The forecaster added that Hongkongers back home had experienced “minor shaking, the duration of which was a few seconds”.

The incident came after the city felt the ripples of a 4.9 magnitude earthquake over the South China Sea during the early hours of May 1.

Hong Kong was also on the periphery of another quake on April 22, which had a magnitude of 5.3. Its epicentre was about 190km west of Kaohsiung, a port city in southern Taiwan, some 450km east of Hong Kong.

The Observatory said tremors from the quakes on Monday and in April would have felt like the “passing of light trucks”.

But tremors from the earthquake in May were more intense and likely caused hanging objects to swing and rattled windows, dishes and doors, since the seismic event was about 300km closer to the city, it said.

Earthquakes are generally measured by their magnitude and intensity. The former is determined by the amount of energy released at the quake’s source, while the latter charts how much the ground shakes at a certain location.

Is Hong Kong reporting more earthquake activity?

Yang Hongfeng, an associate professor at Chinese University’s science faculty, said Hong Kong generally experienced the tremors of nearby quakes six or seven times a year.

“It is common for Hongkongers to feel earthquakes, but we have not noticed a clear increase in earthquake activity in the area this year,” he said.

So far this year, the city has felt the vibrations from seven separate quakes, including five that occurred in Guangdong province.

Yang also noted that earthquakes near Heyuan were not unusual since the construction of the neighbouring Xinfengjiang Reservoir in 1958.

“Three years after it was built, there was a magnitude 6.2 earthquake right next to the dam of the reservoir,” he said. “Since then, Heyuan has become active in regularly producing earthquakes of magnitudes four or less.”

The scholar, who is conducting research in the region, said water from the reservoir could have flowed into the earth’s fault lines, lubricating them and potentially triggering quakes.

Located about 167km northeast of Hong Kong, Heyuan reported 74 quakes with magnitudes of two and above over the last 12 months.

Quakes near the southern Chinese city also accounted for three out of the seven times Hong Kong reported experiencing tremors.

Thousands jolted awake as minor earthquake rattles Hong Kong

Could Hong Kong be hit by a large quake?

The Observatory said Hong Kong’s location affected its chances of being struck by an earthquake of a larger magnitude.

“Most earthquakes in the world occur along the boundaries of crustal plates. Hong Kong lies within the Eurasian Plate and is located far away from the nearest boundary with the Pacific Plate on the Circum-Pacific Seismic Belt that runs through Japan, Taiwan and the Philippines,” it said.

The city’s potential for quakes was much lower than locations such as Japan, Taiwan, the Philippines and western parts of the United States, the Observatory said, explaining those areas lay close to “more seismically active zones”.

Chinese University geophysicist Tan Yen Joe echoed the forecaster’s remarks, saying: “Hong Kong is rarely the epicentre for earthquakes, but we do have faults that are big enough to generate a large-scale earthquake.”

He added that Hong Kong was more likely to be affected by tremors from nearby earthquakes occurring in areas such as Guangdong province.

The city has not recorded any deaths or injuries as a direct result of tremors since official records began in 1905.

The only seismic activity to cause structural damage in Hong Kong was a 7.2 magnitude earthquake that struck Shantou, about 300km away, in 1918 during Lunar New Year celebrations.

The damage included several cracks in the walls of the Observatory’s headquarters.

Is Hong Kong prepared for a larger quake?

Chinese University’s Yang said the city’s “newer buildings should be able to withstand an earthquake with an intensity of seven”.

The intensity of earthquakes is measured on a 12-point scale known as the Modified Mercalli Intensity range. The system takes into account damage assessments and eyewitness accounts, with results also depending on how near someone is to a quake’s epicentre and how close it was to the surface.

“But questions remain about older buildings and whether they would be able to withstand an earthquake similar to the one in 1918,” he said.

Tan, meanwhile, explained the city typically experienced seismic activity that ranked low on the scale.

“The tremors felt in Hong Kong are usually of an intensity of three or four, which is considered minor,” he said. “The biggest threat to the public would be items shaking or swinging that could hit someone if they fell.”

The Buildings Department had also concluded that frequent typhoon activity meant many buildings in the city were built to withstand strong winds and had a certain degree of seismic resistance.

While acknowledging that such buildings were not specifically built to be quake resistant, the department noted earthquakes with an intensity of five to six were only likely to occur locally once every 72 years and those reaching seven might only hit every 475 years.