Where were you? From what I recall, the waves focused or reflected so that the were somewhat stronger in San Francisco than if they had just spread out uniformly.
Loma Prieta was my first quake, two months after I moved there (Sunnyvale).
A U.S. scenario more comparable to Port-au-Prince might be Charleston, which was hit by a major earthquake in 1886. I don’t think the building codes are nearly as strong there, though of course the population isn’t as large either (only 600,000.)
If you want a true nightmare scenario, though, think about a magnitude 6 or 7 quake hitting New York. No earthquakes of this magnitude have been historically recorded — the strongest known was estimated at magnitude 5.2, in 1884. However, it’s estimated (see the link above) that earthquakes of magnitude 6 or 7 hit the area every 670 years and every 3,400 years, respectively.
Regarding the New Madrid Seismic zone, I just got an e-mail about a new report (http://mae.cee.uiuc.edu/publications/2009/Impact%20of%20NMSZ%20Earthquakes%20on%20the%20Central%20USA.pdf large PDF).
Some of the highlights “7.7 magnitude, 715,000 damaged buildings, 86,000 injuries/fatalities, $300 billion in damages.”
Chicago buildings do have to be designed for earthquakes. Mostly bridges and high rises. These structures have low natural frequencies and so are more susceptible for damage from low frequency motion (because of resonance). Low frequency motion just happens to attenuate more slowly and travels farther distances.
This is a relevant article. Geophysicist Ross Stein estimates that in 1950 the same earthquake would cause similar destruction in the developed and undeveloped world, but nowadays a quake in the undeveloped world will cause between 10 and 100 times as much damage. So you’re right that a 7.0 earthquake striking a major US city would cause serious damage, but in somewhere like Haiti it will be much, much worse because of poor building codes.
The North Bay. Sonoma County.
Earthquakes are weird. I’ve always known that the strongest shaking in the 1906 quake was in the Point Reyes area, about 20 miles due west of where I grew up. We used to go walk the earthquake trail on field trips when I was a kid, and see where halves of buildings now 20 feet away from each other, stuff like that. I always thought that was the epicenter of the quake, until a few years ago. Turns out, no. The actual epicenter is off the coast of Daly City, about sixty miles south of Point Reyes. Not being a geologist, I don’t quite understand this, and I find it quite amazing.
Throwing numbers around, but doesn’t a 7.0 have ten times the shaking force of a 6.0?
Also, the type of material that structures sit on determines much of their fate. Some areas roll and shake with a terrible frequency that helps shake buildings down – some others, not so much.
So, it’s hard to go apples-to-apples. A 6.0 in one area could be much different than a 6.0 in another area.
There is a whole lot of “it depends” in answering this question. One, the Haiti quake was quite shallow, so a lot of the energy went directly to the surface and the structures. Two, the soft soil magnifies the intensity of the shaking, and thus the potential for damage.
I show a video every year when we do our earthquakes chapter that compares and contrasts the 1994 Northridge quake to the 1995 Kobe quake. They were exactly 1 year apart–January 17, 1994 and January 17, 1995–and struck in the early hours of the morning. Both were of similar magnitudes, and occurred in an area very familiar and practiced with earthquakes, and with (compared to Haiti) strong building standards. Yet, the Kobe quake killed over 5,000; the Northridge quake, fewer than 70.
A lot of the reasons behind the “Why?” has to do with the local geography and just how the faults shifted. In the Northridge quake, the fault broke diagonally from the bottom up, with most of the energy directed toward the mountains. This spared Northridge from the worst of the shaking. In Kobe, the fault broke under the city, and the seismic waves bounced off of the mountains and returned to the city to do more damage, the way waves in a pond bounce off the shore and return. Plus, the soft soil in Kobe (a port city) resulted in liquifaction–water beneath the ground was shaken to the surface, and structures were sucked down like quicksand.
Cite: Video entitled “The Day the Earth Shook,” published by Nova.
Soooo…my answer to this question would be: Likely not as much damage, but beyond that it depends on how the break occurs on the fault, where the break occurs on the fault, the type of soil, local geography, and building standards.
A lot of the building codes came into effect only after a disaster hits. Then from all points after the code is updated. The problem is most codes put a grandfather clause in place. In otherwords the buildings don’t have to be updated to code till they are sold.
I remember a hotel, our company worked with, in San Francisco was due to be sold several times, but the issue with asbestos removal always prevented it. The asbestos could stay but whoever bought it had to bring it up to code. And the cost of this was so great it made the sale of the hotel, not worth it.
It also depends on what kind of earthquake it is and how shallow/deep it is, what kind if damage a city experiences. Clearly a big factor in Port-au-Prince was the building material and style of building, though.
