Method and use of apparatus for prediction of volcanic eruptions and earthquakes

Abstract: This invention provides method and apparatus to predict accurately volcanic eruptions or the occurrence of earthquakes without the use of a seismometer or an incline level meter. The apparatus includes a neutron sensor (1), a counter (3) and a displaying device (6) to indicate an integrated count number or changes in count number of neutrons radiated from the earth's magma with the prediction being performed on basis of the change in count or integrated count number for a given period of time.

Description: This invention relates to a method and equipment for predicting when a volcanic eruption or earthquake will occur. Since the occurrence of a volcanic eruption or earthquake can cause a great deal of damage to people and property in the danger zone, as for example in the Unzen-Fukendake or the Kanto earthquakes, it is highly desirous to be able to accurately predict such an occurrence to minimize the amount of damage that might ensue. Currently, in order to predict the volcanic eruption through the investigation of volcanic activity, an incline level meter is placed on the volcano skin surface to predict the volcanic eruption by measuring changes in an inclination of the mountain's skin surface caused by a magma's activity. Alternately, a seismometer is placed near the volcano to predict the volcanic eruption by monitoring an occurrence of an earthquake activated by the magna's activity. Moreover, seismometers are placed at a plurality of locations and an incline level meter is also placed at certain sites on the earth's surface in an effort to predict the occurrence of an earthquake gathering different data including seismic intensity obtained, changes in the degree of an inclination of the mountain's skin surface, and the beginning of cracks at the earth's surface layer. GB-A-2183038 discloses a method for predicting earthquakes in which various measurements, for example physical, geophysical, geochemical, geodetic, biological and microbiological measurements are carried out simultaneously at ground level, below ground and above ground. By taking a variety of measurements, the overall accuracy of predictions of volcanic activity may be improved. According to the aforementioned techniques, it is quite difficult to predict the onset of a volcanic eruption accurately because of the ever-fluctuating inclination of the earth's surface caused by the magma's activity and the difficulties associated with locating the incline level meters. Furthermore, when a seismometer is utilized in predicting volcanic eruptions by monitoring changes in seismic intensity without being able to compare it with prior data the accuracy of the prediction is greatly reduced. In many cases, old data will not be available. Similarly, in the prediction of an earthquake the accuracy of the prediction, even when using a plurality of seismometers at carefully selected sites in conjunction with an incline level meter, is oftentimes difficult and the accuracy of such predictions is generally very poor. It is believed that the source of neutrons on the earth's surface is produced by nuclear fusion on the sun, although the count of the neutrons in the background which is normally detected on the earth's surface varies, depending on specific locations and/or environmental factors. However, if a majority of the detected neutrons originated on the sun, the maximum level of detected neutrons should be found at locations that are in direct sunlight during daylight hours and a minimum level of neutrons will be found where there is darkness during nighttime hours. However, preliminary studies indicated that (i) there is almost no differences in neutron counts between daytime hours and nighttime hours, and (ii) it is difficult to distinguish between the integrated counts of neutrons over a long period of time during the daytime hours and nighttime hours, respectively. Methods of neutron detection are known, for example as described in IEEE Transactions on Nuclear Science, Vol NS-29, No. 1 New York, entitled "Monitoring and Detection of Plutonium Movement in Storage Vaults." This paper is directed to measuring the neutron field using a neutron activity sensing apparatus comprising a neutron detector, counter and display means to determine the removal of plutonium, based on the assumption that the neutron field remains unchanged if the plutonium remains undisturbed. According to preliminary studies and measurements of 100-hour duration of neutrons at both Tokyo and Fukuoka cities, it was found that (i) the average value of neutron counts measured at Fukuoka city was more than twice than that detected at Tokyo, and (ii) the neutron count measured at a location six kilometres away from the opposite side of the Sakura Island after 100-hours of continuous measurement was more than three times higher than the averaged value of neutron counts measured at Tokyo. Similarly, it was found that (iii) a neutron count after 100-hour continuous measurement at a site 3 kilometres away from the crater of Mount Aso was more than three times higher than the count level detected at Tokyo, and moreover, (iv) at the summit of Mount Aso from which the crater of the inner volcanic mountain can be observed, a count six to ten times higher than that measured at Tokyo was detected. Furthermore, (v) an average level of the neutron count over