Objectives 1. 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. –____________________ –1 st to be recorded –Travels through _________ & ________ More rigid material. = _____________ Move fastest Solids Liquids Faster

3 major Types of Seismic Waves S waves: secondary waves. –2 nd 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 Waves Primary Waves (P)Secondary Waves (S)Long or Surface Waves (L)  Arrives _____  Moves faster through more __________ material  Moves the ground together and apart along the direction of ___________.  Arrive ______  About _______ Xs slower than the P- waves  Moves faster through more rigid material  Moves the ground at _______ angles to the direction in which the waves are traveling  Arrives last  ___________ of the 3  Travels over the earths surface  Moves the ground like the ___________ waves  Can cause great _____________ when traveling through loose earth 1 st rigid waves 2 nd 1.7 slowest right ocean damage

Recording EQs Seismograph: _________________ _____________________________.  Determines the ____________and not the _________________ of the epicenter. instrument used to detect and record seismic waves distance 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 _____________. difference P S Triangulation

Two recording N.S and E.W vibrations One 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 ScaleMercalli Scale Measures the ___________ or the energy released by an earthquake.  Scale of 1 to 10  Each level releases ______ times more energy than that of the lower level  Largest registered, ______ in Chile  Strong-______ or above  Moderate ______  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 Microquakes intensity I-XII Little damage X total destruction

EARTHQUAKE DAMAGE  Movement 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. Faulting landslides

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