Simplify the following text for a Grade 5 native English-speaking person.
Original: The magnitude of the 1707 event exceeded that of both the 1854 Ansei-T Å kai and Ansei-Nankai earthquakes , based on several observations .
Simplified: There were two other very large earthquakes : the 1854 Ansei-T Å kai and Ansei-Nankai earthquakes . The 1707 was stronger than both .