An earthquake of magnitude 7 or higher in the Tokyo area would kill up to 18,000 people and destroy about 400,000 buildings, according to a government expert panel’s estimates released on Dec. 19.

Japan has recorded a series of powerful aftershocks in the past several hours, including a magnitude 5.7 earthquake near the east coast of Honshu and a 4.9 earthquake in the Hokkaido region shortly ...