An earthquake at 9:46 PM Pacific Standard Time near the east coast of Honshu, Japan, with preliminary magnitude 8.9 has triggered a potentially large tsunami now propagating across the Pacific Ocean.

The Pacific Tsunami Warning Cente (PTWC) in Hilo, Hawaii, has issued a tsunami alert for the entire region. At current, tsunami warning is in effect for more than 20 countries.

“This is the largest earthquake known in Japan," said Kevin McCue, a seismologist at CQUniversity’s campus in Canberra, in a statement to the Australian Science Media Centre (AusSMC).

The quake originated some 400 kilometres north of Tokyo, at 24 kilometres depth. The sudden dislocation of the seafloor generated a tsunami which hit north Japan around 30 minutes later. The quake and tsunami have killed at least 18 people in Japan, and caused severe and widespread destruction.

“Japan has a rigourous earthquake building code and excellent tsunami warning system and evacuation plans,” said James Goff, Co-Director of the Australian Tsunami Research Centre and Natural Hazards Research Lab at the University of New South Wales, in a statement to the AusSMC. "This event will likely provide a severe test for all of them.”

The first of possibly several large waves are expected to reach the Hawaiian Islands at around 03.00 am on Friday morning. Emergency services in Hawaii have begun to evacuate residents and tourists along threatened coastlines. In the Philippines, officials have ordered the evacuation of coastal communities along the country’s eastern coast.

UPDATE: Associated Press reports that tsunami waves have reached Hawaii.

The Pacific Tsunami Warning Center says Kauai was the first island hit early Friday by the tsunami, and the waves surged in Waikiki. Officials predicted Hawaii would experience waves up to 6 feet, and officials spent hours evacuating ahead of the storms.

Image courtesy of Burak Uslu, NOAA