KR20120032122A - Verification method of fracture zone by the anomaly of geomagnetic flux density distribution - Google Patents

Abstract

PURPOSE: A shattered zone distribution checking method due to a magnetic flux density distribution anomaly is provided to be applied to underground water storage exploration, underground mineral exploration, and empty space exploration of underground. CONSTITUTION: A differential-type sensor equipped with a DC magnetic sensor is separately installed from the earth surface to measure. Distance and range to measure are established. A sensor measures magnetic flux density while moving with a constant speed. A detecting device stores the measured magnetic flux density. The detecting device analyzes the distribution of saved magnetic flux density and finds a magnetic anomaly due to a shattered zone among various kinds of magnetic anomalies.

Description

Verification method of fracture zone by the anomaly of geomagnetic flux density distribution

The present invention relates to a method for determining the presence or absence of a fracture zone, the distribution and the center of the fracture zone, and an apparatus for measuring the failure from the geomagnetic abnormality found in the magnetic flux density distribution of the geomagnetism generated by the fracture zone existing in the earth's crust.

Physical exploration or physical exploration is a method of investigating the structure of a geological structure or the presence of deposits from the data of various kinds of physical phenomena observed from the surface of the earth. Depending on the kind of physical phenomenon that leads to the exploration, the seismic wave detection uses the state in which the seismic waves propagate underground. Electric or electrical resistivity detection using electrical conductivity difference, electromagnetic wave detection using transmission and reflection of electromagnetic waves, magnetic field detection using magnetic properties of strata or deposits, radiological detection using natural radiation or artificial radiation, temperature distribution of surface It is divided into geothermal exploration. Such physical exploration is generally used for exploration of underground resources such as petroleum, natural gas, coal, nuclear fuel materials, metal minerals, nonmetallic minerals, geothermal heat, hot springs, groundwater, and geological surveys in civil engineering works. These physical explorations have their own characteristics depending on the physical properties and the exploration methods.

The earth's magnetic field (geomagnetic field), which is explained by the earth's external and internal currents, changes depending on the location of the earth's surface. The geomagnetic field on the Korean peninsula, centered around Seoul, is about 50 μT. At a height of 50 cm or less from the surface of the earth, the strength of the geomagnetic field varies depending on the geology and the structure of the ground. From these local changes in the geomagnetic field, the structural defects of the geologic or strata structure can be found. This physical exploration method is called magnetic exploration. It refers to a method of investigating the magnetic properties of underground rocks, the presence or absence of magnetic material, the geological structure, etc. from the magnetic distribution based on the magnetization rate and residual magnetism of the rock. Therefore, magnetic exploration is not easy in the underground where there is little difference in magnetism. In general, igneous rocks are more magnetic than metamorphic and sedimentary rocks, and basic igneous rocks are often highly magnetic. Metamorphic rocks are less magnetic than igneous rocks, but are generally stronger than sedimentary rocks.

Since the earth's magnetic force is a vector quantity, its magnitude is expressed as total magnetic force, and it can be decomposed into horizontal magnetic force and vertical magnetic force, and can be expressed as dip and declination of earth magnetic force. The magnetic field measured by the magnetometer requires correction of daily changes to compensate for changes caused by the rotation of the earth, and terrain correction is required to compensate for changes in height and shape. After these corrections, an isomagnetic plot is created, from which geologic structures and structural defects can be analyzed.

To analyze the geology or its structure, compare the results of the magnetic anomaly calculation with the actual measurement results from the model of the underground structure, or compare the magnetic force distribution with a certain depth calculated from the measured magnetic anomalies and the measured distribution. do. The aviation magnetic force obtained from the measurement device mounted on the aircraft can eliminate the disturbances caused by the magnetic objects on the ground, so that the magnetic force distribution of the large area can be obtained in a short time. It is used as a means to get an overview of the development of sediments. In addition to airborne magnetic exploration, there is also a marine magnetic exploration that measures the magnetic distribution in the sea by attaching a magnetic sensor to the rear of the ship. This air or ocean magnetic exploration is a method of confirming the magnetic distribution of a large area. Since the spatial resolution is relatively large, it is difficult to obtain a magnetic distribution of a small area.

