It's no secret that Los Angeles is the earthquake capitol of the world. The famous San Andreas fault is only 50 mile away from downtown. What most people don't know is that LAX is built on top of a fault line. So if an earthquake ruptures this fault, where do you land?
You are at the blue star. The red line represents where the Charnock Fault is most likely to be about 1.9 miles below the ground. This line was based off a study in 1978 & 1989. The green line represents where small fragments or jumps in the fault are likely to be. This could suggest that the fault in green used to be part of the Charnock fault and/or has become inactive all together. This line was based off of a study in 1989. To see the original map, please refer to the first works cited link below.
The fault here is called the Charnock Fault and it runs near perpendicular with the runways here at LAX. The fault line goes from here, over thought runways 25L and 25R before crossing Century Blvd. at the intersection of Airport Blvd. It then continues, up to Manchester Blvd just west of the intersection of Sepulveda Blvd before going into the Santa Monica area. So why build one of the world's largest airports on a fault line?
The Charnock Fault is highly inactive, with movement less than that of it's counterpart, the San Andreas Fault. This fault moves at .1 millimeters per year on average, while the San Andreas moves at about 2 inches per year. With so little movement per year, it's a debatable question within the geologic community if the Charnock Fault is active at all. It was discovered well after LAX was constructed and the fault was considered to be least threatening. That being said, the airport continues to thrive and no significant, or measurable, earthquake has happened, yet. Yet, meaning that it's always a possibility that an earthquake may occur, as with all types of faults. According to the City of Los Angeles, the largest earthquake that is believed that can occur along this fault in the worst case scenario is a 6.5. A 6.5 can cause moderate damage, but if the epicenter was at LAX, it could cost billions of dollars in damage and cause hundreds of flights to be canceled. Luckily, this will likely never happen.
The Charnock Fault is a strike strip fault, like the San Andreas and most other faults in southern California. To understand what all this means, you must first understand what a fault line is and how they work to know the dangers of them.
Before I go into any more details lets first discuss the basic fundamentals of how fault lines are created and now they work. The answer can be found in your kitchen, literally. When boiling pasta on the stove, the hotter pasta floats to the surface then when it cools it sinks. This effect has a name. Convection currents in your pot at home and in the earth are nearly identical. There are a few difference though. One is with water, rather than boiling rocks and the other is that one is less a few inches while one is miles deep. Convection currents are continues cycles in the earth's mantel that make hotter rock rise, and cooler rock fall and the cycle begins over and over again. When this happens, it causes fractures in the earth's crust. When fractures occur, a fault line is created.
Now at this point I'm sure you are asking, "What is a fault line?" Well, it is place where two tectonic plates meet and create friction. When this friction is released, an earthquake is formed. This friction is formed by these convection currents. When they move in a circular pattern in one direction, they can push rock with them. When tension is released you get an earthquake in an that moves in waves on the X, Y, and Z axises. X is up or down, Y is right or left, and Z is pivoting side to side.
Depending on the pressure, it can create a magnitude 1 earthquake on the Richter Scale or a 10. A 10 has never happened in recorded history, but is believed to have only occur when large meteors hit the earth. The largest earthquake ever recorded happened in Chile on May 22, 1960. It happened in open waters, just off the coast in the Pacific where it created a Tsunami. You can see my earthcache about that Tsunami here.
A Richter Scale works like this. Say there was a 5.0 earthquake, which are common, and a 7.0, a little less. A 7.0 on the Richter scale is 100 times greater of that of a 5.0 on the same scale. Each decimal point in-between is twice as as bad as the preceding one.
So how do we predict such event? We can use a number of devices that monitor the fault line or zone, as it is more scientifically correct. The fault zone can be monitored by using lasers or GPS. Both have downsides, but both are extremely precise in measuring the activity. By using lasers, we can accurately measure how far the fault moves in a year, which is the same rate as an average human's finger nails grow. GPS systems are a little bit better in tracking the movement and direction of the fault zone. By using survey disks and benchmarks, we can accurately measure the direction and move rate of the fault zone and predict what it will look like in the future.
Now that you know how a fault line works, we can discuss the effects and dangers of them rupturing. One of the most common things to happen is liquefaction. Liquefaction is literally turning the ground into quick sand. Buildings are not being supported by anything so they ultimately fall and sink in this water. To understand liquefaction, think of it like a water bottle with water at the bottom and dry sand at the top. When you shake it, water travels up to the surface as the sand settles. What really happens is that when you shake and bottle full of sand, the elevation gets lower due to small particles of sand go under the larger ones. In reality, this squeezes up groundwater to the surface which makes puddles and can deform the land up to a few feet.
Works Cited
https://www.lawa.org/uploadedFiles/OurLAX/Past_Projects_and_Studies/Past_Publications/Draft%20EIS-EIR_T12_LR.pdf
http://www.planning.lacity.org/eir/LoyolaMarymountUniv/DEIR/IV%20E%20Geology.pdf
http://www.britannica.com/science/soil-liquefaction
http://www.conservation.ca.gov/cgs/information/publications/teacher_features/pages/faults.aspx
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1. Charnock Fault - LAX on the first line of your email.
2. Do you see any evidence of the Charnock Fault here? If so where? If not, why?
3. Based on your observations, if a significant earthquake occurred along this section of the Charnock Fault, would liquefaction be likely to? Explain.
4. As stated above in the description above, what option would you believe would be the most effective in monitoring the geologic activity here?
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