GEOL 240Lg 1st Edition Lecture 22 Outline Current Lecture I. Earthquake Prediction: Observations of Precursory Phenomenon (The 'Holy Grail' of Seismology) Current LectureI. Earthquakes are so sudden, with devastating consequences, earthquake prediction is a matter of great interest. II. “earthquake prediction” is often used to mean two different things.III. 1) in the common usage, it is a highly reliable prediction to measure emergencies. IV. 2) in the second usage, it means an actual statement and not a prediction of future “seismic activity”V. It is highly reliable informationII. Changes in seismic velocity--changes in the speeds at which seismic waves move throughthe Earth's crust--have been identified during and after many earthquakes.III. In a new analysis of the 2004 magnitude 6.0 Parkfield earthquake in California, David Schaff suggests some limits on how changes measured by ambient seismic noise could be used as a pre-earthquake signal. IV. Ambient seismic noise refers to the "background hum" of the Earth--the surface waves found all over the planet's crust that are caused mostly by wind and ocean waves.V. Changes in seismic velocity can be measured using seismic noise observations,VI. which are often recorded continuously at seismic stations and therefore can provide a detailed record of a pre-earthquake time
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