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EAGE-GSM 2nd Asia Pacific Meeting on Near Surface Geoscience and Engineering
- Conference date: April 24-25, 2019
- Location: Kuala Lumpur, Malaysia
- Published: 24 April 2019
61 - 80 of 80 results
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Inversion of 3D Magnetotelluric Data for Geothermal Exploration at Quang Binh Province, Vietnam
More LessSummaryMagnetotelluric (MT) method utilizes natural source from solar wind, thus its investigation depth can vary from a few hundred meters to kilometers or deeper depending on period measurement. MT is usually one of the main geophysical methods to explore deep structures, particularly conductive objects such as faults or geothermal reservoirs. MT inversion can result a conductivity model that may image fault zones or geothermal reservoirs. The MT 2D inversion likely produces distorted images because of 3D effects. Hence, the object can be imaged more robust by using 3D inversion. We applied 3D MT inversion to a dataset acquired in Quang Binh province, Vietnam for geothermal exploration. The dataset measured in nearly thirty stations is processed and exported to the impedance tensor format. We have investigated that the inverted conductivity distribution could provide three-dimensional vision of the fault system in this area.
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Surveying a Slope Deformation along Highway by Application of Unmanned Aerial Vehicle (UAV)
By V. LooSummaryUnmanned Aerial Vehicle (UAV) has been rapidly developed for the past decades. This technique has distinct advantages over traditional methods to produce aerial photographs. It can provide high resolution images with less time and cost. With photogrammetric techniques coupled with software as well as sufficient known parameters (focal length, pixel size, and distance of sensor from ground), the images can be processed to generate the contour map by commercial softwares. This research offers key insights on the application of UAV photogrammetry for slope surveying in civil engineering. The objective of this research is to validate the accuracy of applying photogrammetric methods via UAV surveying for a slope failure. Several surveying points are chosen to compare with the elevation obtained from UAV Photogrammetry. The result shows a difference less than 100mm which was found to be acceptable. The gain in time and labour savings reinforces the prospect of using UAV Photogrammetry as a cost-effective means for surveying of on-going construction site, slope survey, monitoring of slope movement and other application for civil engineering.
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Engineering Geological Assessment of the Mangapoike Landslide, Gisborne NZ and Evidence for Fluid Overpressurisation
Authors S. McGovern, M. Brook and M. CaveSummaryThis project describes the application of field-based and remote sensing techniques used to study a recently occurring large dam-forming slope failure, Southwest of Gisborne New Zealand as shown in Figure 1 . The overall objective of this study was to determine the geological conditions, discontinuities and rock mass properties that led to the triggering of the Mangapoike Landslide. In summary, the study included a detailed field investigation, laboratory testing, numerical modelling as well as an in-depth review of literature and discussions about possible triggering mechanisms.
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A novel constrained approach for improving the precision of downward continuation of potential field data
More LessSummaryWe have developed a new constrained downward continuation scheme for potential field data to estimate the field closer to the sources.
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Magnetotelluric monitoring of electrical resistivity changes in an active fault zone
Authors A. Mahallati and M. MontahaeiSummaryWater, brine, and co2- rich fluids, generally found in fault zones, characterize the long-term strength and rupture distribution in these regions. Furthermore, they produce a large electrical resistivity contrasts with their surroundings, utilizing EM exploration methods like magnetotelluric (MT) as a proper tool to monitor co-seismic variations of physical parameters in a seismogenic zone. To address the question of whether the residual of pre- and post-seismic MT responses can monitor well the physical properties in the rupture area of an earthquake, we investigate a synthetic MT example of an active fault zone.
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Three-Dimensional numerical Simulation of Vertical Line Source Borehole-to-surface electrical method
More LessSummaryThe research on the response of multiple complex three-dimensional well-earth model is helpful to promote the development and application of Borehole-to-surface electrical theory. Model calculation results show the vertical radial stretching of the target body can be counteracted to some extent by adding multiple reflux electrodes. The apparent resistivity on the plane shows that it is difficult to determine the side boundary of the target body near the line source, and the boundary of the target body in the profile is more accurate, the closer the target body is to the line source, the more sensitive the detection is.
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Application of Airborne Gamma Spectrometry in Radioactive Contamination Investigation of Baiyan Obo Rare Earth Mine
More LessSummaryAirborne gamma spectroscopy measurements were carried out at the Bayan Obo deposit in Inner Mongolia with the aim of investigating radioactive contamination around the tailings dam. The measured results show that the main radioactive pollution elements in the rare earth mining area and tailings dam in Inner Mongolia are 232Th. The range of gamma total count higher than 140cps corresponds to the tailings dam in the Bayan Obo area, and the area with high total count rate is the eastern mining area of the Bayan Obo mining area, which is open-pit mining. The radio-nuclear uranium and thorium content plane contour maps show the same pattern. According to the on-site investigation, some anomalies sites on the contour may be related to the pollution of the local rare earth ore deposits on the ground and the surrounding rare earth processing enterprises. The aerial gamma spectrometry is a fast and effective method for environmental Radioactivity monitoring and evaluation.
