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IJOG : Indonesian Journal on Geoscience

IJOG
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Published by Geological Agency of Indonesia

ISSN : 23559314 EISSN : 23559306 DOI : -

Core Subject : Science,

Earth & Planetary Sciences

The spirit to improve the journal to be more credible is increasing, and in 2012 it invited earth scientists in East and Southeast Asia as well as some western countries to join the journal for the editor positions in the Indonesia Journal of Geology. This is also to realize our present goal to internationalize the journal, The Indonesian Journal on Geoscience, which is open for papers of geology, geophysics, geochemistry, geodetics, geography, and soil science. This new born journal is expected to be published three times a year. As an international publication, of course it must all be written in an international language, in this case English. This adds difficulties to the effort to obtain good papers in English to publish although the credit points that an author will get are much higher.

Arjuna Subject : -

Articles 796 Documents

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Site Specific Ground Response Analysis for Quantifying Site Amplification at A Regolith Site Bambang Setiawan
Indonesian Journal on Geoscience Vol 4, No 3 (2017)
Publisher : Geological Agency

DOI: 10.17014/ijog.4.3.159-167A numerical model has demonstrated that it can simulate reasonably well earthquake motions at the ground level during a seismic event. The most widely used model is an equivalent linear approach. The equivalent linear model was used to compute the free-field response of Adelaide regolith during the 1997 Burra earthquake. The aim of this study is to quantify the amplification at the investigated site. The model computed the ground response of horizontally layered soil deposits subjected to transient and vertically propagating shear waves through a one-dimensional-soil column. Each soil layer was assumed to be homogeneous, visco-elastic, and infinite in the horizontal extent. The results of this study were compared to other studies and forward computation of the geotechnical dynamic parameters of the investigated site. The amplification triggered by the 1997 Burra seismic event was deduced. This study reveals the amplification factor up to 3.6 at the studied site.

Seismic Anisotropy Analysis Beneath Sumatra Revealed by Shear-Wave Splitting Arya Dwi Candra; Bagus Jaya Santosa; Gazali Rachman
Indonesian Journal on Geoscience Vol 4, No 3 (2017)
Publisher : Geological Agency

DOI: 10.17014/ijog.4.3.169-179A shear-wave splitting analysis was determined to observe anisotropic structures of an upper mantle layer beneath Sumatra. The data were collected from 35 BMKG stations with the magnitude of more than 6.25 Mw and the epicentre of 85o - 140o. A shear-wave splitting measurement was calculated by using Splitlab based on three methods simultaneously. The result of the shear-wave splitting measurement in the Sumatra Forearc and Fault Zone shows that there are two anisotropic layers. The first layer has a dominant-fast-polarization direction that is parallel with a trench, and has the delay time duration of 0.5 - 0.9 s-. It is presumed that it is caused by a shear-strain as a result of the existences of Mentawai and Sumatra Fault Zones. The second layer has a dominant-fast-polarization direction that is perpendicular to the trench with the delay time duration of about 1.1 - 1.9 s-. It is presumed that it is caused by a movement of a subduction plate on a mantle wedge. The measurement in the backarc shows that there is only one anisotropic layer that is a subduction plate. It is also found that there is a transition of an orientation change on the subduction plate between Sumatra and Java. The change of the polarization direction is probably related to the age difference and the direction velocity of the absolute plate movement (APM) from Sumatra to Java.

Atoll Reef Geomorphology of Sagori Island, SE Sulawesi: A Reconnaissance Study Tubagus Solihuddin
Indonesian Journal on Geoscience Vol 4, No 3 (2017)
Publisher : Geological Agency

DOI: 10.17014/ijog.4.3.181-191The Sagori Atoll of the Kabaena Island, SE Sulawesi is one of Indonesia’s remote tropical reefs and such has received little attention from reef researchers. Non of early scientific expeditions reported either geomorphology or ecology of the Sagori Atoll in detail. This study is the first investigation of the reef geomorphology and associated habitats of Sagori Atoll within a biodiversity of “Coral reef Triangle Initiative - CTI” region, using data from satellite imagery and on ground observation. The Sagori Atoll environment consists of reef-island, atoll rim, and lagoon in which six habitats are associated, including: sand cay, coralgal pavement, sand sheet (intertidal and subtidal), sand-hardground striation, and outer atoll rim and lagoon (shallow and deep). The reef-island is built from sediments that are entirely calcareous, resting on a platform of lithified coral conglomerate. The atoll rim is dominated by coralgal pavement consisting mainly of both encrusting and living coralline algae. The lagoon which is a semi-enclosed pool and opens to the eastern side, consists of sand and scattered corals. The atoll formation is considered to be of nonvolcanic origin, but is rising from the depth of due to anticlinal island subsidence.

