Where do the trade winds occur?
on the equator
in local areas
30° n or s
30° n or s to the equator

The trade winds occur between 30° N or S to the equator.

Explanation:

The Earth has certain latitudes which are covered by winds flowing permanently in 'one direction'. One such wind system is that of the 'easterlies', also known as the 'trade winds'. These flow permanently to the west from the east between 30° north and 30° south to the equator. The wind system gets its name from its attribute of proving helpful to the merchant ships that moved from the east to the west in the medieval period.

Geologists use  seismic waves to  locate an earthquake's epicenter..