More than 100 aftershocks were registered from the quake that rocked the Mexican border town of Mexicali and communities just north of the border Friday night. Downed telephone lines in El Centro and broken windows near the epicenter were the only reported damage. The initial quake registered 5.6 on the Richter scale, said Robert Finn, a spokesman for the California Institute of Technology in Pasadena. The epicenter was about 20 miles southeast of Mexicali. The largest aftershock registered 4.4., Finn said, and the next largest was a 4.3 reading.