Earthquakes

Chapter 5

Earthquakes• What causes and earthquake?

1. _____________________________________2. Stress adds _________ to rock and ___________3. Increased stress makes faults _______________4. This releases the ____________5. ________________ are formed

Plates produce stress on the crustenergy forms faults

slip or breakstored energy

Seismic waves

Earthquakes

• Seismic waves– Start at the ____________ of the earthquake and

_______________________ from it– Three main categories of seismic waves

1. ___________________2. ___________________3. ___________________

epicentermove outward, away

P wavesS waves

Surface waves

Earthquakes• P waves– Sent out from __________ of an earthquake– The first waves to arrive• Called _________________

– _______________________ the ground like an accordion

– Can travel through ______________________

the focus

primary wavesCompress and expand

solids and liquids

Earthquakes• S Waves– Are sent out from ____________of an earthquake– Come after P waves• Called _________________

– ________________________• At an angle of _______ compared to the direction they

are travelling

– ________________________

the focus

secondary waves

Vibrate from side to side90°

Can only travel through solids

Earthquakes• Surface Waves – ________________ that have reached the surface– Move ___________________ P and s waves– Movement is similar to ________________• Particles move _________________________

– Shake building ______________________

P and S wavesslower than

ocean wavesin a circular motion

from side to side

Earthquakes

Earthquakes

• How are Earthquakes Measured?– By the ________________________ they produce– Two scales measure this

1. __________________________2. __________________________

– Third scale measures the amount of energy released by the earthquake3. ____________________________

size of the seismic waves

Modified Mercalli ScaleRichter Scale

Moment Magnitude Scale

Earthquakes

• Modified Mercalli Scale– Rates ________________________ an earthquake

produces– Measured by ________________________– Has ______ steps

the amount of shaking

observations not tools12

Earthquake

Earthquakes

• Richter Scale– Uses ________________– Based on the _______________ of the

earthquake’s seismic waves– Magnitude takes into account the fact that

_________________________________________the seismograph is from the earthquake

a seismographmagnitude

seismic waves get smaller the further away

Earthquakes

Earthquakes

• Moment Magnitude Scale– Rates __________________________ from the

earthquakethe total energy released

Earthquakes

• _____________ of Earthquakes– __________ increase in the magnitude of an

earthquake equals _______ the amount of energy– An earthquake with a magnitude of ___________

produces little damage– One with a magnitude of 6 or more

__________________– Earthquakes with a magnitude of ___________

are rare

MagnitudesOne point

325 or less

causes great damage8 or above

Earthquakes

Earthquakes