 Seismologists use two scales when classifying earthquakes. 2) Modified Mercalli Scale 1) Richter Scale

 In 1935, Charles Richter introduced the concept of earthquake magnitude.  Richter magnitude is determined by measuring the largest amplitude (wave height) recorded on the seismogram.  Measures the Magnitude of an earthquake on a ten (10) point scale.  Largest recorded earthquake had a Richter magnitude equal to 8.6

Magnitude: measure of the strength of an earthquake

Wave amplitude increases tenfold (10X) with each increase in Richter magnitude.  Each increase in 1 in Richter Magnitude represents a 10 fold increase in the wave amplitude (height).  A magnitude 7 earthquake measures 10 times more amplitude than a magnitude 6 earthquake.  A magnitude 8 earthquake measures 10 x 10 (or 100 times) more amplitude than a magnitude 6 earthquake. And so on.

Richter scale  Based on a factor of _____ for each level. Based on a factor of _____ for each level. A magnitude 3 is ____ times as strong as a magnitude 2. A magnitude 3 is ____ times as strong as a magnitude 2. A magnitude 4 is _____ times as strong as a magnitude 2. A magnitude 4 is _____ times as strong as a magnitude 2. How much stronger is a magnitude 7 than a magnitude 4? How much stronger is a magnitude 7 than a magnitude 4? measures the strength of the ground motion  5  6  7 x10 x10 x10 = 1,000 times stronger

Lag Time: Lag Time: The difference in arrival time between the P-wave and the S-wave. The difference in arrival time between the P-wave and the S-wave. How is it calculated? How is it calculated? ∆T (S-P) ∆T (S-P) What is amplitude? What is amplitude? The maximum vibration (height) from equilibrium. The maximum vibration (height) from equilibrium. measured from zero measured from zero

1.Label the beginning of the P-wave on the seismogram. 2.Label the beginning of the S-wave on the seismogram. 3.What is the lag time? _______ 4.What is the amplitude? ______ 5.What was the estimated magnitude? _______

List of greatest magnitude earthquakes Haiti earthquake

 In 1902 G. Mercalli developed a fairly reliable intensity scale which assesses the damage to various types of structures at a specific location.  Note that earthquake intensity is determined by several factors including: 1) Strength of earthquake 2) Distance from epicenter  Measures the Intensity of an earthquake on a twelve (XII) point scale. 3) Nature of surface materials 4) Building design

Intensity: measure of the degree to which an earthquake is felt by people and the amount of damage caused by the earthquake Intensity: measure of the degree to which an earthquake is felt by people and the amount of damage caused by the earthquake Modified Mercalli Scale Modified Mercalli Scale I to XII (eyewitness accounts) I to XII (eyewitness accounts)  The Mercalli scale does not give a true indication of the actual strength of an earthquake because the amount of damage done to different places will largely depend on, the type of materials used and the degree of construction of buildings and structures.

EARTHQUAKE DOMINOES 3 minutes End

 Use the information on the worksheet to determine the Mercalli Intensity Scale for each zip code  Place a on the map where you think the epicenter is located.  Answer all worksheet questions

V V V VI IX VII- VIII VI II-III IX VII- VIII IV II-III IV

Identify the Richter Scale Magnitude of the earthquake? Las Vegas Seismic Station 1.What is the S-P lag time? 2.What is the distance to the earthquake epicenter? 3.What is the S-wave amplitude? 4.What is the magnitude using the nonogram? 6.7