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Identification of potential landslide areas in the Banten with GIS and rock compactness using the b value method
Authors S. Nursarifa, M. Al Macky and A. Umi NafingahSummaryThis study aims to indicate the potential of landslides in the province using geographic information systems and mapping rock strength using the b value method. With geographic information systems, we can make land cover maps, rainfall, rock lithology (geology), soil types and slope maps, from the five maps we can do multi criteria evaluation, so that later we get quantitative interpretation of landslide prone areas based on the fifth integration map. Assisted by rock compactness mapping using the b value method, it is expected that from these two methods we can do an initial mapping and can localize the potential of a landslide disaster.
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Wenner-Array method for an aquifer investigation to deal with the issue of the freshwater crisis in Lam Apeng village
By K. AlfaizSummaryGroundwater is a renewable natural resource, water is also a natural resource that is important and needed by every living thing Increased demand for clean water is proportional to the increase in population and the development of an area, the increasing need for water. But it would be unfortunate if a large water potential. Therefore, a 2D resistivity geoelectric method was used using the Wenner-Array configuration in Lam Apeng Village, Seulimum subdistrict, Aceh Province with the aim of finding out the aquifers. 2D resistivity geoelectric method is used to determine the presence of water distribution in the area. This method looks at the subsurface resistivity values to determine the structure of the layers. Measurements were made by plugging electrodes in 56 electrodes on one track with a line length of 112 m. The electrode is plugged in with a space of 2m. Data processing of 2D geoelectric resistivity method, then processing data using Res2DinV software to display cross sections based on rock resistivity values in the measurement area. Identified groundwater aquifers with resistivity 7.69-18.6 Ωm. Potential aquifers are found in the second layer in the location of Lam Apeng Village, precisely the residents plantation with a depth of 8-20 meters.
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Development of Kaligesing Area as Geotourism and Education Tourism Kaligesing Purworejo Central Java
Authors F.I. Herawati, M.N. Arifin and M.A.Y. MuizdSummaryStudy was carried out on volcanic lithology and limestone lithology in Kaligesing Area, Purworejo District to identify geotourism potential. The research area include of Old Andesite Formation that have age Late Oligocene to Early Miocene and Jonggrangan Formation that have age Early Miocene to Miocene. Kaligesing area has geotourism potential that can improve the local people’s economy in terms of the beauty of morphology formed by geological processes and lithology that support the formation of morphology. Goa Seplawan, Taman Sedandang and Curug Silangit are geotourism object in Kaligesing area. Taman Sedandang and Curug Silangit have lithology igneous rocks andesite included in Old Andesit Formation (OAF). Goa Seplawan have lithology limestone included in Jonggrangan Formation. In this paper we analyzed the most representative ones based mainly on their aesthetic value as well as their geotourism potential. The aim of this paper is to emphasize the geotourism potential of Kaligesing and to determine its strengths, weaknesses, opportunities and threats as well as interactions between them when it comes to tourism development. The results of the SWOT and TOWS analysis indicate that Kaligesing as a tourist destination possesses immense geotourism potential. Keywords : Geotourism, SWOT Analysis, TOWS Analysis, Kaligesing, Purworejo
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Estimation of Tectonic Fault Systems of Mongolian Territory Using Geomagnetic Anomaly Data
Authors D. Badarch and B. TsermaaSummaryThe magnetic anomaly dataset was used to delineate fault parameters and terrane boundaries of the Mongolian territory. The spectral method has been implemented to separate shallow-, intermediate- and deep-seated faults and corresponding figures have been depicted. Also, locations of some new hypothetic faults have been estimated from the geomagnetic dataset.
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Monitoring of landslides along the Southern Kaikoura Transport Corridor, New Zealand
Authors J. Stringer and M. BrookSummaryOn the evening of 14 November 2016 at 00:02 hours local time, a magnitude (Mw) 7.8 earthquake struck the North Canterbury region of New Zealand’s South Island. The earthquake occurred at a depth of ~15.1 km, centred approximately 6.2 km west of the small township of Rotherham, and approximately 4.3 kilometres south-south west of the small township of Waiau. The earthquake ground motions resulted in the widespread damage of housing and infrastmcture throughout North Canterbury, and damage to the road and rail infrastmcture within the South Kaikoura Transport Corridor (SKTC). Indeed, seismically-triggered landslides covered and destroyed parts of the State Highway 1 (SHI) road and rail transport corridor. The aim of this project is to characterise and quantify slope failure rates and processes at selected sites along the South Kaikoura Transport Corridor, using multi-temporal analyses of digital elevation data, extensometer data, and land deformation monitoring using GPS receivers. Thus, several datasets and techniques are used in a comparative approach.
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Geological evaluation of density structure using the multi-level inversion of gravitational data in central Yili Basin
More LessSummaryIn this paper, we use a multi-level inversion of gravitational data to obtain the subsurface density structure of the central area at Baishidun, and discuss the tectonic evolution of the basin.
