In recent times, natural disasters and man-made calamities have been occurring frequently in mainland China, causing the public to be wary of various unusual occurrences. On the evening of September 3, a large number of flying animals were seen circling and gathering in Mianzhu, Sichuan; on the evening of September 4, a booming sound was heard in the sky over Chuzhou, Anhui, sparking speculations.
In Mianzhu, Sichuan on the evening of September 3, a significant number of flying animals were observed circling and gathering, leading many internet users to suspect that this phenomenon was related to an imminent major earthquake.
According to a report by the Xinjing News, on September 4, the Mianzhu Municipal Emergency Bureau stated that there were no earthquake-related early warning information available. The Mianzhu Natural Resources and Planning Bureau mentioned that the majority of the flying animals were swallows, gathering in preparation for their southern migration for the winter.
The official explanation has raised doubts among internet users. Some netizens commented, “Prior to the Wenchuan earthquake, there was also a mass migration of frogs in Mianzhu, which was similarly explained by officials as a normal occurrence…”
Mainland China has experienced frequent earthquakes in recent times, with at least 69 earthquakes of magnitude 3 or higher occurring in ten provinces and regions including Sichuan, Xinjiang, and Qinghai from August 4 to September 4. Among them, there were 15 earthquakes of magnitude 4 or higher and 3 earthquakes of magnitude 5 or higher.
Furthermore, on the evening of September 4, a booming sound was heard in the sky over Chuzhou, Anhui. A video circulated online showed a sudden loud sound over Chuzhou, startling residents and dogs, with another clip showing what appeared to be slight shaking of a camera.
The Chuzhou Municipal Emergency Management Bureau confirmed on its official WeChat account that a booming sound was heard over Chuzhou around 8:10 p.m. on September 4.
Officials stated that they have ruled out earthquakes, mining explosions, and other production safety accidents, preliminarily attributing the phenomenon to a high-altitude sound burst. Following the standard practice, officials emphasized, “Do not spread rumors, do not believe in rumors, do not propagate rumors.”
A sound burst refers to the explosive sound formed on the ground when a flying object generates a shockwave during supersonic flight, typically caused by supersonic flight of fighter jets.
Similar sounds have been frequently reported in various parts of China in recent years.
On February 24, 2022, a similar loud sound was heard in Qinhuangdao, and officials at the time also attributed it to a sound burst.
On May 28, 2024, the “Qinhuangdao loud noise” became a trending topic on mainland social media platforms. Local officials suggested it might be a sound burst, but the public remained unconvinced, questioning whether “sound burst is the scapegoat for all loud noises.”
Around 6:20 p.m. on December 4, 2024, a loud noise was heard in Binhai County, Yancheng City, Jiangsu Province, with the sound being so powerful that even windows vibrated. The local emergency management department speculated that the loud noise might have been caused by an aircraft sound burst.
Around 8:33 p.m. on May 27, 2025, another loud noise was suddenly heard in Binhai, Jiangsu, prompting many to question, “Is it also an aircraft sound burst?”
On the evening of August 20 this year, more than two loud explosions occurred in the main urban area of Yancheng City, Jiangsu. The specific source of the explosions was not officially reported.
Regarding the causes of these abnormal loud noises, current speculations among internet users include military exercises, the entry of meteors or meteorites into the atmosphere causing frictional explosions, or the falling of space debris, among others.