Measuring and Locating Earthquakes

Bellringer 11/5 Put these Roman Numerals in order from least to greatest: lX, Vll, lll, Xl, lV, l, XV

Make a notes section: Title it “Locating Earthquakes.”

Magnitude Energy produced by earthquake Amplitude = Height of wave Richter Scale = numerical rating system used to measure the magnitude of an earthquake

Richter Scale Numbers are determined by amplitude Each successive number represent an increase in amplitude of a factor of 10 Example: Magnitude-8 is 10x larger than magnitude-7 Energy difference is even greater, = 32x

Richter scale http://www.maelor-humanities.org.uk/GCSEhum/Resources/PP-photos/pp-KeyIss3/Richter.scale.jpg

Moment Magnitude Scale Rating scale that measures the energy released by an earthquake taking into account the size of the fault rupture, the amount of movement, and the rock’s stillness

Mercalli Scale Measures intensity of earthquake using Roman Numerals Intensity = amount of damage caused by earthquake Worse damage = higher numeral

http://www.state.il.us/IEMA/images/Mercalli.jpg

Intensity Depends on amplitude of surface waves Surface waves decrease in size with increase distance from focus Intensity decreases as well

Depth of Focus Shallow, Intermediate, Deep Shallow = catastrophic with high intensity Produce greater maximum intensity than deep focus Deep = smaller vibrations

Locating Earthquakes Seismogram and Travel-time Curve allow scientists to determine distance to epicenter Seismogram records time elapsed between arrival of waves Distance is determined by measuring separation of waves on seismogram and identifying the same separation on Travel-Time curve

Adding data from other stations narrows area of focus Three seismograms are needed because one just determines certain distance in any direction Circle is drawn around station with radius equal to distance Adding data from other stations narrows area of focus 2 circles overlap @ 2 points 3 circles overlap @ 1 point = EPICENTER

Epicenter http://wps.prenhall.com/wps/media/objects/3030/3102952/epicenter_tasa_shad.jpg

Seismic Belts seismic belts - separate large regions of little or no seismic activity. It’s where majority of Earthquakes occur.

Most correspond closely with plate boundaries 80% along Circum-Pacific Belt Subduction zone http://upload.wikimedia.org/wikipedia/commons/thumb/0/09/Pacific_Ring_of_Fire.png/800px-Pacific_Ring_of_Fire.png