Geomorphic Analysis in Determining Tectonic Activity Affected by Sumatra Fault in Liwa Region and Its Surrounding Area, Lampung, Indonesia Yudhicara Yudhicara; Dicky Muslim; Adjat Sudradjat
Indonesian Journal on Geoscience Vol 4, No 3 (2017)
Publisher : Geological Agency

DOI: 10.17014/ijog.4.3.193-208The study discusses about characteristics of Sumatra Fault and its tectonic activity in Liwa and the adjacent area. The research uses quantitative methods of verification hypothetical deduction, which starts from the general approach, then it pursues into more specialized and focused ones. While the research work includes field measurements, remote sensing with GIS, and geomorphologic analysis using morphometry, such as: sinousity of mountain front (Smf), percentage of facets, ratio of the width and height of the valley (Vf), bifurcation ratios of the river (Rb), drainage density (Dd), shape of the watershed basin area (Bs), hypsometric curves (HI), and gradient index of stream length (SL). Basically, two blocks separated by the Sumatra Fault do not have a significant difference in tectonic activity, but the tectonic activity change can be seen when the studied area is divided into three blocks (northwest, middle, and southeast), then the change in each part can clearly be seen. Apparently, the tectonic activity in the studied area starts from the southeast continues toward the northwest. It is proved by this research, that geomorphological parameters which are associated with mountain fronts and watershed systems demonstrate the value of the activity increases towards the northwest. Hypsometric curves and a river analysis show that the tectonic activity in the northwest is relatively in a young stage, while towards the southeast it is getting in a mature stage.

Estimated Emplacement Temperatures for a Pyroclastic Deposits from the Sundoro Volcano, Indonesia, using Charcoal Reflectance Analyses Agung Harijoko; Nanda Ayu Safira Mariska; Ferian Anggara
Indonesian Journal on Geoscience Vol 5, No 1 (2018)
Publisher : Geological Agency

DOI: 10.17014/ijog.5.1.1-11This study applies the charcoalification measurement method to infer the emplacement temperature of pyroclastic flow deposits erupted from the Sundoro Volcano, Indonesia. This pyroclastic flow partially covered the Liyangan archeological site, a site where Hindu temples were constructed approximately 1,000 years ago. Five samples of charcoal collected from this area were analyzed for reflectance and elemental composition. Charcoalification temperatures were determined based on mean random optical reflectance values (Ro) plotted on published Ro-Temperature curves. Charcoalification temperatures were also estimated using a published formula based on the charcoal’s hydrogen to carbon (H/C) ratio. These two methods for determining pyroclastic flow deposition temperatures indicated that the pyroclastic deposits that entombed the Liyangan archeological site ranged from 295° to 487°C when they were deposited. This study used very simple, rapid, precise, and low-cost methods of charcoalification temperature measurement to infer the emplacement temperature of a pyroclastic deposit. This estimation procedure could be applied widely to predict emplacement temperatures in volcanic area in Indonesia to enhance volcanic hazard mitigation.

Gliding and Quasi-harmonic Tremor Behaviour of Raung Volcano: November 2014 Crisis Period Case Study Vico Luthfi Ipmawan; Kirbani Sri Brotopuspito; Hetty Triastuty
Indonesian Journal on Geoscience Vol 5, No 1 (2018)
Publisher : Geological Agency

DOI: 10.17014/ijog.5.1.13-21The seismic activity of Raung Volcano was raised on 11 November 2014. As many as 1709 tremors were recorded followed by continuous tremors appearing in late November 2014. Quasi-harmonic and gliding tremors appeared in a spectrogram on 12 November 2014. The quasi-harmonic tremors refer to tremors that have no fully harmonic form in spectrum. The gliding harmonic tremors refer to harmonic tremors that have frequency jumps with either positive or negative increment. After signal restitution processing, the Maximum Entropy Spectral Analysis (MESA) method was applied in Raung recordings resulting the spectrum and the spectrogram of tremors. The quasi-harmonic tremors have the monotonic spectrum in its head and centre segment, and the harmonic one in its tails. There are twenty-four spectrums that show frequency changes between the monotonic and harmonic. The similarity between the fundamental frequency range of the monotonic and harmonic ones suggests that both signals are excited from a common resonator. The alternating of monotonic and harmonic respectively over this period is qualitatively similar with Julian’s synthetic time series about the nonlinear oscillator model. It is suggested that Raung Volcano magma pressure is sizeable to make a chaotic vibration. A pressure increasing in Raung magmatic conduit causes the increasing of P-wave velocity and makes a positive gliding frequency.

The Stability of Metasedimentary Rock in Ranau, Sabah, Malaysia Ismail Abd Rahim; Baba Musta
Indonesian Journal on Geoscience Vol 5, No 1 (2018)
Publisher : Geological Agency

DOI: 10.17014/ijog.5.1.23-31The aim of this paper is to determine the stability of slopes and to propose preliminary rock cut slope protection and stabilization measures for Paleocene to Middle Eocene Trusmadi Formation along Marakau-Kigiok in Ranau, Sabah, Malaysia. The rock of Trusmadi Formation is slightly metamorphosed and dominated by interbeds of sandstone with quartz vein (metagreywacke), metamudstone, shale, slate, sheared sandstone, and mudstone. The rock unit can be divided into four geotechnical units namely arenaceous unit, argillaceous unit, interbedded unit, and sheared unit. Twelve slopes were selected for this study. Geological mapping, discontinuity survey, kinematic analysis, and prescriptive measure were used in this study. Results of this study conclude that the potential modes of failures are planar and wedge. Terrace, surface drainage, weep holes, horizontal drain, vegetation cover, wire mesh, slope reprofiling, and retaining structure were proposed protection and stabilization measures for the slopes in the studied area.

