Dozens of people alerted the Observatory that they felt the magnitude 3.2 earthquake near Sanshui District of Foshan, Guangdong on Sunday.
The quake hit 170 kilometers northwest of Hong Kong at 11.38 am. There were no immediate reports of casualties or damage.
The Hong Kong weather watchdog received over ten locally felt reports of minor shaking, the duration of which was a few seconds.
"Initial estimate gave a local intensity of three on the Modified Mercalli Intensity Scale, that is felt indoors," the Observatory said. "Vibration like the passing of light trucks."