Don, The 1927 Lompoc quake was in my Ph.D. thesis area. It was a thrust quake. I think your comment about the first wave is incorrect (or else, explain why you say this?) The Hosgri fault is a right-lateral strike-slip fault, part of the San Gregorio-San Simeon-Hosgri right-lateral system. There are many who have said the Hosgri is a thrust fault. See my posts below-they are wrong. Helmberger and Sommerville (???) did not check ref) relocated the 1927 quake to well SW of the Hosgri fault. There are some recativated Miocene normal faults out in that area that are large enough to have such a quake....-there are active faults even farther west. My wife and I and others have a pending NSF proposal to study the faults farther west. There were two M5 1/2 thrust quakes in Santa Lucia basin, far to the west. This area has a folded seafloor. there is a high-angle fault that qualitively looks like a partitioned strike slip fault on seismic-with a 100 m seafloor scarp. There is a sharp right offset of Arguello canyon of a couple km at what is probably this fault....this fault system is liable to be the same as the faults west of Baja that allow Baja to move with respect to the Pacific plate...

Of most interest to you Don, is that the 1927 Lompoc earthquake was at the antipode of a swarm of M7s -the largest known swarm of intraplate quakes or something like that. One of the 7s was, if I recall correctly after a decade, 4 days before the Lompoc quake. By antipode, I think within a couple degrees-maybe less....Chris