The correct statement about the earthquake is:
The earthquake was caused by plates moving together. It released a lot of energy, but the observer did not see much damage.
This is because convergent boundaries, where tectonic plates move together, are known to generate high-magnitude earthquakes that release a significant amount of energy. However, low intensity reported by an observer could indicate that the quake was deep underground or happened in a location that did not sustain much structural damage, even though the energy released is high.