Earthquakes Chapter 5. Earthquakes What causes and earthquake?...
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Transcript of Earthquakes Chapter 5. Earthquakes What causes and earthquake?...
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
• 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
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
• 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