I live in earthquake prone Northern California.
I don't think you can retrofit the wall, there's too many things you'd
need to do. Just stuffing rebar down the holes and filling them with
concrete may make the wall stronger, but what's the foundation
underneath? I was within 5 miles of the epicenter of Loma Prieta quake
in '89 and I remember a bunch of cinderblock walls coming down in the
quake. I'd remove it and rebuild it with sufficient footings under
some sufficient vertical support.
Oh wait, idea. You could possibly bolt some 3-4" dia pipes to it every
6 feet or so. This is just a guess. Every 6 feet, dig a 2 foot hole,
put the pipe in, run long bolts thru the pipe, thru the cinderblock,
into a big steel washer/plate on the other side. Probably use about 4
bolts along the length of the pipe. Then fill the hole with concrete.
Realistically, since I don't think there's an easy fix for this, and
since you are probably right that, after a quake, it may come down.
If you're going to put some sweat into this job, get a civil engineer
to take a look at it and give you some good advice. It would cost you
a modest amount, but at least you'd know you were doing the right
thing. Otherwise, you may do a bunch of 'work' to make it good in your
own sight, but the thing would still come down. Look what happened to
the Cypress structure in Oakland during Loma Prieta, and that even had
engineers design it. Bottom line, engineers know quite a bit more now
than they did then and that knowledge will help you out in this