TAPACHULA, México — A 7.3-magnitude earthquake struck southern Mexico and parts of Central America on Friday, seismologists said, with a tsunami alert briefly issued for a stretch of the Pacific coast. Residents felt intense tremors in the Mexican states of Chiapas and Oaxaca as well as in Guatemala and El Salvador, AFP journalists confirmed. Authorities have not yet reported any victims. The U.S. Geological Survey (USGS) said the quake's epicenter was located offshore some 48 kilometers (30 miles) from the town of Aquiles Serdan, at a depth of 18 kilometers. The Mexican seismological service recorded more than 30 aftershocks of various magnitudes, measuring as high as 6.8. The U.S. government issued a tsunami warning for Pacific coastal areas of Mexico and Guatemala, but later said the threat had passed. In Tuxtla Gutierrez, the state capital of Chiapas, there were scenes of panic in the few tall buildings of the city, according to an AFP journalist in the area. "It feels horrible up there," Araceli Sanchez, a government employee who was in a 15-story building, told AFP. "There were peo