EARTHQUAKE DETECTION USING FM RADIO

PRESENTATION BYSAMRIDHI MANTRI

09EEMEC095

CONTENTSWhat is an Earthquake?

Causes and Effects of an Earthquake.

Damages by Earth quake.

FM and its position in Electromagnetic Spectrum.

Propagation of Very High Frequency Wave.

Anomalies Observed in the Reception of FM Radio Waves.

Dual frequency method

Classification of Anomalies.

Earthquake Prediction using Khushida’s Methodology.

Conclusion

Reference

WHAT IS AN EARTHQUAKE ?An earthquake (also known as a quake, tremor or temblor) is the result of a sudden release of energy in the Earth’s crust that creates seismic waves

These seismic waves travels through earth’s interior.

An earthquake's point of initial occurrence is called its focus or hypocenter. The epicenter is the point at ground level directly above the hypocenter.

Absolute magnitude is measured in RICHTER or MOMENT MAGNITUDE SCALE and felt magnitude is measured in MERCALLI INTENSITY SCALE.

CAUSES AND EFFECTS OF AN EARTHQAUKE

May be natural or man-made.

EFFECTS

Shaking and ground rupture

Landslides and avalanches

Fires

Soil liquefaction

Tsunami

Floods

DAMAGES BY EARTHQUAKE

FM AND ELECTROMAGETIC SPECTRUMElectromagnetic Waves : waves consisting of electric and magnetic field orthogonal to each other and to the direction of wave propogation.

FM stands for frequency modulation.

In this signal is modulated according to the frequency of carrier

Usually the bandwidth of FM lies within 88MHz to 108MHz.

VHF (Very High frequency) range is from 30MHz to 300MHz and FM uses this range.

Position of fm in em spectrum

PROPAGATION OF VERY HIGH FREQUENCY WAVES

VHF propagation is called Space wave propagation.

Space wave propagation has two components-

i) Direct component

ii) 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 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.

Ground reflected component: EM wave component that is reflected from earth surface due to different obstacles include reflection and diffraction

ANOMALIES OBSERVED IN THE RECEPTION OF FM RADIO WAVE

Anomalous or strange unwanted reception of radio waves occur beyond the line of sight receiver set.

Short pulses or echoes(duration 100ms) are observed in radio reception due to entry of meteors into the earth’s atmosphere or passage of aircrafts.

Thunderstorms and other weather activities, Geomagnetic disturbances are also responsible for anomalous reception.

Sporadic E layer causes baseline fluctuation. Before and after earthquake occurs a huge baseline fluctuation called EQ echo(pulse duration-1 to 2 min) which makes the radio reception difficult.

Base line fluctuation due to sporadic E

EQUIPMENTS USED FOR THE DETECTION OF ANOMALY IN FM

Components used in equipment

FM receiver /VHF digital tuning receiver - tuned slightly offset to the frequency of the fm radio station.

Yagi-Uda antenna(5 element)-is directed vertically and normal vector of antenna plane is directed with an offset angle towards a FM station located beyond line of sight.

Center tuning meter-output voltage proportional to difference between tuned frequency and input frequency.

Chart recorder-records voltage of center tuning meter.

Co-axial cable-For connections.

POSSIBILITY OF EARTHQUAKE DETECTION BY OBSERVING THE

ANOMALY IN FMRadio 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.

To detect this we have used dual frequency method

DUAL FREQUENCY METHODIn this method we chose the frequency channels from 76 to 90 MHz which is used as for FM broadcasting in Japan.

Therefore EM waves is less affected by noise compared with low frequency band.

In our method, we select two different frequencies (fn and fr) for the observation channels , which have following characteristics:

a) Fn : this frequency channel is selected from 80.8MHz to 81.2MHz, not assigned for any FM broadcasting use in Japan.

b) Fr : this frequency channel is selected from 76MHz to 90MHz except from 80.8MHz to 81.2MHz.

Then, we can identify whether a received signal is artificial waves or a broadband EM wave by the dual frequency method.

At the observatory, four FM antennas are installed on the roof toward east, west, south and north, respectively.

Each of antenna is connected with two synthesize FM tuners to measure the EM levels of fn and fr channels respectively.

Case 1: fluctuation only in fn amateur radio waves

Case 2:fluctuation only in fr FM radio waves

Case 3:fluctuation in both broadband EM waves

FM tuner has a receiving bandwidth of 100kHz/3dB and a noise figure of 2dB. All observation data are stored by the personal computer.

The observation time is adjusted by the GPS clock every hours. We are now operating the systems with 120 FM tuners at 15 observatories in Japan.

The limitation of measuring level is about -120dBm of FM tuner.

Observation Fig. shows the time variations of detected EM waves .A sharp rise is followed by a slower decline in each direction .

Both of the levels of fn and fr frequency channels were similarly fluctuated. The demodulated signal indicated an FM noise sound. Therefore, It is suggested that the detected EM waves are broadband.

The detected levels slowly decreased and returned to the normal level about three hours later.

The detected peak level was not observed toward the epicenter i.e. in west direction.

Detected co-seismic EM waves in VHF band at

Hiroshima City Univ. on Mar 24,2001 at Geiyo EQ

RELATION BETWEEN EARTHQUAKE AND IONOSPHERIC PLASMA

DENSITY VARIATIONPossible mechanism for the generation of electromagnetic waves in the lithosphere is to be identified with the micro-fracturing process of rocks.

These micro-fractures, in turn, involve the breaking of a large number of atomic bonds, i.e. the covalent or ionic bonds giving rise to the crystalline structure of the rocks.

The formation of unbalanced charge distributions, of opposite sign, on the opposite sides of the micro-fractures is to be expected and, consequently, the onset of strong local electric fields which is explaining geo-electric and geomagnetic fields anomalies as well as development of strong ionospheric perturbations preceding strong earthquakes.

CLASSIFICATION OF ANOMALIES

CD:-charge-discharge anomalies

BT:-base-line thickness anomalies

CDS:-charge-discharge dominant with superposed BT

BTS:-base line thickness dominant with superposed CD

EARTHQUAKE PREDICTION USING KhUSHIDA’S METHODOLOGY

Yoshio Khushida and Reiki Khushida first discovered and implemented VHF band in EQ detection.

Forecast of date In most cases the first appearance precedence is in the range of 4-8 days.The maximal anomaly precedence is in the range of 2-3 days and preseismic pause in about 1 day.An early warning can be made after the first appearance of the anomaly.The date of future earthquakes can be forecasted by observing the preseismic maximal of the anomaly strength and it can be refined after observing the preseismic pause.

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.

Therefore the focus location of future earthquakes can be forecasted from the distribution of CD dominance and BT dominance.

CONCLUSIONThus short term earth-quake prediction can be possible by studying the anomalies in fm reception

By dual frequency method

A co-seismic EM phenomenon has been detected in VHF band.

The detected EM waves have broadband spectra.

The VHF emissions have been continued for about three hours, after the seismic wave.

The detected peak level was not observed toward the epicenter.

REFERENCESY.Kushida and R.Kushida,”On the possibility of Earthquake Forecast by Radio observation in the VHF band”T.Yoshida and M.Nishi,”Co-seismic VHF Emission Associated with Earthquakes”Wikipedia Search Engine