Primary Effects – The initial (first) impact of a natural event on people and property
The boy's first day at primary school had an effect on his dad.
Primary effect = First effect
Ground and buildings having collapsed due to an earthquake are examples of the first effects or primary effects of a tectonic hazard.
The primary effects of a big earthquake include the ground shaking, ground splitting open (rupture), buildings collapsing and serious damage to roads, railways and bridges.