According to US outlets, this is the third time that the enigmatic incident, which the media dubbed a "skyquake", has occurred this year. Two previous booms occurred in February and in March, with residents speculating that they had witnessed an earthquake. However, the US Geological Survey later tweeted that the shaking wasn’t a tremor.
A cryptic boom has shaken the US city of San Diego near the border with Mexico, prompting wild speculation among residents. Unlike two previous incidents, which occurred within 10 minutes after 5 pm (local time), the latest one occurred after sunset around 8:20 pm. According to social media users the loud noise prompted residents to rush to their neighbours, asking whether they also felt it.
Everyone’s virtually on their front porch in their bathrobes asking neighbors if they heard a boom
— Jordan Beane (@JordanBeane_SD) June 9, 2021
A sonic boom, explosion, and earthquake were among the most popular "suspects".
a sonic boom just shook our apartment in san diego, that’s a new one for me 😂😅
— alexa (@alexaanddragons) June 9, 2021
It scared the hell out of us. Sounded like a gas explosion.
Mystery shaking felt, boom heard across San Diego County for third time in 2021 https://t.co/wWeMFrszHg
— Ander C. Lark (@DefiantAndi) June 9, 2021
The earthquake scenario was later dismissed by the US Geological Survey, which said that no tremors were recorded in the vicinity of San Diego.
One person suggested that the mysterious boom felt like a severe natural disaster.
honestly what that boom felt like in san diego pic.twitter.com/pZqYVaHBL6
— melissa artobello (@lissawithm) June 9, 2021
Another suggested that the loud noise was likely made by the US Marine Corps, which previously warned residents about the live-fire training.
OK, I think I know where that boom came from, San Diego: pic.twitter.com/zjXXRPk2Gx
— Mariel (@themarielhatter) June 9, 2021
The mayor of San Diego also spoke about the incident and took the opportunity to remind residents to get jabs against COVID-19.
Yes, I heard it.
No, I don’t know what it was.
I’ll share if I get any information.
Get vaccinated if you haven’t yet.#SanDiegoBoom
— Todd Gloria (@ToddGloria) June 9, 2021