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PROCEEDINGS OF THE SEPTEMBER 2000 POST EARTHQUAKE HIGHWAY RESPONSE AND RECOVERY SEMINAR HELD IN ST. LOUIS MISSOURI
WHY HAVE AN EARTHQUAKE CONFERENCE BY GARY PATTERSON
MR. PATTERSON: I would like to acknowledge everyone who has had anything to do with this meeting. It's really a remarkable thing to see this many people together for one purpose. It's a purpose that many scientists in the Central United States think is a very clear and present danger.
I hope you walk away from this presentation today knowing about earthquakes that happen along plate boundaries. The crust of the earth is broken up into pieces where these pieces slide across each other. The sliding is the way most of the world's earthquakes happen.
We do have earthquakes here in the Central United States. They're not for the same reasons that we have earthquakes in plate tectonic boundaries. In the Central United States, we had the largest sequence of earthquakes in continental North America known. How big were they, we're not sure. But they were big and they really happened. That's what Art Johnston said during a luncheon presentation last year at the Federal Highway Administration.
First of all, I would like to point out the background of the maps that I'm showing up on the screen. This is an historic map that we found in the Colorado School of Mining. This is from 1878, and right here it says, "crevasse of earthquake." These features are not here now. They're much more subtle in 1878 than they were in 1811 and 1812. Does that mean they're not there? No. It means that there is a huge river running right over the fault system we talk about all the time. It ebbs and flows and wafts back across that fault zone and erases the surface features of those faults. We'll talk more about this.
The Center for Earthquake Research and Information is the world's leader in the study of intraplate seismicity. When you leave here today, I hope you understand what intraplate seismicity means because it's an important thing to understand if you're going to talk about earthquakes in the central United States.
We have a center of data collection in the state of Tennessee. We´re a former member of the Mid-America Funding Earthquake Center which is a sister organization to the Multidisciplinary Center of Earthquake Engineering Research who is also represented well here today. We also work closely with CUSEC. We are very happy for this arrangement because organizations like CUSEC have the ability to bring many people from many different backgrounds together. People like Dan Siscarello, Patrick Wanker, Ed Gray, and the other earthquake coordinators who are here today. They are together with engineers and scientists to get at the heart of the problems that we´re going to have to deal with someday. It could be tomorrow, could be 50 years. We don't know. But we know there is a good chance something could happen soon, and that worries us.
We don't need to create an urban myth to have jobs. We have work all over the world. New Madrid seismic zone is a lurking danger, a legacy event that only happens every hundred years, the 6.0s, and every 500 to 1,000 years to the 8.0s.
So we're going to start from the very basic geology. To really understand earthquakes, you´ve got to know what drives the earthquake. To do that, we've got to talk about tectonic plates. So what's driving this? We´ve all heard the theory of plate tectonics. The crust of the earth is split up into 12 to 15 major plates that are in different movements relative to one another. So why are those plates moving around? They're moving around because the earth is a heat engine. It's constantly producing new material coming up to the surface of the earth because of the radioactive decay of elements inside the mantle and the core. This causes heat. The heat causes convection currents, mushroom clouds in the mantle. These convection currents push the plates around, especially where a new material, magma, comes up to the surface, solidifies, becomes lava when it gets to the surface, and pushes out on the other plates.
Now, there are probably some seismologists or geologists in the crowd that would say what about the slab pull and ridge push. Yeah, these things happen too, but for brevity's sake, just say that the earth is a heat engine and it powers plate tectonics, the movement of the core.
We know that the Pacific plate around the edges of the Pacific Ocean produce 80 to 90 percent of earthquakes and volcanoes. California would have about 20,000 earthquakes per year instrumentally along this plate boundary zone.
Here is a diagram that would show you one of those places where new material is coming up from the mantle of the earth and creating or solidifying on the ocean crust. As it solidifies it pushes out. This would be a plate boundary. We can imagine this as the Pacific Ocean and this is the western coast of South America, the Andes, maybe, where you have ocean crust butting up into continental crust and being squeezed. This is where you have the most earthquakes. This is mostly the setting around the Pacific Rim, the ring of fire, the surface of the Pacific belt, whatever you would like to call it. This is where most earthquakes happen. This is where most volcanoes happen also.
