Primary effects are those that occur immediately as the earthquakes happens. These include buildings collapsing, roads snd bridges being destroyed and railway lines being buckled. All occur due to the vibration / tremors from the earthquakes.
Secondary effects are the subsequent effects of the earthquake and can be even mre devastating than the primary ones, such as fires, tsunamis, landslides and diseases.

Intro: state your stand
Para 1: explain why primary effects are devastating
Para 2: explain why primary effects can be more severe for example they caught off guard, level of preparedness is lower since people react slower to the sudden earthquake
Para 3: explain why secondary effects are devastating
Para 4: explain how these effects may worsen or aggravate the situation and cause more death toll(epend on your stand)

Make sure an example is given for each paragraph.
Conclusion: outweigh and balance the factors. Summarise your stand