scholarly journals Subsurface structure identification uses derivative analyses of the magnetic data in Candi Umbul-Telomoyo geothermal prospect area

2018 ◽  
Vol 1011 ◽  
pp. 012038
Author(s):  
U Septyasari ◽  
S W Niasari ◽  
P D Maghfira
Keyword(s):  
Magnetic Data ◽  
Structure Identification ◽  
Subsurface Structure

Magnetic inversion to recover the subsurface block structures based on L1 norm and total variation regularization

2021 ◽  
Author(s):  
Mitsuru Utsugi
Keyword(s):  
Total Variation ◽  
Magnetic Data ◽  
Preconditioned Conjugate Gradient ◽  
Inversion Method ◽  
Total Variation Regularization ◽  
Subsurface Structure ◽  
L1 Norm ◽  
Magnetic Inversion ◽  
Original Definition ◽  
Primal Dual

Summary This paper presents a new sparse inversion method based on L1 norm regularization for 3D magnetic data. In isolation, L1 norm regularization yields model elements which are unconstrained by the input data to be exactly zero, leading to a sparse model with compact and focused structure. Here, we complement the L1 norm with a penalty minimizing total variation, the L1 norm of the model gradients; it is expected that the sharp boundaries of the subsurface structure are not compromised by incorporating this penalty. Although this penalty is widely used in the geophysical inversion studies, it is often replaced by an alternative quadratic penalty to ease solution of the penalized inversion problem; in this study, the original definition of the total variation, i.e., form of the L1 norm of the model gradients, is used. To solve the problem with this combined penalty of L1 norm and total variation, this study introduces alternative direction method of multipliers (ADMM), which is a primal-dual optimization algorithm that solves convex penalized problems based on the optimization of an augmented Lagrange function. To improve the computational efficiency of the algorithm to make this method applicable to large-scale magnetic inverse problems, this study applies matrix compression using the wavelet transform and the preconditioned conjugate gradient method. The inversion method is applied to both synthetic tests and real data, the synthetic tests demonstrate that, when subsurface structure is blocky, it can be reproduced almost perfectly.

scholarly journals Seismic imaging in the eastern Scandinavian Caledonides: siting the 2.5 km deep COSC-2 borehole, central Sweden

Solid Earth ◽  
2016 ◽  
Vol 7 (3) ◽  
pp. 769-787 ◽  
Author(s):  
Christopher Juhlin ◽  
Peter Hedin ◽  
David G. Gee ◽  
Henning Lorenz ◽  
Thomas Kalscheuer ◽  
...  
Keyword(s):  
High Pressures ◽  
Hydrological Cycle ◽  
Magnetic Data ◽  
Lower Grade ◽  
Subsurface Structure ◽  
Seismic Profiles ◽  
Scandinavian Caledonides ◽  
Nappe Complex ◽  
Seve Nappe Complex ◽  
Drill Holes

Abstract. The Collisional Orogeny in the Scandinavian Caledonides (COSC) project, a contribution to the International Continental Scientific Drilling Program (ICDP), aims to provide a deeper understanding of mountain belt dynamics. Scientific investigations include a range of topics, from subduction-related tectonics to the present-day hydrological cycle. COSC investigations and drilling activities are focused in central Scandinavia, where rocks from the middle to lower crust of the orogen are exposed near the Swedish–Norwegian border. Here, rock units of particular interest occur in the Seve Nappe Complex (SNC) of the so-called Middle Allochthon and include granulite facies migmatites (locally with evidence of ultra-high pressures) and amphibolite facies gneisses and mafic rocks. This complex overlies greenschist facies metasedimentary rocks of the dolerite-intruded Särv Nappes and underlying, lower grade Jämtlandian Nappes (Lower Allochthon). Reflection seismic profiles have been an important component in the activities to image the subsurface structure in the area. Subhorizontal reflections in the upper 1–2 km are underlain and interlayered with strong west- to northwest-dipping reflections, suggesting significant east-vergent thrusting. Two 2.5 km deep fully cored boreholes are a major component of the project, which will improve our understanding of the subsurface structure and tectonic history of the area. Borehole COSC-1 (IGSN: http://hdl.handle.net/10273/ICDP5054EEW1001), drilled in the summer of 2014, targeted the subduction-related Seve Nappe Complex and the contact with the underlying allochthon. The COSC-2 borehole will be located further east and will investigate the lower grade, mainly Cambro-Silurian rocks of the Lower Allochthon, the Jämtlandian décollement, and penetrate into the crystalline basement rocks to identify the source of some of the northwest-dipping reflections. A series of high-resolution seismic profiles have been acquired along a composite ca. 55 km long profile to help locate the COSC drill holes. We present here the results from this COSC-related composite seismic profile (CSP), including new interpretations based on previously unpublished data acquired between 2011 and 2014. These seismic data, along with shallow drill holes in the Caledonian thrust front and previously acquired seismic, magnetotelluric, and magnetic data, are used to identify two potential drill sites for the COSC-2 borehole.

Chicxulub — Subsurface structure of impact crater infered from gravity and magnetic data

1996 ◽  
Vol 15 (5) ◽  
pp. 357-359 ◽  
Author(s):  
J. O. Campos‐Enriquez ◽  
R. Diaz‐Navarro ◽  
J. M. Espindola ◽  
M. Mena
Keyword(s):  
Impact Crater ◽  
Magnetic Data ◽  
Subsurface Structure ◽  
Gravity And Magnetic ◽  
Gravity And Magnetic Data

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

scholarly journals Ensemble-based Bayesian inversion of CSEM data for subsurface structure identification

2015 ◽  
Vol 201 (3) ◽  
pp. 1849-1867 ◽  
Author(s):  
Svenn Tveit ◽  
Shaaban A. Bakr ◽  
Martha Lien ◽  
Trond Mannseth
Keyword(s):  
Structure Identification ◽  
Bayesian Inversion ◽  
Subsurface Structure
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