For the first time in India a system has been installed to detect and issue early warnings of earthquake. The first system has been installed in capital Dehradun of Uttarakhand which will issue warnings 1-40 seconds before earthquakes of magnitude 5 or more, other such system is planned at Pithoragarh in the Kumaon region of Uttarakhand. This system has been designed and manufactured by Italian firm Space Dynamics.
HOW DOES IT WORKS
The system is incorporated with sensors which are capable to detect P (Primary) and S (Secondary) waves generated during an earthquake. Since P waves are first to be produced and less harmful the detectors can sense them and can issue warning before impending disaster.
P AND S WAVES
Energy released during an earthquake travels in the form of waves around the Earth. Two types of seismic wave exist, P- and S-waves. They are different in the way that they travel through the Earth. P-waves are compression waves that apply a force in the direction of propagation. As the interior of the Earth is almost incompressible, P-waves transmit their energy quite easily through the medium, and thus travel quickly. On the other hand S-waves are shear waves, which means that the motion of the medium is perpendicular to the direction of propagation of the wave. The energy is thus less easily transmitted through the medium, and S-waves are slower. P-waves travel 60% faster than S-waves on average. Dogs and other animals are believed to be capable of detecting P waves hence starts behaving hysterically before earthquake.
AFTER EARLY DETECTION RECORDING BY RICHTER SCALE
1)Seismic waves are the vibrations from earthquakes that travel through the Earth they are recorded on instruments called seismographs which records a zig-zag trace that shows the varying amplitude of ground oscillations beneath the instrument.
2) Sensitive seismographs can detect strong earthquakes from sources anywhere in the world but adjustments are to be made for the variation in the distance between the various seismographs and the epicenter of the earthquakes.
3) The magnitude of an earthquake is determined from the log of the amplitude of waves recorded by seismographs. Because of the logarithmic basis of the scale each whole number increase in magnitude represents a tenfold increase in measured amplitude and about 31 times more energy than the amount associated with the preceding whole number value.
4) Earthquakes with magnitude of about 2.0 or less are usually call micro earthquakes and are generally recorded only on local seismographs while of 4.5 or more are strong enough to be recorded by sensitive seismographs all over the world. Richter scale has no upper limit .
5) Recently another scale called the moment magnitude scale has been devised for more precise study of great earthquakes.
INDIA AND EARTHQUAKE
1) India has been divided into 4 seismic zones by Bureau of Indian Standards based on earthquake data supplied by Indian Meteorological Department namely II, III, IV and V with Zone V being Very severe intensity zone.
2) Recent earthquake in Nepal which was also felt in India was due to the Indian plate continuously moving northward beneath the Eurasian plate at 45mm a year. Nepal stands on the fault called “Thrust Fault” where a sudden release of energy along the fault resulted in one plate jumping on the other.
3) According to a study nearly 60% of the sub-continental landmass is vulnerable to earthquakes.
4) So far India has witnessed earthquake upto max. magnitude of 9.1-9.3 on Boxing Day while worldwide its value is 9.5 in Chile 1960.
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