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https://doi.org/10.31227/osf.i...
Article . 2018 . Peer-reviewed
License: CC BY
Data sources: Crossref
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Open Science Framework
Preprint . 2018
Data sources: Datacite
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Inversi Resistivitas 3-D Menggunakan Metode Elemen Hingga dan Adjoint State

Authors: Agah D. Garnadi; mn indro; Mochamad Tito Julianto; Sri Nurdiati; Febru mochamad februarianto;

Inversi Resistivitas 3-D Menggunakan Metode Elemen Hingga dan Adjoint State

Abstract

Metode resistivitas merupakan salah satu metode eksplorasi yang memanfaatkan satu pasang elektroda yang menginjeksikan arus ke bumi dan memanfaatkan sepasang atau lebih elektroda lainnya untuk mengukur beda potensial listrik. Beda potensial yang terjadi merupakan fungsi tak-linear dari distribusi resistivitas bawah permukaan yang dinyatakan oleh persamaan differensial parsial (PDP) eliptik jenis Poisson.Inversi dari potensial terukur adalah mendapatkan distribusi resistivitas bawah permukaan yang dinyatakan oleh koefisien PDP. Escript adalah sebuah solver berbasis Metode Elemen Hingga (MEH) dengan lingkungan pemrograman berbasis Python yang user friendly. Dengan menggunakan MEH bangun struktur geologi dan topografi yang tak beraturan dengan mudah terakomodasi.Untuk masalah resistivitas, Escript mengimplementasikan pendekatan potensial sekunder, dimana PDP di dekomposisi menjadi potensial primer yang diakibatkan oleh sumber arus dan potensial sekunder yang diakibatkan oleh perubahan akibat adanya distribusi resistivitas. Potensial primer dihitung secara analitik dan masalah syarat batas untuk potensial sekunder dicari solusinya menggunakan MEH nodal. Pendekatan ini menghapuskan singularitas yang diakibatkan oleh sumber arus dan memberikan model resistivitas 3D yang lebih akurat.Untuk menyelesaikan masalah inversi, Escript menggunakan strategi 'first optimize then discretize' menggunakan skema quasi-Newton dalam bentuk metode limited-memory Broyden-Fletcher-Goldfarb-Shanno (L-BFGS). Evaluasi cost-function memerlukan PDP sekunder untuk setiap pasang arus sumber dan solusi dari PDP adjoint-state yang terkait dengan gradien cost-function terhadap resistivitas bawah permukaan. Hessian dari suku regularisasi digunakan sebagai pre-conditioner, yang memerlukan solusi PDP tambahan untuk setiap langkah iterasi. Solusi PDP tambahan ini ternyata dengan natural dapat dirumuskan dengan mudah dalam kerangka MEH.Diperlihatkan sejumlah contoh numerik berasal dari survey geolistrik sintetik, antara lain skema Schlumberger.

Keywords

Engineering, Applied Mathematics, FOS: Mathematics, Physical Sciences and Mathematics, Partial Differential Equations, Numerical Analysis and Computation, Environmental Sciences

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selected citations
These citations are derived from selected sources.
This is an alternative to the "Influence" indicator, which also reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).
BIP!Citations provided by BIP!
popularity
This indicator reflects the "current" impact/attention (the "hype") of an article in the research community at large, based on the underlying citation network.
BIP!Popularity provided by BIP!
influence
This indicator reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).
BIP!Influence provided by BIP!
impulse
This indicator reflects the initial momentum of an article directly after its publication, based on the underlying citation network.
BIP!Impulse provided by BIP!
0
Average
Average
Average
hybrid