scholarly journals Interpretation of Near Surface Based on the Magnetic Data at Geothermal Area, Jaboi, Sabang

2019 ◽  
Vol 8 (3) ◽  
pp. 90-93
Author(s):  
Dinni Mahmudi ◽  
Muhammad Isa ◽  
Didik Sugiyanto
Keyword(s):  
Magnetic Field ◽  
Magnetic Anomalies ◽  
Magnetic Data ◽  
Geothermal Area ◽  
Reference Field ◽  
Subsurface Structure ◽  
International Geomagnetic Reference Field ◽  
Total Magnetic Field ◽  
International Geomagnetic Reference ◽  
Proton Precession Magnetometer

Telah dilakukan penelitian geofisika menggunakan metode magnetik untuk mendapatkan struktur bawah permukaan di daerah prospek panas bumi Jaboi, Sukajaya, Kota Sabang. Pengukuran medan magnetik total dilakukan pada 40 titik menggunakan Proton Precession Magnetometer (PPM). Daerah Jaboi memiliki sudut inkinasi -4.416 dan deklinasi -0.875 dengan nilai medan magnetik total berkisar antara 41550 hingga 42600 nT. Untuk mendapatkan nilai anomali magnetik dilakukan koreksi diurnal dan koreksi IGRF (International Geomagnetic Reference Field). Setelah koreksi dilakukan diperoleh nilai anomali magnetik daerah panas bumi Jaboi antara -200 nT sampai dengan -950 nT. Selanjutnya hasil anomali magnetik ini digunakan dalam memodelkan struktur bawah permukaan dengan panjang lintasan 1800 m dari Tenggara-Barat Laut. Berdasarkan interpretasi data anomali magnetik menunjukkan daerah penelitian didominasi oleh anomali rendah yang berarti daerah manifestasi panas bumi. Interpretasi anomali tinggi dan rendah menunjukkan adanya patahan yang diduga sebagai patahan Ceuneuhot. Dari hasil pemodelan 2D menggunakan software Mag2DC, menunjukkan bahwa terdapat 5 lapisan dengan kedalaman 0 - 1000 m. Lapisan-lapisan ini adalah soil ( = 0,00 x 10-6 SI), andesit terubah (  = 13,408 x 10-6 SI), breksi tufa terubah (  = 12,686 x 10-6 SI), andesit terubah (  = 13,423 x 10-6 SI) dan breksi andesit (  = 13,535 x 10-6 SI). Melalui pemodelan ini diyakini zona patahan adalah patahan Ceuneuhot. Geophysical reasearch by using magnetic method was done in order to obtain subsurface structure of geothermal prospect area Jaboi, Sukajaya, Sabang City. The measurement of total magnetic field was taken at 40 points using Proton Precession Magnetometer (PPM). Jaboi area has an inklination angle -4.416 and declination angle -0.875 which has total magnetic field range between 41550 to 42600 nT. Diurnal Correction and IGRF (International Geomagnetic Reference Field) correction was used to obtain magnetic anomalies. The values of magnetic anomalies in Jaboi Geothermal Area is -200 to -950 nT. The result of magnetic anomalies was used to modelled the subsurface structure with profile distance is about 1800 m from Southeast to Northwest. Based on the magnetic anomalies data, the reaserch area dominated by low anomalies that indicated geothermal manifestation area. High and low magnetic anomalies indicated a fault that estimated as Ceuneuhot fault. From the result of 2D modelling using software Mag2DC, showed that the research area consist of 5 subsurface structure from 0 – 1000 m depth. The layers are soil (  = 0.00 × 10-6 SI), altered andesite (  = 13.408 × 10-6 SI), altered breccia-tuff (  = 12.686 × 10-6 SI), altered andesite (  = 13.423 × 10-6 SI), and breccia-andesite (  = 13.535 × 10-6 SI). Also from the model was  obtained the Ceuneuhot fault zone.  Keywords: Magnetik, Anomali Magnetik, Struktur Bawah Permukaan, Panas Bumi

AD HOC COMMITTEE ON MAGNETIC FIELD MODELS

Geophysics ◽  
1976 ◽  
Vol 41 (4) ◽  
pp. 796-797
Keyword(s):  
Magnetic Field ◽  
Working Group ◽  
Ad Hoc ◽  
Field Model ◽  
International Association ◽  
Geological Survey ◽  
Reference Field ◽  
International Geomagnetic Reference Field ◽  
International Geomagnetic Reference ◽  
Purdue University

