'an explosion happened' is correct and usable in written English.
You can use it to describe a sudden, loud, and destructive event, such as a bomb detonating. For example, "An explosion happened near the town square, and the resulting blast shook the entire street."
If an explosion happened now, we first have to say whether it's a manmade event or whether it's an earthquake.
Eyewitness, Ahmad Ajmal, told the Associated Press news agency: "When I got out of the vehicle and started walking, an explosion happened, the same vehicle I was in is there and destroyed".
Abdul Majid, a chef at the restaurant, told AFP news agency that he was sitting with his friends "in the kitchen when an explosion happened and smoke filled the kitchen".
"At around 19 10 on 30 April, an explosion happened at the passenger exit of Urumqi South Station when Train K453 from Chengdu to Urumqi arrived at the station, causing casualties," Xinjiang's local government news portal said.
"We used to sleep on the floor ― not in bed ― so that when an explosion happened, the glass wouldn't shatter on us," explained the girl, who eventually fled the capital city of Sana'a with her family to escape the dangers of living in a war zone.
When an explosion happens, ambulances roar through the narrow streets.
When an explosion happens on the launching pad or soon after liftoff, it is a spectacular, costly and potentially life-threatening event.
Crystals start to build up a year prior to eruptions and peak just before an explosion happens, the team reports online today in Science.
"If an explosion happens, there's a risk at all scales," USGS volcanologist Donald Swanson told the Post.
Toffler: As I like to say, you put the combustible elements together, and you gotta walk out of the room and occasionally an explosion happens.
If you are in a crowd scene and an explosion happens react like you would normally.