The present invention effectively measures and acquires magnetic flux density regardless of the area of the exploration area from the magnetic sensor by using a magnetic sensor capable of measuring the magnetic flux density of a DC component that can irradiate the earth magnetic field with the magnetic flux density of the region to be explored. The present invention provides a method for confirming the distribution of crushed bands due to the magnetic flux density distribution abnormality of the geomagnetism by analyzing the obtained magnetic flux density distribution with a detector and finding only magnetic anomalies caused by crushing bands from various types of magnetic abnormalities found in the magnetic flux density distribution. Make it a challenge.

In addition, another object of the present invention is to provide a magnetic flux density distribution measuring apparatus of a crushing zone distribution for verifying the distribution of magnetic flux density after measuring the magnetic flux density of the geomagnetic field and storing the measured magnetic flux density.

In addition, the present invention provides a method for identifying the presence of underground minerals and groundwater in the base and the distribution and center of the distribution by analyzing the magnetic flux density obtained from the measurement result of the magnetic flux density distribution according to the method of confirming the distribution of the crushing band Is another challenge.

The method for checking the crushing band distribution due to the magnetic flux density distribution abnormality of the geomagnetism of the present invention that solves the above problems is to measure a differential mode sensor having a DC magnetic sensor that detects a magnetic flux density change of four or more times per second. After installation at a certain distance from the ground surface, set the distance and range to be measured and measure the magnetic flux density while moving the sensor at a constant speed, and the measured magnetic flux density is acquired and stored with a detector composed of an interface and a PC. And analyzing the distribution of the obtained and stored magnetic flux densities to find only the magnetic abnormality caused by the crushing band from various kinds of magnetic abnormalities.

Here, the differential sensor is characterized in that it comprises a three-axis DC magnetic sensor in the x, y, z-axis three directions.

Here, the differential sensor is composed of two, the first differential sensor is located within 0.5m from the ground surface, the second differential sensor is located at a distance of 1.5 ~ 2.0m from the ground surface, the first differential sensor and the second differential type The distance from the sensor is configured to be 1.0 ~ 2.0m is characterized by measuring the magnetic flux density.

Here, the moving speed of the differential sensor is characterized in that 0.1 ~ 50 m / sec.

According to the present invention, by analyzing the magnetic flux density obtained from the measurement result of the magnetic flux density distribution obtained according to the above-described measuring method there is provided a method for confirming the presence of underground minerals and groundwater in the basement and their distribution and the center of the distribution do.

According to the present invention, two differential sensor units having a DC magnetic force sensor detecting a magnetic flux density change of four or more times per second, which are installed at a predetermined distance from the ground to be measured, and the magnetic flux density detected from the differential sensor unit. An interface for acquiring and storing changes and a PC for analyzing and displaying the information stored in the interface; The differential sensor part comprises a lower sensor part installed within 0.5 m from the ground surface and an upper sensor part located at a height of 1.5 to 2.0 m, and the two sensors are installed so that the mutual separation distance is 1.0 to 2.0 m, and 0.1 to 50 m. Provided is a magnetic flux density distribution measuring device of a geomagnetism for determining the magnetic flux density while moving at a moving speed of m / sec.

Here, the differential sensor is characterized in that it comprises a three-axis DC magnetic sensor in the x, y, z-axis three directions.

According to the present invention, by using the magnetic flux density distribution measuring device described above to perform the electric and electromagnetic wave detection method applied to the crushing band distribution confirmation method at the same time to analyze the magnetic flux density obtained from the measurement result of the magnetic flux density distribution underground underground minerals Methods are provided for determining the presence or absence of groundwater and groundwater, and their distribution and center of distribution.

According to the present invention, the method for checking the crushing band distribution due to the magnetic flux density distribution of the geomagnetism is very small in the case of structural defects such as the boundary of the strata, the fault plane, the crack, the fracture plane, the joint, the crush zone, and the small void. The length can range from tens of meters to hundreds of kilometers, but its width is only a few mm to hundreds of millimeters, which is difficult to find by conventional aviation or ocean magnetic exploration. In addition, due to changes in the Earth's magnetic force, it is not easy to identify structural defects having a very narrow width by magnetic exploration. Other types of physical exploration methods besides magnetic exploration are used to identify relatively large structural defects of at least 1m in width, which makes it difficult to identify very small structural defects. In the present invention, the small-scale defects having such a narrow width can be confirmed by magnetic sensing, so the distance and the distance between the measurement points should be small due to spatial resolution, and the effect of minimizing the change of the geomagnetism has an effect.

