GLG 112 1st Edition Lecture 14Outline of Last Lecture I. Seismic WavesA. Body Waves1. P-waves (primary)a. Speedb. Movement c. What we feel2. S-waves (secondary)a. Speed b. Movementc. What we feelB. Surface wavesII. Measuring seismic wavesOutline of Current Lecture I. Magnitude (quantitative)A. Richter scale1. How is it calculated?2. What is it based on?3. Problems B. Moment Magnitude Scale 1. How is it calculated?2. What is it based on?II. Earthquake intensity (qualitative)Current LectureThe magnitude of an earthquake is measured quantitatively in two ways. The Richter scale is the first scale that was used to measure earthquake magnitude. It takes oneseismogram and measures two things. It measures the difference of P and S wave arrival time (i.e. the distance from the epicenter). It also measures the amplitude of the greatest shaking. The Richter scale is based on the amount of shaking and the logarithmic scale (i.e. each increase in magnitude=ten times more shaking). There are a couple problems with this scale. First, it only works with small earthquakes. Second, it doesn’t work with different rock types (i.e.it basically only works in southern California).These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.The Moment Magnitude Scale is the updated scale. It is calculated by the size of the fault, the amount of slip, and the rock strength. It is based on the cause of the earthquake and the energy release. For each increase in magnitude there is about 32 times more energy. The intensity of an earthquake is measured
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