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The earthquake occurred at 1.25 pm local time and had a surface-wave magnitude of 7.3. The main event was followed by an aftershock 3 hours later with a magnitude of 6.0. The main earthquake epicenter was located 170 km from the capital, Algiers. -from Author
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At 3:57 a.m on the morning after Christmas Day 1979, a large area of northern England and southern Scotland was shaken by an earthquake. In the mesoseismal area, a few miles north of Carlisle, chimneys toppled into the streets or fell through roofs, and people ran in panic into the open. Over a much wider area, including the densely populated industrial area of central Scotland, people were awakened, and ornaments and other small objects were disturbed. At distances over 120 miles from the epicenter, only a few people noted the tremor. Northern Ireland and the Isle of Man also expereienced the tremor but reportedly at no very great intensity. The distrubed area covered approximately 45,00 square miles.
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On a stormy night in October 1836, H.M.S Beagle hove to and dropped anchor at Falmouth, a remote harbor in southwest England. Charles Darwin, the ship's naturalist, came ashore to take the mail coach to Shrewsbury. This was inauspicious end to an epic 5-year voyage around the coast of South America, the results of which were to have a tumultuous impact on scientific thought that has lasted to this day.
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To supplement data in the report Preliminary Determination of Epicenters (PDE), the National earthquake Information Service (NEIS) also publishes a quarterly circular, Earthquakes in the United States. This provides information on the felt area of U.S earthquakes and their intensity. The main purpose is to describe the larger effects of these earthquakes so that they can be used in seismic risk studies, site evaluations for nuclear power plants, and answering inquiries by the general public.
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During the first 2 months of 1974, earthquakes caused fatalities in Peru and Turkey. The largest earthquake during the period was a magnitude 7.2 shock in the New Hebrides Islands. A local tsunami was generated by a magnitude 7.0 earthquake in the Solomon Islands. The relative quiet that characterized world seismicity during the last year continued through the period. There have been no great earthquakes (magnitude 8.0 or larger) since January 10, 1971, when a magnitude 8.1 shock occurred in western New Guinea.
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Southern California has more active faults located close to large, urban population centers than any other region in the United States. Reduction of risk to life and property posed by potential earthquakes along these active faults is a primary motivation for a cooperative earthquake research program between the U.S Geological Survey and major universities in Southern California.
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Many of the measurements of phyiscal properties being made in earthquake prediction studies are based on the premise that these properties are influenced by stresses and strains, especially so near the failure point. Electrical properties of rocks are controlled by the fluid in the pores and cracks in the rocks. Because these regions are most influenced by stresses, one should expect electrical measurements to be sensitive measures of changing stresses and strains. Nevertheless, the strain changes we are dealing with are very small, and, consequently, we need very sensitive instruments to detect them.
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The most significant event that has affected the geyser basins of Yellowstone National Park since its discovery was the Hebgen Lake earthquake, which occurred at 11:37 PM on August 17, 1959, with a Richter magnitude of 7.1. The epicenter of this earthquake was just west of the park, about 48 km northwest of the Upper Geyser Basin. No earthquake of comparable intensity had jarred the geyser basins in historic times. More hydrothermal changes occurred in response to this disturbance than during the previous 90 years of the park's history. Among the thousands of thermal springs in Yellowstone Park, Seismic Geyser is one of the few that it totally recent in origin. It is not quiescent or dormant spring that was reactivated;...