In addition, the present invention has a lot of factors affecting the magnetic force distribution on the surface or inside thereof. Ferromagnetic materials, such as nails and iron bars, are left in the surface, or ferromagnetic materials, such as beams and iron pipes and tubes, are buried underground. In order to obtain the magnetic force distribution that excludes the influence of the surface or the ferromagnetic material buried underground, the magnetic force sensor should be located at a height of 1.5-2.0m from the ground surface. In order to check the size, shape and location of ferromagnetic materials buried in the surface or underground, the position of the sensor should be located close to the ground surface. Two sensors are required to meet these two conditions, and each sensor needs to be located within 1.5-2.0m from the ground and within 0.5m from the ground. The magnetic force distributions identified from these can be compared and analyzed to identify ferromagnetic materials buried in the surface and underground, and then the structure of the strata and its structural defects can be identified.

In the present invention, in order to identify structural defects having a small width of several mm to several hundred mm, a sensor having a spatial resolution of several mm should be used, and the measurement is completed in a very short time to exclude the influence of the change of geomagnetism. Should be. If the change of magnetic flux density is measured at 5mm intervals on a straight line of 2m length, the magnetic flux density should be investigated at 401 measurement points. In this case, when the magnetic flux density distribution is investigated by the method specified in ASTM, a measurement time of about 1 to 5 hours is used. For this purpose, it is necessary to calibrate the measured magnetic force value with the reference magnet obtained by installing the reference magnetometer in the place where the magnetic force is stabilized to correct the change of day. If these measurements were taken on 10 straight lines of 2 m length with a width of 100 mm, it would take 10 to 50 hours. Such a measuring method takes a lot of time, and thus is not effective for checking the magnetic force distribution. When using a highly sensitive magnetic sensor with a very short data acquisition time (DAT), the time required for the entire measurement can be reduced to less than a few minutes, thus eliminating the work of geomagnetism.

In addition, by analyzing the magnetic flux density obtained from the measurement results of the magnetic flux density distribution by simultaneously conducting electrical and electromagnetic surveys applying the method of the present invention, the presence or absence of underground minerals and groundwater present in the basement, and their distribution and center of distribution The effect can be confirmed more accurately.

1 is a sensor arrangement diagram of a fluxgate type three-axis magnetic sensor,
2 is a conceptual diagram of a connection between a differential magnetic sensor and a computer for control and signal processing;
Figure 3 is a photograph of the arrangement and motor drive device of the three-axis fluxgate magnetic sensor,
4 is a variation diagram of magnetic flux density distribution shown in computer simulation results for stratum boundaries, large fracture surfaces and fracture zones.
Figure 5a is a photograph of a rectangular parallelepiped for measuring the magnetic flux density distribution change of the geomagnetic field,
FIG. 5B is a diagram showing the surface portion of the surface of the magnetic flux density measured on the ground after filling the pit of FIG. 5A; FIG.
Figure 6a is a view showing the change in the magnetic flux density vertical component (Bz) measured in Figure 5b,
FIG. 6B is a magnetic flux density distribution diagram showing FIG. 6A as an isomagnetic flux density; FIG.
Figure 7a is a photograph of creating an empty space in the basement using a rectangular parallelepiped and a cylinder made of PVC,
FIG. 7B is an isomagnetic flux density distribution surveyed from the earth's surface after covering FIG. 7A with soil,
8 is a vertical component change diagram of the magnetic flux density irradiated from 150mm (B _{z , 150} ), 1,150mm (B _{z , 1150} ) high from the ground at Yeungnam University playground,
FIG. 9 is a diagram of noise included in B _{z, 150} in FIG. 8;
10 is a vertical component change diagram of the magnetic flux density irradiated at the boundary of the strata in the elderly in Gyeongbuk,
11 is a vertical component change diagram of the magnetic flux density irradiated from the top of a large fracture surface in Yongin, Gyeonggi-do,
12 is a photograph of a crushing stand located near the Yeongcheon IC of Gyeongbu Expressway,
13 (a) is a vertical component change diagram of magnetic flux density irradiated on the crushing zone of FIG. 12,
13 (b) is a magnetic anomaly change diagram included in B _{z, 150} of FIG. 13 (a),
14 is a vertical component change diagram of magnetic flux density at the crushing zone irradiated in Uva, Sri Lanka,
FIG. 15 is an electrical resistivity detection result diagram of the dipole-dipole arrangement method irradiated at the same place as in FIG. 14; FIG.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention will be described in more detail with reference to the accompanying drawings.

