Complex sentence: The quake occurred on the 32nd anniversary of the 1985 Mexico City earthquake, which killed about 10,000 people, commemorated with a national earthquake drill at 11 a.m. local time, two hours before this earthquake struck.
Split into simpler sentences: The quake occurred on the 32nd anniversary of the 1985 Mexico City earthquake, which killed about 10,000 people. The earthquake was commemorated with a national earthquake drill at 11 a.m. local time, two hours before the earthquake struck.