The 4.2 magnitude earthquake had concerned residents phoning authorities. Photo / AP Expand The 4.2 magnitude earthquake had concerned residents phoning authorities. Photo / AP A rare earthquake has rattled Hong Kong, prompting concerned local residents to call the authorities, the Hong Kong Observatory says. There were no reports of damage from the quake which had a magnitude of 4.2, according to the US Geological Survey, adding that it struck at a relatively shallow depth of 19km in tyhe early hours of the morning. It hit the Chinese province of Guangdong, some 11km northeast of Dongguan - a factory hub - which is around 100km from Hong Kong. The Hong Kong Observatory measured the quake at 4.5 magnitude and said it was felt by residents in the glitzy financial hub.