2-20-18 Earthquakes

Do Now: Take out your homework and complete the following in your science notebook. Compare and contrast the three types of seismic waves Distinguish between an earthquake focus and an earthquake epicenter.

Do Now: Take out your homework and complete the following in your science notebook. Contrast the three types of seismic waves. Wave Type Motion Properties Primary Rock particles move back and forth parallel to the wave. Fastest Travels through solids and liquids Secondary Rock particles vibrate perpendicular to the direction of the wave Slower than P-waves, faster than surface waves Cannot travel through liquids Surface Rock particles move in a rolling motion in the same direction as the wave. Slowest seismic wave Travels on Earth’s surface

Do Now: Take out your homework and complete the following in your science notebook. 2. Distinguish between an earthquake focus and an earthquake epicenter. The focus of an earthquake is where movement along the fault occurs. The epicenter is the point on Earth’s surface directly above an earthquake’s focus.

Quiz on Wednesday, 2/21 What is an earthquake? Parts of an earthquake Types of seismic waves Where do earthquakes occur? Types of faults How do scientists monitor earthquakes? Scales Triangulation

Why does this matter? Mapping Earth’s Interior Seismologists: scientists that study earthquakes. Sismologo: cientifico que estudia los terremotos They use the properties of seismic waves to map Earth’s interior. P-waves and S-waves at different depths within Earth’s interior travel at different speeds.

Why does this matter? Mapping Earth’s Interior Through extensive earthquake studies, seismologists discovered S- waves cannot travel through the outer core, proving that Earth’s outer core is liquid unlike the solid inner core. By analyzing P-wave speed travelling through the core, seismologists discovered the core is made of mostly iron and nickel.

Why does this matter? Earthquake risk Because earthquakes threaten people’s lives and property, seismologists study the probability that an earthquake will occur in a given area. Probability is one of several factors that contribute to earthquake risk assessment.

Why does this matter? Earthquake Risk Seismometer: an instrument that measures and records ground motion and the distance and direction that seismic waves travel. Sismometro: instrument que mide y registra el movimiento del suelo y que determina la distancia de las ondas sismicas. Ground motion is recorded as a seismogram: a graphical illustration of earthquake waves. sismograma: ilustracion grafica de las ondas sismicas.

Locating an earthquake’s epicenter Seismologists use a method called triangulation to locate an earthquake’s epicenter. Triangulation uses the speeds and travel times of seismic waves to determine the distance to the epicenter from at least 3 different seismometers.

Describing Earthquake Magnitude Scientists can use three different scales to measure and describe earthquakes. The Richter magnitude scale uses the amount of ground motion at a given distance from an earthquake to determine magnitude. Each increase of 1 unit represents 10x the amount of ground motion on a seismogram. Ex: a magnitude 8 earthquakes produces 10 times greater shaking than a magnitude 7 earthquake and 100 times greater shaking than a magnitude 6 earthquake does.

Describing Earthquake Magnitude The moment magnitude scale measures the total amount of energy released by the earthquake. For each increase of one unit on the scale, the earthquake releases 31.5x more energy. Ex: a magnitude 8 earthquake releases more than 992x the amount of energy than that of a magnitude 6 earthquake.

Determining Earthquake Intensity The Modified Mercalli scale measures earthquake intensity based on descriptions of the earthquake’s effects on people and structures.

Earthquake Risk Seismologists use probability and study earthquake history, the geology around a fault, the population density, and the building design in an area to evaluate risk. Areas that experienced earthquakes in the past will likely experience earthquakes again. Based on this information, engineers design earthquake-safe structures to withstand the shaking during an earthquake.

Lesson 1 - VS The focus is the area on a fault where an earthquake begins.

Lesson 1 - VS Earthquakes occur along plate boundaries.

Lesson 1 - VS Seismologists assess earthquake risk by studying past earthquake activity and local geology.

Homework Review: Earthquakes How are the locations of earthquakes related to plate boundaries? The buildup and release of stress along plate boundaries cause earthquakes. What are the three types of faults, and how do blocks of rock move along each one? Strike-slip, normal, and reverse are the three types of faults. At a strike-slip fault, blocks move horizontally past each other in opposite directions. At a normal fault, blocks pull apart. At a reverse fault, blocks push inward toward each other.

Homework Review: Earthquakes What are three scales that seismologists use to analyze earthquakes, and what does each measure? Seismologists use the Richter magnitude scale and the moment magnitude scale to measure earthquake magnitude. They use the Modified Mercalli scale to measure earthquake intensity. How do people use the earthquake risk information that seismologists provide? Engineers use the information to help them design structures that will stand the shaking of earthquakes. Governments use the information to plan for the occurrence of future earthquakes.

Lesson 1 - Now Do you agree or disagree? 1. Earth’s crust is broken into rigid slabs of rock that move, causing earthquakes and volcanic eruptions. 2. Earthquakes cause energy waves that travel through Earth. 3. Earthquakes can be predicted.

Quiz-Quiz-Trade Students quiz a partner, get quizzed by a partner, and then trade cards to repeat the process with a new partner. Stand up, hand up, pair up Partner A quizzes Partner B answers Partner A coaches and/or praises Switch roles Partners trade cards, thank each other, and find new partners. Repeat steps 1-6 until the teacher calls time.