TAIPEI — A 7.4-magnitude earthquake, followed by several strong aftershocks, struck off the east coast of Taiwan on Wednesday morning, damaging buildings, causing landslides and prompting tsunami warnings in both Taiwan and Japan. The earthquake, which the U.S. Geological Survey said measured 7.4 in magnitude, hit about 15 miles south of Hualien county just before 8 a.m. local time. Taiwan’s Central Weather Administration recorded it at 7.2. It was the largest earthquake to hit Taiwan in 25 years, and was felt in parts of Japan and China, too.