Instrumental epicenter and origin time for the Manix earthquake are 34°58′ N, 116° 32′ W., 07:58:04 P.S.T. (15:58:04 G.C.T.), April 10, 1947. The probable error of location does not exceed a few kilometers. Certain aftershocks originated south of the main shock. Initial recorded compressions and dilatations are consistent with left-hand strike-slip on a previously identified fault which trends about N 70° E. Trace phenomena, to be reported later, were produced. Other effects, including damage, in the heavily shaken area are described.