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I personally saw the destruction a 7.1 earthquake caused the small town of Santa Cruz, California in 1989 and this was in an area accustomed to earthquakes with fairly solid building codes...
If you're referring to the infamous Loma Prieta earthquake (aka the 880 quake or the World Series quake), that one measured 6.9 on the Moment Magnitude scale which has superceded the Richter scale, which would have measured it at 7.0. The 7.1 figure comes from the Surface-wave Magnitude scale, which is yet another whole different formula for calculating earthquake magnitude. So if we're comparing Apples to Apples here, Loma Prieta was 6.9 Mw and Haiti was 7.0 Mw.
But the comparison of these two quakes actually does give you a very real way to imagine why the Haiti quake had so much more devastation and so many more deaths, when you consider that most of the deaths in the San Francisco Bay area (41 of the 57) were caused when the 880 double decker freeway collapsed, crushing the cars that were driving on the lower deck. Imagine thousands of 880-style concrete structures around Port-au-Prince and you've got a good idea why the Haiti quake was so much more devastating than the Loma Prieta quake was. (It also makes a difference that the Loma Prieta quake's epicenter was in an unpopulated forest area up in the mountains.) And also, see my further reply below. . .
Quote:
Originally Posted by Little-Acorn
The Haiti eartquake was of almost identical magnitude, and was closer to the major cities of Dominican Republic than the Santa Cruz earthquake was to some of the major structures it destroyed.
It's a very common misperception that, for instance, 6.9 and 7.0 are "close" in magnitude because there's a relatively insignificant difference numerically. However, the scale used to measure an earthquake is based on a logarithmic formula, and each whole number higher an earthquake measures, its amplitude is 10 times greater and its power is 31 times greater. So even a small decimal higher in magnitude is significantly greater in power and energy.
One way to conceptualize differences in earthquake magnitude is to know the approximate equivalent of seismic energy to an explosion of TNT. A 6.9 earthquake is approximately equal in energy 26.8 megatons of TNT. A 7.0 earthquake is approximately equal in energy to 32 megatons of TNT. That's nearly a full 20% greater power for just that 0.1 difference in magnitude.
An earthquake with a magnitude of 6.9 is considered "Strong", yet an earthquake with a magnitude of 7.0 is considered "Major".
Quote:
Originally Posted by city414
a earthquake of that magnitude should have been felt in the DR, earthquakes that happened in california has been felt far away
Who said it wasn't felt? I've felt a lot of earthquakes that happened dozens and even over a hundred miles away. But feeling an earthquake and experiencing damage from one are two completely different things. Not all shaking is equal.
We are hearing horrible damage reports from various cities in Haiti, after the earthquake. The capital, Port-au-Prince, is said to be almost completely destroyed, with literally hundreds of thousands of people killed.
But I am curious: Haiti is half of an island in the Caribbean, near Cuba. The other half of the island is a country called Dominican Republic. Some of its cities are only 20 miles from Port-au-Prince.
Why are we hearing NO reports of damage, deaths etc. from the Dominican Republic?
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My google search yielded a compilation of the following information:
1. The island of Hispaniola (Haiti +DR) sits in the middle of two tectonic faults:
a.) the Septentrional fault that runs east to west on the northern part of the island and
b.) the Enriquillo-Plaintain Garden fault that runs east-west on the southern part of the island.
2. The epicenter of the quake (a point from which the "earth shaking" waves radiate) was located 10 miles southwest of Port au Prince (away from the DR). Thus, the epicenter of the quake was located just south of the Enriquillo-Plaintain Garden fault.
3. The intensity of the quake at the epicenter was measured at roughly M7.0 on the Moment Magnitude Scale (MMS). The MMS replaced the old Richter scale.
4. One earthquake number in the MMS is approximately 31 times more powerful than the previous lower number. The shock waves that were felt in the DR were measured at approx. M4.0. I'm not a seismologist, but to me that means that the intensity of the earthquake in Port au Prince was almost 100 times more powerful than what they registered in the DR.That is the reason for there being relatively no damage in the DR as opposed to Port au Prince. That is why you are not hearing reports from damage in the DR: they felt the quake, but it was much, much less intense there and, it caused no damage.
