As usual, simple answers create more questions. You are absolutely correct about the Mexico quake. And remember that Loma Prieta was not centered near San Francisco or Oakland, but did plenty of damage there. Same reasons----really poor soil and amplification of earthquake waves.

Something of the same thing happens in LA due to the basin--the quake waves reflect and refract to cause damage in areas away from the epicenter.

Cheers, PennyB