Seismogram
The seismogram is the graphic recording of earthquake waves and other ground movements as a function of time. Seismograms are recorded using a seismograph . This has been possible since 1875; The first long-distance quake was not recorded until 1889.
From a seismogram, for example, conclusions can be drawn about earthquakes , volcanic activities , but also other events such as strong explosions. In geophysics , seismograms are analyzed in order to draw conclusions about the structure of the earth. The natural oscillation frequency of structures can also be determined from seismograms .
Historically, seismograms were recorded using line recorders, which continuously recorded the measurement values as a function of time on a roll of paper. Some used pens on ordinary paper, while others used light beams on photosensitive paper. Today practically all seismograms are recorded digitally in order to simplify computer-controlled analyzes. Nevertheless, classic seismographs are still occasionally used today, especially for clear presentations for the public. They are essential for earthquake measurements based on the Richter scale .
Strong earthquake near the Nicobar Islands , July 24, 2005, magnitude 7.3
Earthquake in the Indian Ocean 2004 (“tsunami quake”), December 26, 2004, magnitude 9.3
American Canyon Earthquake 2014
The seismograms shown above are intended to give a visual impression of different magnitudes and were not selected based on scientific aspects.
The task is to deduce the causes from such recordings, as quantitatively as possible. This is mathematically referred to as a typical " inverse problem ". The solution is generally possible, including in practice.
Web links
- REV, the Rapid Earthquake Viewer - worldwide recorded seismograms of current earthquakes as well as major earthquakes in the past