a 500-hour continuous measurement period at a location about five kilometres away from the crater of currently active Unzen Fukendake Mountain was recorded that was more than five times higher than the averaged value measured at Tokyo; and (vi) this measurement was more than ten times higher than that detected at Tokyo in respect of levels of neutron counts. The large amount of neutrons was detected just prior to an event involving the massive flow of volcanic rocks having a potential cause to a great deal of harm to both human beings and property. According to the present invention, a method of monitoring seismic activity and predicting the occurrence of volcanic eruptions or earthquakes comprises the steps of measuring the neutron flux radiated from the magma of the inner shell of the earth, monitoring the activity of the magma based on the measured neutron flux, and predicting the occurrence of volcanic eruptions or earthquakes based on the monitored activity of the magma. In a first embodiment of this invention the neutron flux at the earth's magna (inner shell of the earth) is integrated over a predetermined period of time. In a second embodiment of the invention, a continuous measurement of neutrons being radiated from the inner shell of the earth (magma layer) is performed and a prediction is made based on changes in the magma's activity obtained by monitoring changes in the neutron flux over a predetermined period of time. In carrying out the present invention uses a neutron sensor, a counter to count neutrons and a display device for displaying the neutron count to detect the neutron count radiated from the magma. Two embodiments of a method and use of an apparatus in accordance with this invention will now be described with reference to the accompanying drawings; in which:- Fig. 1 is a chart showing the setting of reference levels for neutron measurements according to the present invention; Fig. 2 illustrates a block diagram for the present prediction apparatus used to predict a volcanic eruption or earthquake; Fig. 3 is a neutron count exhibited by a display device according to one embodiment of the invention; Fig. 4 is a block diagram of apparatus for predicting a volcanic eruption or earthquake; and Fig. 5 is another example of a displayed neutron count according to the second embodiment of the present invention. Referring now to Figs. 1 through 5, the structure and function of equipment designed for the prediction of volcanic eruptions or earthquakes will be described in greater detail. Fig. 1 shows a chart of the counter reference levels for neutron measurement used in the practice of the invention. The reference level (which is eventually the lower limit) for the neutron measurement is needed in order to prevent undesired errors from occurring caused by noise generated by other substances. Figs. 2 and 4 show block diagrams of a prediction apparatus for volcanic eruptions or earthquakes according to first and second embodiments, respectively, of this invention. Figs. 3 and 5 show examples of displaying means according to the first and second embodiments of the present invention, respectively. As previously mentioned, in the practice of the present invention continuous measurements are conducted on neutrons over 100 hour periods at various locations including Fukuoka city, the opposite side of Sakura Island, near the crater and summit of the inner volcanic of Mount Aso, near the crater of Unzen Fukendake, and the city of Tokyo. It was observed that the detected neutron count level increased as one approached the volcano's crater, when compared to the averaged level value obtained at Tokyo over a continuous 100 hour period. It is well known that the existence of neutrons is derived from nuclear fusion reactions. However, as mentioned previously, the level of neutrons measured on the earth did not show any distinguishable differences between daytime and nighttime measurements. It is therefore suggested that the majority of detected neutrons on the earth are not produced as previously thought by reactions on the sun, but rather originate from nuclear reactions which are still taking place inside the gradually cooling earth. Consequently, the degree of the magma's activity generated by nuclear fusion (which is still occurring inside the earth) is related to the occurrence of volcanic eruptions and earthquakes. The degree of activity of the magma is also almost proportional to the detected value of neutrons per a given period of time. Hence, the degree of magma's activity can be detected with accuracy based on the neutron count level detected at a certain location near volcanic craters or within volcanic regions. Since the neutron can strongly penetrate many substances, neutrons can pass upwardly through thick layers of rock from the earth's core to the earth's surface with a slight loss of the count level. The penetrating neutrons can thus be detected and utilized as indicators of the earth's activity to predict the onset of earthquakes and volcanic eruptions. As seen in Fig. 2, according to the first embodiment of the present invention, the output terminal of a neutron sensor 1 is connected to a counter 3 through a level setter 2. A D/A converter 5 is connected to an output terminal of the counter 3. A display device 6 is connected to an output of the D/A converter and an output terminal of a time pulse generator 7 is connected to the reset terminal