Yet, why is it that in many stable continental regions, historically, we have had very large earthquakes? This is something that we´d like to know more about. We've done a lot of science in the central US in the last 25 years. California has been studying their seismic problem instrumentally for a hundred years. We´ve got a lot of catching up to do. We don´t have all the answers.
When you leave here today, I hope you know we do realize earthquakes in the central U.S. Everyone in the scientific community knows, although we'll bicker and argue, we've had many damaging earthquakes in the central United States. Historically, besides 1811 and 1812, these types of events could happen again. I´m talking about 6.0, 7.0 magnitude earthquakes.
We've heard people talk this morning about a 6.7 earthquake in 1994 in Northridge, California. Fifteen seconds of strong ground motion caused $20 billion of damage. You know about Turkey, a 7.4 earthquake that killed 20,000 people. Taiwan was a 7.6 earthquake, much larger than Turkey, yet only 2,000 people died. Why is that? You can hardly say that Taiwan is not a densely populated country. It's because of their engineers. They lost 60 bridges in that earthquake, that's true, but their engineering standards are generally very high.
What you do is very important to us. Bridges, continuation of businesses, economic loss is very important. We've seen it time and time again all over the country, all over the world.
One of the most important features in California, of course, is the San Andreas fault. It's very well studied. I would like to point out that in California, this is near the epicenter of the Northridge earthquake in 1994. This fault wasn't known. Well, at least it wasn't known to be active. Some of the petroleum companies had information on the fault but they didn't know what its recurring interval for movement was. They didn't pass the information on. Why didn't we know this fault was there? Why didn't California know this fault was there? It's called a blind thrust fault. This means that this part is in a river valley. The fault surface expression has been erased by rivers.
Does that sound familiar? That's exactly the problem that we face here in the central United States. It does happen. Instead of being buried in hard rock beneath 90 feet of sediment like it is in California, our hard rocks are buried 3,000 feet beneath us in Memphis. This is a big problem.
Also something that we should also consider is, after the New Deal, about 800 miles of levees were laid in the lower Mississippi Valley as part of the WPA work. We compliment the Corps of Engineers for everything they do. They don't have any control over the problems in a quake with these levees. This is a levee that was damaged in 1994 in the Northridge earthquake. It's hardened, has an asphalt covering, has low relief, and a gentle slope. This is not what our levees look like.
What would we do at I-55 behind the setback levee if we have high water and we have a 6.0 thrust fault, an actual ground displacement that breaks some of those things? These are things we are concerned with.
So plate tectonics are pushing the plates around. Well, that still doesn't explain how rocks can store energy and supply a burst of energy that actually causes an earthquake.
It's based in something called the elastic rebound theory, which means basically that rocks have to behave kind of like a rubber band. They have to be able to stretch and store energy to have tension. Well, if that happens along the fault and plate boundaries, those faults and plate boundaries aren't these nice flat features that we've portrayed them as. They're jagged jigsaw puzzle odd angled pieces that when they have motion on them, they tend to hang up in places. Where they hang up is where we're going to have the earthquakes. Because the pressure continues, and when the pressure exceeds the strength of the rock, the fault gives way and we have an earthquake.
In the San Andreas after Loma Prieta, we had what we call a strike slip earthquake, where the movement is horizontal. The ground hasn't come up, it's moved sideways along this. This is an olive orchard and you can see the rows aren't straight anymore but the ground is flat. After an earthquake, this is the elastic rebound theory in action.
California has been studying their problems for a long time. They have sunk a tremendous amount of resources into the scientific effort and as a result of that they can come up with beautiful diagrams like this or animations like this that can show you the synthesis of plate tectonics around their area.
What the attitude and the relationship of all the faults that surround us are, we don't know. They're 3,000 feet beneath us. It costs hundreds of thousands of dollars to dig holes down 3,000 feet.
Here's another digital animation from California. Watch Nevada, California, and Baja form here. This is 30 million years ago, coming on 20 million years ago, ten million years ago. We'll see Baja start to form right here. It took a tremendous amount of science and many years of study to learn what this picture is. In the central US, we've got a lot of catching up to do.
Engineers come to me every day wanting answers to questions that are relevant to California as far as their standards. We don't have all the answers. We're still working on that.
I had the opportunity to go to Taiwan after the ChiChi earthquake September 21 last year. I'd like to share a few pictures. There may be some lessons we can learn.
