2.5D Forward Modeling Dan 3D Inverse Modeling Pada Data Aeromagnetik Untuk Identifikasi Geometri Dyke di Ngunguru, Whangarei District, New Zealand

Aulia, Zakia Rahma (2026) 2.5D Forward Modeling Dan 3D Inverse Modeling Pada Data Aeromagnetik Untuk Identifikasi Geometri Dyke di Ngunguru, Whangarei District, New Zealand. Other thesis, Institut Teknologi Sepuluh Nopember.

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Abstract

Ngunguru merupakan bagian dari Whangarei District, New Zealand terletak pada sistem half graben yang berarah NNW – SSE dan dipengaruhi oleh keberadaan sesar Mezosoik Harbour Fault. Kondisi tektonik ini dapat menjadi jalur bagi magma untuk naik ke permukaan yang membentuk dyke. Penelitian ini bertujuan untuk mengidentifikasi pola anomali magnetik dari data Total Magnetic Intensity/Anomaly (TMI) yang didapatkan dari studi aeromagnetik, menentukan parameter geometri dyke melalui pendekatan 2.5D forward model dan 3D inverse model, serta menjelaskan model dyke yang representatif dengan geologi regional. Hasil forward model didapatkan geometri dyke berbentuk sub vertikal dengan kedalaman ~100–156 m, lebar ~106–150 m, kemiringan ~31°–46. Inversi 3D dikerjakan dengan parameter ℓp (1,1,1,1) dalam dua mode yang berbeda: vektor (magnetic vector inversion atau MVI) dan skalar (magnetic scalar inversion atau MSI). Dari hasil MSI didapatkan geometri dyke berbentuk tabular dengan dipping curam dengan nilai suseptibilitas 0.04–0.06SI, sedangkan hasil MVI didapatkan nilai magnetisasi sebesar 0.04 – 0.08 A/m, dengan inklinasi sebesar -90° hingga -60°, dan deklinasi -180° hingga 0°. Dyke yang tersusun atas mikrodiorit merekam magnetisasi remanen pada saat pembekuan dalam kondisi geomagnet normal, sehingga Natural Remanenent Magnetization sejajar dengan medan geomagnet International Geomagnetic Reference Field. Kondisi tersebut menyebabkan hasil MVI mendekati arah IGRF yang mengindikasikan bahwa dyke didominasi oleh komponen induksi. Integrasi ketiga pendekatan pemodelan menunjukkan bahwa dyke di wilayah Ngunguru merupakan tubuh intrusi tabular sub – vertikal dengan dipping ke arah northeast yang sesuai dengan litologi mikrodiorit dan tektonik regional.
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Ngunguru is part of the Whangarei District in New Zealand and is located within a NNW–SSE-trending half-graben system influenced by the Mesozoic Harbour Fault. These tectonic conditions may serve as pathways for magma to rise to the surface, forming dykes. This study aims to identify magnetic anomaly patterns from Total Magnetic Intensity/Anomaly (TMI) data obtained from an aeromagnetic survey, determine dyke geometric parameters using a 2.5D forward model and a 3D inverse model, and describe a dyke model representative of the regional geology. The forward modelling results indicate a sub-vertical dyke geometry with a depth of ~100–156 m, a width of ~106–150 m, and an inclination of ~31°–46°. The 3D inversion was performed using ℓp parameters (1, 1, 1, 1) in two different modes: vector (magnetic vector inversion or MVI) and scalar (magnetic scalar inversion or MSI). The MSI results revealed a tabular dyke geometry with a steep dip and susceptibility values of 0.04–0.06 SI, while the MVI results yielded magnetisation values of 0.04–0.08 A/m, with an inclination ranging from -90° to -60° and a declination from -180° to 0°. The dyke, composed of microdiorite, recorded its remanent magnetisation at the time of solidification under normal geomagnetic conditions so that the natural remanent magnetisation is parallel to the International Geomagnetic Reference Field (IGRF). These conditions cause the MVI results to align closely with the IGRF direction, indicating that the dyke is dominated by an inductive component. The integration of the three modelling approaches indicates that the dyke in the Ngunguru area is a subvertical tabular intrusive body dipping to the northeast, consistent with the microdiorite lithology and regional tectonics.

Item Type:	Thesis (Other)
Uncontrolled Keywords:	Aeromagnetik, Anomali Magnetik, Dyke, Forward Modeling, Inversi Skalar, Inversi Vektor, Ngunguru. Aeromagnetic, Magnetic Anomaly, Dyke, Forward Modeling, Scalar Inversion, Vector Inversion, Ngunguru.
Subjects:	Q Science > QE Geology Q Science > QE Geology > QE601 Geology, Structural
Divisions:	Faculty of Civil, Planning, and Geo Engineering (CIVPLAN) > Geophysics Engineering > 33201-(S1) Undergraduate Thesis
Depositing User:	Zakia Rahma Aulia
Date Deposited:	22 Jun 2026 00:47
Last Modified:	22 Jun 2026 00:47
URI:	http://repository.its.ac.id/id/eprint/133902

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