside have been Feb. 26, and March 3, 15, 17, 25 and 29. Most of the incidents have taken place from about 8-10 p.m. There’s no discernible pattern as far as days of the week.

#BerkeleyBoom reports.
#BerkeleyBoom reports. Source: Twitter/Berkeleyside

Berkeleyside has twice reported on the boom, first on Feb. 26. In that instance, calls about a single “loud report,” in police parlance, caused the the 911 switchboard lines to light up, reported dispatchers over the scanner. Police went out to the 2800 block of Acton Street at 8:40 p.m., but ultimately didn’t find anything.

Wrote Paul Rauber on Twitter: “Kid wanted to know what huge report just now was. Treasure Island shelling W. Berkeley? I said ask @berkeleyside, they’ll know.”

That night, Tajalli Love wrote that the noise sounded like a small explosion from a pipe bomb or something similar. From Alcatraz Avenue and Sacramento Street, Love added, “Windows shook.”

Dan Bostonweeks wrote that he “saw a flash from 55th & San Pablo before the bang.”

Two nights later, Feb. 28, a handful of people thought they heard it again.

Wrote Barbara Henry on Berkeleyside’s Facebook page: “So, I hope that whoever or whatever is causing the loud startling explosive sounds in South Berkeley every other night this week is found out soon. It is not amusing.”

The next night, one local resident said he thought he had found the cause. Jim Emerson said, also on Berkeleyside’s Facebook page, “Explosive mystery solved in South Berkeley. For second night a loud boom rattled windows, vibrated floorboards and set off car alarms. This time (maybe it was about 9:30?) an orange colored, apparently homemade, fireworks rocket streaked upwards in the sky and really spooked my dog while he was attending to his evening business. It appeared to originate near Ashby and Sacramento, though it have been closer to Alcatraz.”

March 3, many local residents said they heard the sound a third time, at about 9:40 p.m.

Reader reports about the #BerkeleyBoom on Twitter on March 3.
Reader reports about the #BerkeleyBoom on Twitter on March 3.

Berkeley Police spokeswoman Officer Jennifer Coats said officers did respond to a loud report call that night, but didn’t find anything.

The #BerkeleyBoom hashtag appears to have originated Feb. 26 when Twitter user Domain Awareness wrote: “The Great #BerkeleyBoom Mystery @berkeleyside will get to the bottom of this ASAP.”

Since then, at least 70 people have pondered online about the boom, sharing theories and information about it on Twitter. The label built momentum as the booms continued, causing even those who had not heard the sound to weigh in. Wrote Fire Catcher: “This #Berkeleyboom sounds like a catchy new exercise craze like zumba.”

Some wondered if it might be linked to the AC Transit hydrogen refueling station at San Pablo Avenue and 47th Street, or to a PG&E equipment problem of some kind. But officials reported no outages or associated problems.

Berkeley nights were largely free of the boom for the better part of the next two weeks. Then, March 15, a slew of new reports came in around South Berkeley. And roughly a dozen more tweets about the sound surfaced over the next couple days.

Wrote Eric Smillie: “Now I think every noise is a #Berkeleyboom,” to which Brock Winstead responded, “Wait, I just heard a boom. Same boom? Competing booms? Boomtown?! I need to lie down.” Smillie replied: “How to know if a mystery boom is the mystery boom? Booms beget booms.”

On March 25, last Wednesday, about a dozen people said they heard the sound around 8:20 p.m. Most of those reports were in South Berkeley, but some said they thought they heard it north of downtown, at Hearst and Martin Luther King Jr. Way, and on University Avenue at Curtis Street.

“IT’S BACK,” wrote one person on Twitter. Another described it as a “big echo-y bang near McGee,” adding: “I’m not going out there.”

Another noted that it was louder that before, from Ward Street and San Pablo Avenue, but said there were “No smoke plumes visible.”

Twitter reports about the #BerkeleyBoom on Twitter on March 25.
Twitter reports about the #BerkeleyBoom on Twitter on March 25.

Acting Lt. Joseph Okies of the Berkeley Police Department said officers were dispatched to the area north of San Pablo Park that night, but found no signs of a crime.

A slew of additional reports, including nearby intersections, came in Sunday, March 29, causing one person on Twitter to wonder if perhaps the sound is “an elaborate plot to get Twitter users to reveal their addresses?”

One suggested that a phenomenon called an “earthquake boom,” also called Seneca guns, might be responsible. (See what the USGS has to say about that sound.)

The true cause has yet to be confirmed, but some people believe they have seen signs of the boom. In addition to Emerson’s March 1 report (“orange colored, apparently homemade, fireworks rocket”), in one instance, firefighters told dispatch they saw fireworks, in South Berkeley around Dohr Street, that they believed to be the cause.

Wrote a local resident in mid-March: “Our neighbor list keeps saying they’re M100s set off by kids, some claim to have seen it.”

One woman said she “saw the flash beforehand.” Said another, who also wondered if fireworks might be responsible: “saw a flash of white light just a second before the #berkeleyboom.”

And so the boom remains a mystery, but that hasn’t stopped the theories. The sound has even prompted at least one person to posit — in what could, without too much difficulty, be heard as a bit of verse — that the boom has a definite rebellious streak.

Wrote Blake Jenkins over the weekend on Twitter: “Homemade rockets? Sometimes there’s smoke and contrail. So subversive, so #berkeleyboom.”

If you’ve heard the #BerkeleyBoom, please let us know in the comments what makes this sound so distinctive, and whether you have other ideas about what might be the cause. What, if anything, can or should be done about it? 

Wall Street Journal joins the fun after a thoughtful note to a Berkeley thief goes viral (03.25.15)
Berkeley email spam mishap spawns community spirit (03.24.15)
Photos: With some rain comes a rainbow over Berkeley (03.23.15)
A Berkeley note to Wall Street Journal thief gets results (03.19.15)
‘To the man who has been taking my Wall Street Journal’ (03.19.15)

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Emilie Raguso (former senior editor, news) joined Berkeleyside in 2012 and covered politics, public safety and development until her departure in 2022. In 2017, Emilie was named Journalist...