Arun 795 Report post Posted October 18, 2005 The 7.4 magnitude devastating earthquake in Pakistan on October 8 has raised several questions and posed new problems for scientists and engineers. But the most frequently asked question is whether it is possible to predict the occurrence of an earthquake. The answer to this question is, 'yes, to a sufficient degree of accuracy, about a few hours before the occurrence of an earthquake.' The earthquake precursors discussed here are exclusively for moderate to large earthquakes, meaning earthquakes of magnitude 6.0 or more on the Richter Scale. Earthquakes of lesser magnitude may or may not necessarily exhibit all the precursors. Short term precursors: These could be seen by the common man and are highly reliable. People in seismically active areas may keep a copy of this article for further use. There are several types of short term precursors which could be seen and observed by different strata of society. Seismo-electromagnetic precursor: This is a very reliable short term precursor. It occurs and is exhibited about 10 to 20 hours before the quake. Before the occurrence of an earthquake the subsurface temperature rises. As a result of this the geomagnetic field is reduced. The reduction in geomagnetic field adversely affects the propagation of electromagnetic waves. This is experienced abundantly on the radio, television and telephone. If one is tuning the radio at 1000 kHz, then the same station will be received in the potential epicentral area, about 10 to 30 hours before the quake, at higher frequencies. Maybe 1100, 1200, 1300, 1800, 1900, 2000 kHz or so. Similarly, reception on television is affected by audio, visual and spectral disturbances. The telephone's reception is also adversely affected and there is a continuous disturbance that you can hear. Apart from this, a recent reliable precursor is the mobile telephone. It has been found that about 100 to 150 minutes before the occurrence of an earthquake, mobile telephones start non-functioning or malfunctioning. The timespan indicated is sufficient to take all necessary mitigatory measures. A word of caution: all the above precursors are valid only when seen and manifested extensively. Failure of one or two instruments should not be taken as a seismic precursor. To read more about all types of seismic precursors, follow this link ! Share this post Link to post Share on other sites
Utsav 0 Report post Posted October 18, 2005 It Rocks dude! Share this post Link to post Share on other sites
ashoksoft 83 Report post Posted October 18, 2005 Shaky news ... and real deep down to earth way to find that shatter beneath ya feet cheers Ashok Share this post Link to post Share on other sites
