TOKYO — The Japanese box office plunged 18% to $2.34 billion last year, on admissions down 17% to 145 million, according to figures compiled by the Motion Picture Producers Assn. of Japan.The March 11 earthquake and tsunami, which left nearly 20,000 dead and missing, and caused the meltdown of three reactors at the Fukushima Daiichi nuclear plant, shuttered theaters in wide swaths of the country for weeks. The feared power blackouts never materialized during the peak summer season, however, allowing a return to normal operation for theater owners. Another problem was a lack of blockbusters, both domestic and foreign. A total of 54 pics passed the ¥1 billion ($13 million) mark, traditionally considered the measure of a hit — six more than in 2010 — but only eight earned more than ¥4 billion yen ($52 billion) compared with 11 in 2010. The B.O. for local pics dropped 16% to $1.29 billion; foreign pics’ earnings fell 20% to $1.06 billion. For the fourth year in a row local fare beat the imports in market share, with 55%. The highest-earning pic was “Harry Potter and the Deathly Hallows: Part 2″ with $124 million, while leader for the home team was the Studio Ghibli toon “From Up on Poppy Hill,” which scored $77 million. The number of screens, 3,396, was nearly unchanged from 2010.