Jurnal Geofisika Eksplorasi
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DELINEATION OF SUBSIDENCE IN THE ALTERATION ZONE IN ULUBELU GEOTHERMAL FIELD BASED ON INTERFEROMETRY SYNTHETIC APERTURE RADAR TIME SERIES
Full text linkUlubelu is a geothermal region managed by Pertamina Geothermal Energy (PGE) located in Mount Kukusan, Sula, Kabawok, Kuripan and Rindingan. The learning of subsidence is required for disaster mitigation. This research use 33 SAR data of Sentinel1-A which bundled for generate an APS and then using multi temporal analysis to generate InSAR time series from 2018 September to 2017 April. InSAR time series can detect indication of subsidence practically and quickly. Decrease velocity of subsidence in the Ulubelu geothermal region is an average of 3,3 mm/yr (X=453.558, Y=9.412.437, 48 S zone. This subsidence is domination by altered rocks compaction. In the other hand, the geological structure (faults) and lithology also surface loading affected the subsidence. Pekon Gn. Tiga, Karang Rejo, Muara Dua and Pagar Alam are the worst of subsidence area. Mitigation must to be clear early for areas that have the worst subsidence in Ulubelu geothermal field
ANALISIS ANOMALI SINYAL ULTRA LOW FREQUENCY BERDASARKAN DATA PENGUKURAN GEOMAGNETIK SEBAGAI INDIKATOR PREKURSOR GEMPABUMI WILAYAH LAMPUNG TAHUN 2016
Full text linkRegional research had been done to analysis anomalies signal of ultra low frequency based on measurement data as an indicator of the geomagnetic earthquake precursor of lampung in 2016. To achieve purpose of the study conducted by the following steps: (i) Calculation of the total magnetic field of data; (ii) Daily Trend Analysis; (iii) the Fourier transform of the data Geomagnetic Anomaly; (iv) Localization Frequency ULF; (v) Calculation of Ratio Vertical-Horizontal (Polarization Ratio Z / H); (vi) Correction magnetic storms or Disturbance Strom Time (DST); (vii) the identification of earthquake precursors; (viii) Determination of OnsetTime, leadtime,and the direction of precursors. The results of the analysis of ten earthquakes with a magnitude above 5 MW have precursors between 11 to 30 days before an earthquake. Nine out of ten earthquakes studied had an earthquake precursors and precursors that do not have, this is because the distance is too far from the station Magdas in Liwa, West Lampung. Thus it can be seen that the precursor using the magnetic data can be used to make short-term predictions
ANALISIS PENDUGAAN BAHAYA KEGEMPAAN DI BATUAN DASAR UNTUK WILAYAH LAMPUNG MENGGUNAKAN METODE PSHA
Full text linkAnalysis of seismic hazard estimation is one method for estimating the effect of earthquakes. The purpose of this study was to determine the maximum value of ground acceleration in bedrock or PGA values for the Lampung Province region. This analysis of seismic hazard estimation is carried out by a probabilistic seismic hazard analysis (PSHA) method. In the process of estimating the influence of earthquakes, the PSHA method principally uses 3 types of earthquake sources, namely the source of background earthquakes, subduction earthquakes (earthquake subduction) and fault earthquakes (faut). The calculation of the estimated seismic hazard value is carried out using the 2007 USGS PSHA program. The distribution of seismic hazard values for the Lampung Province region on bedrock with a 500-year return period or a 10% probability on the PGA condition (T = 0) is 0.1 g to 1, 3 g and a 2500 year return period or a probability of 2% in the PGA condition (T = 0) is 0.1 g to 1.3 g
IDENTIFIKASI CEKUNGAN HIDROKARBON “RAE†BERDASARKAN DATA MAGNETOTELURIK DI DAERAH BULA, MALUKU
Full text linkThe research had been performed using Magnetotelluric to get a 2D model based on variations in resistivity of the subsurface rock. The purpose of this study was to determine the hydrocarbon formation zone. The research method to achieve the research objectives, among others, the first filtering performed on the data with a robust process. This process consists of Robust No Weight, Robust Rho Variance and Ordinary Cohenerency. The second step is done to change the format Selection XPR And Edi. A third inversion resistivity model for the review get a 2D cross section. Based on the findings of the eight data processing methods of measurement points obtained information Magnetotelluric rock formations. Formation hidrokrabon What are the areas is research a reservoir and caprock. The layer in 1600 m – 2700 m depth from the surface which resisvity 12 -33 m assumpted as clay cap. While the layer in 2700 m – 5000 m depth from the surface with high resistivity 41- 250 m is assumpted as oil sands (reservoir). The trap zone of this hidrocarbon formation categorized into structural trap which is the trap of anticline
STUDI SIFAT TERMAL BATUAN DAERAH LAPANGAN PANAS BUMI WAY RATAI BERDASARKAN PENGUKURAN METODE KONDUKTIVITAS TERMAL
