A lot of this also has to do with how close to populated areas the earthquake is, and if the same quake happened today, the damage would be much less due to better construction.
That's overstating things by quite a bit. There was severe damage and fatalities but 'destroyed a lot of San Francisco' was 1906, an estimated 7.9 followed by fires.
destroyed a lot of San Francisco
PS: I lost my proverbial "I survived the Loma Prieta in San Jose" t-shirt. Lost half a swimming pool, bookshelves, dishes and so on... our furniture was anchored to the wall studs and computer monitors and other electronics were industrial Velcroed to surfaces.
Not sure how to compensate for distance, but my gut feel says that's about equivalent to a 5.9 in SF itself?