In the case of very small structural defects such as stratum boundaries, faults, cracks, fractures, joints, crushing zones and small voids, their length can range from tens of m to hundreds of kilometers, but its width can be It is only a few millimeters to a few millimeters in diameter, making it difficult to find by air or sea magnetic exploration. In addition, due to changes in the Earth's magnetic force, it is not easy to identify structural defects having a very narrow width by magnetic exploration. Other types of physical exploration methods besides magnetic exploration are also used to identify relatively large structural defects of at least 1 m in width, making it difficult to identify very small structural defects.

In order to be able to identify small-scale defects with such narrow widths, the magnetic force distribution should be investigated near the surface of the earth, the distance and distance between measurement points should be small due to spatial resolution, and the influence of the change of geomagnetism should be minimized. do.

The disturbance of magnetic force distribution by ferromagnetic material in underground underground or surface which is the most problematic in magnetic exploration is operated in differential mode by placing two magnetic sensors within 1.5 ~ 2.0m from the ground and 0.5m from the ground, respectively. This will help identify the cause and eliminate disturbance in the magnetic distribution. In addition, a sensor with a spatial resolution of 1 mm or less is required to identify small structural defects, and the data acquisition time of the sensor must be very short in order to exclude the influence of the change of geomagnetism.

According to the present invention, the method for confirming the distribution of the crushing band is to set a distance and a range to be measured after a predetermined distance from the ground surface to measure a differential sensor having a DC magnetic sensor detecting a magnetic flux density change of 4 or more times per second. The magnetic flux density is measured while moving the sensor at a constant speed, and the measured magnetic flux density is acquired and stored with a detector composed of an interface and a PC, and the distribution of the magnetic flux densities obtained and stored is analyzed from various types of magnetic abnormalities. This is done by analyzing the magnetic flux density distribution abnormality of geomagnetism which finds only magnetic abnormality by crushing zone.

The differential sensor is preferably configured to include a three-axis DC magnetic sensor in the x, y, z-axis three directions.

The differential sensor is composed of two, one at each of the upper and lower parts, the first differential sensor (lower sensor) is located within 0.5 m from the ground surface, the second differential sensor (upper sensor) is located at a distance of 1.5 ~ 2.0 m from the ground surface The distance between the first differential sensor and the second differential sensor is preferably 1.0 to 2.0 m to measure the magnetic flux density.

Moving speed of the differential sensor is preferably set to 0.1 ~ 50 m / sec to measure. Details of the change in the moving speed will be described below.

In addition, according to the present invention, two differential sensor units having a DC magnetic force sensor for detecting at least four magnetic flux density changes per second installed at a predetermined distance from the ground to be measured and the magnetic flux density detected from the differential sensor unit An interface for acquiring and storing changes of the PC and a PC for analyzing and displaying the information stored in the interface; The differential sensor part comprises a lower sensor part installed within 0.5 m from the ground surface and an upper sensor part positioned at a height of 1.5 to 2.0 m, and the two sensors are installed so that the mutual separation distance is 1.0 to 2.0 m, and 0.1 to 50 m. A magnetic flux density distribution measuring device of a geomagnetism for crushing zone distribution checking for measuring magnetic flux density while moving at a movement speed of / sec is provided.

According to the present invention, by analyzing the magnetic flux density obtained from the measurement result of the magnetic flux density distribution according to the crushing zone identification method of the present invention as described above, the presence or absence of underground minerals and groundwater present in the basement, and their distribution and the center of the distribution You can also check

If the present invention as described above in more detail,

There are many types of magnetic sensors that can measure the magnetic flux density of DC components that can irradiate the earth's magnetism. Among them, fluxgate (FG) sensors and giant magnetoresistance (GMR) sensors are vector fluxes. The x-component, y-component, and z-component of can be measured simultaneously. Among the FG type sensors, the bar type (bar-type) is excellent in directionality, it is possible to measure the three-axis component of the magnetic flux at the same time using three sensors as shown in Fig. The three sensors must be exactly perpendicular to each other, and each sensor must be accurately calibrated using a Helmholtz coil. Like the FG type sensor, the GMR type sensor must be calibrated exactly and perpendicular to each other.

The data acquisition time of FG type and GMR type sensors should be very fast, at least 1 msec. For data acquisition times of less than 1 m seconds, a reader or computer can be used to take at least 10 data per second.

