Investigating the crushed rock, J.Thomson / GNS Science
Have a think about the big picture here: You are very close to, or on top of the Wellington Fault itself. This fault extends down perhaps 25 kms below you, quite possibly all the way through the Australian Plate that you are standing on, to the plate boundary fault on the upper surface of the Pacific Plate. Because the Wellington Fault, and its local companions such as the Ohariu and Wairarapa faults are in the crust above the plate boundary they are known as upper plate faults (as opposed to the plate boundary fault). The Wellington Fault extends south from where you are standing all the way through Wellington City and into Cook Strait, and also to the north through Kaitoke into the Tararuas and beyond.
Now that you have the overview, you can appreciate that with the relentless collision of the Australian and Pacific tectonic plates occuring at a rate of roughly 40mm per year in this region, the forces at work along such a fault are unimaginably huge. The rocks along the fault are usually locked together, only rupturing every 700 to 1000 years or so in large earthquakes. Typically these might move the rock 4 or 5 metres sideways in what geologist call a 'dextral' movement (ie: looking across the fault the opposite side moves to the right). There will also be perhaps 1 metre of vertical movement at the same time.
Looking closely at the exposed rocks do you think they are mainly fault gouge or fault breccia? How wide is the area of the crush zone that you can see exposed?