12.2 and 12.3 Notes

Studying Earthquakes & Earthquakes and society

Sections 12.2 & 12.3

· seismology - study of earthquakes and seismic waves· seismographs - instrument that records earthquake waves

produce seismograms (tracing of earthquake motion)the larger the zig zags the bigger the earthquake

Recording Earthquakes

Locating an Earthquake· uses the arrival times of P and S waves· longer lag time indicates an earthquake farther away· lag-time graph shows relationship between P & S wave travel time and epicenter distance

1 MATA: What type of wave(s) are used to determine the location of an earthquake?

A P waves

B surface waves

C S waves

D body waves

E Love waves

Click for quick animation

· today, computers perform complex calculations to locate epicenter· before computers, 3 seismograph recordings were needed to locate epicenter

radius of circle = distance from station to epicenter

point where all circles intersect indicates epicenter

Locating an Earthquake Magnitude· total am. of energy released during an earthquake· determined by measuring the amount of ground motion caused by an earthquake· moment magnitude - uses fault size and distance that fault blocks move to determine magnitude

larger the number, stronger the earthquake· largest recorded earthquake = 9.5· 2.5 and lower not usually felt by humans

12.2 and 12.3 Notes

· amount of damage caused by an earthquake· earthquake's intensity depends on it

1. magnitude2. distance between epicenter and affected area3. local geology4. duration5. human infrastructure

· measured on modified Mercalli scale (Roman numerals I-XII)

Intensity 2 ___________ is the study of earthquakes.

A Intensity

B Magnitude

C Lag-time

D Seismology

3 Which of the following does NOT influence the intensity of an earthquake?

A duration of earthquake

B distance between fault and focus

C magnitude

D human infrastructure

E local geology

Click for Japan tsunami

Destruction of Quakes· depends on magnitude and proximity to a populated area· structural damage

intensity, duration of vibration, type of ground beneath building, design or structure· tsunamis (large ocean waves generated by quakes)

sudden drop or rise in ocean floor or underwater landslideincrease in height as they approach shore

· fire/explosion (broken power or gas lines)· landslides (triggered by vibrations)· flooding (broken dams/levies)

4 True or false. The bigger the quake and closer it is to a city the more destructive it might be.

True

False

Earthquake Safety· before

be prepared· during

stay calmindoors - stand in doorway or under a

desk/table, stay away from windows and heavy furniture

car - stop the car in a safe place· after

be cautiouswear closed toe shoes

12.2 and 12.3 Notes

Predicting Earthquakes· NO reliable way· methods of prediction

1. seismic gaps - zones of low earthquake activity2. foreshocks - little earthquakes before big ones3. changes in rocks - tilting, strain, cracks4. monitor natural gas seepage from strained or

fractured rock

5 True or false. Predicting earthquakes is easy!

True

False