Penerapan Metode Combined-Inversion pada Data Resistivitas 2D Konfigurasi Dipole-Dipole dan Wenner-Schlumberger di Daerah Karst Desa Gedompol, Kabupaten Pacitan

Padlilah, Muthi’ul (2021) Penerapan Metode Combined-Inversion pada Data Resistivitas 2D Konfigurasi Dipole-Dipole dan Wenner-Schlumberger di Daerah Karst Desa Gedompol, Kabupaten Pacitan. Undergraduate thesis, Institut Teknologi Sepuluh Nopember.

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Abstract

Kawasan karst Pacitan tersusun oleh batuan karbonat yang mudah larut akibat adanya proses karstifikasi. Batuan karbonat ini memiliki banyak rongga percelahan yang menjadikan drainase bawah permukaan lebih berkembang dalam bentuk aliran sungai bawah permukaan. Penelitian dilakukan di Desa Gedompol, Kecamatan Donorojo, Kabupaten Pacitan dengan menggunakan metode geolistrik resistivitas konfigurasi Dipole-Dipole dan Wenner Schlumberger. Akuisisi data dilakukan pada 3 lokasi berbeda dengan menggunakan kedua konfigurasi sehingga dihasilkan 6 lintasan yaitu Dipole-1, Dipole-2, Dipole-3, WS-1, WS-2, dan WS-3 yang memiliki panjang lintasan 230 meter. Penerapan kedua konfigurasi tersebut juga perlu didukung oleh metode pengolahan yang tepat. Adanya kompleksitas kawasan karst menjadi salah satu pertimbangan dalam menentukan metode pengolahan yang sesuai. Maka dari itu, digunakan metode Combined Inversion untuk dapat menentukan nilai parameter inversi yang sesuai serta mengetahui distribusi nilai resistivitas 2D yang dihasilkan sehingga anomali sungai bawah permukaan dapat teridentifikasi. Penerapan combined inversion paling optimal ditunjukkan pada penampang konfigurasi Dipole-Dipole dikarenakan damping factor yang digunakan untuk menghasilkan absolute error terkecil adalah 0,05 dan 0,1. Hal ini disebabkan distribusi data yang dihasilkan cukup baik sehingga hanya diperlukan nilai damping factor yang kecil untuk meredam noise. Selain itu, adanya karakteristik data yang cenderung stabil menghasilkan iterasi yang lebih sedikit daripada konfigurasi Wenner-Schlumberger. Sementara itu, anomali sungai bawah permukaan teridentifikasi pada penampang 2D konfigurasi Dipole-Dipole di kedalaman 5 – 35 meter dengan nilai resistivitas berkisar antara 1,26 – 12,4 Ω.m. Anomali ini berbentuk rongga akibat pengaruh sistem perkembangan sungai bawah permukaan yang termasuk ke dalam zona vadose. Anomali sungai bawah permukaan ini tervalidasi oleh penampang 1D VES dan teridentifikasi pada zona akuifer. ===================================================================================================== The Pacitan karst area is composed of carbonate rocks that soluble easily due to the karstification process. This carbonate rock has many crevices that make subsurface drainage more developed and formed subsurface river flows. The research was conducted in Gedompol Village, Donorojo District, Pacitan Regency using the geoelectrical resistivity method of Dipole-Dipole and Wenner Schlumberger configurations. Data acquisition was carried out at 3 different locations using both configurations resulting in 6 lines, namely Dipole-1, Dipole-2, Dipole-3, WS-1, WS-2, and WS-3 with track length of 230 meters. The application of two configurations also needs to be supported by the right processing method. The complexity of the karst area was one of the considerations in determining the appropriate processing method. Therefore, the Combined Inversion method is used to determine the appropriate inversion parameter values and determine the distribution of resulting 2D resistivity values that subsurface river anomalies can be identified. The most optimal application of combined inversion is shown in the cross-section of the Dipole-Dipole configuration, because the damping factor produces the smallest absolute error which are 0.05 and 0.1. This is because the distribution of resulting data is quite good, so only the smallest damping factor value is needed to reduce noise. In addition, the existence of data characteristics that tends to be stable, produces fewer iterations than Wenner-Schlumberger configuration. Meanwhile, subsurface river anomalies are identified in a 2D cross-section of the Dipole-Dipole configuration at depth of 5 – 35 meters with resistivity values ranging from 1.26 – 12.4 Ω.m. This anomaly is in the form of a cavity due to the influence of the subsurface river development system which is included in the vadose zone. This subsurface river anomaly was validated by the 1D VES section and identified in the aquifer zone.

Item Type: Thesis (Undergraduate)
Uncontrolled Keywords: Combined-Inversion, Karst, Konfigurasi Dipole-Dipole, Konfigurasi Wenner-Schlumberger, Sungai Bawah Permukaan, Dipole-Dipole Configuration, Subsurface River, Wenner-Schlumberger Configuration
Subjects: G Geography. Anthropology. Recreation > GB Physical geography > GB1003.2 Groundwater.
G Geography. Anthropology. Recreation > GB Physical geography > GB600 Karst conservation.
Q Science > QE Geology > QE471 Sedimentary rocks. Sedimentology
T Technology > T Technology (General) > T57.5 Data Processing
Divisions: Faculty of Civil, Planning, and Geo Engineering (CIVPLAN) > Geophysics Engineering > 33201-(S1) Undergraduate Thesis
Depositing User: Muthi'ul Padlilah
Date Deposited: 26 Aug 2021 06:14
Last Modified: 26 Aug 2021 06:14
URI: https://repository.its.ac.id/id/eprint/89480

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