They are all at the edges if continents
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When you mention to distribution of epicenters, I assume you're asking about the distribution of earthquakes. Most mountain ranges are built along plate boundaries where the plates are crashing together. This collision of tectonic plates can result in a crumpling of the crust (as you find in the Himalayas) or a buckling of the crust over a zone of subduction (subduction being where one tectonic plate is pushed over another).
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