There is no doubt that Taiwan is an active interplate setting where you have lots of earthquakes. However, this earthquake was in western Taiwan. They have earthquakes there, but they don't have a lot. Something that really impressed me, in talking to locals, they said, we haven't had a big earthquake since 1935. We feel a few every now and then. Scientists said that the big one might happen. We didn't listen. That hit home with me.
Does anyone see anything odd about this photograph? Can you see the oil cans embedded in the first story slab of this building? We're talking bridge engineers, but this is still an engineering problem, or contractors' problem, which it could be. The first story has failed here and there were many casualties in this facility.
This is a little town in the west central part of Taiwan called Shikang, where the geological setting greatly influenced the damage from this earthquake. We need to understand the geology to get at the problems we could face when an earthquake happens.
We tracked the Chelungpu fault for 60 kilometers, through cities, mountains, and jungles. This fault came out of the mountains into the river valley and it splayed into three different thrust faults. A thrust fault is where one side comes up relative to the other one. This basically tripled the damage through this small town, and probably tripled the casualties. This is a dam on the northern end of the Shikang and this is not the main thrust of the fault. The dam is being rebuilt now. Taiwan lost a total of 60 bridges in this earthquake. This one was repaired in a matter of days. They don't need proclamations from the president to get the military moving. That's why we're very concerned and happy that CUSEC and other people are involved in the EMAC. We really like it where people start moving before the president tells them to. That's extremely important, we've learned that lesson.
Another lesson we've learned is this: This is a brand new facility in Taiwan, but it's built right on the fault, right on the hanging wall. That means it's built right on the site that came up during the earthquake. It's also built right on top of a boulder bed, perfectly rounded boulders. The slabs of these facilities were slapping together for 30 to 45 seconds.
I think in the last year, I've talked to 4,500 kids, 10,000 people in professional meetings and I usually tell them the earth isn't going to swallow you up in an earthquake. If you're right on top of a fault, especially a hanging wall thrust fault, anything can happen. It doesn't matter how well engineered that structure is. When you have a displacement of meters and ground vibration that continue for long duration, it's very difficult to engineer a structure that's going to stay.
This bridge is very important in the little town of Shikang. The scarp on the right of the waterfall was not there a year ago. It's the amount of the offset during the earthquake. It came up and formed during the earthquake. The bridge did not fail in the initial earthquake but it failed in an aftershock. We'll talk about New Madrid and 18 events greater than 6.0 that happened in a three-month span. We've only just begun to address what we're going to do in aftershocks but it's a very important part of the picture.
This is what the bridge looked like after the main shock. Given it's just hanging there, and it wouldn't take much of a shock to knock it down. Whenever you've got a bridge inspector under this pile, you want to know about aftershocks and you want to get the best and most rapid information you can get on aftershocks. You need to be prepared.
This is another bridge at Chushan where the displacement of the superstructure was much greater than the base. There was no connection between the individual slabs from pier to pier. The bridge has failed. This was the common mode of failure is the displacement that exceeded half the base of the pillar.
Taiwan makes most of the world's motherboards. The silicone valley in Taiwan lost power for several intervals along several days. It caused the stock market to be affected. It caused the price of toys to go up. Toys use computer chips and caused the price of computers to go up incrementally. These are all things you have to worry about.
Just south of Nwufeng when we were under this bridge, we had an aftershock and I can testify now that aftershocks are inspirations because we really got out from underneath there very fast. I know now that I won't wait to feel the ground vibrate. If I see people acting strange while I am underneath a compromised bridge, I'm out of there.
The map on the left shows you the geology of western Taiwan. Young sediments are these yellow sediments here, meaning they're getting progressively older. The fault that ruptured was the Chelunpu fault. I think you can see here how the geology controlled this fault pattern. It's right where two different sediments of two different densities connect, or come together, and this is where the fault broke.
It's extremely important to understand the geology and the seismology related with the seismicity.
This diagram on your right is the background seismicity in west central Taiwan over a period of about 30 years. All these are little earthquakes that happened over a period of 30 years. The epicenter of the ChiChi earthquake was right here.
What I would like to point out is that we saw damage in a town called Taichung probably 40 kilometers away from the epicenter. It was much like what we saw in the Marina district after the Loma Prieta, which was 60 miles away from the epicenter. Why? These are young, unconsolidated sediments that react differently to earthquakes than hard stone.
