Ann: Second Quarter Activities Report, page-39

Teddyward from the seems to allude to your presumption of designed to fail and allow horizontal movement :

"Lateral resistance :
Lateral resistance to sliding from seismic actions is generally resisted by friction between the slab and the underlying ground surface. In areas of high seismicity additional resistance to sliding is provided by the use of shear keys. Shear keys consist of drilled piles of 900mm depth spread around the perimeter of the slab to lock the slab into the ground. Where shear keys are required they will me indicated on the drawings provided. [refer figure 4.2] In some circumstances shear keys are not adopted even in high seismic areas (such as the Canterbury Region). Where shear keys are not adopted in high seismic zones additional measures need to be taken to protect services which run through the slab from being damaged under a serviceability earthquake event."

http://alliedconcrete.co.nz/images/documents/ALLIED_SUPERSLAB_MANUAL_v1.pdf

You sound like you are in the industry (I am not ) so I defer to your opinion