Earthquakes - so far so good, but I grew up in LA and lived through multiple large-ish quakes (Northridge). One big difference is that many small rural towns only have one road in or out, so a quake could block the road, leaving you stranded, possibly without power. This is the case along the west coast of the South Island.

Food - groceries are pricey! It was surprisingly expensive given the lower wages here. CA seems to be catching up though!

Mosquitoes - comparable to LA, less than Sonoma County. Smaller too. But here on the South Island we also have sandflies. They vary by region. West Coast has them bad in some remote spots.

Earthquake risk is similar to California, with very low (but not zero) risk in many places, e.g. Auckland.

The food is generally excellent in urban areas - cafe culture rules for those who can afford it.

Main issue is cost of living - housing and food costs are kind of silly relative to average income.

Mosquitos are really not an issue - people up north might have a different experience, but from Auckland on down, no one needs screens.