As earthquake waves move from hard rocks into soft rocks, the earthquake wave slows down. The energy doesn't just disappear. The net effect is commonly that the earthquake waves will become larger, more ground motion for the same magnitude earthquake. Another geologic principle that we need to address is liquefaction. I think the bridges I've seen go up in the last 20 years seem to address that quite well.
Another section in the mountains of Taiwan is called Pulei. It's a mountain basin. It's an old valley and it's still young consolidated sediment. There was no ground surface rupture in that town. Yet we saw entire blocks of failed buildings and bridges. The first stories were gone. This was another good example of amplification. Most of the damaged buildings that we saw were between 12 and 16 stories. The periods of the building matched the periods of the waves of the earthquake. You all know that principle. It's real; it happens; we've seen it.
Now, let's turn the picture to significant earthquakes in north and eastern North America. The 1811 ones aren't the only quakes we've had in the central United States. In 1843 we had a low magnitude 6 epicentered near Marked Tree, Arkansas, about 35 miles northwest of Memphis.
In 1895 we had a mid to high magnitude 6 earthquake in Charleston, Missouri. I don't need to remind you that Northridge was only a 6.7 earthquake and caused $20 billion worth of damage in a community that's basically prepared for earthquakes.
I'm here today to tell you that the probability of a huge earthquake is low. It's possible and I think our critical facilities and transportation networks should reflect that. The real danger is from a mid 6 earthquake that could cause tremendous loss of life and structures, especially in the epicentral area and have a lot of side effects within 60 to 100 miles of the event.
We need to be worried about these 6.0, 6.5s. We don't need to scare the public with the possible but improbable advent of an 8.0. It doesn't do any good. We need to plan for the probable and expect the improbable someday. These 6.0, 7.0 range earthquakes can do a lot of damage. A 6.0 earthquake in Armenia, Colombia last January knocked down 75 buildings. It was followed by a 4.0 aftershock that knocked down 25 buildings.
A 5.9 in Athens, Greece, which was actually an aftershock of the Turkey earthquake, I don't know how many buildings were lost, but a lot of them.
6.0s can do a lot of damage, especially when you have amplification factors and unknown site conditions.
So, how do we know where the faults are if they're all buried in the New Madrid seismic zone? Well, because of the elastic rebound theory, we know that earthquakes happen on faults or plate boundaries. Some faults move every 10,000 years, some faults move every four or five years.
What we've done here is taken all these epicenters of earthquakes, plotted them on a map over a period of time from1974 to 1994 where the earthquakes cluster, or where the most active faults are. By doing this, the New Madrid seismic zone emerges, here, not just as one fault, but a complex fault system whose energies are related. When you have an earthquake on one, it may trigger earthquakes on the other.
I would also like you to note this pink dot here at the very bottom. Before this earthquake we didn't know all these little micro tremors were happening. St. Louis University had some instruments out in 1974 and they began to put these pieces of this puzzle together.
In 1976 we had a 5.0 magnitude earthquake in Marked Tree, Arkansas. This earthquake was felt over 280,000 square kilometers in seven states. If you're in California, does anybody remember the Hector Mine's earthquake last October? That was a 7.0 earthquake and it was barely felt 100 miles away. That's a very important point and I'll come back to that in a few minutes.
This 5.0 caused limited phone and power outage from Jonesboro, Arkansas to Union City, Tennessee. It caused architectural damage to nine fire department buildings in the Memphis area and some of the cracks in the foundations are still there in Station No. 46 downtown. It caused limited architectural damage to buildings all over northeast Arkansas. What are the probabilities? We're talking about a 6. A 6 would release 32 times more energy than this 5.0. It's a clear and present danger.
Also, the other areas we're very concerned about are the Wabash seismic zone to the north and the St. Louis fault system that we're very close to. I know much less about these northern fault systems. They're obviously a very present danger also that needs a tremendous amount of study, especially because of their proximity to large urban centers like St. Louis.
Here's a close up of just the New Madrid seismic zone and again you can see the 1976 5.0 earthquake and its proximity to Memphis.
Let's move to the little town of New Madrid. New Madrid, Missouri, was established in 1783. This was the western frontier of the United States then. There were only 4,000 non-native Americans between St. Louis and Natchez, Mississippi. They lived in log cabins. Log cabins are good earthquake structures. I think the first brick building west of the Mississippi was in 1821 in St. Genevieve, the old brick house. There were common wood log structures that performed well in earthquakes as far as life safety standards.
