Complex sentence: The earthquake which occured in 1906 about 400 km NW of Exmouth occurred before world earthquake monitoring had really developed, with an estimated magnitude of 7.5, it is probably the largest earthquake known to have occurred in the Australian region.
Split into simpler sentences: The earthquake which occured in 1906 about 400 km NW of Exmouth occurred before world earthquake monitoring had really developed. With an estimated magnitude of 7.5, it is probably the largest earthquake known to have occurred in the Australian region.