Full text linkResearch on Way Ratai geothermal field has been done by measuring the thermal conductivity method. The thermal conductivity data is used to generate a map of the dispersion of heat conductively conductive rocks in the geothermal system. The result of measurement by thermal conductivity method in Way Ratai geothermal field is data of k (conductivity), Rt (thermal resistivity), and T (temperature). The value of the measured conductivity data in the geothermal field has range between 0.056-0.664 W/mK, the measured thermal resistivity value has range between 1.344-17.527mK/W, and the measured temperature value is between 22.68-52.59°C. The difference value of rock’s thermal conductivity is influenced by several factors, which is the existing geological structures in the field such as normal faults and lineaments, the presence of alteration, also the manifestation zone of hot water or hot vapor that caused from fumaroles
ANALISIS KETEBALAN LAPISAN SEDIMEN DAN INDEKS KERENTANAN SEISMIK KOTA JAMBI BAGIAN TIMUR
Full text linkA Research was carried about analysis of sediment layer thickness and seismic vulnerability index in eastern Jambi City. The purpose of this research was to  determine the effect of sediment layer thickness on seismic vulnerability index in eastern Jambi City based on microtremor data. The Acquisition data of microtremor is 25 points spread in research area. Processing data was carried out using the HVSR (Horizontal to Vertical Spectra Ratio) method to obtain the H/V curve. This curve represents the value of the natural frequency (f0) and amplification factor (A0). Based on the results of data processing obtained, the range of natural frequency (f0) value is 1.04 – 3.78 Hz, the range of amplification factor (A0) value is 1.13 - 4.88 times, the range of sediment layer thickness (h) value is 16.46 – 61.45 meters, and the range of seismic vulnerability index (Kg) value is 0.70 - 20.18×10-6 cm2/s. The results showed that the distribution of seismic vulnerability index (Kg) correlated relatively well with sediment layer thickness of the research area. The high zone of seismic vulnerability index (Kg) is relatively associated with alluvial deposits and also the sediment layer thickness of more than 30 meters. The high zone of seismic vulnerability index (Kg) is concentrated in Pasir Panjang, Tanjung Raden to Olak Kemang in Danau Teluk sub-district and Tanjung Sari in Jambi Timur sub-district
OPTIMALISASI DATA LANDSAT 8 UNTUK PEMETAAN DAERAH RAWAN BANJIR DENGAN NDVI dan NDWI ( Studi Kasus : Kota Bengkulu )
Full text linkIndonesia is classified as a tropical region with rainfall data ranging from medium to high. This has become one of the causes of frequent flooding. Bengkulu which is one of the provinces in Indonesia, has a topography that is at an elevation of 0-16 meters above sea level with 70% flat topography and 30% small hilly. Swamp area dominates the lowlands so that it cannot optimally absorb water into the soil. This study identifies areas with potential flooding using data obtained through Landsat 8 and processes them using the NDVI and NDWI methods. NDVI detected and classified a map into five classifications; dry land with red colour, scarce vegetation with yellow pigment, sparse vegetation with soft green colour, solid vegetation with a dark green colour. Meanwhile, NDWI classified into 3 categories; medium wetness with a brown colour, dry land with beige colour and high wet area with a blue colour
KARAKTERISASI RESERVOAR MELALUI ANALISIS PETROFISIKA BERDASARKAN DATA LOG SUMUR “TRD†FORMASI AIR BENAKAT
Full text linkThe research area was located in South Sumatra Basin on Air Benakat Formation at South-East Jambi Province. The research conducted to know productive the interest zone by petrophysics analysis (volume shale water saturation, and porosity) and its characteristics by well-log. The lithology of TRD Well is sandstone with a few foraminifera. The interpretation based on the petrophysical analysis porosity of the 7th zone on TRD-10 is average 12,4%, saturation water 19,4% and volume shale 6,2%; the 7th zone on TRD-11 well is average porosity 16,2%, saturation water 41,3%, and volume shale 22%; the 11th zone on TRD-14 well is average porosity 33,2%, saturation water 21,2% and volume shale 1,2%; The 6th zone TRD-15 well, porosity 7,02%, saturation water 32,3% and volume shale 5,6%; On the TRD-17 well of the 7th zone is average the porosity 9,04%, saturation water 25,6% and volume shale 4,6%; and 4th zone of TRD-19 well, porosity 23,2% Saturation water 13,5% and volume shale 7,1%. The characteristics of hydrocarbon reservoir on TRD Wells have low water saturation is less than 50%, porosity more than 5% and volume shale less than 25%. From the result of petrophysics parameter value used as the indicator of the productive zone and interpreted that sand reservoir on well TRD has potentially for the reservoir zone with gas prospect