The Wilmar Avenue fault is a late Quaternary reverse fault in southwestern San Luis Obispo County, California, that one of us (S.P.N.) identified in 1986. Mapping shows that the fault is at the southeastern base of the San Luis Range and contributed to the uplift of the range. The fault is divided into two structural sections: a western section that is a discrete fault zone that places lower Miocene rocks above overturned upper Pliocene strata, and an eastern segment that is partly a blind fault expressed at the surface in a monoclinal fault propagation fold.

In both sections an upper Pliocene marine sand unit is offset vertically by 250 to 300 m, and offsets late Pleistocene marine terraces. Late Quaternary slip rates for both segments derived from the offset terraces are estimated at between 0.04 and 0.07 m/Ka. Although Holocene slip-rate data are lacking, the Wilmar Avenue fault zone is considered to be part of the seismogenic southwestern boundary zone of the San Luis/Pismo block (Slemmons and Clark, 1991) and could pose a seismic hazard to nearby communities.