Residents of Auckland, New Zealand, reported a loud explosive noise on the night of Saturday, May 30, which some residents believed may have been a weapons test occurring nearby.

Stuff.co.nz reported that the incident occurred at around 11.30 PM local time on Saturday night. Police had no explanation for the sound, although fireworks had not been ruled out.

The report describes that the sound had been heard over a wide area:

The noise was heard in the Mt Albert, Mt Roskill and Three Kings area – as well as far away as Waterview to the west and Papakura to the south.

Resident Ash Ball said there was a massive explosion which woke up the neighbourhood. “It shook our house and woke us up with a hell of a fright.”

The Stuff piece elaborates on the incident, noting that some residents “are convinced something more untoward is going on.” Referring to Twitter accounts in the area for speculative ideas about the noise, the Stuff article cites theories that a bomb exploding, or perhaps a sonic boom from aircraft passing over, might have been to blame.

It does, however, also note reports from last June that occurred in the area, where mystery booms were reported across northwestern Auckland. The theory at that time had been training exercises being carried out at the Kaipara Bomb Range had led to reports of mystery noises.

Similar theories about explosive tests were offered late last summer and into the winter months for a rash of boom reports that began occurring around Kansas and Ohio in the United States. However, looking at the history of boom reports in various locales, it is interesting to note that the booms tend to spike in clusters of reports that occur annually. For instance, between the winter months of 1977 and 1978, more than 600 reports of mystery booms were documented along the east coast of the United States, particularly around southern New Jersey. A similar rash of reports occurred around this time of year in the 1990s, and the last two winters have seen this trend again, where reports have spiked in the cooler weather months. The greatest number of U.S. reports occurred in the northeast and midwestern states, especially New Jersey and the Great Lakes region.

Apparent trends like these strongly favor cryoseisms or “frost quakes” as an explanation, although the booms are reported throughout all parts of the year, and as we discuss elsewhere on this site, a number of conditions that range from geological phenomenon to weather activity have been cited as causes behind loud booming sounds and similar anomalous noises in nature.

Temperature data for the Auckland area on the night in question saw a temperature low of 41.5 °F, according to Wunderground.com. However, coinciding with the time of the boom (roughly 11:30 PM local time), temperatures  were hovering around 54.1 °F. 

Update: Local officials are now saying that fireworks were observed in the area, and that the booms may have been the result of fireworks, the spent casings for which were purportedly found at Hillsborough cemetary.

Image by Sandy Austin, Flickr.