Philippine officials say that years of disaster-preparedness drills helped prevent a larger casualty toll when one of the strongest earthquakes in 50 years struck the south and left 55 people dead with 31 others still missing. The 7.8 magnitude offshore quake struck Monday off the southern province of Sarangani. The temblor also injured about 1,120 people and displaced more than 45,000 people. About half the displaced were still in emergency shelters on Friday. The quake damaged more than 12,600 houses across farming towns and cities. Provincial officials said that many were still too traumatized to return home because of strong aftershocks.