Complex sentence: He and training partner Galen Rupp had originally planned on running a 10,000 m race in New Zealand, but after it was cancelled due to the Christchurch earthquake and damage done to the track, they entered the half-marathon in New York.
Split into simpler sentences: He and training partner Galen Rupp had originally planned on running a 10,000 m race in New Zealand. However, after the race was cancelled due to the Christchurch earthquake and damage done to the track, they entered the half-marathon in New York.