EFFECT OF EARTHQUAKE ON OZONE CONCENTRATION AT SOME INDIAN STATIONS-A REVIEW

N.V.Krishna Prasad. Atmospheric ozone concentration and its change when earthquakes with magnitude greater than 5.0 on the Richter scale that occurred in some parts of India between August 2009 to January 2016 have been studied with the help of satellite data obtained from Total Ozone Mapping Spectrometer (TOMS), and Ozone Monitoring Instrument. The ozone concentration was found to be low on the day of occurrence of earthquake, then increased gradually after the earthquake and reached a maximum value and thereafter reduced to its normal value. The enhancement in ozone concentration depends on the earthquakes magnitude, its depth, direction of wind and also the location of the epicenter.

Atmospheric ozone concentration and its change when earthquakes with magnitude greater than 5.0 on the Richter scale that occurred in some parts of India between August 2009 to January 2016 have been studied with the help of satellite data obtained from Total Ozone Mapping Spectrometer (TOMS), and Ozone Monitoring Instrument. The ozone concentration was found to be low on the day of occurrence of earthquake, then increased gradually after the earthquake and reached a maximum value and thereafter reduced to its normal value. The enhancement in ozone concentration depends on the earthquakes magnitude, its depth, direction of wind and also the location of the epicenter.

Introduction:-
Monitoring and analyzation of the variation in profiles of atmospheric trace gases was very significant for weather forecasting, climate modeling and environmental monitoring in regular life. W e k n o w t h a t s t r a t os p h e r i c oz on e plays a vital role in the chemistry of the earth's atmosphere which is naturally formed by chemical reactions involving ultraviolet sunlight and oxygen molecules. In the last thirty years, it has been discovered that stratospheric ozone is depleting as a result of anthropogenic pollutants. There are a number of chemical reactions that can deplete stratospheric ozone. However, some of the most significant of these involves the catalytic destruction of ozone by halogen radicals such as chlorine and bromine. In addition to these reactions natural disasters like earth quakes also have impact of variability in ozone concentration. Hence it is very important to study the variability of ozone concentration if any due to earth quake which may alter the incoming UV radiation and also changes in the dynamics of the climate.
Earth's crust is made up of tectonic plates that fit together to form the outer shell of the earth. The force due to release of energy by the movement of these plates give rise to earthquake of different magnitudes. During this time heat is produced which in turn heats the atmosphere in contact with it. This heat may be transferred to the upper surface because of gravity waves produced due to change in temperature. This phenomenon causes low atmospheric pressure region at the earthquake site ( Pal,2002). (Singh et al. 2007) reported that high electric fields will be developed in the earthquake active regions few days prior to strong earthquake and may penetrate into the ionosphere that create specific irregularities of electron concentrations over the active regions. These consequences may lead to a large amount of particle precipitation at stratospheric altitudes (Tertyshinikov 1996). All these facts may give rise to some changes in the ozone concentration.

Data:-
Total ozone data has been obtained from the website http://www.esrl.noaa.gov/gmd/grad/neubrew/SatO3DataTimeSeries.jsp . The data was collected by satellites Nimbus-7 Total Ozone Mapping Spectrometer (TOMS), Earth probe TOMS and Ozone Monitoring Instrument (OMI). TOMS and OMI provide high resolution daily global information about the total ozone content of the atmosphere by measuring ultraviolet sunlight backscattered from the ground.

Results and discussion:-
Changes in atmospheric ozone concentration for 9 Indian stations where earthquake with a magnitude greater than 5.0 on the Richter scale that occurred during the period August 2009 to January 2016 has been studied. The table below represents the stations at which earth quake occurred and their magnitude.   The trend of variation in total ozone concentration after earth quake for Indian capital New Delhi was shown in Figure 1. Here it is observed that ozone concentration was low on the day of the earthquake and the ozone concentration increased gradually. (Tronin,2002 andSingh et al.,2007 reported the same trend). The ozone concentration reached a maximum value within 10 days and further decreased to its normal value. The ozone concentration on the day of earthquake which is 269 DU varied up to a range of 287 DU-311 DU ie nearly 18 DU to 45 DU.
The trend of variation in total ozone concentration after earth quake for 8 other Indian stations along with New Delhi was shown in Figure 2. Here the trends are same with slight change in ozone variation after earth quake. The change in ozone concentrations for these stations on day of earthquake and their maximum values after earthquake are listed below

Conclusions:-
Ozone data obtained from satellite instruments have been used to investigate the variations in atmospheric ozone concentration for some Indian stations which encountered strong earthquakes. The ozone concentration was found to be low on the day of the earthquake and increased thereafter. Dynamical disturbances, wind direction and transport processes may have a greater influence on the observed increase in ozone concentration compared to photochemical production of tropospheric ozone from some of the gases emitted from the earth's interior during earthquakes. However, since ground based trace gas monitoring measurements are not available at the time and place of occurrence of the earthquakes, it is difficult to conclude strongly on the mechanism leading to the observed increase in ozone concentration.