2/24/15 To-Do ► Get your 19.3 notes out and have them ready. ► We’re going to investigate possible Mercalli Intensity values for different pictures. We’ll then map out an epicenter using Mercalli Intensity values. ► HS-ESS1-2. ► I can compare and contrast earthquake magnitude and intensity and the scales used to measure each.

19.3 – Measuring and Locating Earthquakes

Magnitude ► Magnitude = a measure of 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 of largest seismic wave ► 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

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 ► Comparison with Richter:  New Madrid, MO Richter scale MMS 8.1  San Francisco, CA Richter scale MMS 7.7  Prince William, AK Richter scale MMS 9.2  Northridge, CA Richter scale MMS 6.7

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

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

Locating Earthquakes Cont. ► Multiple 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 2 points  3 circles 1 point = EPICENTER

Epicenter

Seismic Belts ► Majority of Earthquakes occur along seismic belts that separate large regions of little or no seismic activity

► Most correspond closely with plate boundaries ► 80% along Circum-Pacific Belt  Subduction zone

In-Class Assignment ► Get out a new sheet of paper! ► Mini Lab pg. 541 ► Ignore #1 ► Turn in Traced Map with labeled intensities, contour lines, and analysis question answers at the end of class