Basic Geophysics

Robinson, Enders A.; Clark, Dean

doi:10.1190/1.9781560803461

Cited by 7 publications

(6 citation statements)

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“…Complete Bouguer Anomali (CBA) merupakan selisih antara nilai gayaberat pengamatan dengan gayaberat teoritik yang didefinisikan pada titik pengamatan bukan pada bidang referensi, baik elipsoid maupun muka laut rata-rata. Complete Bouguer Anomali (CBA) diberikan dalam persamaan (Robinson, 1988…”

Section: Complete Bouguer Anomali (Cba)unclassified

Pemodelan Dan Analisa Struktur Bawah Permukaan Daerah Prospek Panasbumi Kepahiang Berdasarkan Metode Gayaberat

Sihombing

Rustadi

2020

JGE

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ABSTRAKTelah dilakukan penelitian di daerah Kepahiang menggunakan data gayaberat dengan tujuan mengidentifikasi patahan berdasarkan analisis Second Vertical Derivative (SVD) dan menafsirkan struktur bawah permukaan berdasarkan model inversi 3D dari anomali Bouguer dan anomali residual. Daerah penelitian memiliki anomali Bouguer antara 38 mGal -74 mGal, dimana nilai anomali Bouguer tinggi memiliki rentang nilai 63,2 mGal -74 mGal yang berada di arah barat daya daerah penelitian. Sedangkan nilai anomali Bouguer rendah memiliki rentang nilai 38 mGal -47 mGal yang berada di arah utara daerah penelitian. Untuk mengetahui keberadaan struktur patahan di daerah penelitian, dilakukan filtering Second Vertical Derivative (SVD) pada peta anomali Bouguer, Regional dan Residual. Pola struktur patahan ditunjukkan dengan kontur bernilai nol dan diapit kontur tinggi dan rendah. Dari hasil analisis SVD anomali Bouguer lengkap dan SVD anomali residual terdapat 8 (delapan) patahan, sedangkan dari SVD anomali regional terdapat 4 (empat) patahan. Pemodelan inversi 3D anomali residual dilakukan untuk membuktikan keberadaan patahan yang dianalisis berdasarkan filtering Second Vertical Derivative (SVD). Berdasarkan hasil inversi 3D anomali residual didapatkan satu (1) reservoar di arah utara daerah penelitian dan dua (2) di arah barat daerah penelitian dengan kontras densitas dari -0,0719356 gr/cm 3 sampai -0,236053 gr/cm 3 dengan kedalaman dari 0 meter sampai 4.705 meter. ABSTRACTResearch has been conducted in Kepahiang area using gravity data with the aim of identify faults based on analysis of the Second Vertical Derivative (SVD) and interpreting structure sub-surface of the based on 3D inverse modelling from Bouguer anomaly and residual anomaly. The research area have an Bouguer anomaly between 38 mGal -74 mGal, where the high Bouguer anomaly value has a value range of 63,2 mGal -74 mGal located in the southwest direction of the research area. Whereas the low Bouguer anomaly value has a range of values 38 mGal -47 mGal located in the north of the research area. To know the existence of fault structure in research area, conducted filtering Second Vertical Derivative (SVD) on the map Bouguer anomaly, regional and residual. The structure faulting is shown with contour of zero and between the contours of high and low. From the analysis of SVD complete anomaly Bouguer and SVD residual anomaly there are 8 (eight) faulting, while from SVD regional anomaly there are 4 (four) fault. 3D inversion modeling of the residual anomaly was done to prove the existence of the fault analyzed based on filtering Second Vertical Derivative (SVD). Based on the results of inversion 3D residual anomaly been gained one (1) reservoir in a northern direction research area and two (2) in the direction of west the research area by a contrast the density of -0,0719356 gr/ until -0,236053 gr/ with a depth of 0 meters up to 4.705 meters.

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Section: Complete Bouguer Anomali (Cba)unclassified

Pemodelan Dan Analisa Struktur Bawah Permukaan Daerah Prospek Panasbumi Kepahiang Berdasarkan Metode Gayaberat

Sihombing

Rustadi

2020

JGE

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“…Keberhasilan metode resistivity bergantung pada kontras resistivitas yang terukur antar sifat fisik dari target dan medium sekitarnya [1] . Lorong sungai bawah tanah merupakan rongga udara yang cukup besar sehingga memiliki nilai resistivitas yang sangat besar dibandingkan dengan material sekitarnya [4] . Penelitian tentang karst menggunakan metode resistivity telah dilakukan oleh Gautam et.…”

Section: Pendahuluanunclassified

Identification Karst Underground River System in Gebangharjo Village, Pracimantoro using Tomography Resistivity Methode with Wenner-Schlumberger’s Configuration

