I need some help if you can Why is it a concern when a fault does not move for a very long time? What are other areas on earth where convergent plate boundaries exist?

1. If a fault doesn't move for a very long time. There won't be a Earthquake there.

2.Island arcs and oceanic trenches occur when both of the plates are made of oceanic crust. Zones of active seafloor spreading can also occur behind the island arc, known as back-arc basins. These are often associated with submarine volcanoes.

Explanation:

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because there are alot of mountains