Complex sentence: In 1978, the plant was closed for nine months while modifications were made to improve its resistance to earthquakes, following discovery both of major building construction errors and of the close proximity of a previously unknown faultline.
Split into simpler sentences: In 1978, the plant was closed for nine months while modifications were made to improve its resistance to earthquakes. This followed the discovery both of major building construction errors and of the close proximity of a previously unknown faultline.