EARTHQUAKES

Natalie Bolen11/9/2009

MY EXPERIENCE

On April 18thth, 2008 I was sleeping soundly in my bed at 4:40am, when I woke up to a rumbling sound and my entire room shaking. I jumped out of bed, sleepy and disoriented. I made it to the door way before the shaking stopped. Once it stopped, I walked out into the hallway and several of my residents had awoken and were standing in the hallway wondering what had just happened. It took only seconds for us to realize that it must have been an earthquake. I have always had a basic knowledge of earthquakes, but ever since this experience, I have been curious about earthquakes. Hopefully this project will answer some of my questions!

MY QUESTIONS

What caused this earthquake? What do scientists use to measure the

an earthquake? How far away was the earthquake felt? What is the history of Earthquakes in

Southern Indiana/Illinois? What is the potential for future

earthquakes?

WHAT CAUSES AN EARTHQUAKE

An earthquake occurs when two plates of the earth suddenly slip past one another. The surface where they slip is called the fault . The location below the earth’s surface where the earthquake starts is called the hypocenter, and the location directly above it on the surface of the earth is called the epicenter.

Sometimes an earthquake has foreshocks. These are smaller earthquakes that happen in the same place as the larger earthquake that follows. Scientists can’t tell that an earthquake is a foreshock until the larger earthquake happens. The largest, main earthquake is called the main shock. Main shocks always have aftershocks that follow. These are smaller earthquakes that occur afterwards in the same place as the main earthquake. Depending on the size of the main shock, aftershocks can continue for weeks, months, and even years after the main shock, however, sometimes they are too weak to be felt.

WHAT CAUSES AN EARTHQUAKE

The Midwest, primarily, southeast Missouri and southwest Illinois, is home to the New Madrid seismic zone, a network of deep cracks in the earth’s surface. The fault is at the center of the country’s most active seismic zone east of the Rockies. The New Madrid Seismic Zone is where the earthquake that I felt occurred.

WHAT CAUSED THE EARTHQUAKE?

“The New Madrid Seismic Zone is made up of reactivated faults that formed when what is now North America began to split apart during the breakup about 750 million years ago. Faults were created along the rift and igneous rocks formed from magma that was being pushed towards the surface. The resulting rift system failed but has remained as a scar deep underground. Another unsuccessful attempt at rifting 200 million years ago created more faults, which made the area weaker. The resulting geological structures make up the Reelfoot Rift, and have since been deeply buried by younger sediments. But the ancient faults appear to have made the rocks deep in the Earth's crust in the New Madrid area mechanically weaker than much of the rest of North America, thus causing earthquakes.

WHAT CAUSED THIS EARTHQUAKE?

Many earthquakes occur on the New Madrid Fault Line every year, although most are too weak to be felt by the public.

The red bulls-eye marks the epicenter of the earthquake that I felt on the map.

The epicenter was: 7 km (5 miles) NNE

(13°) from Bellmont, IL

60 km (38 miles) NNW (331°) from Evansville, IN

206 km (128 miles) E (95°) from St. Louis, MO

HOW FAR AWAY WAS IT FELT?

The Associated Press says that the earthquake I felt in my room at USI was felt as far away as Georgia, Kansas, and the upper peninsula of Michigan. It was also felt in Memphis and Clarksville Tennessee.

HOW DO SCIENTISTS MEASURE AN EARTHQUAKE?

Earthquakes are recorded by instruments called seismographs. The recording they make is

called a seismogram. The seismograph has a base that sits firmly in the ground, and a heavy

weight that hangs free. When an earthquake causes the ground to shake, the base of the

seismograph shakes too, but the hanging weight does not. Instead the spring or string that it is hanging from absorbs all the movement. The

difference in position between the both parts of the seismograph is what is recorded.

HOW DO SCIENTISTS MEASURE AN EARTHQUAKE?