5. While it is true that Haiti is the poorest country in the Western hemisphere and that their "building codes" are woefully inadequate, please remember that Haiti, as well as the rest of the region, has to contend with another force of nature darn near every year: hurricanes and lesser tropical storms that also cause damage. I'm not a structural engineer, but it has to be difficult as well as expensive to build a structure that can protect occupants against both types of disaster.
6. Earthquakes are the result of pressure build up below the surface of the earth. I found no published evidence that deforestation has an impact of seismic activity. Please, do correct me if I'm wrong.
7. Finally, please remember that ANYTHING built by humankind can be destroyed by Mother Nature in just minutes.
N.B. I actually spent time reading from numerous sources, rather than provide links without reading. Hope this helped.
If you're referring to the infamous Loma Prieta earthquake (aka the 880 quake or the World Series quake), that one measured 6.9 on the Moment Magnitude scale which has superceded the Richter scale, which would have measured it at 7.0. The 7.1 figure comes from the Surface-wave Magnitude scale, which is yet another whole different formula for calculating earthquake magnitude. So if we're comparing Apples to Apples here, Loma Prieta was 6.9 Mw and Haiti was 7.0 Mw.
But the comparison of these two quakes actually does give you a very real way to imagine why the Haiti quake had so much more devastation and so many more deaths, when you consider that most of the deaths in the San Francisco Bay area (41 of the 57) were caused when the 880 double decker freeway collapsed, crushing the cars that were driving on the lower deck. Imagine thousands of 880-style concrete structures around Port-au-Prince and you've got a good idea why the Haiti quake was so much more devastating than the Loma Prieta quake was. (It also makes a difference that the Loma Prieta quake's epicenter was in an unpopulated forest area up in the mountains.) And also, see my further reply below. . . It's a very common misperception that, for instance, 6.9 and 7.0 are "close" in magnitude because there's a relatively insignificant difference numerically. However, the scale used to measure an earthquake is based on a logarithmic formula, and each whole number higher an earthquake measures, its amplitude is 10 times greater and its power is 31 times greater. So even a small decimal higher in magnitude is significantly greater in power and energy.
One way to conceptualize differences in earthquake magnitude is to know the approximate equivalent of seismic energy to an explosion of TNT. A 6.9 earthquake is approximately equal in energy 26.8 megatons of TNT. A 7.0 earthquake is approximately equal in energy to 32 megatons of TNT. That's nearly a full 20% greater power for just that 0.1 difference in magnitude.
An earthquake with a magnitude of 6.9 is considered "Strong", yet an earthquake with a magnitude of 7.0 is considered "Major".
Who said it wasn't felt? I've felt a lot of earthquakes that happened dozens and even over a hundred miles away. But feeling an earthquake and experiencing damage from one are two completely different things. Not all shaking is equal.
Very good post and intelligent post.
I wish I would have read your post before posting my own. Yet, I'm glad I did some research on my own because I learned a lot.
I live in the midwest and have never experienced an earthquake.
Well, now is a good time to learn then. Since the midwest is a big area and varies by who uses the phrase so I don't know how close you are to the New Madrid Missouri earthquake zone. Although there were no seismographs in use in the 19th century, there have been 3 severe earthquakes in southern MO since Europeans settled in the area. They were in 1811, 1843 and 1895.
I had read somewhere that the 1843 one was the most violent in the US ever but I have no confirmation of that. It's not just California, Alaska and Hawaii that have them.
I'm pretty sure that the building codes in MO are not nearly as strong as in CA. Regardless of how strong the buildings are built if a strong earthquake hits anywhwere in the US collapse won't be the big problem, it will be fire.
In the 1906 (?) SF earthquake fire cause much more death and damage than collapse. Ruptured gas mains, your gas water heater falling over and rupturing its supply line and ruptured water lines are a deadly combination.