Purwanto

Darsono

Koesuma

2017

Indonesian J Appl Phys

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This research is conducted using 4 lines data with 750 meters in length. Tomography resistivity with Wenner-Schlumberger configuration is used as this research methodology to take the data with a = 50 meters and n=1, 2, 3, 4, 5, 6. Resistivitymeter OYO 2119C McOHM-EL model is used as the instrument. Furthermore, the data is processed with two softwares; Res 2 Dinv ver. 3.56.22 to get 2D resistivity section and Rock Work 16 to make 3D model of the site. The underground river's chamber is made by hollow carbonate rocks with the resistivity of >412 Ωm and 117,6 Ωm -412 Ωm for limestone's resistivity as its capsrock. Researching to the depth of 173 meters, underground rivers are shown in the line 2 in the depth of 65 to 134 meters, 65 to 173 meters in the line 3, and in the cross section of line 3 and line 4. While in the line 1, another chamber is found within the depth of 12.5 to 40 meters. It is expected that the underground river is flowing to the south because of the chamber in line 3 and line 4 are lower than line 2.

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“…Once gravity signal is a result of all possible effects (Telford et al, 1990;Blakely, 1996), a very careful data processing is required. They include: (i) residual anomalies, usually the main goal in a study; (ii) longer-wavelength regional components from deep-large geological sources; and (iii) shorter-wavelength noise from errors and/or shallow sources (Robinson, 1988;Telford et al, 1990;Hinze et al, 2013). Therefore, the separation of regional and residual data becomes necessary.…”

Section: Introductionmentioning

confidence: 99%

Residual Gravity Anomaly of Brazilian Marajó Basin Using Crustal Modeling: Identifying Structural and Tectonic Features

Santos-Junior¹,

Martins²,

Ribeiro‐Filho³

2019

Braz J Geophys

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ABSTRACT. Dealing with gravity data at complex geological environments is a hard task because regional and residual anomalies are unknown. Due to the fact former techniques do not apply geologic information for separating gravity data, interpretation could lead to common mistakes. In order to allow a better interpretation at sedimentary basins, we applied a different approach for separating regional and residual anomalies for gravity data: the crustal modeling procedure. This approach consists on discretizing the Earth’s crust in prismatic cells and calculating the predicted signal due to Earth’s crust. We set horizontal dimensions of each prism, while the top and bottom are defined by Earth’s topography and depth of crust-mantle boundary, usually called Moho. Additionally, when the predicted signal is calculated, the residual anomaly is obtained from simple subtraction. We applied our methodology at Marajó basin (North, Brazil), where previous geological studies identified a system of faults and grabens, also known as Marajó graben system. Moreover, our results are well compared with previous interpretation through the seismic method, exemplifying the approach’s quality and efficiency. We believe, therefore, that the crustal modeling approach should be considered for studying any Brazilian sedimentary basin and other interesting areas.Keywords: crustal modeling; residual gravity anomaly; Marajó basin; Marajó graben system. RESUMO. Interpretar dados gravimétricos em ambientes geológicos de grande complexidade é uma tarefa difícil de ser realizada, visto que anomalias regionais e residuais são desconhecidas. Devido ao fato de que conhecidas técnicas de separação regional-residual não consideram informações geológicas, a interpretação final pode fornecer resultados equivocados. A fim de permitir uma melhor interpretação nas bacias sedimentares, aplicamos uma diferente abordagem para separação regional-residual: a modelagem crustal. Esta abordagem consiste em discretizar a crosta terrestre em células prismáticas e calcular o sinal regional predito. Definimos as dimensões horizontais de cada prisma, enquanto o topo e a base são definidos pela topografia e profundidade da interface crosta-manto, respectivamente. Após o cálculo do sinal predito, a anomalia residual é calculada via subtração. Aplicamos nossa metodologia na bacia do Marajó (região Norte, Brasil), onde estudos geológicos identificaram um sistema de falhas e grábens, definido por sistema de gráben do Marajó. Nossos resultados apresentam boa correspondência quando comparados com interpretações realizadas via método sísmico, o que exemplifica a qualidade e eficiência da nossa proposta. Acreditamos, portanto, que esta abordagem de modelagem crustal deve ser considerada para o estudo de qualquer bacia sedimentar brasileira e de outras regiões de interesse.Palavras-chave: modelagem crustal; anomalia gravimétrica residual; bacia do Marajó; sistema de gráben do Marajó.

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Basic Geophysics

Cited by 7 publications

References 0 publications

Pemodelan Dan Analisa Struktur Bawah Permukaan Daerah Prospek Panasbumi Kepahiang Berdasarkan Metode Gayaberat

Pemodelan Dan Analisa Struktur Bawah Permukaan Daerah Prospek Panasbumi Kepahiang Berdasarkan Metode Gayaberat

Identification Karst Underground River System in Gebangharjo Village, Pracimantoro using Tomography Resistivity Methode with Wenner-Schlumberger’s Configuration

Residual Gravity Anomaly of Brazilian Marajó Basin Using Crustal Modeling: Identifying Structural and Tectonic Features

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