Complex sentence: The 1939 Chillán earthquake (Spanish "terremoto de Chillán de 1939") was a major earthquake in south-central Chile, is is currently the single earthquake that has caused most deaths in Chile.
Split into simpler sentences: The 1939 Chillán earthquake (Spanish "terremoto de Chillán de 1939") was a major earthquake in south-central Chile. It is currently the single earthquake that has caused most deaths in Chile.