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"The study area has been subjected to intense fracturing or brittle deformation resulting in five main trends of lineaments and faults, i.e. (1) the Group A (the Perantanaan Fault Group) with a mean of direction N95°E/ N275°E, (2) the Group B (the Gorontalo Fault Group) with a mean of direction N125°E/ N305°E, (3) the Group C (the Paleleh Fault Group) with a mean of direction 165°E /N335°E, (4) the Group D (the Randangan Fault Group) with a mean of direction N25°E/ N205°E and (5) the Group E (the Kuandang Fault Group) having a mean of trend of N55°E/ N235°E. The complexity of structural pattern in the study area has been interpreted to be due to stress system evolution during Neogene - Pleistocene. The changing stress system orientation has reactivated the preexisting faults of the five groups with different sense of movements from the older deformation.The nearly E-W trending lineaments of Group A or the Perantanaan Fault Group coincide with trend of the long axis of ridges and valleys or depression areas which are covered by volcanic rocks, lake deposits, and alluvium of Quaternary age. This group of structures was presumably developed as reverse or thrust faults during Late Neogene which later on to have beem reactivated as normal faults due to extensional tectonics of the North Sulawesi area during Plesitocene."

"ABSTRAKDalam usaha mendongkrak perekonomian di daerah Jawa dan Sumatra,Pemerintah berencana membangun Jembatan Selat Sunda (JSS) guna melancarkantransportasi arus barang antarkedua pulau tersebut. Dibutuhkan berbagai macamdata untuk menentukan teknologi jembatan yang akan digunakan, salah satunyaadalah data geoid. Penelitian ini bertujuan untuk memetakan geoid di wilayahSelat Sunda dan sekitarnya dari data anomali gayaberat free-air hasil pengukurandan model geopotensial dengan menerapkan metode remove-restore. Digunakandata gayaberat sejumlah lebih dari 5,672 titik yang tersebar di darat dan laut sertamodel geopotensial global EGM2008. Undulasi geoid didapatkan dari hasilintegrasi Stokes pada kombinasi anomali gayaberat free-air dan modelgeopotensial. Hasil perhitungan menunjukkan undulasi geoid yang ada di daerahpenelitian memiliki nilai yang bervariasi dengan nilai minimum -2.06 m danmaksimum 13.29 m. Sementara, bagian Tenggara (SE) Pulau Sumatra dan BaratLaut (NW) Pulau Jawa memiliki undulasi geoid yang sama. Hasil undulasi geoidtersebut dapat digunakan sebagai bidang referensi untuk menentukan ketinggianvertikal atau tinggi orthometrik.

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ABSTRACTIn an effort to boost the economy in the areas of Java and Sumatra, the

Government plans to build the Sunda Strait Bridge (Jembatan Selat Sunda) to

expedite the flow of goods transport between the two islands. It takes a wide

range of data to determine a bridge technology that will be used, one of which is

geoid data. This study aims to map the geoid in the vicinity of the Sunda Strait

from gravity data measurements which is free-air anomaly and geopotential model

by applying remove-restore method. More than 5.672 points gravity data were

used spread over land and sea as well as models of global geopotensial EGM2008.

Geoid undulations obtained from the Stokes integration on a combination of freeair

gravity anomaly and geopotential models. Calculation results show that geoid

undulations in the study area has a value that varies with the minimum value of

-2.06 m and a maximum of 13.29 m. Meanwhile, the Southeast (SE) island of

Sumatra and Northwest (NW) Java has the same geoid undulations. The results of

geoid undulations can be used as a reference field to determine the vertical height

or orthometric height."

"Kawasan Industri Pulogadung termasuk kawasan yang mengalami pembatasan penggunaan air tanah. Untuk menjaga ketersediaan air tanah dan mencegah eksploitasi yang berlebihan, penting untuk mengidentifikasi potensi air tanah agar pemanfaatannya dapat berlangsung secara berkelanjutan. Penelitian ini menggunakan metode geolistrik resistivitas dan penerapan hukum archie. Pengukuran geolistrik terdiri dari 4 lintasan menggunakan konfigurasi Wenner karena mampu untuk pengukuran yang lebih dangkal dan memiliki sensitivitas yang baik terhadap variasi resistivitas horizontal, lalu dikaitkan dengan nilai resistivitas dari sampel tanah. Selanjutnya mengukur konduktivitas listrik dari 4 sampel air tanah, untuk menghitung faktor formasi yang diperoleh dari penerapan hukum archie untuk menunjukkan hubungan antara resistivitas batuan yang sepenuhnya jenuh air (resistivitas formasi basah) dengan resistivitas air formasi. Hasil dari pengolahan data mendapatkan nilai resistivitas berkisar 1.72 – 96.2 Ω.m dan nilai F factor berkisar 0- 10 mohs. Untuk mengetahui jenis akuifer dari data resistivitas, kemudian dilakukan korelasi antara penampang 2D resistivitas dengan penampang F factor. Hasil dari korelasi menunjukkan terdapat lapisan akuifer bebas (unconfined aquifer) diduga adanya pasiran yang dapat menyimpan dan mengalirkan air dengan nilai resistivitas sekitar < 9.64 Ω.m dan kondisi akuifer buruk di lapisan akuifer dengan nilai F factor < 2 mohs. Potensi akuifer menyebar pada kedalaman 5-20 m, dengan sebaran akuifer merata pada lintasan GL24, lintasan GL25 menyebar kearah barat daya, lintasan GL26 dan GL28 menyebar kearah timur laut.

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Pulogadung Industrial Estate includes areas that experience restrictions on groundwater use. To maintain groundwater availability and prevent over-exploitation, it is important to identify groundwater potential to sustain its utilization. This research uses the resistivity geoelectric method and the application of Archie's law. Geoelectric measurements consisted of 4 passes using the Wenner configuration because it is capable of shallower measurements and has good sensitivity to horizontal resistivity variations, then associated with the resistivity value of the soil sample. It was further measuring the electrical conductivity of the 4 groundwater samples, to calculate the formation factor obtained from applying Archie's law to show the relationship between the resistivity of fully water-saturated rock (resistivity of wet formation) and the resistivity of formation water. Data processing results obtained resistivity values ranging from 1.72 - 96.2 Ω.m and F factor values ranging from 0-10 mohs. To determine the type of aquifer from the resistivity data, a correlation between the 2D resistivity cross-section and the F factor cross-section is then made. The results of the correlation show that there is an unconfined aquifer layer, suspected to be a sandy layer that can store and drain water with a resistivity value of < 9.64 Ω.m and poor aquifer conditions in the aquifer layer with an F factor value of < 2 mohs. The potential aquifer spreads at a depth of 5-20 m, with the distribution of aquifers evenly distributed on the GL24 track, GL25 track spreads towards the southwest, and GL26 and GL28 track spreads towards the northeast."