A powerful earthquake that sent boulders tumbling onto a national highway, injured more than 100 people across a wide swath of northern Japan, officials said on Thursday. The quake, which had a preliminary magnitude of 6.8, came just one month after a 7.2 magnitude temblor killed at least 12 people in Japan's northern mountains. Japan's meteorological agency said the earthquake struck shortly after midnight at a depth of about 105 km near the coast of Iwate, which is 450 km northeast of Tokyo, where shaking was also felt. Most of the injuries were minor and none were life threatening, said a National Police Agency official on condition of anonymity, citing department policy. The earthquake caused strong shaking for about 40 seconds in many areas of northern Japan. Life quickly returned to normal, however. "Everything