At least 15 earthquakes hit the Hualien region of East Taiwan Sunday, with the heaviest measuring 5.6, the Central Weather Bureau said. The most serious tremor hit at 5:34 p.m. and was felt across most of Northern Taiwan, though no immediate damage was reported.

A total of 14 quakes had their epicenter located at a distance roughly between 16 and 21 kilometers northeast of the Hsiulin Earthquake Monitoring Station. An additional temblor, at 5.52 p.m., hit 21.4 kilometers south of Nan'ao in Ilan County, in an area on the east coast not so far from the Hualien area.

The Central Weather Bureau explained the high number of quakes as a rarely seen series of small quakes leading up to the main tremor, and followed by aftershocks.

The quakes hit an area already well-known for its frequent tremors, and signified a normal release of energy, the bureau said, adding that the total number of shocks Sunday actually numbered more than 40, but most could not be felt.

The first quake of the day struck at 9:26 a.m. and measured 4.4, according to the bureau. The next quake didn't occur until 1:44 p.m., but was registered at 4.9. After 3 p.m., the quakes followed each other at a more rapid tempo, with the scale diminishing ranging from 4.2 to 3.8, according to bureau news releases.

The last and largest quake occurred at a depth of 8 kilometers under the ocean. Its intensity reached 5 in Hoping, Hualien County, and in Nan'ao in neighboring Ilan County, and 3 in Hualien City, the weather bureau said.

Earthquakes often hit Taiwan, with the most lethal of recent times striking Central Taiwan's Nantou County on September 21, 1999, leaving more than 2,300 people dead islandwide.