Final answer:
The field event described, involving the throwing of a 16-pound object and associated with festivals in honor of Thor, is the hammer throw.
Step-by-step explanation:
The field event being described, where a 16-pound object is hurled and which was once practiced at festivals honoring Thor, is the hammer throw. This field event involves a heavy weight at the end of a wire, which athletes swing around their head and release to achieve maximum distance. The heavy weight, sometimes referred to as a 'hammer', is consistent with the mythical associations of Thor with a hammer. However, this description does not match the shot put, javelin throw, or discus throw, where the weights, shapes, and techniques of throwing vary significantly from those used in the hammer throw.