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Suatu wilayah yang memiliki kondisi geologi yang sama dapat memberikan respon yang berbeda terhadap efek getaran tanah, bergantung pada karakteristik batuan penyusun formasi di wilayah itu. Fenomena ini disebut site effect. Spektra ambient noise yang diperoleh dari pengukuran mikrotremor dapat digunakan untuk menentukan respon suatu site khususnya frekuensi dominan lapisan sedimen. Respon frekuensi ini berhubungan dengan ketebalan lapisan sedimen. Berdasarkan formasi geologinya, Kota Palu tersusun atas endapan aluvium berumur holosen yang menjadi sedimen penyusun paling muda di wilayah tersebut. Penelitian ini bertujuan untuk memperoleh estimasi ketebalan lapisan sedimen di tiga titik pengukuran mikrotremor dari nilai spektrum horizontal to vertical () yang merempresentasi frekuensi dominan (f0) serta kecepatan gelombang geser (Vs) lapisan sedimen. Hasil yang diperoleh memperlihatkan nilai frekuensi dominan tanah f0

This research was carried out in Lappae, Bone Regency, an area that was supposedly having difficulty with water sources, remarkably in the dry season. This research aims to determine the water source location and the type of aquifer layer using the Geoelectric resistivity method with the Wenner-Schlumberger configuration. The results showed that the aquifer zone, which was thought to be a sandstone layer, was located at various depths ranging from 25-60 meters with a resistivity value of 25-150 Ωm. Meanwhile, bedrock layers are limestone with a resistivity value of 300 - 1200 Ω m. Based on the type of aquifer layer in the area, namely sandstone and limestone, the aquifer can be classified as a free aquifer because it only has a waterproof layer underneath

The Biromaru area is located on the Palu-Koro fault line so it is very prone to earthquake shocks. This area is one of the zones that experienced destruction and caused heavy damage to settlements and various infrastructure. In an effort to mitigate seismic disasters, it is necessary to carry out studies related to rock dynamics in the area. This study was conducted with the aim of knowing the dynamic characteristics of rocks using micro tremor data. The dynamic characteristics of the rock are determined based on several parameters, including the average speed of the shear waves at a depth of 30 meters, and amplification factor. The results showed that this area has a type of still rock structure. Thus, the study area has a high susceptibility to damage due to earthquakes.

The earthquake of September 28, 2018, has caused changes in the structure of subsurface rocks in the Palu Valley of Central Sulawesi. Differences in rock structure occur due to deformation by seismic waves generated by the earthquake. Analysis of structural changes and strain of rock carrying surfaces is performed using the geomagnetic method. This study aims to map the fractures and local faults below the surface after the earthquake. Magnetic measurements are carried out using the Proton Precision Magnetometer with several measuring points of more than 856 stations. The measured magnetic data was corrected to obtain the total magnetic field intensity. Euler deconvolution is then performed to estimate depth and estimate subsurface, structure models. The results showed that the study area was identified by local fault and fractures below the surface, with depths ranging from 0 to 2000 meters. Local fractures and fractures formed are generally north-south trending following the Palu Koro fault.

Sulawesi has complex tectonic, signed by fault like Palu-Koro Fault, Walennae Fault, Matano Fault, Batui Fault and others. Mostly fault located on Southern Sulawesi and it caused earthquake in Southern Sulawesi. The aim at this study is to learn fault characteristic by focal mechanisms in Southern Sulawesi. Focal mechanism is method to analyze movement mechanism based on first polarity of earthquake P-wave to determine fault caused by earthquake fault which caused earthquake. In this study is located on Southern Sulawesi with 2°26’ - 6°50’ S and 118° -123°50’ E during 1976 – 2016 from Global-CMT. The hypocenter plotted to identify location of the earthquake. The fault parameter, such as strike, dip and slip plotted to interpret focal mechanism of fault caused earthquake. The data plotted by GMT to get distribution focal mechanism on Southern Sulawesi which shown 46 beach-balls. For interpretation, it divided into 3 regions; region I show oblique-reverse fault related to Makassar Thrust. Region II show left-strike-slip fault related to Matano Fault activity. Region I shows Paternoster fault and earthquake by sea spreading at Bone Gulf; Walennae Fault with strike-slip fault activity. Region III the most complex region show normal fault related to Tolo Fault activity. Region III shows Kolaka fault with strike-slip fault activity and earthquake by interaction between micro-continent observed as oblique-reverse fault activity.. The focal mechanism in this study effectively to observe the fault activity which can be used as guided for earthquake mitigation.

Metode geolistrik resistivitas merupakan salah satu metode geofisika dengan uji tidak merusak (non-destructive test) sifat fisik asli tanah atau batuan. Penginjeksian arus listrik pada permukaan tanah merupakan ciri dari metode ini, yang kemudian diikuti dengan pembacaan beda potensial melalui sepasang elektroda lainnya. Konfigurasi elektroda arus dan potensial dikondisikan berdasarkan konfigurasi Werner-Schlumberger. Akuisisi data diperoleh dari 3 lokasi yang berbeda untuk memperoleh pemahaman tentang struktur bawah permukaan yang lebih baik. Interpretasi terhadap material lapisan tanah dilakukan dengan memanfaatkan penampang resistivitas setelah dilakukan pengolahan data menggunakan software Res2dinv. Hasil yang diperoleh adalah variasi nilai resistivitas dan interpretasi lapisan tanah untuk masing masing lokasi pengambilan data.

