GEOLOGY MACC Bill Palmer Lecture 12 Earthquakes. GEOLOGY-Earthquakes  Probably the most terrifying geologic event  Occur suddenly, often without warning.

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Presentation transcript:

GEOLOGY MACC Bill Palmer Lecture 12 Earthquakes

GEOLOGY-Earthquakes  Probably the most terrifying geologic event  Occur suddenly, often without warning  May last less than 5 minutes and cause tremendous destruction  Remember that Earthquakes create Tsunamis TSUNAMI-Dec. 26, ,000 killed

GEOLOGY-Earthquakes  Don’t damage the land very much but destroy the built environment  We cannot control or predict with accuracy  Most powerful earthquake in lower 48 state recorded history took place in Missouri

GEOLOGY-Earthquakes  Measuring Earthquakes (Two different scales)  Richter Scale  A Measure of MAGNITUDE of an Earthquake  Measured by instruments  Each number is ten times larger than preceding number  A 5 is 10X greater than a 4  A 7 is 1000X greater than a 4  Largest measured are 9  Damage to structures begins at 5.5

GEOLOGY-Earthquakes  Measuring Earthquakes (Two different scales)  Mercalli Scale (handout provided) INTENSITY  Measures damages to the built environment  I. Not felt  II. Felt by most people  III. Felt indoors; pictures swing  IV. Heavier objects swing, fells like passing truck  V. Felt outdoors, sleepers awake, doors swing open

GEOLOGY-Earthquakes  Measuring Earthquakes (Two different scales)  Mercalli Scale  VI. Felt by all; Walk unsteady; plaster cracks; small bells ring  VII. Difficult to stand; chimneys break  VIII. Smokestacks fail; driving difficult; some walls fail  IX. Panic; Frames crack; underground pipes broken; cracks in ground; bridges fail

GEOLOGY-Earthquakes  Measuring Earthquakes (Two different scales)  Mercalli Scale  X. Many buildings fail; dams damaged; landslides  XI. Rails bent; underground pipelines fail  XII. Damage nearly total, large rock masses dispalced objects thrown into air  (see handout for more details)

GEOLOGY-Earthquakes  Focus and Epicenter  FOCUS-The exact place in the ground where the earthquake takes place  EPICENTER-The point on the earth’s surface directly above the focus.

GEOLOGY-Earthquakes Focus and Epicenter

GEOLOGY-Earthquakes  Finding the Epicenter  Earthquakes produce three types of waves  P-Travel at the fastest speed  S-Travel at medium speed  L-Travel the slowest  These waves can be measured on a Seismograph and the distance from the seismograph determined  Using THREE seismographs the exact epicenter can be determined

GEOLOGY-Earthquakes Seismograph The seismograph is basically a pendulum with moving paper beneath. Waves cause the pendulum to swing and the result is shown on paper

GEOLOGY-Earthquakes

 What Mercalli rating would you give each of the earthquakes ?

GEOLOGY-Earthquakes  What Mercalli rating would you give each of the earthquakes ?

GEOLOGY-Earthquakes  What Mercalli rating would you give each of the earthquakes ?

GEOLOGY-Earthquakes  What Mercalli rating would you give each of the earthquakes ?

GEOLOGY-Earthquakes  Some infamous earthquakes-San Francisco 1906  3,000 dead  225,000 homeless  28,000 buildings destroyed

GEOLOGY-Earthquakes  Some infamous earthquakes-San Francisco 1906  Richter =  Mercalli=

GEOLOGY-Earthquakes  Some infamous earthquakes-San Francisco 1906  The damage from this earthquake was worsened by the fire that was caused when natural gas pipelines burst and caught fire.

GEOLOGY-Earthquakes  Some infamous earthquakes-Alaska 1964  Richter=9.2  Largest in North America  Lasted 4 minutes  10,000 aftershocks  Created 70 ft Tsunami

GEOLOGY-Earthquakes Alaska-1964

GEOLOGY-Earthquakes  Missouri  New Madrid Earthquake  Felt over 50,000 square miles  Richter=8.0  Seismologist estimate there is a 90% chance of a 7.0 or greater EQ in next 50 yrs

GEOLOGY-Earthquakes Created Lakes-Reelfoot Bells Rang in Philadelphia Buildings in Savannah GA cracked Mississippi River course was altered Not many people in area so loss of life and damages minimal

GEOLOGY-Earthquakes  Comparison of the impact of the New Madrid EQ to the 1906 San Francisco EQ.

GEOLOGY-Earthquakes  Mercalli Impact-Columbia is in V.

GEOLOGY-Earthquakes  12,000,000 people live in EQ zone-St. Louis, Memphis, Evansville, Louisville, Cape Girardeau  Same quake today could kill 100,000 and trillions of dollars of damage  PROBLEM-Minor quakes relieve pressure and prevent larger quakes. We need minor quakes!

GEOLOGY-Earthquakes LINKS TO DAILY EARTHQUAKE REPORTS

GEOLOGY-Earthquakes-Wrap ups  1. Define an Earthquake  2. What are the Focus and Epicenter?  3. How is the epicenter determined?  4. What is the Richter scale and what does it measure?  5. What is the Mercalli scale and what does it measure?

GEOLOGY-Earthquakes-Wrap ups  6. What are the characteristics of the 1906 San Francisco EQ?  7. What are the characteristics of the 1964 Alaska EQ?  8. What are the characteristics of the New Madrid EQ?  9. What are the chances for a major EQ in MO?  10. Why should be be concerned everyday there is not a major EQ in New Madrid?