This is a cartoon and it´s incredibly over dramatized because it's describing damage from the 1895 Charleston earthquake in St. Louis. I don't think anybody believes that the damage was nearly this bad but it does show some quite important features that are going to fail. The guy in the middle of the street might get run over by the scared horse. The guy underneath the heavy facade is going to the hospital. Just like the 1968 earthquake you had not far from here that caused some bricks to fall down and sent some kids to the hospital.
Tall heavy structures, top-heavy structures, these are the things that are going to fail. The old buildings made from un-reinforced masonry, the old bridges, railroad bridges included, of un-reinforced masonry, these are the things we need to plan for.
So how do we know New Madrid happened at all? Well, we know that 18 times along the Atlantic seaboard earthquakes were felt from the New Madrid seismic zone. That's a long way away. Hundreds of miles away these earthquakes were felt distinctly, reported in many different newspapers along the Atlantic seaboard. When we say eighteen 6.0 earthquakes, we may be underestimating their actual size. Three of these events were felt all the way in Canada. We believe those varied from 7.5 to 8.2. You'll hear us argue over it for the next century. That´s not the point. The point is that they were very big, they really happened, and they could happen again.
The people who we get accounts from right in the epicentral area ruffians. They were merchants and farmers, good-hearted people, such as a man named Mathias Speed. He was on the river near New Madrid in the third principal event in 1812. He had a pretty good crew. He was tied up to the river near New Madrid during the evening when the third principal event happened. His journal says that his boat was propelled upstream for ten minutes as fast as a horse could run, 30, 40 miles, we don't know.
We don't think that the Mississippi River ran backwards all the way from New Orleans to St. Louis, it's not feasible. This fault that came up through the Mississippi River during this event was maybe 15 feet and the river is 60 feet deep. It´s not going to make a dam that backs up the river. It is going to cause some current changes that are going to last for a few minutes when it´s soft unconsolidated sediment. The river is powerful. It´s going to eat right through that and you´re not going to have long-term current reversals that run hundreds of miles.
There were landslides along the Mississippi River in the bluffs all the way from Hickman, Kentucky and all the way to Natchez, Mississippi. That's a tremendous amount of landslides with a tremendous amount of transportation networks that were based at some of those bluffs. Those landslides went right down into the river in many cases. When you dump dirt into the river, you can cause some incredible current changes also.
Eyewitnesses may have seen many current reversals in the river but they were probably away from the New Madrid seismic zone proper. These reversals were probably caused by landslides or some type of in-filling event. Some people used the term lateral spreading when the banks of creeks and rivers failed during earthquakes.
So the accounts we get from the journals of these people are generally crossed referenced. They say generally the same thing. They talk about damage and the inability to stand up. The documents say over 1,500 acres of trees were leveled in this earthquake. The little prairie where the Charleston dike or bridge is completely destroyed. Two houses were left in the town of 100. And that town actually used to be on the Tennessee side. Now it's on the Missouri side.
USGS, the United States Geological Survey, has been instrumental in bringing the efforts of many people like CUSEC and CERI to the forefront and their acknowledgment of the actual earthquake risk that's out there. The Federal government is saying that yes, there is a 90 percent chance of a six to seven earthquake happening in the next 50 years. The federal government is saying, we're not doing enough and we need to do more. That's why we're glad that people like you are doing more and are continuing to make plans based on the lessons learned from other places like California.
This is the land set image of the Mississippi River. Right here is the little town of New Madrid. This fault is one of the few you can actually see on the ground. This is a flood plain and flood plains are generally flat. The Reelfoot fault can be traced from its northeastern or northwestern extension northwest of New Madrid to the bluff line so that's 60 to 100 feet above the flood plain of the Mississippi River.
Along the edges of the bluffs is where we had failure in 1811 and 1812. The Reelfoot Lake was formed because of the third principal event in the New Madrid earthquake series. It's a thrust fault and it came up right through Running Reelfoot Bayou Creek. There was about 15 feet of displacement around a little spot called Blue Bank. This dammed up Running Reelfoot Bayou Creek. The southwest side came up and the northeast side went down. Mathias Speed was not really in New Madrid but on the side that came up so his boat was propelled upstream for a few minutes. This is where there could have been current reversals because of the thrust fault.
