China's earthquake authorities are investigating an unusual sequence of twin 5.2-magnitude earthquakes that struck the same district in Guangxi Zhuang autonomous region within less than 24 hours, triggering widespread tremors and secondary geological hazards, including sinkholes.

The latest earthquake struck Liunan district in Liuzhou at 9:44 pm on Monday at a depth of 8 kilometers, according to the China Earthquake Networks Center (CENC). Earlier the same day, another 5.2-magnitude quake hit nearly the identical location at 12:21 am, also at a depth of 8 km.

CENC said the epicenters of the two quakes were only about 1 kilometer apart. Tremors were widely felt across Guangxi and neighboring Guangdong province, with many residents reporting strong shaking on social media.

Researchers with the CENC said the two earthquakes reflected a concentrated release of tectonic stress that had accumulated in the fault line over a long period.

"Short-term consecutive earthquakes above magnitude 5 are relatively uncommon, but not unprecedented," Han Yanyan, a researcher with the CENC, said in an interview with China Central Television. Han cited previous twin earthquake events in Jilin province in 2013 and Yiliang county in Yunnan province in 2012.

Han also said preliminary investigations found no direct link between the earthquakes and recent rainfall. She added that aftershocks may continue for some time and warned residents to stay away from old or structurally weak buildings that could pose secondary risks.

According to the Guangxi Earthquake Agency, the quakes were likely triggered by activity along the Baipeng fault, about 3 km from the epicenter. The agency said waveform analysis indicated the event was a typical tectonic earthquake, according to a report of Nanguo Morning Post, a subsidiary of Guangxi Daily.

Liuzhou sits near the Hechi-Yizhou fault zone and the Guilin-Nanning fault zone, both of which are considered to have relatively low seismic activity, according to the Guangxi Earthquake Agency.

The agency said the dual events were shallow-focus quakes. Their relatively shallow depths allowed seismic energy to reach the surface without much dissipation, which amplified movement at the surface level.

Many residents living in high-rise buildings described the shaking as feeling "like being on ocean waves". The Guangxi Earthquake Agency attributed this to long-lasting seismic waves generated by shallow quakes, resonance effects between buildings and seismic motion, and the "whip effect", in which upper floors sway more strongly.

Authorities also said Liuzhou's extensive karst geology amplified the seismic waves. More than 70 percent of the city's underground area is classified as highly developed karst terrain.

Following the earthquakes, several circular sinkholes appeared in Liunan district. Experts from the Guangxi Geological Environment Monitoring Station said the collapses were earthquake-induced secondary geological disasters linked to the region's fragile karst system, according to a report from CGTN.

The experts said seismic activity likely destabilized underground karst cavities, causing overlying soil layers to collapse. Three sinkhole sites have so far been identified, including one in a pond and two near roads in Taiyangcun township.

Emergency teams have launched inspections and real-time monitoring to assess whether additional collapses or geological hazards may emerge, local authorities said.

Historically, the area within 100 km of the epicenter has recorded five earthquakes above magnitude 4.7. The strongest on record was a magnitude 5.5 earthquake in Rongshui county in 1695, according to the Guangxi Earthquake Agency. The latest earthquakes are therefore close to the region's historical upper limit for seismic activity.