How is it that, with the continuous movement of the tectonic plates, the Panama and Suez canals still operate after all these years?
The tectonic plates are moving s l o w l y. See the Moorland School’s tectonic plate page.
Or here at the US Geological Services page
I understand that they move slowly, but even one inch (2.5cm) per year over one hundred years would seem to add up. Even if the canal is not exactly on the fault, the pressure sould seem to have a warping effect. No?
They will warp only if they are close enough to a plate boundary to make a difference, or – more dramatically – if they actually cross a plate boundary.
1.) As Papermache Prince noted, much tectonic movement is relatively slow. Some, of course, is a little quicker paced (earthquakes), and it’s interesting to note that both of the sites you mention are at or near plate boundaries.
2.) There a bazillion faults, all over the world, that continuously make accomodations for relief of stresses within the earth’s crust at regional and very localized levels.
3.) The proof’s in the pudding; both canals are still there and intact, as are many much older structures around the world.
This makes me curious as to what sort of earthquake damage the canals may have suffered.
I wonder exactly what makes up the canal - is the Panama canal simply a long hole with gates in it, meaning that it can be redug periodically, or is it stone-or-concrete-lined, marked repair dificult?
The Panama Canal is a series of lakes, which are dredged periodically, with concrete-and-steel locks and earthen dams. While Panama is certainly subject to some tectonic activity (neighboring Nicaragua has had some nasty earthquakes), I don’t recall ever hearing of anything in Panama itself (although that’s no guarantee). 
If there’s any drift going on, it hasn’t hurt anything.
Thank you, everyone! I guess when the locks no longer “hold water” we’ll hear about it!
For plate movement to save any effect on canals they need to be a lot deeper. As far as the plates are concerned, canals are little more than surface scratches. They are not rifts in the surface of the planet.
So if the plates are moving the canals are moving with them.
Adding to Futile Gesture’s answer one way to look at the OP question is to think of a canal as a small cut on your hand & your hand as a plate. Even if you move your hand very slowly, almost imperceptibly, there is no real pressure on the cut. The plate to canal ratio is much larger (in some cases your hand would need to be several square miles & the movement would be much slower).
You could ask the same question, & get the same answer, about subways and bridges too.
Keep track of the California Aqueduct which parallels the San Andreas fault for quite a stretch and crosses it a couple of times.
The Los Angels Aqueduct parallels and is within a quarter of a mile of the Owens Valley fault for a lot of its length and also crosses it in places.
I don’t know about the California Aqueduct but the LA Aqueduct is emptied and repaired about once a year. I would suppose that any slight damage resulting from fault creep is taken care of then.
A major fault shift where a canal, road, bridge is near or crosses the fault causes damage to that facility which becomes just another part of the general quake damage. For example, in the Sylmar quake northwest of downtown LA, a reservoir earth dam was so weakened that the reservoir was emptied, or nearly so, as fast as possible.
Thank you everyone - this was just one of those nagging, random questions that occasionally slap the brain cells around.
It has certainly shown me the fantastic value of this site, though! Since I have three grandchildren living at home with me, you will undoubtedly be hearing from me again!!