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EAGE-HAGI 1st Asia Pacific Meeting on Near Surface Geoscience and Engineering
- Conference date: April 9-13, 2018
- Location: Yogyakarta, Indonesia
- Published: 09 April 2018
61 - 80 of 115 results
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Integration of High Resolution Geoelectrical Resistivity and Refraction Seismic Profiling for Exploration of Groundwater
Authors S.C.H. Lee, A.G. Rafek and M.N.A. ZakariahSummaryThis paper presents the integration of high resolution geoelectrical resistivity and seismic refraction profiling for exploration of groundwater: case history from Chemor, Perak, Malaysia. The survey line is conducted at the intersection of two major faults where it is suspected to detect potential aquifers in limestone hardrock along the major fractures. Seismic refraction survey is used to determine the velocity of energy transmitted through the rock. Geoelectrical resistivity survey involved the use of new electrodes arrangement and sequence of measurements for Wenner-Schlumberger array and Dipole-Dipole array for geophysical field data acquisition in order to increase its data density and sensitivity to obtain high resolution 2-D subsurface imaging. The parameters that were taken into consideration while choosing the two most suitable arrays to be used were their sensitivity to vertical boundary, signal strength and total number of datum points. Data Levels Synthesization (DLS) technique also developed which involved the merging of data levels and datum points of Dipole-Dipole array and Wenner-Schlumberger array during resistivity data processing stage. DLS technique has effectively produced a high resolution 2-D geoelectrical resistivity image with enhanced horizontal and vertical resolution.
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A viable eco-friendly solution to meet India’s growing energy needs
By S.K. SharmaSummaryGeothermal reservoirs in India are of low to medium enthalpy type where surface temperatures vary from 80 to 105°C thus requiring a Binary Power Plant to convert their geothermal energy into electricity. Such generation of electricity through geothermal resource is preferable due to its eco-friendly nature whereas much environmental hazards are associated with the coal and nuclear projects.
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Prediction of Caprock and Structure of Candi Gedongsongo Geothermal System from AMT Data
Authors N. Alviandari, Yatini, F. Sulistyo, A. Suprobo, M. Rizki, B. T. Baihaqi and T. Y. YudhantoSummaryGeophysical investigation with AMT method conducted based on the existence of the surface manifestations on Candi Gedongsongo area and appear to identify the structure of the suspected fault as a weak zone both as recharge area and the emergence of the manifestation zone. This investigation was done on the post volcanic belt of older subduction zone that have significant geothermal gradient by the depth AMT data acquisition was done with Stratagem Unit 26716–01 Rev D by Geometrics that calculate true resistivity with its inversion then modeled on 2D model to identify the fault structure and 3D model to shows the caprock geometry. As a result there are 2 faults shows that has strike and dip of N350oE / 60o that continues from north to south and the second fault shown on P1 but the strike and dip can not be known. The caprock identified on high resistivity value ranges between 1000 -100,000 ohm.m with andesite lithology lying under elevation of 1000 m.
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Magnetotelluric Phase Tensor Application to Geothemal Modeling
More LessSummaryPhase tensor analysis generate invariant parameters such as the ellipticity (Φmax and Φmin) and slope angle of phase tensor (β) determine the dimensionality of the impedance tensor. If the structure of 1-D, then Φmax and Φmin will be equal, so the phase tensor form will be a circle with β is zero or near zero, for structur of 2-D the value Φmax ≠ Φmin while β is still zero or near zero and for 3D structure all components in tensor each impedance has a value and β ≠ 0 with a value of β< 3°. The results of the above phase tensor analysis show that the 1-D and 2-D structures are shown at frequencies of 320 Hz to 0.2 Hz (the period of 0.003 1s to 5.4s) and 3-D structures are shown at less from frequencies 0.11 Hz (period 9.588s). If the graphical representation non-symmetrical ellipse 2-D to the ellipse axis this because β ≠ 0, so it needs to be rotated to the ellipse axis with the angular value generated by calculation of α-β is -10o.
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Geology, Geochemistry and Geophysics of Guci Geothermal Prospect Area, Central Java.
Authors E. Gaffar, H. Permana, Y. Sudrajat, S. Indarto, H. Bakti and H. NurohmanSummaryGeothermal exploration have conducted in the Guci area. The methods were geology, geochemistry, geophysics and Radon. The Slamet Mountain Complex activity is controlled by the straight-line structure of the northwest - southeast, southwest - northeast direction of the main structure. The straightness of the northwest - southeast trending structures generally controls the activity of the old Mount Slamet or the Mingkrik Complex whereas the young volcanic activity is controlled by the southwest – northeast direction.