of counter 3. Particle detecting using the ionization phenomenon cannot be achieved with neutrons because neutrons do not possess an electric charge. A secondary neutron produced by a reaction with the atomic nucleus of a substance is used herein as the detected material. The most commonly used nucleus reaction is a ¹⁰B(n, ) n Li reaction, in which BF3 gas is reacted with the neutron and HE⁺ is produced at the negative electrode as electric current. The output of the sensor 1 is connected to the input on level setter 2 and neutrons whose count level exceeds the predetermined level of the reference value are counted by the counter 3. The counted output from the counter 3 is D/A-converted through a D/A converter 5 then coupled into a display device 6 to display the count on a recording chart. A pulse coming from the time pulse generator F is supplied to the counter 3 and the counter 3 is reset for each selected unit time, so that the integrated patterns 10a ∼ 10e of counted number per unit time "a" is displayed on the chart, as seen in Figs. 2 and 3. With such constructed apparatus for the prediction of volcanic eruptions or earthquakes, unusual level of detected neutrons due to the intensified activity of the magma - prior to the eruption of the volcano or the occurrence of an earthquake - will be noted on the integrated pattern records on the chart per unit period of time by neutron sensor 1 which has been placed at an appropriate location. Consequently, by observing any abnormality from the patterns 10a ∼ 10e displayed on the recording chart of the displaying device 6, a precise prediction of occurrence of volcanic eruptions or earthquakes can be achieved. When a digital displaying device is employed as a displaying means in the first embodiment of the invention, the D/A converter can be eliminated. In the second embodiment of the invention, as shown in Fig. 4, an output terminal of the neutron sensor 1 is connected to the counter 3 through level setter 2. An output terminal of the counter 3 is connected to a latch circuit 8. An output terminal of a clock generator 15 is also connected to an input to the latch circuit 8, and further connected to the counter 3 through a delay circuit 16. An output terminal of the latch circuit 8 is connected to input port 11. The input terminal 11, RAM 12 and output port 14 are all connected to the CPU 13. D/A converter 5 is connected to output port 14, and the displaying device 6 is connected to the output terminal of the D/A converter 5. In the second embodiment of the present invention, an output of the neutron sensor 1 is connected to the level setter 2 to select a neutron count exceeding a selected reference value, which is later counted by the counter 3. Data obtained during a given period of time is latched by the latch circuit 8 and the count number applied to the input port 11 through an output signal of the delay circuit 16. An input signal to input port 11 is passed into RAM 12 through CPU 13. A certain number of data points selected from the newest data will be summed by the CPU 13, converted to an analogue signal by the D/A converter through output port 14, and supplied to the displaying device 6. The counted number of neutrons per unit period of time is displayed on the recording chart of display device 6, as shown in Fig. 5. In the second embodiment, the changing rate of the count number of detected neutrons is read-out from the displayed pattern 10A. In this case, it is known when the changing rate of the counted number of the pattern 10A displayed on the chart exceeds a certain reference level, a volcanic eruption or the occurrence of the earthquake is imminent. That is, whenever the count number exceeds a certain reference level indicating that the magma's energy is increased, an eruption or earthquake will follow. By this second embodiment, an accurate prediction of the volcanic eruption or occurrence of the earthquake can be achieved based on the increased changing rate of the count number of detected neutrons. If a digital displaying device is used as a display device, the D/A converter can be eliminated.

Claims: A method of monitoring seismic activity and thereby predicting the occurrence of volcanic eruptions or earthquakes characterised by the steps of measuring the neutron flux radiated from the magma of the inner shell of the earth, monitoring the activity of the magma based on the measured neutron flux, and predicting the occurrence of volcanic eruptions or earthquakes based on the monitored activity of the magma. A method according to claim 1, in which the measured neutron flux is integrated over time and the activity of the magma is based on the integrated neutron count. A method according to claim 1 or 2, in which changes in the neutron flux are measured and the activity of the magma is based on the changes that occur in the neutron flux. Use of an apparatus comprising a neutron sensor, counter means for counting sensed neutrons and display means for displaying the output of the counter for detecting neutrons radiated from the magma of the inner shell of the earth to thereby monitor seismic activity so as to predict the occurrence of volcanic activity or earthquakes.

Inventors: YASUNAGA SOICHIRO, YASUNAGA, SOICHIRO, YASUNAGA, SOICHIRO, C/O RIKEN DENSHI CO., LTD.
Applicants: RIKEN DENSHI CO LTD, RIKEN DENSHI CO. LTD.
Application year: 1991
Main classification: G01T3
IPC codes: G01V1, G01V5, G01T3