"reading" cracks on walls

Can you determine the orgin/nature of wall cracks by their shape and pattern? Most of the cracks in my (50 year old) house:

1.Are on walls running north-south
2.Run flat (parallel to the floor) at their north end, then turn abruptly “uphill” in a sharp diagonal at their south end. *(Something like an L shape where the bottom of the L points north and the vertical of the “L” leans at a 10 degree angle towards the south.)

The pattern can’t be a coincidence. Is this indicitive of minor earthquake damage? Construction flaws? Fault movement?

p.s. anyone who replies “yeah, it means you got too much time on your hands” gets an honorary kick in the butt. (:

Do the horizontal cracks look as if they formed by compression or expansion ? In other words do they gape, or are they tightly pressed together and possibly even protruding ?
Can you tell by close examination of the vertical crack which side of the fault line is moving downward relative to the other ? Wallpaper patterns could tell you this, or if the walls are plaster there may be hair or dust that’s been split between the sides of the crack.
It sounds as if one side of your foundation is settling faster than the other, or it could just be that the support structure for the 2nd story (or roof) is settling on one side. Then again it be nothing worse than the plaster pulling down on the underlying lathe supports; plaster walls are very heavy.

Did some investigation- the northernmost (and highest) edge of the cracks protrudes slightly over the low edge.
Oddly, upon close investigation I noticed plastered-over “ghost” cracks that all ran the other way (with the vertical “arm” of the fault shot upward from the north end).
My best guess (I’m not an expert) is that the current cracks were inhereted from the Northridge Quake (1984, Los Angeles area), and the older, painted and patched cracks that point the other way were formed in the San Fernando (1970’s same area). Will check cracks on neighboring buildings to see if the same pattern shows up.