Complex sentence: Earthquake monitoring in the country started as early as 1898, with the establishment of an earthquake observatory at Alipore, Kolkata after the great Shillong Plateau earthquake in 1897.
Split into simpler sentences: Earthquake monitoring in the country started as early as 1898, with the establishment of an earthquake observatory at Alipore, Kolkata. This followed the great Shillong Plateau earthquake in 1897.