The Early Holocene Vertebrate Faunas from Seropan Cave, Gunung Sewu, Yogyakarta, Indonesia Erick Setiyabudi; Bambang Prasthisto; Iwan Kurniawan; Teguh Jatmiko
Indonesian Journal on Geoscience Vol 5, No 1 (2018)
Publisher : Geological Agency

DOI: 10.17014/ijog.5.1.33-45An excavation of a vertebrate fossil site was carried out in 2012 in the Seropan Cave of Gunung Sewu karst area, Wonosari, Yogyakarta. Among the discovered mammal fossils there are Cervus sp., Sus verrucosus, Bubalus sp., and Panthera cf. pardus. Small mammal bone fragments of GSP (Gua Seropan/Seropan Cave) Nos. 38, 67, 91-113 have been analyzed for C14 radiocarbon age dating, which gave a date of 9,450 ± 400 yrs. B.P. or Early Holocene. The Seropan fauna is part of the succession series of Braholo fauna that migrated before the Late Pleistocene, and was isolated after the last Ice Age. The Seropan fauna developed and adapted their morphology to the local habitat.

Petrography and Mineral Chemistry of Magmatic and Hydrothermal Biotite in Porphyry Copper-Gold Deposits: A Tool for Understanding Mineralizing Fluid Compositional Changes During Alteration Processes Arifudin Idrus
Indonesian Journal on Geoscience Vol 5, No 1 (2018)
Publisher : Geological Agency

DOI: 10.17014/ijog.5.1.47-64This study aims to understand the petrography and chemistry of both magmatic and hydrothermal biotites in porphyry copper-gold deposits, and to evaluate the fluid compositional changes during alteration processes. A total of 206 biotite grains from selected rock samples taken from the Batu Hijau porphyry Cu-Au deposit was analyzed. Detailed petrography and biotite chemistry analysis were performed on thin sections and polished thin sections, respectively, representing various rocks and alteration types. A JEOL JXA-8900R electron microprobe analyzer (EMPA) was used for the chemistry analysis. The biotite is texturally divided into magmatic and hydrothermal types. Ti, Fe, and F contents can be used to distinguish the two biotite types chemically. Some oxide and halogen contents of biotite from various rocks and alteration types demonstrate a systematic variation in chemical composition. Biotite halogen chemistry shows a systematic increase in log (XCl/XOH) and decrease in log (XF/XOH) values from biotite (potassic) through chlorite-sericite (intermediate argillic) to actinolite (inner propylitic) zones. The y-intercepts on the log (XCl/XOH) vs. XMg and log (XF/XOH) vs. XFe plotted for biotite from potassic and intermediate argillic zones are similar or slightly different. In contrast, the y-intercepts on the log (XCl/XOH) vs. XMg and log (XF/XOH) vs. XFe plotted for biotite from inner propylitic zone display different values in comparison to the two alteration zones. Halogen (F,Cl) fugacity ratios in biotite show a similar pattern: in the potassic and intermediate argillic zones they show little variation, whereas in the inner propylitic zone they are distinctly different. These features suggest the hydrothermal fluid composition remained fairly constant in the inner part of the deposit during the potassic and intermediate argillic alteration events, but changed significantly towards the outer part affected by inner propylitic alteration. High halogen content, particularly Cl, in hydrothermal biotite may portray that copper and gold were transported in mineralizing fluids in the form of chloride complexes CuCl2- and AuCl2-, respectively.

Lateral Reservoir Drainage in some Indonesia’s Sedimentary Basins and Its Implication to Hydrodynamic Trapping Agus Mochamad Ramdhan; Lambok Maringan Hutasoit; Edy Slameto
Indonesian Journal on Geoscience Vol 5, No 1 (2018)
Publisher : Geological Agency

DOI: 10.17014/ijog.5.1.65-80Lateral reservoir drainage is a hydrodynamic flow type driven by the difference in overpressure. It can lead to hydrodynamically tilted hydrocarbon water contact, and open an opportunity of finding oil and gas in places where previously are not considered as potential traps. In this paper, some examples of the presence of hydrodynamic traps in Indonesia’s sedimentary basin are discussed. Tilted hydrocarbon water contacts are present in some fields in the Lower Kutai Basin, and our interpretation is that regional lateral reservoir drainage is present in this basin and is responsible for the tilted contacts. It is also interpreted that lateral reservoir drainage leading to tilted hydrocarbon water contacts may be present at the Arun Field - North Sumatra Basin, Vorwata Field - Bintuni Basin, and BD Field - offshore East Java Basin. As most Indonesia’s sedimentary basins are overpressured, the presence of lateral reservoir drainage driven by overpressure difference in the same stratigraphic unit is very plausible to occur, opening the opportunity for hydrodynamically tilted hydrocarbon water contact to be present.

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Contact Name
Ivan Ferdian

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Location
Kota bandung,

Jawa barat

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