When a sensor composed of magnetic sensors in three directions of x, y, and z-axis is called a sensor system, a differential sensor is composed of two sensor systems as shown in FIG. 2, and the distance between the upper and lower sensors is 1.0 to 2.0 m. do. The further the distance is, the less the influence of the surface or underground burial on the output of the sensor located above. The physical quantity irradiated as a differential sensor includes six x, y, z-axis components (Bx, By, Bz) and total magnetic flux density (Bt: Bt ² = Bx ² + By ² +) of magnetic flux density at the height of the sensor located above and below. Bz ² ) Information on 12 magnetic flux densities is obtained, including two and four differences between each component. Since many types and large amounts of data are acquired at the same time, an interface between the sensor and the PC and a PC are used for data acquisition, storage, and display as shown in FIG.

Since the spatial resolution is determined by the moving speed of the sensor, the moving method and the moving speed of the sensor are important factors in measuring the fracture zone on the ground. The faster the moving speed, the larger the space between the measuring points and the lower the spatial resolution. If the sensor is shaken from side to side or up and down during measurement, the measuring direction of each sensor changes, and the measured value of each sensor changes because the magnetic flux density is a vector. Therefore, do not change the position or direction of the sensor during measurement. To this end, the sensor device is preferably moved to a motor-driven belt as shown in FIG. 3 or mounted on a motorcycle or a motor vehicle.

When the computer simulation is performed using the Maxwell equation, the shape change of the magnetic flux density distribution at the boundary of the fracture zone and the strata is as shown in FIG. 4. In all three geologic defects, there are (+) / (-) peak pairs. However, the difference between the peak-to-peak values of the peak pairs is not large at the boundary of the strata, and the distance between the two peaks is also short. The peak-to-peak value is large at the fracture surface, and the distance between the peaks is also longer than the boundary of the strata. Both cases consist of a single peak pair. The crushing zone has a large peak-to-peak value, a long distance between the peaks, and above all, several of these peak pairs exist simultaneously. This is the result of a geological shape in which the fracture zone exists where several fracture surfaces overlap or intersect with each other.

Other types of physical exploration that receive and analyze a transmitted or reflected signal by transmitting a signal source are active technologies that use the transmission and reception of signals, so the distance from the destination to the target structural defects Can be predicted. In this case, many kinds of noise are involved during transmission and reflection and reception at the target. Magnetic force detection is a passive technology that investigates structural defects from the distribution disturbed by the target when the magnetic field lines of geomagnetism break through the surface without using the transmitting signal, so there is insufficient information about distance. However, the probability of noise involvement is relatively low compared to active technologies.

When identifying geologic defects from magnetic anomalies in geomagnetic distribution, information on the depth to where they exist is difficult to obtain. However, if the degree of magnetic abnormality is large and strong, it can be expected to exist near the surface of the earth or actually have a large-scale structural defect. If the degree of abnormality is small or weak, the structural defect can be deeply located or can be predicted as a small-scale defect.

By comparing and analyzing the magnetic flux density distribution results investigated using the differential sensor system of FIG. 2 and the computer simulation results of FIG. 4, structural defects present in the basement can be confirmed. In order to identify the depth or location of structural defects, active techniques such as electric or electromagnetic radiation can be used.

Hereinafter, the present invention will be described in more detail with reference to preferred embodiments. However, the present invention is not limited to the following examples.

[Example]

(1) Magnetic force distribution measurement

3-axis fluxgate magnetometer (Le USA Inc., model FGM-4DTAM), scanning magnetometer (FTK, model GeoMag-101) and 24-channel magnetometer (FTK, model GeoMag) -Strata) was used. The data acquisition time of the magnetometer is 0.5m seconds, and the data acquisition speed is 20 times per second per channel. The FGM-4DTAM, a reference magnetometer, was installed where the magnetic force was stabilized for the correction of daily variation. The magnetic flux density obtained from this was set as the reference magnetic force.

The position of the sensor is moved by using a motor, and FIG. 3 shows a mounting state of the sensor and a device for moving the sensor by using a motor-driven belt. The sensor moved continuously at a speed of 2 m / min, and the spatial resolution when taking data from the sensor was 1 data / mm.

