What is the lateral ground acceleration, at the fault line, during a strike-slip earthquake?
It can be high but is bounded because the slip velocity on fault (as it slips during an earthquake) is usually of the order of 1-3 m/sec.

Kaikoura earthquake (M7.8 strike slip event) had a max PGA of 3.1 g (second highest ever recorded) but it is attributed due to flapping effect. See here for more details.