•Objectives1. Compare the 3 types of seismic waves.2. Discuss the method scientists use to pinpoint an Earthquake (EQ).3. Discuss the method most commonly used to measure the magnitude of EQs.

3 major Types of Seismic Waves

•P waves: primary wave.– ____________________– 1st to be recorded– Travels through _________ & ________

•More rigid material. = _____________

Move fastest

Solids Liquids

Faster

3 major Types of Seismic Waves

•S waves: secondary waves.– 2nd waves to be recorded– Only travel trough __________________Solids

3 major Types of Seismic Waves

•L waves: surface waves, also called ____________ waves.– Converted from P & S waves when they

reach they ____________________– Slowest-moving waves

•__________________ to be recorded

– Cause surface to rise & fall

Long

Reach the surface

Last

Comparing Seismic WavesPrimary Waves (P) Secondary Waves (S) Long or Surface

Waves (L)

Arrives _____Moves faster through more __________ materialMoves the ground together and apart along the direction of ___________.

Arrive ______

About _______ Xs slower than the P- wavesMoves faster through more rigid materialMoves the ground at _______ angles to the direction in which the waves are traveling

Arrives last___________ of the 3Travels over the earths surfaceMoves the ground like the ___________ waves Can cause great _____________ when traveling through loose earth

1st

rigid

waves

2nd

1.7slowest

right

ocean

damage

Recording EQs•Seismograph: _________________

_____________________________.Determines the ____________and not the

_________________ of the epicenter.

instrument used to detect and record seismic wavesdistance

direction

Distance-Determined by seismograph-scientists analyze the ____________ between the arrival times of the ____ and the _____ waves.

Locating the epicenter-At least 3 seismograph is needed to locate the epicenter. The method is called _____________.

differenceP

S

Triangulation

Two recording N.S and E.W vibrationsTwo recording N.S and E.W vibrations

One recording vertical vibrationsOne recording vertical vibrations

Locating an EQ• Scientists compare time diff. btwn P

& S waves.– Plot on graph to get distance to ____________Epicenter

EX: 3 seismographs at locations A, B, and C, determined the distance of each point from the epicenter.

Point A (seismograph 1)is 500 km, point B (seismograph 2) is 800 km and point C is 1200 km (seismograph 3) away from the epicenter. Locate the epicenter.

Locating an EQ• Need ____ plots to locate epicenter

– Point where all 3 circles meet is location of __________________

3

Epicenter

Richter Scale Mercalli ScaleMeasures the ___________ or the energy released by an earthquake.Scale of 1 to 10Each level releases ______ times more energy than that of the lower levelLargest registered, ______ in Chile 1960.Strong-______ or aboveModerate ______Minor-____________________-2.5 or less. Can not be felt by people

Expresses the _________ or the amount of damage it causes.

Shown by Roman numerals from _______________.I-II- Low intensity, ___________________Up to ______- Higher intensity, well built structures destroyed.XII- ______________ ___________________

magnitude

31.7

9.5

76-7

2.5-6Microquakes

intensity

I-XII

Little damageX

totaldestruction

EARTHQUAKE DAMAGEMovement of the ____________ itself seldom causes many deaths or injuries. Most injuries result from the collapse of the buildings, ___________________ and falling objects.

ground

Flying glass

Flood Fire

Landslide

Damages

•Most buildings are not designed to withstand the swaying motion caused by ______________________.•Buildings may collapse, sway violently, or tip over to the neighboring structure.•Tall buildings should be built on soil or rock that is firm. Loose soil and rock can vibrate like jelly.

earthquakes

_____________ and under water ______________ can cause tsunamis. Tsunamis can cause massive death and damages.

Faultinglandslides

SSWWS:Seismic Sea Wave Warning System: Seismic network around the Pacific Ocean.Allows scientists to estimate the arrival times of the _________________ at different locations.tsunamis