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 crust energyforms faults slip or break stored energy Seismic waves

Earthquakes Seismic waves – Start at the ____________ of the earthquake and _______________________ from it – Three main categories of seismic waves 1.___________________ 2.___________________ 3.___________________ epicenter move outward, away P waves S 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 waves Compress 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 side 90° 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 waves slower than ocean waves in 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 earthquake 3. ____________________________ size of the seismic waves Modified Mercalli Scale Richter Scale Moment Magnitude Scale

Earthquakes Modified Mercalli Scale – Rates ________________________ an earthquake produces – Measured by ________________________ – Has ______ steps the amount of shaking observations not tools 12

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 seismograph magnitude seismic waves get smaller the further away

Earthquakes

Moment Magnitude Scale – Rates __________________________ from the earthquake the 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 Magnitudes One point 32 5 or less causes great damage 8 or above

Earthquakes