19-06-2012, 03:42 PM
EARTHQUAKE DETECTION USING FM RADIO
EARTHQUAKE DETECTION .pptx (Size: 2.09 MB / Downloads: 125)
FM AND ITS POSITION IN ELECTROMAGETIC SPECTRUM
Electromagnetic Waves
FM stands for frequency modulation.
Usually the bandwidth of FM lies within 88MHz -- 108MHz.
VHF (Very High frequency) range is from 30MHz to 300MHz and fm uses this range.
PROPAGATION OF VERY HIGH FREQUENCY WAVES
VHF propagation is called Space wave propagation.
Space wave propagation has two components-(a)Direct component,
(b)Indirect or ground reflected component.
Direct component is propagated by two methods
(a)Line of sight propagation:-Limited by Curvature of Earth and Height of transmitting and receiving antennas.
(b)Scatter propagation:-occurs in ionospheric E-layer due to blobes of air mass and from the ionized trials of meteors ,geomagnetic field variation etc.
Usually the VHF wave penetrates the ionosphere and are lost , but due to the high concentration, electrons and ions in the E-layer having vibration frequency greater than the frequency of FM waves scattering occurs.
POSSIBILITY OF EARTHQUAKE DETECTION BY OBSERVING THE ANOMALY IN FM
Radio echo used to appear one to several times in a day and before two to three weeks of earthquake occurrence. After two to nine days from the last appearance of echo earthquake have occurred.
High density plasma in ionosphere E layer over the epicenter before and after earthquake.
A co-seismic EM phenomenon has been detected in VHF band.
The VHF emissions have been continued for about three hours, after the seismic wave.
The starting times of VHF emissions corresponded to arrival times of seismic P- and S-wave, respectively.
Forecast of focus location
Each receiver is assumed to have a sensitivity region.
Mainly depends on CD component.
When CD anomalies or CDS anomalies are observed by receiver, sensitive region contain the foci of future earthquake .
BT anomalies are observed if the foci of the future earthquake is out of the sensitive regions.
BTS anomalies are observed by vicinal receiver in the case the foci of the future earthquake is located close to the border of the sensitive region.
The time constant of CD component is about 5-10 min for underground earthquake. Time constant is about 1-2 min when foci of future earthquake is located closer to the sea-shore
Therefore the focus location of future earthquakes can be forecasted from the distribution of CD dominance and BT dominance.
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FM AND ITS POSITION IN ELECTROMAGETIC SPECTRUM
Electromagnetic Waves
FM stands for frequency modulation.
Usually the bandwidth of FM lies within 88MHz -- 108MHz.
VHF (Very High frequency) range is from 30MHz to 300MHz and fm uses this range.
PROPAGATION OF VERY HIGH FREQUENCY WAVES
VHF propagation is called Space wave propagation.
Space wave propagation has two components-(a)Direct component,
(b)Indirect or ground reflected component.
Direct component is propagated by two methods
(a)Line of sight propagation:-Limited by Curvature of Earth and Height of transmitting and receiving antennas.
(b)Scatter propagation:-occurs in ionospheric E-layer due to blobes of air mass and from the ionized trials of meteors ,geomagnetic field variation etc.
Usually the VHF wave penetrates the ionosphere and are lost , but due to the high concentration, electrons and ions in the E-layer having vibration frequency greater than the frequency of FM waves scattering occurs.
POSSIBILITY OF EARTHQUAKE DETECTION BY OBSERVING THE ANOMALY IN FM
Radio echo used to appear one to several times in a day and before two to three weeks of earthquake occurrence. After two to nine days from the last appearance of echo earthquake have occurred.
High density plasma in ionosphere E layer over the epicenter before and after earthquake.
A co-seismic EM phenomenon has been detected in VHF band.
The VHF emissions have been continued for about three hours, after the seismic wave.
The starting times of VHF emissions corresponded to arrival times of seismic P- and S-wave, respectively.
Forecast of focus location
Each receiver is assumed to have a sensitivity region.
Mainly depends on CD component.
When CD anomalies or CDS anomalies are observed by receiver, sensitive region contain the foci of future earthquake .
BT anomalies are observed if the foci of the future earthquake is out of the sensitive regions.
BTS anomalies are observed by vicinal receiver in the case the foci of the future earthquake is located close to the border of the sensitive region.
The time constant of CD component is about 5-10 min for underground earthquake. Time constant is about 1-2 min when foci of future earthquake is located closer to the sea-shore
Therefore the focus location of future earthquakes can be forecasted from the distribution of CD dominance and BT dominance.