A series of strong aftershocks rattled Taiwan, less than a day after a deadly 6.4-magnitude earthquake struck Hualien city on the island's east coast.
The latest aftershock, a 5.7-magnitude tremor, is the most powerful one yet.
The temblor struck on Wednesday (Feb 7) night, 19km northeast of Hualien at a depth of 10.8km, according to the US Geological Survey.
The area saw six tremors of magnitude 5 and above in the 24 hours since Tuesday's quake, USGS data showed.
Taiwan's government noted that the earthquake took place near Hualien, where recovery efforts are still ongoing.
As of late Wednesday, at least seven people in the city were killed and 67 still missing, with rescuers combing the rubble of collapsed buildings and survivors recounting their escape from a dangerously tilting apartment block.
INTENSITY, NUMBER OF TREMORS 'UNPRECEDENTED'
The intensity and number of foreshocks and aftershocks are unprecedented in the region, Focus Taiwan reported on Wednesday, citing Taiwan's Central Weather Bureau.
From Feb 4 to Tuesday night's 6.4-magnitude quake, 94 shocks were recorded.
Between then and 1pm on Wednesday, 150 aftershocks were recorded.
"This is unprecedented and not a normal release of energy," Chen Kuo-chang, acting director of the Central Weather Bureau's Seismology Centre told Taiwanese media.
Taiwan experiences 20 to 25 earthquakes of magnitude of 5.0 or higher each year and the sequence over the past few days has already accounted for nearly half of that number, he added.
The bureau warned of more aftershocks, adding that it does not rule out the possibility of strong quakes of magnitude 6.0 or higher.