I'm pretty sure that the building codes in MO are not nearly as strong as in CA.
My father is a structural and civil engineer in MO, and I can assure you, the building codes are absolutely as strong as in CA. In fact, in a sick twist of irony, he had just landed in Los Angeles for an earthquake engineering seminar, just a couple of hours before the infamous 880 quake mentioned above.
My father is a structural and civil engineer in MO, and I can assure you, the building codes are absolutely as strong as in CA. In fact, in a sick twist of irony, he had just landed in Los Angeles for an earthquake engineering seminar, just a couple of hours before the infamous 880 quake mentioned above.
So responding in a condescending and insulting manner after being snarky in the first place? It's comments like those in your post that poison so many conversations in forums like these, and its trollish.
I agree. It was just a simple question. No need for such a sarcastic answer. And by the way, NVXPlorer, there would never be a report of a bridge falling down in Walnut Creek because it's inland from the bay, and there are no bridges there.
Well, now is a good time to learn then. Since the midwest is a big area and varies by who uses the phrase so I don't know how close you are to the New Madrid Missouri earthquake zone. Although there were no seismographs in use in the 19th century, there have been 3 severe earthquakes in southern MO since Europeans settled in the area. They were in 1811, 1843 and 1895.
I had read somewhere that the 1843 one was the most violent in the US ever but I have no confirmation of that. It's not just California, Alaska and Hawaii that have them.
I'm pretty sure that the building codes in MO are not nearly as strong as in CA. Regardless of how strong the buildings are built if a strong earthquake hits anywhwere in the US collapse won't be the big problem, it will be fire.
In the 1906 (?) SF earthquake fire cause much more death and damage than collapse. Ruptured gas mains, your gas water heater falling over and rupturing its supply line and ruptured water lines are a deadly combination.
golfgod
I agree that I would like to become more educated in earthquakes. Actually, I attended college and obtained my undergraduate degree in southern illinois near the new madrid fault. I however, never experienced earthquakes in my tenure there.
As an Architect though, I can tell you that the strength of the building, in conventional terms "vertical loading", is not really important in terms of collapse during an earthquake as is horizontal loading. For obvious reasons, buildings in the mid-west are designed to resist some horizontal loads like wind, but not enough so to resist the power of an earthquake which exerts pretty heavy horizontal displacement. Though fire would be an issue of course, there would be some pretty massive destruction due to lack of horizontal reinforcement in buildings in this area.
My father is a structural and civil engineer in MO, and I can assure you, the building codes are absolutely as strong as in CA. In fact, in a sick twist of irony, he had just landed in Los Angeles for an earthquake engineering seminar, just a couple of hours before the infamous 880 quake mentioned above.
I disagree. Code compliance is much less stringent in the mid-west in regard to enforcement of structural improvements to resist lateral displacement.
Most recognized published building codes seperate earthquake resistant design from the rest of the building code. For this reason, select areas, typically California adopts enforcement of these sections while most other places in the country do not.
I was wondering the same thing. My assumption is that Dominican buildings and communities are better built, but this is only my assumption. Knowing nothing about the geography of the island, there may be factors in the geographical makeup that also played a role in the destruction of Haiti but not the Dominican Republic. i heard on the radio this morning that they are using Dominican airports to land relief planes since the Haitian airport was basically destroyed.
Of course, this is all speculative on my part, I too wouldn't mind hearing about how the quake affected the Dominicans.
Yes, places like Santo Domingo have much better infra-structure, thus why they suffered damage, but their entire country is not flattened like a pancake.
The government in the Dominican Rep is less corrupt than Haiti and the country is a lot more stable. So the infra-structure has got to be better.
This is further proof that dumping money into a country does not fix problems. All the $3 BILLION Dollars the USA has wasted in Haiti since 1993 in "relief and country building" have only filled the coffers of liberal politicians that have run that country for the last 20 years (since the dictatorship ended in Haiti). See: Haiti - Wikipedia, the free encyclopedia
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