A moderate earthquake rocked the Sierra near Bishop, but no damage was reported. The temblor measured 5.4 on the Richter scale, said Dennis Meredith, a spokesman for Caltech. He said the epicenter was 20 miles northwest of Bishop along U. S. 395. However, seismologists at the University of California, Berkeley, and the U. S. Geological Survey measured it at 4.9 and said the epicenter was 12 miles northwest of Bishop. The monitoring stations use different instruments and often report different readings.