Reelfoot Lake may have been formed somewhat due to Mississippi River water running in from up here. We do know that Reelfoot Lake was formed because of this earthquake bringing up enough sediment to block the creek and it's still there.
This is a work done by Joe Johnson, Paul Bodin and Buddy Schweig. It shows the change in the course of the Mississippi River as a result of the 1811, 1812 earthquakes. The pink is the present course of the river. The blue is the course of the river in 1811, 1812. The island you see there disappeared within a matter of months. New Madrid didn't just fall into the river. It was already in trouble before the earthquakes with caving in problems and landslide problems. But eventually, the river meandered completely through the old town of New Madrid and it had to be relocated.
This change over an area of hundreds of kilometers of the river is a dramatic indication of the power that was demonstrated during these earthquakes.
One of the most insightful things that scientists have done with the New Madrid seismic zone in the last 20 years is through a science called paleoseismology. We know 1811, 1843, 1895 happened. What about before that? In places where you have earthquakes, a lot of them usually have mountains. Why don't we have mountains here? All those little white dots you see -- this is the St. Francis River Basin about six miles across, about four miles tall in northeastern Arkansas. Most of the little white dots you see here are earthquake features called sand blows. When you take wet unconsolidated sand and you put a river gumbo over it, the silt comes out and forms a clay cap over the river sand. So when you take that wet, unconsolidated sand, cap it with this relatively impermeable clay, then you shake the sand, the pressure inside the sand increases. The pour pressure between the grains of sand increases. The water wants to escape. When the pour pressure exceeds the strength of this clay cap, it will burst through and forms a sand volcano or what we call a sand blow.
Now, there are many different manifestations of liquefaction. You can get lateral spread along the creeks and riverbanks where the banks fail. You can get differential settlement of buildings as we saw in Kobe. Everybody has seen the pictures of the buildings that went over in Kobe. Sand blows are a relic feature that demonstrate a large amount of ground shaking. In the 1895 event, high magnitude 6, we had about 16 square kilometers, according to Steve Obermeier, that was liquefied, mostly around Bertrand to Ste. Genevieve. These are well documented. You can still go out and see them now.
So that gives us kind of a lower limit on what kind of an earthquake it takes to make sand blows. We think it's about in the 6 to 6.5 range before you even start liquefying the soil. Of course it's predicated on the amount of water that's available, the duration, the length of the ground motion, all those things are important. We know that.
This is near New Madrid, the same thing. You can see the white dots here, a real low flying plane here. My son said, these aren't sand blows, they're just holes in the clouds, dad.
Here we see a fissure sand blow formed from another large earthquake that happened in the eastern United States, low-magnitude 7earthquake in Charleston, Missouri, in 1895. These types of fissure sand blows are very common where you get large cracks and sand comes up through the cracks.
Let's recap so we can wind this down. In the United States, the most active seismic zone east of the Continental Divide, without a doubt is the New Madrid seismic zone. It's the site of the most powerful earthquake sequence in the continental U.S. history. An average of 150 earthquakes per year are monitored in and around the New Madrid seismic zone by several institutions. St. Louis University operates 12 broadband instruments. CERI operates 14 broadband instruments and eight for short period assistance. We're also working with Virginia Tech and the University of Southern Carolina. All these universities are internet connected. You can you go straight to one of our web sites and get information on the most recent earthquakes.
This is very important. The geologic setting in the New Madrid seismic zone allows earthquake waves to travel great distances. The perfect example is the effects felt from the 5.0-magnitude earthquake in 1976. It was felt over 280,000 square kilometers, seven states. Compared to the Hector Mines earthquake that was barely felt 100 miles away in Las Vegas or a hundred miles away in Los Angeles.
Earthquake waves can travel great distances in the hard cold rocks that make the continent float. They're not like the rocks in California and not nearly as fractured. They're much colder here. The rocks on the clay tectonic boundary of San Andreas are relatively hotter, especially in the deserts. They absorb more energy. Here, the energy dissipates, has lower attenuation, and can travel greater distances. This is well exemplified if we take a Mercalli scale drawing for a damage area. For those of you not familiar with the Mercalli scale, it's a scale that goes from one to 12 and basically at 6, you start getting building damage. So this is the building damage area from two different earthquakes. These magnitudes are somewhat disputed but I think San Francisco in 1906 has been revised to 7.9 moment magnitude. The New Madrid seismic zone earthquakes of 1811, 1812 were nearly equivalent but we'll always argue about the size. Just remember, they really happened; they were really big; and they can really happen again.