Areas which indicate Radon content can be interpreted that areas with low permeability, medium (Kalipedes), and high (Guci) are the areas passed by fault section. The radon content measured in the Guci and Kalipedes areas is high-high enough, indicating high permeability - high enough, ie> 40 dpm / L
Type of hot water in the Guci area based on the content of Cl, SO4, and HCO3, Guci areas (GC) generally indicate the type of bicarbonate. Hot water in a Guci in a geothermal system is called an outflow.
Magnetoteluric measurement result can be seen that geothermal prospect area for Guci and surrounding area is at Mount Mingkrik area.
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Depth Prediction of Gravity Data by Using Continous Wavelet Transform
More LessSummaryNawangan-Tegalombo is one of the mineralization zone in Indonesia. The research area is located in Pacitan-East Java. The mineralization zone is described by gravity anomaly which is there high gravity anomaly in reserach area. The depth prediction of the mineralization zone is calculated by continous wavelet transform with Morlet and Doubechies as mother wavelet. The source depth of the research area is around 1 km.
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Mineralization System with Magnetic Method in Kluwih, Pacitan, Central Java
Authors Fatimah, Muh Isnanto, Vergillio Asqueli, Audi Tri Lavanto and Faisal SangajiSummaryOre minerals are found disseminated sulfide ore pyrite, arsenopyrite, chalcopyrite, enargite and malachite. From measurements of geomagnetic found high magnetic anomaly< 700 nT surrounded by a low magnetic values and form a circular pattern, it is an indication of the pattern of anomalies of the porphyry system that is closed by the argillic lithocap. Based on data integration of geological, geochemical and geophysical the mineralization in the Pacitan area in the interpretation were in the proximal part of the High Sulphidation and suspicion leads to the porphyry deposits are still covered by the lithocaps.
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Ground Magnetic Survey for Shallow Iron Ore Prospecting
Authors H. Grandis and P. SumintadirejaSummaryA ground magnetic survey was conducted to delineate the existence of iron boulders located at shallow depth covered by soils. Typically, iron ore resources prospecting is done along with the extraction activities by digging or excavating using heavy equipment (backhoe). The geophysical survey aimed to avoid such trial-and-error process was part of our institution’s community services in Pelaihari district, Tanah Laut regency, South Kalimantan province, Indonesia. The relatively simple data processing and analyses of magnetic data were performed by using standard tools, i.e. freely available software and modelling codes. Our results showed the effectiveness of the iron boulders prospecting by using the ground magnetic method.
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Integrated Gravity and AMT Survey in Exploration of Primary Tin Deposit
Authors K. Apriliyanthy and M. YunusSummaryAn integrated Geophysical survey are Gravity and AMT has been carried out in Bangka Island to make a delineation of granite that is thought to be the source of tin mineralization.
Gravity anomalies show a high density around the edge of the maps, this high anomaly coincide with metasediment. While the low anomaly is related with alteration zone that surrounded the medium anomaly, it is interpreted as granite.
AMT inversion show an anomaly that confirmed the existence of granite which high density and high resistivity. This is supported by the existence of the low resistivity and low density as kaolin alteration zone that surrounded the anomaly.
The two fault direction are shown by Gravity map and also evident in AMT data. Fault with the trend of NW-SE from Gravity map is coincide with AMT Section, there is a low resistivity contrast extended downward that looks like a fault. On the other side, the high resistivity and high density is highly probable a metasediment unit which is resistive and dense but slipped NE-SW as shown in the gravity map.
The Gravity and AMT surveys delineated the existence of potential of the primary tin deposit of the granite at Bangka Island.
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Analysis of Microzonation Seismic Vulnerability Index around Repaking Village, Boyolali, Central Java using HVSR Method
Authors S.A. Widita, M. Kurniado, M.A. Girash and T.M. IrnakaSummaryMicrozonation analysis for seismic vulnerability was aimed to map the earthquake-vulnerable area at Repaking village, Wonosegoro Sub-district, Boyolali region, Central Java. Seismic vulnerability microzonation was done to map the vulnerability of a region based on its ambient seismic wave. The processing method that was used in this study was Horizontal to Vertical Spectrum Ratio (HVSR) method. In this study, HVSR method was used to analyze the site effect parameter prior to the seismic vulnerability. The parameter refers to Sediment Thickness (H) and Seismic Vulnerability Index. Those parameters are defined by generating Natural frequency (Fo) and Amplification Factor (Ao). The output of this study is the distribution of seismic vulnerability, which can give information about the hazard consequences, particularly on earthquake events.
