Complex sentence: There, venom drops onto his face periodically from a snake placed by the jötunn Skaði, and when his wife Sigyn empties the bucket she is using to collect the dripping venom, the pain he experiences causes convulsions, resulting in earthquakes.
Split into simpler sentences: There, venom drops onto his face periodically from a snake placed by the jötunn Skaði. Loki's wife Sigyn collects the venom into a bucket, but whenever she leaves to empty it, the drops reach Loki's face, and the pain he experiences causes convulsions, resulting in earthquakes.