A boundary element method is utilized to find numerical solutions to boundary value problems of trigonometrically graded media governed by a spatially varying coefficients anisotropic-diffusion convection equation. The variable coefficients equation is firstly transformed into a constant coefficients equation for which a boundary integral equation can be formulated. A boundary element method (BEM) is then derived from the boundary integral equation. Some problems are considered. The numerical solutions justify the validity of the analysis used to derive the boundary element method with accurate and consistent solutions. A FORTRAN script is developed for the computation of the solutions. The computation shows that the BEM procedure elapses very efficient time in producing the solutions. In addition, results obtained from the considered examples show the effect of the anisotropy of the media on the solutions. An example of a layered material is presented as an illustration of the application.

Indonesia is one of the tropical countries that only has two seasons, namely the dry season and the rainy season. The prolonged dry season caused the villagers in Sampakang having difficulties in obtaining clean water sources. This research conducted in Sampakang, Maros, Indonesia aims to obtain groundwater that can be used as a spring for villagers. The research was conducted using the Geoelectrical Resistivity Method Wenner Schlumberger configuration with a total trajectory of 56 m. The results of the analysis showed that the soil structure consists of shallow groundwater and the RMS error is 2.2%. Where the thickness of the aquifer layer is 9 m and was found at a depth of 2.5 m-11.5 m. Aquifer layer in the form of alluvium deposits with a resistivity value of about 100 Ωm.

A boundary element method is derived for the solution of static elasticity problems of quadratically graded isotropic materials. Some particular problems are considered to illustrate the application of the method.

A boundary element method is utilized to find numerical solutions to boundary value problems of exponentially graded media governed by a spatially varying coefficients anisotropic-diffusion convection equation. The variable coefficients equation is firstly transformed into a constant coefficients equation for which a boundary integral equation can be formulated. A boundary element method (BEM) is then derived from the boundary integral equation. Some problems are considered. The numerical solutions justify the validity of the analysis used to derive the boundary element method with accurate and consistent solutions. A FORTRAN script is developed for the computation of the solutions. The computation shows that the BEM procedure elapses very efficient time in producing the solutions. In addition, results obtained from the considered examples show the effect of the anisotropy of the media on the solutions. An example of a layered material is presented as an illustration of the application.

The International Conference on Geoscience (ICoGeS) is organized by the Study Program of Geophysics, Faculty of Mathematics and Natural Sciences, Hasanuddin University, Indonesia in cooperation with Indonesian Association of Geophysicist (HAGI), Indonesian Student Association of Geophysics–V Region (HMGI), Society of Exploration Geophysicists (SEG) Hasanuddin University Student Center, Society of Petroleum Engineer (SPE) Hasanuddin University Student Chapter, European Association of Geoscientist & Engineers (EAGE) Hasanuddin University Student Chapter. The objectives are to bring together scholars, researchers and experts from diverse areas of backgrounds and applications. A special goal of the conference is to promote an interaction and exchange of knowledge and experiences among scientists and practitioners especially in geoscience theoretical and experimental studies. This 1st ICoGes was held in Makassar (Capital city of South Sulawesi Province) on 1st – 2nd of November 2018 with the main theme “Geoscience and Technology for Better Environment”. We have six keynote speakers coming from Terra Australis Geophysica Pty. Ltd. Australia (Mr. Koya Suto), Hasanuddin University Indonesia (Prof. Dr. Dadang A. Suriamihardja), Bandung Institute of Technology Indonesia (Prof. Satria Bijaksana, PhD), Universiti Malaysia Kelantan Malaysia (Prof. Madya Dr. Aweng A/I Eh Rak), Universiti Malaysia Kelantan Malaysia (Dr. Arham Muchtar A. Bahar), Bandung Institute of Technology Indonesia (Dr. David P. Sahara). Erfan Syamsuddin (Chairman) and Moh. Ivan Azis (Editor in Chief) * The 1st International Conference on Geoscience (ICoGes 2018) Publication Geophysics Study Program Faculty of Mathematics and Natural Sciences Hasanuddin University Tamalanrea, Makassar, 90245, Indonesia *E-mail: mohivanazis@yahoo.co.id

This paper presents a case study of reconstructing past landslide failure models in a napal geological formation by undertaking a series of geoelectrical tomographies and geotechnical bor-SPT surveys. Study area is located in the National Artery Road 135 Kilometres, Majene – Mamuju, West Sulawesi. Geological formation found in the area is Napal Pambauang Formation. Massive ground movement is obviously detected in the area, and several landslide events have been occured in the last 10 years. In order to derive an effective technnique of mitigating the landslide in the area, past landslide failure models are needed to reconstruct. Therefore, 2D geoelectric tomographies survey combined several geotechnical bors were undertaken. A Framework of geophysics and geotechnical investigations was developed and implemented. The results show that slope failure models can be mapped, following unique patterns in the subsurface resistivity models. The finding slope failure models are well agreement with successive scarp patterns founded in the slope area. Past and recent landslides and future landslide are derived and this can be employed to design effective landslide mitigation strategies.

