The mainland Chinese cities of Shanwei and Huizhou in Guangdong province were closer to the epicentre, data from the United States Geological Survey showed.

Honorary professor Chan Lung-sang, of the University of Hong Kong’s department of earth sciences, said the tremor was one of the more significant ones to hit the city in recent years.

“Earthquakes along coastal South China are not rare. This one … measured a III to IV degrees on the intensity scale, which is among the highest over the past 15 years or so,” Chan said.

With Hong Kong located in a zone known as the Southeast China Coastal Active Seismic Belt, Chan said light earthquakes with a magnitude of 3 to 4 were common, with bigger ones clocking in above 6 taking place within 150km of the city every century or so.

“An event that affects [Hong Kong] does not have to be very close. A sufficiently big one that occurs, say, 200km from Hong Kong, may cause some extent of damage,” he said. “The chance of having a significant one in our lifetime is low, but we should always be prepared, even for low-risk incidents.”

Chan added that the 1918 Shantou earthquake, with a magnitude of 7.3, caused some damage in Hong Kong, in addition to the destruction and high number of casualties in the mainland Chinese city itself.

Professor Owen Richard Bernhart, from Baptist University’s geography department, also reassured residents that minor earthquakes were common around the region and typically did not cause significant damage.

Still, Monday’s quake caught some locals off guard. One 26-year-old Hongkonger, who gave her name as Patricia, said she was shaken awake by the tremor last night, believing at first that it was her body that was trembling.

She only realised it had been an earthquake after checking her phone and seeing social media posts about the incident.

“The thought of an earthquake didn’t cross my mind, as [it is] somewhat unthinkable in Hong Kong,” said Patricia, who lives in an 8th-floor flat in Tin Hau. “Strange times in Hong Kong.”

Another resident, who gave his name as John William, was still awake when he felt his bed, wardrobe and door start rattling. The 23-year-old also found out on social media that his friends were experiencing similar things.

“I was in shock. To think an earthquake can make its way here to Hong Kong,” he said. “I couldn’t sleep afterwards after thinking of worst-case scenarios. But in the end, I was just glad it wasn’t strong enough to a point stuff could start falling down.”

Some internet users have also criticised the Observatory for broadcasting the earthquake’s information later than expected. But in a social media post, the weather forecaster said it typically issued earthquake reports more quickly only when the magnitude was 5 or above.

Its earthquake system collects real-time data from local and global seismic networks, which can calculate the time, magnitude and epicentre in a few minutes.

But the Observatory said the limitations of the science involved meant supplying accurate, advance warnings was impossible.

“Earthquakes that cause locally felt vibrations usually occur within a few hundred kilometres. Due to the short distance, the instruments and people can basically only sense them synchronously,” it said.