Also - not all buildings are earthquake proof - only modern ones. Older ones can still fall down fairly easily.
Finally - when push comes to shove (pun intended), a 6.0+ is just going to do a lot of damage regardless of your precautions - particularly around store shelves, roads, etc...
A 7.0 isn't just a little bit worse than a 6.0. It's 10 times worse. And an 8.0 is 100 times more powerful than a 6.0.
So we're not too terribly concerned with these smaller quakes, even if 6.0 is still pretty big. The one we worry about is hundreds of times more powerful. There are some levels of energy you simply can't prepare for.
Don't mean to fear-monger, but that is the truth.
"The temblor struck about six miles south of Napa around 3:20 a.m., according to the United States Geological Survey. It was the most powerful earthquake to hit the Bay Area since the Loma Prieta earthquake of 1989, which collapsed a section of the Bay Bridge. The shaking was felt over an area that encompassed hundreds of miles.
The earthquake threw much of the Napa Valley — normally an edenic retreat famed for its wine and fine dining — into chaos of falling glass and collapsing bricks. Dozens of water and gas mains were ruptured, and at least six fires broke out, including one in a mobile home park that destroyed four homes and damaged two others. Thousands remained without power."
Now, can you imagine what a 10x more powerful earthquake at 7.0 would do? (Roads, Bridges, and Buildings collapsed).
An 8.0 would be so catastrophic that deaths would be in the hundreds, and damage would be horrific.
Granted a lot of infrastructure is equipped for this (gas was shut off in my apartment for example), but it's possible to be prepared for this.
Apart from being centered very close to Napa this earthquake was also fairly shallow (10km) so it was significantly more intense (albeit in a small, not heavily populated area) even though it was of the same magnitude. http://earthquake.usgs.gov/earthquakes/shakemap/nc/shake/722...
(I say that based on the numbers, not having first-hand experience with either quake)
Preliminary reports put the damage to in California in the neighborhood of $1 Billion.
It's important to repeat that this was the biggest earthquake the Bay Area (an area that certainly gets its share of earthquakes) has seen in 25 years.
That was from Napa this morning. Imagine if someone were standing under that? Now multiply by tens of thousands of homes and businesses.
The buildings themselves are designed to survive, but many are old and not up to code, because you only have to make a building earthquake safe when you sell it or renovate it.
Also, many people do not secure large objects to the wall. And sometimes it is the small objects that are the problem. Wine bottles, mirrors, anything that can shatter and fling glass everywhere.
I myself leaved in place, where I thought never can have earthquake, but at some point was woke up but 1.5 magnitude. I think almost every place on Earth can have earthquake at some point.
I believe up to 2.0 they are not felt by humans, only recorded by seismographs.