This field research is located in a geothermal area expressed by the existence of hot springs. A complex geological structure has shown that the area was in the Palu-Koro fault. The purpose of the study is to achieve a model of subsurface of the area using data collected over gravity data and magnetic data. The two Data were compared in order to validate the models. Furthermore 2-dimensional modeling was performed using two gravity and magnetic lines by means of geo-sys software from Geosoft. The results of the models have a bit difference response by means of the existence of residual indicator that expected as a geothermal reservoir due to fault activity

Talang Akar Formation is a proven hydrocarbon source rock in South Sumatra basin. The formation contains dominant shale at the top, with some sandstone interbeds. This study uses 3 crude oil sample and 10 well-cutting obtained from two well (SMT-1 & SMT-2) in Prabumulih oil field. We used biomarkers and carbon isotopes (δ13C) data to determine the paleodepositional environment of Talang Akar Formation. The biomarkers data were obtained from gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS) analysis of normal alkanes, isoprenoids, triterpene, and steranes. Carbon isotopes (δ13C) include saturated and aromatic fractions. The pristine (Pr) to phytane (Ph) ratio is a good indicator of the depositional environment. Higher values of Pr/Ph ratio i.e. ≥3.0 indicate oxidizing conditions i.e. terrestrial while lower values in the range of 1.0-3.0 suggests siliciclastic-dominated marine conditions. However, very low values i.e. ≤ 1.0 indicate reducing conditions or fresh and brackish water conditions. The results in this research show that Pr/Ph ratios range from 7.90-16.66, characteristic of high wax crude oils, primarily originated in fluviatile and deltaic environment containing a significant amount of terrestrial organic matter. Similarly, the resultant ratios of Pr/n-C17 and Ph/n-C18 in SMT-1 and SMT-2 wells range from 0.91-10.72 and 0.11-1.29 respectively, which reflect that most of kerogen was derived from humic source and tend towards an oxidative environment of deposition. Cross-plot of carbon-13 isotopes (δ13C) shows saturated versus aromatic fraction. The resultant plot indicate a deltaic to marginal marine environment for SMT-2 well and a more marine environment for SMT-1 well. The oil/source rock correlation analysis using biomarker data shows that the oils in Prabumulih field is correlated with the oils in source rock of Talang Akar Formation. This study concludes that the source rock contains abundant humic organic matter that was deposited in a transitional (Fluvio-deltaic) to marginal marine environment under oxic conditions.

Focal mechanism used on tectonic regime study which is fault type determination in South Sulawesi. Fault parameter data consist of strike, dip and rake determined based on the first arrival polarity at earthquake waveform manually picked. The result were several beach-ball diagrams on 2010 – 2017 in South Sulawesi. Three reverse-oblique types, normal-oblique type and normal type caused by Palu-Koro Fault. In other pattern, there were Makassar Thrust: reverse type, two strike-slip types and four normal-oblique types. Walennae Fault signed by reverse type. Two reverse-oblique types and two normal-oblique types affected by Parang Loe Fault. All of them showed tectonic regime nowadays in South Sulawesi is complex.

Eksplorasi dan eksploitasi di Indonesia saat ini masih terfokus pada energi konvensional hidrokarbon dibandingkan energi nonkonvensional hidrokarbon seperti gas serpih. Gas serpih adalah salah satu energi nonkonvensional yang kaya material organic dan mencapai kematangan, pada kondisi dan tipe tertentu mampu berfungsi sebagai reservoir minyak dan gas. Jendela awal kematangan pada kedalaman 1200-2200 m dan kategori tipe kerogen II/III menghasilkan minyak dan gas.

Telah dilakukan penelitian untuk mengidentifikasi sebaran bijih besi di Kecamatan Walenrang, Kabupaten Luwu, Sulawesi Selatan dengan menggunakan metoda geolistrik tahanan jenis konfigurasi Wenner-Schlumberger. Hasil survey resistivity berupa penampang 2-D dan blok model 3-D yang memberikan informasi mengenai sebaran bijih besi, dimana penyebaran terbesar berada di sebelah barat daerah penelitian dengan arah timur laut - barat daya. Data resistivitas dari penampang resistivitas 2-D yang diperoleh dari pengukuran lintasan 1 sampai dengan pengukuran lintasan 4 di lapangan yaitu zona lapisan bijih besi magnetite berada pada resistivitas ρ < 40 Ωm, zona pelapukan batuan andesit dengan resistivitas 40 Ωm < ρ < 250 Ωm dan zona batuan basalt dengan resistivitas tinggi ρ > 250 Ωm yang sesuai dengan yang ditemukan bagian barat daerah penelitian yaitu di lembah buntu Mario dan buntu Sikuku hingga ke buntu Andulan bagian utara ada boulder magnetis yang tersebar di aliran sungai lamasi diperkirakan berasal dari zona potasik.