(2) Magnetic abnormality due to density difference

Underground vacant spaces in different densities and fill areas were created at the outdoor experiment site of Hazama Institute of Technology, 515-1, Karima, Tsukuba City, Ibaraki, Japan. In order to give a difference in density, as shown in FIG. 5 (a), a pit of a cuboid having a width of 1m, a length of 1.5m, and a depth of 1m was dug into an open ground and then filled with soil dug therein. At this time, the difference in density before and after refilling the soil was not measured. However, since the amount of soil remaining after refilling was about 10%, the density of the refilled floor was estimated to be lower than that of the original floor. The magnetic flux density distribution at 20 cm above the ground surface was investigated.

Figure 5b shows the order and position of the scan with the sensor, a total of 12 scans at 10cm intervals, one scan consists of 30cm unearthed and 135cm unearthed, scan 1 and scan 12 corresponds to the part not dug out. 6A is a result of measuring the vertical component (Bz) of the magnetic flux density. The distribution change obtained therefrom is shown in FIG. 6B, and the unit of the magnetic flux density is mG (0.1 μT). In scans 1, 2, 11, and 12, the change in magnetic flux density was irregular, which seems to be independent of the excavation of the pit, possibly due to the nature of the ground. Scans 3 through 10 show the lowest magnetic flux density at the center of the cuboid and increase toward the outside. In the case of scan 3-10, the values vary depending on the scan at 0-30cm, but the magnetic flux density decreases toward the center at 30-165cm. In other words, the magnetic flux density is lowered at the place where it is covered after digging, and irregular changes are shown at or near the area where the original ground itself is characterized. This feature can be clearly seen in Figure 6b, which shows the distribution change in the scanned area.

(3) Magnetic abnormalities caused by empty spaces in the basement

In order to investigate the effect of the empty space in the underground on the magnetic force distribution as shown in Figure 7a a cube made of foamed styrofoam (0.5m long, 0.5m long, 0.5m high) and a cylinder 0.5m in diameter, 0.5m long Placed and buried in dirt. Foamed styrofoam is expected to be nearly equal to the permeability of air due to its low density and low permeability.

In Fig. 7B, the rectangular box A represents the boundary between the excavated portion and the unexposed portion, where the magnetic flux density is irregularly distributed in the range of 34.7-35.5 μT. By the way, inside the rectangular box B indicated by the dotted line, the magnetic flux density gradually decreases toward the center of the box, at 34.2 μT. The decrease in magnetic force toward the inside of the excavated portion was also observed in the vertical component distribution of magnetic flux density. By the way, box A, which is the boundary between the cover and the uncovered after digging, is not clearly distinguished in the magnetic flux density distribution.

(4) magnetic anomalies near the earth's surface

Overlapping or many small faults form a single fractured fractured rock, ranging from a few centimeters to hundreds of meters. The ground where the crushing zone is located is weak and erodes and collapses rapidly. If the clay in the crushing zone is washed away, it becomes a passage of groundwater. In the deep underground fault crushing zone, crushed rock is formed, and when it is relatively shallow, fault clay or fault angular rock is easily formed. Civil engineering works such as tunnels often cause water accidents or land collapse along fault fault zones, causing accidents.

8 is a result of observing a change in the vertical component (Bz) of the magnetic flux density according to the measurement height from the surface. The survey site is north of Yeongnam University Grand Stadium, and there is Samcheonji, a reservoir 15m east, measured in a direction parallel to the banks of Samcheonji. The total measurement distance here is 16m. Bz and ₁₁₅₀ are vertical components of magnetic flux density measured at a height of 1,150 mm from the ground, and Bz and ₁₅₀ are vertical components of magnetic flux density measured at a height of 150 mm. In general, the magnetic flux density measured at 0.15 m near the ground is generally larger than the magnetic flux density measured at 1.15 m. In the case of measuring at 0.15m, components such as noise are included, and filtering and arranging only components such as noise in the measurement result may yield a result as illustrated in FIG. 9. The change in magnetic flux density at two heights is almost the same, as measured at a low point of 0.15 m, as large as 0.6-1.5 μT compared to that measured at 1.15 m. The magnetic anomaly shown in FIG. 5 has the same tendency to change according to the measurement height, and since the intensity decreases at 1.15 m as compared with 0.15 m, it seems to represent a large-scale magnetic anomaly occurring at the core or the ceiling.

