Introduction to Earthquakes Ms. Underberger March 15, 2016

Introductory Video videos/earthquake-101

Earthquake Strong, shaking movements of the earth’s crust

Tremor A movement of the earth’s crust that we may not feel

Focus The point beneath the earth’s surface where an earthquake begins.

Epicenter Place on earth directly above the focus. The surface of the earth shakes the hardest here

Seismic Waves The energy created by the slipping of rocks in faults They travel from the focus in all directions

Seismograph An instrument that measures earthquakes It records the movements in the Earth’s crust on a piece of paper Higher lines= stronger earthquake

Seismologist An earthquake scientist who studies the areas of Earth where earthquakes are likely to occur and where they have occurred How a seismograph works: earthquakes.php

Seismic Waves March 17, 2016

Seismic Waves Rap About Seismic Waves with a Slinky

What are Seismic Waves? Seismic waves are vibrations that travel through Earth carrying energy released by an earthquake The speed and path of the waves partially depends on the material through with the waves travel There are three types of waves: P, S, and L Earthquakes send only P and S waves from its focus. L waves can develop wherever P and S waves reach the surface

Types of Seismic Waves There are three types of seismic waves: 1. Primary Waves (P-Waves) 2. Secondary Waves (S- Waves) 3. Surface/Long Waves (L-Waves)

Primary/P-Waves Arrive first in an earthquake Compress and expand ground like an accordion Fastest moving waves Push and pull on particles Move through solid, liquids, and gasses

Secondary/S-Waves Arrive second in an earthquake Vibrate from side to side When they reach the surface, they shake violently Only move through solids

Surface/L-Waves Occur when the P and S waves reach the surface Slowest moving waves Make the ground roll like ocean waves Shake buildings from side to side Can travel through solids

Bringing it all Together Answer these questions on the back of your paper What are the similarities between P, S, and L waves? What are the differences between P, S, and L waves? How do waves play a role in earthquakes? (think about how they impact buildings on land)

Measuring Earthquakes Ms. Underberger December 17, 2014

Modified Mercalli Scale Rates the amount of shaking from an earthquake Only people’s eyes are used- no instruments Useful in regions where there are no instruments to measure earthquakes

Magnitude A number that geologists assign to an earthquake based on the earthquake’s size Takes into account that seismic waves get smaller the farther a seismograph is from the earthquake The effects of an earthquake increase with magnitude

Richter Scale How magnitude is measured Rate the size of earthquakes based on the earthquake’s waves as recorded by seismographs.

Moment Magnitude Scale Used to rate the total energy an earthquake releases Number is determined using seismographs and other sources Each 1-point increase = 32 times more energy released!