Research There are forces within the earth that are bending and straining the relatively thin crust we call home. Although scientists and engineers do not full understand these forces, we know that they cause the earth’s crust to bend until it snaps. This action is called an earthquake. Earthquakes can cause extensive damage to building, roadways, and infrastructure. That is why there are research teams that focus on earthquakes and designs for buildings that can help withstand the forces that can dome from the earth’s crust. Therefore for you to design and build your tower, you will research earthquake and engineering design terms throughout this presentation.

Earthquake Terms Please read the following slides. As you read, fill out the Science and Technology Work Book titled, Please read the following slides. As you read, fill out the Science and Technology Work Book titled, “Epicenter Towers.”

Earthquakes Engineers and scientists have been studying earthquakes and the effects that they have on structures for years. Together, they are working on construction techniques to reduce damage caused by forces within the earth.

Measuring Earthquakes Scientists called seismologists use a machine called a seismograph to measure earthquakes. When an earthquake strikes, it shakes the bedrock which the seismograph is attached to, causing the pen to move while the paper remains still, thus making a jagged line. Seismologists then read the seismogram and interpret the intensity of the earthquake. Scientists called seismologists use a machine called a seismograph to measure earthquakes. When an earthquake strikes, it shakes the bedrock which the seismograph is attached to, causing the pen to move while the paper remains still, thus making a jagged line. Seismologists then read the seismogram and interpret the intensity of the earthquake.

Measuring Earthquakes Scientists use a method of measurement called the Richter Scale to describe the magnitude (strength) of an earthquake. The scale starts at zero and goes as high as necessary. Each number on the scale represents an earthquake with about 30 times more power than the previous number. Therefore, an earthquake that registers a “7” on the Richter Scale would be 30 times more powerful than one that registered a “6.” Therefore the higher the number on the Richter Scale, the higher the magnitude. Scientists use a method of measurement called the Richter Scale to describe the magnitude (strength) of an earthquake. The scale starts at zero and goes as high as necessary. Each number on the scale represents an earthquake with about 30 times more power than the previous number. Therefore, an earthquake that registers a “7” on the Richter Scale would be 30 times more powerful than one that registered a “6.” Therefore the higher the number on the Richter Scale, the higher the magnitude.Richter Scale Richter Scale

Types of Earthquake Waves Knowing the characteristics of earthquake waves help geologists determine the locations of earthquakes and the characteristics of the earth’s layers. This information is fundamental to the development of earthquake resistant structures. Knowing the characteristics of earthquake waves help geologists determine the locations of earthquakes and the characteristics of the earth’s layers. This information is fundamental to the development of earthquake resistant structures.

Types of Earthquake Waves There are three types of earthquake waves:  Primary Waves (P waves)  Secondary Waves (S waves)  Surface Waves

Watch the following illustration to help you understand how P waves and S waves work. The Slinky and The Rope Earthquakes generate several kinds of seismic waves including P, for "Primary" and S, for "Secondary" waves. P Waves The P waves move in a compressional motion similar to the motion of a slinky, while the S waves move in a shear motion perpendicular to the direction the wave is travelling.travelling S Waves

Primary Waves  The fastest of all three types of waves  P waves travel between 5 and 13 km/second  Represented by the compression waves of the slinky on the previous slide.  Can pass through liquids, solids and gasses  Expand and compress materials in their path  Move buildings back and forth  The compression causes a slight vibration that would rattle dishes, or shake any unstable objects  These waves warn people that an earthquake is happening and can give people time to prepare for the movement to come.  On a seismograph, p waves appear as a smooth up and down line.

Secondary Waves  Travel slower than P waves.  Their velocity is about 55% of the related P wave  Represented by the movement of a rope  Can pass through only solids, not liquids or gasses  S waves shake buildings up and down and from side to side  On a seismograph, S waves appear on as jagged up and down lines

Surface Waves  The slowest wave of all  Travel along the earth’s surface  Their rolling motion (much like an ocean wave) breaks up roads and buildings thus causing the most structural damage  They cause part of a building to move up, while another part of the building is moving down  Please click the following to see how earthquake waves appear on a seismograph:  How Do I Read a Seismograph? How Do I Read a Seismograph? How Do I Read a Seismograph?

P and S Waves Illustration Click on the following link that illustrates how both primary and secondary waves affect the earth’s surface. Click on the following link that illustrates how both primary and secondary waves affect the earth’s surface. Observe animations of earthquake waves. Observe animations of earthquake waves. Observe animations of earthquake waves. Observe animations of earthquake waves.

Time  The length of time between the arrival of P and S waves gives an indication to the origin of the earthquake. The shorter the time the closer the focus of the earthquake is.

Focus  The focus is the location at which the energy of an earthquake is released and waves originate.  Earthquakes generally occur at depths around 30 km but may occur at depths of 600 km or more.

Epicenter  The epicenter is the point on Earth’s surface directly above the focus of an earthquake. The strongest shaking often occurs at this point.

Conclusion  You have just learned and studied earthquakes and how they can affect the surface of the earth. Your task will be to design and construct a tower that can withstand the intensity of an earthquake. As you have learned, background knowledge is the key to efficient design and construction. Hopefully, this presentation will help you to defeat the “epicenter tower eliminator.”

Are you up to the challenge?