In Bz and ₁₁₅₀ measured at 1.15 m, the magnetic anomaly corresponding to noise is 0.05 μT or less, but in Bz and ₁₅₀ measured at 0.15 m, the magnetic anomaly shown in FIG. 9 can be obtained. The magnetic anomaly shown in FIG. 9 is observed at 0.15 m, but almost disappears at 1.15 m, which is mainly considered to be a small scale magnetic anomaly occurring in the sky and the earth. The magnitude of the magnetic anomaly shown in this figure is up to 0.65 μT, characterized by the appearance of peak and negative peaks. Low intensity but many similar peak pairs are observed.

(5) Identification of strata boundaries and fracture surfaces from magnetic anomalies

Figure 10 shows the magnetic flux density change at the boundary layer observed in Gyeongbuk old age. The positive and negative peaks are paired, and the distance between the positive and negative peaks is much smaller than 0.5m. Peak-to-peak values appear below 1 μT. 11 is a magnetic flux density change in the large fracture surface observed in Gyeonggi Yongin. The gap gap at the fracture surface was up to 50 mm. The pair of positive and negative peaks in the magnetic flux density curve is the same as the boundary of the strata, but the distance between the positive and negative peaks is about 6 m and the peak-peak value is 33 μT. Much larger than that. This difference in magnetic abnormality is almost similar to the computer simulation results shown in FIG.

As described above, the strata boundary and the large fracture surface can be easily identified from the difference of magnetic abnormality in the magnetic flux density distribution.

(6) Identification of crushing zone from magnetic abnormality

According to the computer simulation results of FIG. 4, it is possible to identify the stratum boundary, fracture surface, and fracture zone from magnetic abnormalities in the magnetic flux density distribution. In the field test results of FIGS. 10 and 11, the stratum boundary and the fracture surface are easily identified from the difference in magnetic abnormality.

In the case of crushing band, it was checked whether it could be identified from magnetic abnormality.

12 is a crushing zone confirmed at the road opening site located in Yeongcheon, Gyeongbuk, the width of the crushing zone is about 3m, the intruded layer located in the center and the broken crushing zone is broken at both boundaries. The change of the magnetic flux density was measured on the flat land just above the crushing zone, and the result is shown in FIG. 13A. The vertical component (Bz, ₁₁₅₀ ) of magnetic flux density measured at 1.15m height from the ground was 35.3 μT without change depending on the position, and slightly lower than the average of the vertical component (Bz, ₁₅₀ ) at 0.15m measured at the same time. see. No magnetic abnormality is assumed to occur in the natural state, such as Bz, ₁₅₀ measured at 0.15 m in FIG. 8.

The vertical component (Bz, ₁₅₀ ) at 0.15m shows a lot of change depending on the position, unlike Bz, ₁₁₅₀ . At a height of 0.15m, the magnetic flux density is about 35.5 μT in the absence of magnetic anomalies, and the lowest peak is 32.8 μT and the highest 37.5 μT between A and B where the crushing zone is located, and the peak-peak value is 4.7 μT. There are / (-) peak pairs. That is, where there are peak pairs, there is a much higher magnetic flux density than the average value, and there are many peak pairs with different peak-peak values.

13B shows only the magnetic abnormality caused by the crushing band by filtering the results of Bz and ₁₅₀ . The peak characteristic of the crushing band is characterized by the pairing of the (+) and (-) peaks. The peak of the (+) peak is 2.0 μT and the peak of the (-) peak is observed to be -2.7 μT. The distribution of FIG. 11B tends to be almost similar to that of FIG. 9, where the peak-peak value is much higher in FIG. 8B than in FIG. 6. The reason why the peak-peak value is large can be considered as follows.

First, when the degree of magnetic abnormality in the two places is almost the same, the cause of the magnetic abnormality of FIG. 13B is much closer to the ground surface than in FIG. 9. As can be seen from FIG. 12, the crushing zone, which is the cause of the magnetic abnormality of FIG. Second, when the magnetic abnormalities of the two locations are different, it corresponds to that of FIG. 13B which causes much stronger magnetic abnormalities than in FIG. 6. Since the magnetic anomaly observed at 0.15m in height disappears at 1.15m in height, it is clear that the cause of the magnetic abnormality exists on or near the surface. Accordingly, it is assumed that the case of FIG. 13B is a structural defect that is much stronger than the case of FIG. 9.

As described above, the fracture zone shows a magnetic abnormality that is completely different from the magnetic abnormality observed in the stratum boundary or fracture surface.

From this, the empty space, the boundary of the strata, the fracture surface and the fracture zone can be easily identified from the difference of the magnetic abnormality present in the magnetic flux density distribution.