The building damage area is up to 20 times greater around the New Madrid zone than San Francisco from a similar magnitude event. You put the same magnitude event in California and compare it to one in Tennessee, Missouri, or Arkansas and you get a much larger area of building and bridge damage. It's not something we made up; it's a fact.
We don't know the exact attenuation relationships but we're working on it diligently with many people.
Let's move to my town, Memphis. How many people are here from Memphis? One other person? With such a high level meeting such as this, the city that's closest to the seismic zone is not represented very well.
Many projects are going on right now in west Tennessee including the retrofitting of the Memphis I-40 Bridge. This is a $100 million project sponsored by the Tennessee Department of Transportation and the Arkansas Department of Transportation to make this bridge safe and operable in a large earthquake. Supposedly it could go down to two lanes but it will be there after a large principal New Madrid event.
Many of you probably understand much more about these pictures than I do because you're bridge engineers. On this bridge, we're going to use bearing isolators in place of the existing connections. We're going to instrument this bridge at every connection between the girder system and the piers to get real-time information. That means we're going to telemeter the information from any ground motions of this bridge back to our web site and you can get that information very quickly.
Another bridge is the I-55 bridge from Caruthersville to Dyersburg. I don't think any progress has been made on this bridge. This bridge is right near the epicenter of one of the principal events in 1811 and 1812. Any earthquake here will be a thrust event. This is the type of event that's very hard to design for in extremely deep liquefiable soils.
So how do we know these earthquakes are happening? Well, we didn't do it easily. It takes a lot of work to employ seismic stations all around the earthquakes that happen here. It takes a lot of work and a lot of time and a lot of staff to get that information back to the places that can use it in rapid time.
I would like to mention that the U.S. Geological Survey has embarked on something called the Advanced National Seismic System. All the instruments you see here are weak motion instruments. They don't do engineers much good. We don't get acceleration values but we can get a velocity and then back out an acceleration. The Advanced National Seismic System will revamp all the seismic systems in the United States. It will provide strong ground motion instruments for different regions. We hope to get 20 strong ground motion stations next year: ten for Memphis and ten for St. Louis. If we can get more, they would probably get placed in Evansville or Paducah and wherever else we can.
We're fighting for this money right now. The bill has been approved at 1 percent of its funded level. So most of what we're doing, we're doing on our own. But the Advanced National Seismic System is a link between the engineering community and the seismic monitoring community. It's acceleration based and not intensity based. It can give you information in rapid time.
Another major initiative is the seismic-hazard mapping project in the USGS. There is no doubt that these types of maps save lives. They're also the basis for building codes. Unlike ATZ 21 or the old AASHTO standards, it's not based on intensity. It's based on accelerations. We understand the new AASHTO standards are being revamped based on acceleration. So the seismic-hazard maps from the USGS are the basis for the building code. They provide an extremely good web site at the National Standard Mapping Center, mapping project center. You can get an unmodified acceleration for a site just by putting in the ZIP code, longitude and latitude.
I think the USGS has learned to establish better end users, especially here in the central United States. They're very busy, that's not the reason that they're not interacting more. They're working on these products. These products will start coming out in the next year or two and be very helpful to the engineering community. When they make a map like this, it takes into account every earthquake that we know has happened. It's a very, very good system. It needs still more refining because the basic science hasn´t fully matured yet.
But this is the way the world is going. The international building code will be acceleration based. It will be modified in some way due to input from a lot of people in this room.
The earthquakes we have here can't be compared directly to those in California. Even though we don't know all the answers, we've learned and know a lot. We would be glad to share any information with any of you in this room. There are a lot of people to turn to: St. Louis University, University of Memphis, CUSEC, and other engineering communities. We're really impressed with the type of interaction you have with the engineers like Glenn Fulkerson of the Federal Highway Administration who has been working to increase the awareness of earthquakes in mid-America.
We have big problems in other urban areas, large urban areas in the central United States, big problems, and big political problems. The only way we can solve these is through an engineering community that comes together and says on top of this. We hope we can get some help.
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