But the size of the area affected can vary a great deal.
I grew up on the inside edge of the red zone of the New Madrid Fault Zone. As a child, I was used to the small rumblings of the earth that we called “earthquakes.” I thought only the big earthquakes happened in California or somewhere else. I didn’t know the history of my own area–northwest Tennessee.
This chart shows how far away the New Madrid earthquakes of 1811 and 1812 could be felt. (They rang church bells in Boston.)
And from the same site:
Memphis (in West Tennessee) is the largest city in Tennessee and has the potential for being greatly affected. But so does St. Louis and possibly New Orleans, Savannah, Charleston, Nashville, Detroit, Chicago, Knoxville and points north. These earthquakes originally caused many fissures and drop-offs. I wouldn’t think that it would take much to topple tall buildings that weren’t built with earthquakes in mind. But I’m not an engineer and my views are purely speculative.
I think you are right-modern skyscrapers would be OK, but those 130+year old brick tenement buildings would collapselike houses of cards. Every once in a while, one of them does-inadequate foundations and new excavations-plus the lack of structural steel means disaster.
Maybe. The type of shaking that would be most damaging to small 130 year old buildings would be high frequency motion. Most of that would have attenuated before it reached Chicago.
I lived 20 years ago through the 1989 Newcastle earthquake – only 5.6 on the Richter scale, but hitting a city where a lot of the buildings were brick, and constructed up to 100 years previously. 13 people died – 9 in the collapse of one building, which had apparently not be constructed up the the pre-earthquake building standards. If it had been 7.0 on the Richter scale, there would have been considerably more loss of life.
(My house is about half-way between the two sites with loss of life in that earthquake, and a couple of days after was inside the “no-go” area set up by the government to prevent looting, etc.)
Of course, Australia is a first-world country, and was able to cope with the disaster with its own resources, including 1 billion AUD in insurance pay-outs (some of which I received).
In 2006, Hawaii had a 6.7 earthquake. Shook the ground for maybe 10 seconds, and damage was fairly minimal. For instance, in our house, it knocked some pictures sideways (but not off the wall).
Yet, somehow, it was enough to knock out our power for nearly 24 hours! However, I think that had more to do with the electric company.
Wow. Thanks everybody. This is one interesting thread.
I guess the take home here is that a quake as strong or stronger as in Haiti along SOME faults in the USA might bring about some significant loss of life.
I was shown that video in a college class in 2000. The course name was Geological Disasters, known on campus as “Rocks for Jocks” since it had the reputation of being an easy earth science course for non-majors. The section I took wasn’t at all easy and suffered considerable attrition, but I learned a great deal.
Anyway, I remember the same comparison from that class. I also remember another difference, though my memory isn’t sharp. As I recall much of the damage and many of the casualties in the Kobe quake occurred in older neighborhoods that had been built in a traditional style consisting of wooden frames supporting stone tile roofs. These structures had been grandfathered in as new quake proof codes came into play. As a result, post-Kobe quake, Japan changed its laws exempting traditional architecture etc.
I went thru the Nisqually earthquake (6.8) in a frame house, in a suburb of Seattle, that was built in 1965. It shivered and shook, but we never even suffered a crack in the walls. Only damage was a broken glass that fell off a shelf.
Am still amazed at how fast a cat can dematerialize when a quake hits.
The earthquake mentioned above in Turkey hilighted the fact one contractor had gone cheap and used sand from the seashore for mixing cement. Apparently the salt residue made the concrete much less reliable and quite a few buildings crumbled.
Similarly in Taiwan several years ago, a collapsed hi-rise from an earthquake revealed the builder had gone cheap by dumping those metal cooking-oil cans into the concrete forms to reduce the amount of concrete used. (Just what you want in a hi-rise, right???) the problem is that often the corruption and bribery are worse in the newer areas of the world.
This is no different than with other safety rules. Places like China and India are going through what other emerging nations did a few decades ago, and what America and Europe learned in the early 1900’s wrt fire codes and enforcing them, for example.
Obviously construction is key. The US Embassy in PoP was damaged only minimally as it was built to withstand quakes and it has served as a refuge/makeshift hospital for many US citizens in Haiti during the quake. Unfortunately, the same cannot be said for the housing in which the US officers live. One FSO was killed when her house collapsed on her.
There’s a pretty big fault line that runs right under Salt Lake City. The Wasatch Fault is known to produce earthquakes of a 7.5 magnitude. That city is overdue for a major quake, and the building codes there aren’t that strict.
It’s a disaster waiting to happen.