You may be familiar with the New Madrid earthquakes of 1812-13. They were the largest quakes on the mainland USA. Fortunately this area was sparcely populated at the time. If an equilivant quake would hit this area again, it would NOT be good news for the large cities of St. Louis and Memphis!
What geological physical evidence remains of those 1812-13 earthquakes? On the west side of the Mississippi River, only sand boils. Yes, you are standing at the sight of what is called a sand boil. Sand boils are all the visual evidence you can see in this area of the New Madrid earthquake. So when I was wanting to write this earthcache, The BIG one! R U at RISK? I figured that I would start here! You may want to check-out earthcache GC2M4PN -- EARTHQUAKES! Sand boils & Liquefaction Earthcache .
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The Big One--New Madrid
If a big earthquake occurred in the New Madrid, Missouri region again--Would you have enough time to be warned before the seismic waves hit your area?
One major earthquake happened in New Madrid on December 16, 1811 and measured 8.6 on the Richter Scale. Five weeks later on January 23, 1812, a second one occurred that was measured 8.4. Finally a third earthquake occurred two weeks later on Feburary 7, 1812, and measured 8.7on the Richter Scale.
Earthquakes
Earthquakes are the result of forces deep within the earth's interior that continually affect its surface. The energy from these forces is stored in a variety of ways within the rocks. When the energy is released suddenly--by shearing movements along faults in the crust of the earth--an earthquake results.
The area of the earth where the sudden rupture takes place is called the focus or hypocenter of the earthquake. The point on the earth's surface directly above the hypocenter is called the epicenter of the earthquake.
The Richter Scale
The Richter Scale is the measure of the magnitude of seismic waves from an earthquake and measures how much the ground ground shakes 60 miles from the earthquake's epicenter.
The scale is logaritharc, that is, the amphitude of the waves increases by powers of 10 in relation to the Richter magnitude numbers. The energy released in an earthquake can be approximated by an equasion that includes the magnitude and the distance from the seismograph to the earthquake's epicanter.
Like ripples fromed when a pebble is dropped into water, earthquake waves travel outward in all directions, gradually losing energy, with its intensity, earth movement and ground damage generally decreasing at greater distances from the earthquake's epicenter.
Seismic Waves
The mechanical properties of the rocks pass through quickly organize the waves into two types of seismic waves. Compressed waves, also known as the primary or P waves, travel the fastest, at speeds of 5 miles per second in the earth's crust. Sheer waves, the damaging waves, also known as secondary or S waves, move more slowly through the earth's crust at 3 miles per second. P waves shake the ground back and forth, while the S waves shake the ground up and down.
TO CLAIM CREDIT for this earthcache, please answer the following questions and e-mail answers to my profile BEFORE you submit this as a 'FIND'--THANKs!
!-To prove that you have been to the site of this earthquake, looking to the southeast of the posted coordinates, you see a large mound which is the remains of a 'sand blow' or 'sand boil.' Estimate the height of the mound and choose the size of this 'sand boil' A-size of an auto B-size of a house or C-size of a baseball field?
2-On your GPS or map, calculate the distance from your home to New Madrid, Missouri. If the primary wave travels at the speed of 5 miles per sec, --how long will it take for you to feel the first tremors after an 8.7 earthquake occurs in Mew Madrid?
3-If the damage causing secondary wave travels at 3 miles per sec, -- how long will it take for you to start seeing the damage after an 8.7 earthquake in New Madrid?
4-By subtracting 1 from 2, how much warning would you have to take cover?
5-If the Richter number drops by approximately 1 for every 125 miles the wave travel, using the table BELOW, what degree of damage would another 8.7 earthquake in New Madrid, Missouri be expected to cause at your residence?
This is my 43rd published earthcache---THERE R TWO (2) EARTHCACHES AT THIS SITE! DID U GET THE OTHER ONE TOOO?