Big +1. We noticed the one up near D.C. here in E. TN. No damage but it felt like a large truck going by rattling the office trailer. IIRC they said the underlying geology is such that it transmitted the quake like a rung bell.

Here's an example of what role the plate can play. Red is strong shaking, yellow moderate.

Hikermor has a good point about what the point of most seismic retrofitting is. I think the popular understanding is that it makes an old (sometimes VERY old) brick building with old, crumbly mortar impervious to earthquake damage, but that is generally not the case. Most retrofitting jobs seem to be intended to prevent the structure from collapsing onto occupants during the quake itself. Beyond that, such as whether the structure is still functional/habitable, is a whole different matter.

So, I think the news I see is doing a disservice when it reports that retrofitting "failed" when it may have actually done exactly what it was intended to do. Just because a structure is damaged (sometimes severely) and becomes red tagged does not mean the retrofitting failed, unless the job was specifically designed do just that.

On a related note, I was reading that even for the folks with earthquake insurance, most probably will not benefit from it because real estate prices are so high in the area and that the cost of most damage will not exceed the 5-10% deductible that exists on most policies.

Bit late to the party--I was awake at 3:20am, at the time of the quake, in San Francisco. My house is on solid ground and not on sand or landfill like many other parts of San Francisco. To me, I felt a moderate bump, and then the house seemed to feel "squirrely" for 5-10 seconds. My coworker in the East Bay said it feel like a giant was violently jerking his condo back and forth, and another coworker in the East Bay slept right through it, so people definitely felt different things in the Bay Area.

I tuned to the news and radio right away, but didn't see anything at all, so I shrugged and finally went to bed. When I woke up around 10:30am, I was shocked that all the stations were showing non-stop news coverage and how badly Napa City had been hit. I guess it takes time to ramp up the newsroom, call in anchors and such in the middle of the night.

Yes and no. You are correct that many (most?) retrofits of old buildings are meant to protect life & limb, not necessarily keep the building useable after the quake. However, protecting life and limb also includes people outside the building injured by falling debris. As the article I linked noted, had the quake happened at other times of day there easily could have been dozens killed and injured in the wine bar on the sidewalk below the building. But then again, as the article also notes, there is simply no economically feasible way to reinforce the brick facade on many of those old buildings. We can only try to do the best we can with old buildings, and accept some risk.

Along the same lines, here is an article about the boy who was badly injured by a collapsing fireplace. Most people who are injured in earthquakes (at least in 1st world countries) are not hurt by the whole building collapsing, but rather by falling stuff inside the building. There is a reason that the experts recommend Drop, Cover, and Hold!

For quick information (within minutes of the event), it is hard to beat the USGS - http://earthquake.usgs.gov/earthquakes/map/

In some cases, a brick wall/façade can be reinforced by applying a polymer backing layer that actually bonds to each brick, but it's generally not feasible for every square foot of a structure. Techniques that rely on reinforcing bars bolted to a wall won't anchor every brick in place.

This Napa quake does reinforce the idea that the most dangerous place (assuming you're not sleeping next to a brick (unreinforced?) fireplace at a slumber party, like the one seriously injured teen) is to stay away from the interface between inside/outside of a building. In general, if you're inside, stay inside during the shaking. If you're outside, stay outside. Falling bricks could have killed people. In a Third World country with little to no building codes, I'd want to get out of any building ASAP during a quake, but not someplace like California.

I saw at least a couple interviews with people at the mobile home park who were injured because their homes had shifted off the foundations and they fell because the stairs were no longer lined up with the front door. Another guy had a small apiary next to his mobile home and he dislocated his hip when he went to check on his birds and stepped into a hole after his unit had shifted over from it used to be. I'm not sure if they had flashlights or not and whether they would have made a difference, particularly when you've just woken up at 3:20am.

Lasting 4 minutes and 38 seconds, it was the most powerful recorded earthquake in U.S. and North American history, and the second most powerful ever measured by seismograph. It had a moment magnitude of 9.2, making it the second strongest earthquake in recorded history — the strongest being the 1960 Valdivia earthquake in Chile.

1964 Alaskan Earthquake ( Good Friday Earthquake ) - http://en.wikipedia.org/wiki/1964_Alaska_earthquake

Everyone on Reddit kept saying "Wow, that was long" for the Napa earthquake. It was only 20 seconds long. I guess most are only about 5-10 seconds. I cannot imagine constant shaking for nearly 5 minutes.

I saw at least a couple interviews with people at the mobile home park who were injured because their homes had shifted off the foundations and they fell because the stairs were no longer lined up with the front door. Another guy had a small apiary next to his mobile home and he dislocated his hip when he went to check on his birds and stepped into a hole after his unit had shifted over from it used to be. I'm not sure if they had flashlights or not and whether they would have made a difference, particularly when you've just woken up at 3:20am.

Above is a good reason to keep a headlamp available at the bedside, rather than a flashlight. When wishing to exit your structure, after doing the Drop, Duck, and Cover, using a headlamp gives you 2 free hands to steady yourself or break a fall if an aftershock hits

Front page article in the LA Times re unreinforced brick buildings - http://www.latimes.com/local/lanow/la-me...ory.html#page=1

Basically, they are bad juju.