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Comprehensive Analysis of Microtremor data to identify potential landslide (Study Case: KM23 Ponorogo-Trenggalek Road)
Authors B. Ramadhany, S. Sungkono, A. Rohman, D.D. Warnana and S. LestariSummaryPrincipal component analysis from microtremor data can be used to identify the potential landslide with azimuth and dip correlation, also the principal component data is compared with soil vulnerability index based on the calculation.
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Successtivity of Frequency Ratio to Predict Landslide, Study Case Daerah Istimewa Yogyakarta and Surrounded Area
Authors L. H. K. Pratiwi, A. Setianto, Y. P. Nusantara and A. WarmanSummaryTo reduce landslide hazard’s damage potension, it’s necessary to do a mitigation by mapping the landslide susceptibility area. Frequency Ratio is still rarely to be applied in Indonesia. This research is made to shows the accuration rate of the frequency ratio method application in Indonesia, especially in the Special Region of Yogyakarta and Central Java, so it can be a renewal for landslide hazard mapping method in Indonesia, which can help the landslide hazard mitigation. Landslide occurance in Special Region of Yogyakarta and Central Java is controlled by triggering factors such as slope, lithology, distance from drainage, distance from geological strucure, precipitation, and landuse. The result of landslide hazard mapping in this area indicates that the most triggering factor is the slope factor, especially the steep slope. The validation of this landslide hazard map using frequency ratio method shows the accuration rate is about <80%, so this method is good to be applied to produce a landslide hazard map.
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Conditioning of Stratigraphic Forward Modelling Using Geostatistics
Authors B. B. Ramadhana, S. Tyson, V. Bianchi and F. ZhouSummaryThe combination of Stratigraphic Forward Modelling and geostatistical technique can be used to improve the quality and comprehensiveness of the sedimentary reservoir model then reduce the costly data collection procedures to understand the reservoirs. The Stratigraphic forward modelling (SFM) is a process-based method comprising s realistic complexities and heterogeneities of its subsurface sedimentary architecture and may be applied in generating an enhanced model where limited well and seismic data available. The proposed method in this study is to generate a large SFM-basin scale then identify a field-scale location within this and applying some relevant transformation factor that matches the field conceptual deposition. Grainsize distributions may be inferred from well logs and compared against the grain size model in the SFM. Set of differences or residuals can be analyzed spatially and modeled using geostatistical techniques. Adding the modeled residuals to the SFM grain size will ensure that the hard data is honored. It is expected that more reasonable and defendable model characterization can be generated along with the main co-existed uncertainties and risks that can be captured and analyzed. The proposed methodology will incorporate the best advantage of each technique: process-based method for geological realism and Geostatistic methods for data conditioning
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Seismic Surface Wave in Irregular Dispersive Medium
By J. SafaniSummaryThe use of seismic surface wave method in civil engineering applications (such as determination of locations of building and bridge foundations, railway and highway route) become common practice in recent years. It is because this method provides shear-wave velocity, a parameter that directly related to shear strength of the subsurface structure which is an important parameter in civil engineering. In this paper, we discussed accuracy of the surface wave method in identifying the subsurface structure having irregular dispersive characteristic. Numerical and field tests were presented. Results from the numerical and field tests showed excellent ability of the surface wave method in delineating the subsurface medium with irregular dispersive characteristic. Comparison of a field test to the borehole data confirmed the ability.
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Joint Inversion of Rayleigh-wave Dispersion Curve for Near-Surface S-Wave Velocity Estimation
Authors A. Rubaiyn, J. Safani and A. PriyonoSummaryThe most important step in surface wave method is inverting Rayleigh wave dispersion curve for near-surface shear-wave velocity estimation. Joint inversion of Rayleigh wave dispersion curve has been developed. We combine the advantages of two different optimization methods, the genetic algorithm (GA) and Occam’s Algorithm. First, we use GA with small number generation to get the possible output solution, then we improve the solution (shear-wave velocity and thickness of layer) using Occam’s algorithm. We use several synthetic models to show performance of the joint inversion. Numerical errors are shown to appraise the value accuracy inversion model. Inversion of the synthetic dispersion curves for the four layers model provides most accurate solution models with is 0.0005 % and is 0.001%. Whereas, that for the six layers model also presents accurate result with is 1.48% and is 12.51 %. These errors indicate that the accuracy apply successfully join inversion scheme and promising application of surface wave.
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Effect of variation of shallow Vs profile from the MCMC inversion to variability of nonlinear soil amplification
Authors Saifuddin and H. YamanakaSummaryIn this study, we discuss effects of an observational error of phase velocity on a shallow phase velocity profile from a numerical case. Uncertainty in S-wave velocity profile is obtained from inversion of the phase velocity using the Markov-Chain Monte Carlo. The uncertainty of S-wave velocity profile is used to estimate the variability of nonlinear soil amplification. Variability of linear amplification is also estimated as the comparison to the nonlinear one. We find that the nonlinear amplification has less variability than linear response because of decrease of shear modulus and the increase of damping in nonlinear amplification.