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Estimation of group velocity of Green’s function in the sedimentary basin from crosscorrelation of ambient noise around
Authors K. Chimoto, H. Yamanaka, S. Tsuno, M. Korenaga, H. Miyake and S. SennaSummaryThe Fujikawa-kako fault zone in central Japan is one of the most active faults. For the strong motion prediction, it is necessary to construct S-wave velocity structure model of sedimentary layers around the fault zone. Several 3D velocity structure models has been proposed in the area. In order to choose the appropriate velocity structure model, we used seismic interferometry to retrieve Green’s functions and estimated group velocity of Rayleigh wave from the crosscorrelation function. The crosscorrelation functions in the vertical component propagate with the velocity of 1 km/s. Group velocity of the Green’s function was estimated using Frequency-Time Analysis. We observed clear group velocity between the stations pairs across the fault. The estimated velocity was slower than the theoretical velocity of the existing model. There is possibility to use group velocity for the improvement of the existing S-wave velocity structure model.
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Reconnaissance Survey of Limestone Cliff in Bukit Takun, Templers Park by Terrestrial
Authors M.A. Hellmy, R.F. Muhammad, M.K. Shuib, T.F. Ng and W.H. AbdullahSummaryBukit Takun is one of the remaining limestone hills within Klang Valley. The steep sided cliff faces of Bukit Takun make it a popular place for rock climbers. Located at Templer Park Rawang, Bukit Takun cliff is around 300 meter high and the longest continuous walls are up to 230 meter from ground making it the largest climbing area in Klang region. The capability of terrestrial LiDAR to create 3D data of the cliff face remotely from far proved that it is an effective and helpful approach to study and understand the steep sided limestone cliff in Klang Valley. This is because most of the limestone cliff occur with high elevation and for some of them, direct access is almost impossible due to thick vegetation. This limitation, restrict the rockfall assessment only at the bottom of the cliff face where direct access can be obtain. The presented data also deliver information to the rock climbers on the location of the overhanging block and its safety. Furthermore, precise cliff face data from the point cloud helps the climbers propose a new climbing route in the future.
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U-238 in IOCG Sin Quyen deposit, North Vietnam
More LessSummaryNatural radioisotope application in earth science is used domination now day. For example: to determine timing of underground water by ratio of U-238/U-234; to observe and predict young magma or earthquake activities by radon (Rn-222) research; to mineral prospecting or geochemical mapping based on study of the behavior or distribution of natural radionuclides on surface; or investigating non-radioactive mines based on relation with radioactive field. In this topic, the distribution and 3D modeling of uranium ore bodies will be create based on study of U-238 isotope in IOCG Sin Quyen deposit, North Vietnam.
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Determination of resonant properties of near-surface layer using microtremor data
Authors Y. Kolesnikov and K. FedinSummaryWe study the possibilities of direct determination of the resonant properties of near-surface sediments using microtremor records. The results of the passive seismic observations showed that the averaging amplitude spectra of a large number of noise records makes it possible to extract the standing waves generated in the near-surface layer from the microtremor. The frequencies of these waves (natural frequencies of the sediment layer) characterize the resonant properties of the near-surface sediments, and their amplitudes can be used to estimate the ground motion amplification relative to nearby places where unconsolidated sediments are absent. Recording both vertical and horizontal microtremor components allows to estimate the Poisson’s ratio of near-surface soils.
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Seismic noise spectral analysis techniques to monitor unstable rock blocks
Authors M. Taruselli, D. Arosio, L. Longoni, M. Papini and L. ZanziSummaryThis study presents the analysis of the ambient seismic noise collected on a small limestone block that was forced to fail during a field test. We compare different spectral analysis techniques with the objective of investigating their performances and suitability to monitor the rock block stability over time. Ambient vibration datasets were first pre-processed before the spectral analysis was carried out. The outcomes clearly show a variation in spectral content when approaching rock ultimate failure, especially when considering spectrograms and horizontal-to-vertical spectral ratio curves. This agrees with the assumption that the collapse of an unstable rock is preceded by a drop of its natural frequency due to the deterioration of rock bridges. The obtained results confirm the potential of ambient noise spectral analysis as a reliable tool to improve our capabilities of rock failure forecasting.
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Determination of Uniaxial Compressive Strength of Granite Rock Samples using Electrical Resistivity Measurement: NDT
Authors S. Ranjbar and S. Karimi NasabSummaryThe uniaxial compressive strength (UCS) is one of the most important design parameters in a rock engineering projects and it should be determined as a prerequisite for geotechnical studies. Since direct determination of geomechanical properties of rocks are usually expensive, time consuming and only capable in local geomechanical properties determination, simple and non-destructive test can be used as alternative method to have a good understanding of the rock behavior. Geophysical electrical techniques as a non-destructive test can be used both in the laboratory and in-situ. In this research, special electrodes were connected to the granite core samples to measure changes of the electrical resistivity values during the uniaxial compressive strength tests. A combination of the obtained results from the compressive strength tests and the electrical resistivity measurements illustrated the initial compression behavior of the rock samples and the development of micro-cracks before the sample failure. A strong logarithmic correlation between resistivity and uniaxial compressive strength was found by increasing the number of samples and using statistical analysis.
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