more at scitech.quickfound.net "National Aeronautics and Space Administration... This film discusses the threat of earthquakes to the city of San Francisco. The footage depicts damage sustained by San Francisco in 1906 and in Los Angeles later in the 20th century. The film also explains the cause of earthquakes, as well as the fault systems that are the prime targets for future earthquakes." Public domain film from the National Archives, slightly cropped to remove uneven edges, with the aspect ratio corrected, and mild video noise reduction applied. The soundtrack was also processed with volume normalization, noise reduction, clipping reduction, and equalization .en.wikipedia.org An earthquake (also known as a quake, tremor or temblor) is the result of a sudden release of energy in the Earth's crust that creates seismic waves... Earthquakes are measured using observations from seismometers. The moment magnitude is the most common scale on which earthquakes larger than approximately 5 are reported... earthquakes smaller than magnitude 5 reported by national seismological observatories are measured mostly on the local magnitude scale, also referred to as the Richter scale. These two scales are numerically similar... Magnitude 3 or lower earthquakes are mostly almost imperceptible and magnitude 7 and over potentially cause serious damage... The largest earthquakes in historic times have been of magnitude slightly over 9... The most recent large earthquake of magnitude 9.0 or ...

• published: 27 Feb 2012
• views: 3638
• author: Jeff Quitney