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A Comparison of Tele-seismic Receiver Function in the Different Geological Units in Central Java
Authors P. Ariyanto, M.S. Rosid, Syuhada and Y. JanuartiSummaryIn this study, we derived crustal properties and shear wave velocity structures from analysis of teleseismic receiver function using Neighbourhoods Algorithm in the different geological units in Central Java. The results present here are the estimates of shear wave velocity models beneath 6 stations and the model of thickness of layer each geological unit. We observed the Moho depth at Central Java is about 22 to 38 km. In southern Central Java, the receiver function indicate a middle crustal low velocity zone, as Merapi Lawu Anomaly (MLA). The conversion Ps phase of the subducting Indo-Australian Plate is observed at several station at around 8.0 to 10.0 s. Several station that show high complexity data of receiver function require further study. They include stations at Quaternary Volcanoes and The Central Deppresion Zone of Java.
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Converted-Wave Seismic Reflection as an Alternative Key to Unlock Near Surface Imaging
Authors M. Oktariena and W. TriyosoSummaryNear surface phenomenon, such as shallow soft soil and gas cloud, has been proven for years as one of the obstacle in geotechnical and petroleum industry. Present as the anomaly to its lithological surrounding, these phenomenon have a similar characteristic in which triggering an imaging quality degradation, especially captured in conventional seismic reflection. Conventional seismic reflection is widely applicable for a deep target imaging, but it’s not impossible to use for a shallow target purpose. Multicomponent seismic survey records conventional both PP-wave reflection and converted PS-wave reflection. Obtained from converted-wave seismic, the characteristic of S-Wave brings along its unique capability of only propagating in solid medium. Through synthetic model based on real velocity data, this research will unveil the ability of converted-wave seismic in assisting conventional seismic for imaging purpose. With the interest located in shallow depth, a different approach will be conducted to bring in the best feature of each seismic wave behavior. The result reveals a series of simple seismic attribute and post-stack seismic inversion just the right approach to handle the intermeshing characteristic of PP&PS seismic reflection. Reducing ambiguity of PP seismic, PS seismic provides a highly improved imaging even when it is a near surface phenomenon.
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Effect of Dipping Layer in Source Energy Distribution of Ambient Noise
By C. LinSummaryGeophysical methods are effective ways to investigate the landslide area. Among them, passive surface wave method is an effective and economic way to measure the shear wave velocity profile especially in large-scale deep-seated landslide case. The influence of topography and dipping layers in the results of it is still not clear. As a preliminary study, we firstly focus on the effect of dipping layers. 3D numerical simulations based on spectral element method were conducted to study the effect. Ambient noises were numerically simulated for 2D array Spatial Autocorrelation method (SPAC) and for 1D array Multichannel Analysis of Passive Surface Wave method (MAPS). According to the results, the bias between the experiment dispersion curve and the theoretical ones in the centre of the array mainly come from the non-uniform source energy distribution. The dispersion curves retrieve from MAPS is much sensitive to the effect than the one from SPAC. The source energy distribution altered by the dipping layers and the dominant azimuth of the source energy would be frequency dependent. A frequency dependent correction can be applied to MAPS but the solution for SPAC needs further study.
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3x3C Seismic’s Sensitivity Analysis on Near-Surface towards Full Waveform Inversion
Authors T. M Irnaka, R. Brossier and L. MétivierSummaryFull Waveform Inversion (FWI) is a high-resolution seismic imaging tool which has been intensively developed during the past decade. At the near surface scale, FWI faces several challenges including 3D acquisition deployment, a strong presence of elastic effects, relatively high attenuation effects, and difficulties to propagate high-frequency waves. In order to better characterize such shallow targets, one of the solutions is to take into account data from multi-component sources and receivers. In this study, we analyze the benefit of 3x3C seismic data: 3x3C seismic is an acquisition technique which contains three orthogonal directions of the source and three component receivers. Although 3x3C seismic is feasible in practice, the benefit of such data for FWI is still not clear. This research uses two different synthetic models to assess the interest of 3x3C seismic data through the construction and analysis of the sensitivity kernel of both P-wave and S-wave velocities for each wave type (P-wave, S-wave, and surface wave), and each component. The results show that 3x3C data provide complementary information on the kinematic, dynamic and polarization of the wave propagation, yielding a potentially better reconstruction of the subsurface properties.
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