American Museum of Natural History: 8^th Grade

Earthquake

Objective:
1. Students will learn reasoning skills.
2. Students will learn using powers of 10 and scientific notation with the worksheet.
3. Students will understand the consequences following earthquake.
4. Students will be able to make educated guesses based on earthquake's

damages.

Materials needed: Pencil, paper, Mercalli Scale sheet, worksheet, question sheet

Background:
An earthquake's energyrelease is measure on the Richter scale. Numbers from one to ten are used to describe the forces of an earthquake. Dr. Charles F. Richter developed the scale in 1935 as a measure of the magnitude of the
seismic waves produced at an earthquake's source. An increase of one unit on the Richter scale, from magnitude 2 to 3, corresponds to a tenfold increase in the amplitude of the waves that shake the ground. That means the energy
release of magnitude 3 earthquake is ten times greater than a magnitude 2 and one hundred times greater than a magnitude 1 earthquake. Another scale commonly used is the Revised Modified Mercalli Intensity Scale. It measures the way an earthquake feels to people and lists possible damages.

Mercalli # Damage

I Felt by only a few people under especially favorable conditions.
II Felt by some peopleespecially on the upper floors of buildings.
III Noticeable to people indoors especially on upper floors. Feels like a passing truck. Standing cars may rock.
IV Felt indoors by most people, outdoors by some. Some sleeping people awakened. Dishes rattle, windows shake, doors swing, walls make cracking sounds. Standing cars rock noticeably.
V Felt by almost everyone. Many sleeping people awakened. Some dishes and windows broken. Unbalanced objects overturned. Pendulum clocks may stop. Poles and trees may sway.
VI Felt by all. Some heavy furniture moved. Some fallen plaster or wallboard. Books fall off shelves. People walk unsteadily. Damage slight.
VII Slight damage in weedesigned buildings. Moderate damage in ordinary buildings. Heavy damage in poorly designed buildings. Some chimneys collapse. Landslides and caveins along sand and gravel banks. Large bells ring.
VIII Slight damage in welldesigned buildings. Heavy damage in ordinary and poorly built buildings. Chimneys and factory shacks destroyed. Columns, monuments and wall fall. Heavy furniture overturned. Tree branches broken. Frame houses move on foundations if not bolted down.

IX Considerable damage in specially designed buildings. Welldesigned structures are bent. Great damage and partial collapse in well designed buildings. Buildings shifted off foundations. Serious damage to reservoirs. Conspicuous ground cracks. Liquefaction.

X Some wellbuilt wooden structures destroyed. Most masonry structures destroyed. Serious damage to dams, water barriers and embankments. Considerable landslides along riverbanks and steep slopes near highways.
XI A few, if any, structure remain standing. Bridges destroyed. Railroad tracks bent greatly. Wide ground cracks. Landslides widespread. Underground pipes completely out of service. People may not be able to walk during the event.

XII Total destruction. Objects thrown into the air. Nothing level.

Procedure:
Fill the blank boxes on the Richter/Mercalli Data Table with the appropriate numbers then answer the questions in complete sentences.
Questions:
1. How many times stronger in energyrelease was the 1933 Japan earthquake than the 1992 Columbia, MD earthquake?
A: The Japan quake was a little greater than 1x 108 times more powerful than the Maryland quake.
2. How many times stronger in energyrelease was the 1985 Mexico earthquake than the 1988 Armenia earthquake?
            A: The Mexico quake was 10 times greater than the Armenia quake.
3. Use the Mercalli and Richter damage lists to describe what a person living in Valdez, Alaska, would have seen after the 1964 earthquake.
            A: (From the charts) Bridges collapsed. Railroad tracks bent greatly. Underground pipes broken. Large   rocks moved. Few, if any, structures remained standing. Wide ground cracked. Landslides were widespread. People may not be able to walk during the event.
4. A problem exists with the Mercalli scale. During relatively mild earthquakes, a phenomenon called liquefaction occurs when watersoaked, sandy soil vibrates. Buildings and other structures literally sink into the soil! Assume an earthquake has a Richter intensity of three and liquefaction occurs. Assign a Mercalli number to the damage and write an explanation about the obvious discrepancy.
            A: Though the quakes registered only three on the Richter scale, the Mercalli damages would be ranked IX and possibly up to XI. The reason for the discrepancy is that liquefaction is not mentioned until IX on the Mercalli
scale, though it may occur at lower intensities on the Richter scale.

Blank space answers
Richter # Times Stronger than Magnitude 1 Power of Ten
9 100,000,000 1 x 108
8 10,000,000 1 x 107
7 1,000,000 1 x 106
6 100,000 1 x 105
5 10,000 1 x 104
4 1,000 1 x 103
3 100 1 x 102
2 10 1 x 101
1 10 1 x 100

Closure:
Can we prevent damages resulted from an earthquake?
What can we do to make the damage smallest possible?

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