Shear Wall Failure Mechanisms
 
Top of Wall - Centerline
 

 
Note the misalignment of the sheathing at the top of the wall.  The top plate can be seen where the right hand panel has shifted with respect to the framing.  A gap between the two panels has also opened up.
 
A close up of the above picture, this image shows a good example of nail pull-through - one of the two failure mechanisms of this wall.