EARTHQUAKES

Chapter 6 Honors earth science

http://earthquake.usgs.gov/

appsApps

• Quake Feed• Earthquake! Earthquake map and

alerts• Earthquake- Quake Tracker

LARGEST QUAKES SINCE 1900

• Chile 1960 9.5• Alaska 1964 9.2• Alaska 1957 9.1• Sumatra 2004 9.1• Japan 2011 9.0• Chile 2010 8.8

MAJOR RECENT QUAKES

• Sumatra 9.1 12/26/04 230,000• Haiti 7.0 1/12/10 316,000• Chile 8.8 2/27/10 810• Japan 9.0 3/11/11 28,000 +• Chile 8.2 2014 6• Nepal 7.8 4/25/2015 8,000+

What is an Earthquake?

• Vibration of earth from rapid release of energy (from plate boundaries)

• Focus-

• Epicenter-

After shocks

• Smaller quakes following “main shock”• Plate readjusting to new location

faults

Normal faulttensional stressalong divergent boundaries

footwall

Hanging wall

Reverse (thrust) faultcompressional stressalong convergent boundaries

footwall

Hanging wall

Strike slipshearing stressalong transform boundaries

San Andreas Fault

EARTHQUAKE WAVES

A seismogram records wave amplitude vs. time

GPS seismometer

Seismograph

P waves

• Primary• travel fastest• travels through

solids AND liquids• compressional

wave– push/pull

Primary (P) waves

S waves

• Secondary• travels only

through solids (NOT liquids)

• Up and down motion

Secondary (S) waves

Surface waves

• Travel on surface• slow• Movement is

similar to water waves

Michigan quake 5/2/15

Mantle info:core info: outer=

inner=

A time-travel graph is used to find the distance to the epicenter

The epicenter is located using three or more seismograph

INTENSITY OF QUAKE

• Depends on– energy released (magnitude)– distance from epicenter– rock type (soft=worse)– Depth (shallow=worse)

SCALES

• Richter (1935)• 1 to ?

– each step 10x more energy than previous step

• Moment Magnitude – Mw– Good for large

quakes– Most accurate

• Mercalli (1902)– measures damage– I- XII

Who wants to move to CA?

Intra plate earthquakes

• Occasionally a quake will occur in the middle of a plate- INTRAPLATE– stress fractures? Ancient faults– Volcanic?

Michigan earthquakes

• Year Date Lat. Long. Mag. City • 1877 Aug 17 42.40 83.25 3.2 Greenfield • 1938 Mar 13 42.08 83.17 3.8 Gibralter • 1938 Mar 14 42.08 83.17 ? Gibralter• 1947 Aug 10 41.928 85.004 4.7 Coldwater • 1977 Oct 26 47.1 87.1 2.7 L Superior • 1980 Apr 29 47.2 87.8 0.5 L Superior • 1982 Nov 26 42.17 85.48 2.5 Scotts • 1994 Sep 02 42.57 84.64 3.4 Central Lansing• 2001 Oct 23 42.34 84.76 2.9 Prairie L

NEW MADRID EARTHQUAKES

• Magnitude 8.1 (approx)

• Dec. 1811-1812• 5th worst

earthquake in US history

• Rang church bells in Detroit

• Made Mississippi River flow backwards

•

Earthquake hazards

• Structural damage– Most common

• Tsunamis• Fires (electrical lines + gas lines)• Landslides• liquifaction

Liquifaction

Formation of a tsunami

Japan tsunami 2011 video

tsumami

Bay Bridge 1989

Kobe, Japan

Alaskan school, Good Friday 1964

                            

Olympia Washington, 1949

Bird’s eye view of tents among rubble in Tangshan

Pakistan 2005

What to do in a earthquake?• Protect yourself

from falling debris– Under tables– Duck and cover

• DO NOT– Light fire (gas

leaks?)– Go to basement!