An SEG ad‐hoc committee on Magnetic Field Models was formed as one result of the Zmuda Memorial Field Model Conference (Regan and Cain, 1975a). The chairman of the committee is Michael S. Reford, Geoterrex Ltd., and committee members are William J. Hinze, Purdue University, Peter J. Hood, Geological Survey of Canada, and Robert D. Regan, U.S. Geological Survey. The main objective of the committee was to produce an SEG resolution on the revision of the International Geomagnetic Reference Field (IGRF) to be submitted to the International Association of Geomagnetism and Aeronomy’s (IAGA) working group 1.1.

International Geomagnetic Reference Field Revision 1987

Geophysics ◽  
1988 ◽  
Vol 53 (4) ◽  
pp. 576-578 ◽  
Author(s):  
D. R. Barraclough
Keyword(s):  
Charged Particle ◽  
Mathematical Models ◽  
Secular Variation ◽  
Spherical Harmonic ◽  
Geomagnetic Field ◽  
Magnetic Anomalies ◽  
Reference Field ◽  
International Geomagnetic Reference Field ◽  
International Geomagnetic Reference ◽  
Field Revision

The International Geomagnetic Reference Field (IGRF) is a series of mathematical models of the main geomagnetic field and its secular variation, the models consisting of sets of spherical harmonic (or Gauss) coefficients. The IGRF has become a widely used means of deriving values of geomagnetic field components in, for example, studies of magnetic anomalies and investigations of charged particle motions in the ionosphere and the magnetosphere.

scholarly journals The 10th generation international geomagnetic reference field

2005 ◽  
Vol 151 (3-4) ◽  
pp. 320-322 ◽  
Author(s):  
S. Maus ◽  
S. Macmillan ◽  
T. Chernova ◽  
S. Choi ◽  
D. Dater ◽  
...  
Keyword(s):  
Reference Field ◽  
International Geomagnetic Reference Field ◽  
International Geomagnetic Reference

scholarly journals The 9th-Generation International Geomagnetic Reference Field

2003 ◽  
Vol 155 (3) ◽  
pp. 1051-1056 ◽  
Author(s):  
◽  
S. Macmillan ◽  
S. Maus ◽  
T. Bondar ◽  
A. Chambodut ◽  
...  
Keyword(s):  
Reference Field ◽  
International Geomagnetic Reference Field ◽  
International Geomagnetic Reference

Euler’s differential equation and the identification of the magnetic point‐pole and point‐dipole sources

Geophysics ◽  
1984 ◽  
Vol 49 (9) ◽  
pp. 1549-1553 ◽  
Author(s):  
J. O. Barongo
Keyword(s):  
Magnetic Field ◽  
Differential Equation ◽  
Magnetic Anomalies ◽  
Field Vector ◽  
Magnetic Data ◽  
Dipole Source ◽  
Point Dipole ◽  
Main Subject ◽  
Depth Extent ◽  
Dipole Sources

The concept of point‐pole and point‐dipole in interpretation of magnetic data is often employed in the analysis of magnetic anomalies (or their derivatives) caused by geologic bodies whose geometric shapes approach those of (1) narrow prisms of infinite depth extent aligned, more or less, in the direction of the inducing earth’s magnetic field, and (2) spheres, respectively. The two geologic bodies are assumed to be magnetically polarized in the direction of the Earth’s total magnetic field vector (Figure 1). One problem that perhaps is not realized when interpretations are carried out on such anomalies, especially in regions of high magnetic latitudes (45–90 degrees), is that of being unable to differentiate an anomaly due to a point‐pole from that due to a point‐dipole source. The two anomalies look more or less alike at those latitudes (Figure 2). Hood (1971) presented a graphical procedure of determining depth to the top/center of the point pole/dipole in which he assumed prior knowledge of the anomaly type. While it is essential and mandatory to make an assumption such as this, it is very important to go a step further and carry out a test on the anomaly to check whether the assumption made is correct. The procedure to do this is the main subject of this note. I start off by first using some method that does not involve Euler’s differential equation to determine depth to the top/center of the suspected causative body. Then I employ the determined depth to identify the causative body from the graphical diagram of Hood (1971, Figure 26).

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