They measure the Magnitude . Magnitude is a measure of the amount of energy released during

an earthquake. This is measured on the Richter scale. The Richter scale was invented, in the 1930s by Dr. Charles Richter, a seismologist at the California Institute of Technology. It is a measure of the largest seismic wave recorded on a seismograph located 100 kilometers from the epicenter of the earthquake.

The size of an earthquake depends on the size of the fault and the amount of slip on the fault, To measure an earthquake, scientists use seismogram recordings made on the seismographs at the surface of the earth to determine how large the earthquake was A short, somewhat straight line signifies a small earthquake, and a long unstraight line means a large earthquake.

HOW DO SCIENTISTS MEASURE AN EARTHQUAKE?

They measure the Intensity:Unlike magnitude, where each earthquake only has one, an earthquake can have a varying number of intensities depending on where you are during the earthquake. For example, someone running outside may not feel the earthquake at all, which signifies a low intensity, while someone in a skyscraper may feel the whole building shake which signifies a higher intensity.

EARTHQUAKE HISTORY

New Madrid, Missouri Earthquakes 1811-1812These earthquakes gave the name to the New Madrid Fault, where the April 28, 2008 earthquake occurred. From December 1811 to February 1812, a series of earthquakes occurred in Missouri and were felt throughout Illinois, Indiana, and Kentucky. They ranged from 8.2-9.0 on the Richter Scale. These earthquakes were felt as far away as New York City and Boston, Massachusetts. The quakes even permanently changed the course of the Mississippi River. Hundreds of aftershocks strong enough to be felt occurred until 1817.

**The picture to the right shows damage caused by one of the 1811-1812 earthquakes.

EARTHQUAKE HISTORY

DATE/PLACE/MAGNITUDE October 31, 1895: Charleston, Missouri- M 6.6 November 9, 1968: Dale, Illinois- M 5.4 May 25,1909: Aurora, Illinois – M 5.1 November 9, 1968: Southern Illinois – M 5.3 June 10, 1987: Near Olney, Illinois – M 5.1 June 28, 2004: Illinois – M 4.2 January 2, 2006: Illinois – M 3.6

POTENTIAL FOR FUTURE EARTHQUAKES In a report filed in November 2008, The U.S. Federal Emergency

Agency stated that a serious earthquake in the New Madrid Seismic Zone could result in "the highest economic losses due to a natural disaster in the United States," further predicting "widespread and catastrophic" damage across Alabama, Arkansas, Illinois, Indiana, Kentucky, Mississippi, Missouri and particularly Tennessee, where a 7.7 magnitude quake or greater would cause damage to tens of thousands of structures affecting water distribution, transportation, and other infrastructure.

The potential for more earthquakes and their impact today on largely populated cities in and around the seismic zone has generated much research devoted to understanding the New Madrid Seismic Zone. By studying evidence of past quakes and closely monitoring ground motion and current earthquake activity, scientists attempt to understand their causes and recurrence intervals, although earthquakes can never be prevented.

INDIANA ACADEMIC STANDARDS

5.1.4- Give examples of technology, such as telescopes, microscopes, and cameras, (seismographs) that enable scientists and others to observe things that are too small or too far away to be seen without them and to study the motion of objects that are moving very rapidly or are hardly moving.

6.3.12- Describe ways human beings protect themselves from adverse weather conditions.

6.3.22- Demonstrate that vibrations in materials set up wavelike disturbances, such as sound and earthquake waves, that spread away from the source.

RESOURCES

http://www.crh.noaa.gov/ilx/?n=18apr08quake

http://www.eas.slu.edu/Earthquake_Center/SEISMICITY/NewMadridGeneral.html

http://wx-man.com/blog/?p=886 http://www.buzzle.com/articles/what-ca

uses-earthquake.html http://vulcan.wr.usgs.gov/Glossary/Seis

micity/what_causes_earthquakes.html http://www.geography-site.co.uk/pages/

physical/earth/cause.html