GEOL 240Lg 1st Edition Lecture 15 Outline Current Lecture I. Interpreting Seismograms: Just What Happened in that Earthquake, Anyway? II. MapsIII. Diagram of Seismograms (continuation)Current LectureI. Topic: Earthquake Focal MechanismsII. Earthquake focal mechanisms, displayed as these characteristic "beach-ball" plots, are a simple way of representing the types of faults in areas of active tectonics. III. This display gives a brief introduction to interpreting the beach-ball patterns, conventionally illustrated on maps. IV. Move the cursor over the index on the left to see the diagrams.V. Seismologists refer to the direction of slip in an earthquake and the orientation of the fault on which it occurs as the focal mechanism. VI. They use information from seismograms to calculate the focal mechanism and typically display it on maps as a "beach ball" symbol.VII. This symbol is the projection on a horizontal plane of the lower half of an imaginary, spherical shell (focal sphere) surrounding the earthquake source
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