(7) Groundwater exploration at crushing zone confirmed from magnetic abnormality

Since the crushing zone in the solidified rock layer corresponds to the empty space, there is a high probability that the groundwater is distributed. Therefore, for groundwater exploration, the magnetic anomalies present in the magnetic flux density distribution are first identified, and electrical resistivity exploration is carried out by dipole-dipole method at the center of magnetic anomaly. Then, the identification of crushing band due to magnetic abnormality was verified.

FIG. 14 shows changes in magnetic flux density measured in the vicinity of Pallewela, Uva Province, Sri Lanka. The latitude is 7 degrees north latitude, close to the equator. The rainfall here is very dry, less than 500 mm per year, compared to 3,800 mm of annual rainfall in Colombo. The total magnetic force B _T varies in the range 0.397-0.403 μT with very small deviations of about 0.003 μT. The area indicated by the arrow is the center of the crushing zone, showing a change of 0.394-0.408 μT with a deviation of 0.014 μT. The results of conducting the electrical resistivity exploration centering on this are shown in FIG. 15. The crushing zone exists at about 90-100m, and it can be seen that the electrical resistivity of the place is low compared to other places. As a result of the drilling test, the weathering zone was finished at about 40m and fresh rock appeared, and the crushing zone was found at 93m. As expected from the electrical resistivity survey, the crushing zone had groundwater, which was about 550 cubic meters (m ³ ) per day.

As shown in the above verification results, the fracture zone can be confirmed from the magnetic abnormality in the magnetic flux density distribution, and it can be confirmed by other physical exploration methods.

The exploration of crushing zone due to magnetic abnormality can be used to secure underground resources in combination with electric resistivity exploration or electromagnetic wave exploration. At this time, the magnetic anomaly method is most effective in identifying the distribution and center of the crushing zone, and it can be confirmed that the exploration time is one of the shortest useful methods.

Claims (7)

After installing a differential sensor equipped with a DC magnetic sensor that detects the magnetic flux density change more than four times per second, a certain distance away from the surface to be measured, set the distance and range to be measured and move the sensor at a constant speed. The magnetic flux density is measured, and the measured magnetic flux density is acquired and stored with a detector consisting of an interface and a PC. The magnetic flux density is found by analyzing the distribution of the obtained and stored magnetic flux densities from various types of magnetic abnormalities. Method of verifying crush zone distribution due to magnetic flux density distribution error.
The method of claim 1,
The differential sensor comprises a three-axis DC magnetic sensor in the three x, y, z-axis direction, characterized in that the crushing band distribution check by the magnetic flux density distribution of the geomagnetism.
The method of claim 1,
The differential sensor is composed of two, the first differential sensor is located within 0.5 m from the ground surface, the second differential sensor is located at a distance of 1.5 to 2.0 m from the ground surface, the first differential sensor and the second differential sensor and The separation distance of the crushing zone distribution method according to the magnetic flux density distribution of the geomagnetic, characterized in that the magnetic flux density is measured to be configured to 1.0 ~ 2.0 m.
The method of claim 1,
The movement speed of the differential sensor is 0.1 ~ 50 m / sec crushed band distribution check method due to the magnetic flux density distribution of the geomagnetism.
Acquire and store the change of the magnetic flux density detected by the differential sensor unit and two differential sensor units having a DC magnetic force sensor for detecting at least four magnetic flux density changes per second installed at a predetermined distance from the ground to be measured. Interface and a PC for analyzing and displaying the information stored in the interface,
The differential sensor unit is composed of a lower sensor unit installed within 0.5 m from the ground surface and the upper sensor unit located at a height of 1.5 ~ 2.0 m, the two sensors are installed so that the mutual separation distance is 1.0 ~ 2.0 m,
A magnetic flux density distribution measuring device of a geomagnetism for crushing zone distribution, characterized by measuring the magnetic flux density while moving at a movement speed of 0.1 ~ 50 m / sec.
The method of claim 5, wherein
The differential sensor is a magnetic flux density distribution measuring device of the geomagnetic crushing zone, characterized in that it comprises a three-axis DC magnetic force sensor in the x, y, z-axis three directions.
Claims 1 to 4 of the magnetic flux density obtained from the measurement results of the magnetic flux density distribution according to any one of the method to determine the presence or absence of underground minerals and groundwater, and their distribution and the center of the distribution.

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