Complex sentence: Modern estimates, based on geological data, give the earthquake a magnitude of approximately 8 on the moment magnitude scale or XI on the Mercalli scale, though more recent discoveries have shown that it was 7.9.
Split into simpler sentences: Modern estimates, based on geological data, give the earthquake a magnitude of approximately 8 on the moment magnitude scale or XI on the Mercalli scale. But more recent discoveries have shown that it was 7.9.