While I can't rule out earthquake damage, I would have to say there are much more likely reasons. Earthquakes 3 and below on the Richter scale are easlier felt but very rarely cause any damage. Earthquakes 4-5 can crack masonary walls, but the bottom line is buildings that were poorly constructed are the most suspectable. Block walls are notorious for having hairline crack issues, just by their nature. The soil that was backfilled around your basement walls puts a horizontal force agaist it. Block walls have great compressional strength (the downdown force from the weight of your house), but poor strenght from lateral forces. Poor drainage enhances this problem-living on a ridge, you should have good drainage, but were your french drains installed with plenty of filter material? Where they installed with care? I have actually seen cases where the drains were installed where water could pool around the footing, without draining.
More serious is the fact you are on a ridge. Chances are your house foundation has been cut into the bank on one side and filled on the other. Soil creep (soil moves downhill) will put great stress on the uphill (cut) side of your foundation. Poor compaction can lead to serious settleing on the downhill side, and even with good compaction, will not stop soil creep if the slope is steep. There have been cases of well build structures actually sliding down hillsides due to poor siting (too steep of slope or poor underlying geology).

Anyhow, don't want to alarm you, but I wouldn't worry about earthquakes, just enjoy the view