San Francisco 1989: Fire erupts in the hard-hit "Marina District" of the city.

                                                                                      

                                                       

                                                                                                  

     

What is an Earthquake?• Natural rapid shaking of

LITHOSPHERE (CRUST)LITHOSPHERE (CRUST)• Releases ENERGYENERGY stored in rocks

What Happens to Rock?

-Uplifted– RAISED UPRAISED UP Ex: Fossil 100 meters ABOVEABOVE sea level

-MOST sedimentary rocks show ORIGINAL ORIGINAL HORIZONTALITYHORIZONTALITY

DEFORMED LAYERSDEFORMED LAYERS

-Faulted -displaced along a CRACKCRACK

-Folded- BENT or BENT or CURVEDCURVED

Where do Earthquakes START?

-Start at one particular point called FOCUSFOCUS

FOCUS –Point BENEATHBENEATH earth’s surface where

rock breaks under stress

-Point ONON surface directly above focus is called EPICENTER

Measuring Earthquakes- Instruments used to measure

earthquake called SEISMOGRAPHSEISMOGRAPH 

The needle records motion of the earth, it leaves a wavy line.

Seismogram•The recording is called a SEISMOGRAMSEISMOGRAM

Measuring Earthquakes

-Energy of quake is carried through SEISMIC WAVESSEISMIC WAVES

3 TYPES:1) P waves2) S waves 3) SURFACE WAVES

P waves

- Move through SOLIDS SOLIDS & LIQUIDSLIQUIDS

- PHURSTPHURST to arrive at epicenter

- PRIMARYPRIMARY WAVES- Vibrate in the SAMESAME direction the waves are moving

S waves

-Move ONLY through SOLIDSSOLIDS

-SECONDSECOND to arrive at epicenter

-SECONDARY SECONDARY WAVESWAVES

-Vibrate at RIGHT RIGHT ANGLESANGLES to the direction the waves are moving

Detecting & Measuring Seismic Waves

 -3 rating scales to measure earthquakes:

1) Mercalli scaleMercalli scale 2) Richter scaleRichter scale 3) Moment magnitude scaleMoment magnitude scale

Mercalli Scale

Richter ScaleRichter scale

no. No. of

earthquakes per year

Typical effects of this magnitude

< 3.4 800 000 Detected only by seismometers

3.5 - 4.2 30 000 J ust about noticeable indoors

4.3 - 4.8 4 800 Most people notice them, windows rattle.

4.9 - 5.4 1400 Everyone notices them, dishes may break, open doors swing.

5.5 - 6.1 500 Slight damage to buildings, plaster cracks, bricks fall.

6.2 6.9 100 Much damage to buildings: chimneys fall, houses move on foundations.

7.0 - 7.3 15 Serious damage: bridges twist, walls fracture, buildings may collapse.

7.4 - 7.9 4 Great damage, most buildings collapse.

> 8.0 One every 5 to 10 years

Total damage, surface waves seen, objects thrown in the air.

Moment magnitude scale

• Most OFTENOFTEN used to measure strength of earthquake

• Use Use HEIGHTHEIGHT of wiggles on seismograms to infer total amount of energy

Earthquake SAFETY?

3) Proper PLANNING & CONSTRUCTION

of building

1) DROP, COVER, HOLD

2) Earthquake DRILLS

Tsunami

• LARGE UNDERWATERLARGE UNDERWATER earthquake• Caused by FAULTINGFAULTING associated with an

earthquake

DAMAGE of INDONESIA TSUNAMI

Height of Tsunami Waves

How would a map showing the location of active volcanoes compare to the map showing the location of earthquake epicenter?

ANS: (2)

1) Small percentage of volcano locations would be in the same regions as the epicenter

2) Large percentage of volcano locations would be in the same regions as the epicenter

3)There would be no match between the locations of the volcanoes and the epicenters

4)The location of the volcanoes and the epicenters would only match in the ocean regions

Earthquakes generate P-waves and S-waves. Compared to the speed of

the S-waves in a given Earth’s material,

the speed of the P-waves is 1) always slower 2) always faster 3) always the same 4) sometimes faster & sometimes

slower ANS: (2)