45 results on '"Ismail, Nazli"'
Search Results
2. The use of magnetic and geoelectrical methods to locate buried ancient artificial canals and wells around the cultural heritage of Indrapatra Fort, Aceh, Indonesia
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Ismail, Nazli, Yanis, Muhammad, and Asyqari, Amir
- Published
- 2023
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3. Suspended sediment transport generated by non-hydrostatic hydrodynamics in Northern Waters of Aceh, Indonesia
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Setiawan, Ichsan, Haditiar, Yudi, Syukri, Muhammad, Ismail, Nazli, and Rizal, Syamsul
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- 2023
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4. Application of ground-penetrating radar for shallow subsurface investigation at the coastal area of lhok village, lhoong, aceh besar regency, aceh
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Nanda Muhammad, Ismail Nazli, Mahlia Muna, Amril Farhadila, Munir Badrul, Asyqari Amir, Khatimah Husnul, and Haditiar Yudi
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Microbiology ,QR1-502 ,Physiology ,QP1-981 ,Zoology ,QL1-991 - Abstract
This research aims to identify subsurface layers in the coastal area of Lhok Village, Lhoong, Aceh Besar Regency, Aceh. Ground Penetrating Radar (GPR) was the primary method to extract information concerning concealed geological structures beneath the Earth's surface, including in coastal areas. GPR is a non-destructive geophysical technique that utilizes electromagnetic waves to explore and map subsurface layers. However, data collection involved field surveys utilizing GPR equipment directed at the ground's surface. During the survey, radar data was processed and analysed to pinpoint various subsurface level. The obtained information contributes to a deeper understanding of the region's geological characteristics and subsurface layers. Additionally, it aids in assessing geological risks, facilitating construction planning, and conserving natural resources in the area. Here, the outcomes of this study may also serve as a foundation for further research in geology and geophysics within the Aceh Coastal region.
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- 2024
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5. Fingerprinting sources of beach sands by grain-size, using mid-infrared spectroscopy (MIRS) and portable XRF. Implications for coastal recovery along a tsunami-struck delta coastline
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Chapkanski, Stoil, Brocard, Gilles, Lavigne, Franck, Meilianda, Ella, Ismail, Nazli, Darusman, Darusman, and Goiran, Jean-Philippe
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- 2022
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6. Shallow Structure Fault and Fracture Mapping in Jaboi Volcano, Indonesia, Using VLF–EM and Electrical Resistivity Methods
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Yanis, Muhammad, Ismail, Nazli, and Abdullah, Faisal
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- 2022
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7. Near surface electrical resistivity structures around an active fault trace in Weh Island, Indonesia
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Nanda Muhammad, Rizal Syamsul, Abdullah Faisal, Idroes Rinaldi, and Ismail Nazli
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shallow structure ,rapture ,seulimeum segment ,great sumatran fault ,paleo-seismic ,Technology ,Technology (General) ,T1-995 ,Science ,Science (General) ,Q1-390 - Abstract
Near-surface investigation has been carried out in Cot Abeuk, Weh Island, Indonesia. The area is part of the Seulimeum segment active fault, the northernmost branch of the Great Sumatran Fault. We measured two parallel electrical resistivity tomography profiles on the area with the direction perpendicular to the fault strike. The length of profile 1 and profile 2 are 111 m and 125 m, respectively, with 1 meter spacing between electrodes. Along the Profile 2, VLF-EM and Geomagnetic data were also acquired for complementary. The 2D inverted resistivity models show some minor fractures, which can be related to ruptures in the past. The structure was made by weathering rocks, clay and andesite. The models align with the analytic signal of total magnetic field anomalies as well as in-phase, Fraser filter and conductivity model derived from VLM-EM data. Following the successful models, this location is a potential candidate for paleo-seismological excavation.
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- 2021
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8. Identification of the distribution of archaeological artifacts in the area of wastewater treatment installation in the city of Banda Aceh using magnetic methods.
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Ramadhan, Gilang A., Azzam, Abiy B., Mahendra, T. Tiara, Zainal, Muzakir, Nanda, Muhammad, Asyqari, Amir, and Ismail, Nazli
- Abstract
The construction of the Banda Aceh Wastewater Treatment Plant has been delayed due to the discovery of archaeological artifacts in the construction area. In an effort to protect the existence of archaeological artifacts, a survey using the magnetic method was carried out to identify the distribution of archaeological artifacts. Total magnetic field intensity data were measured using the Proton Precession Magnetometer (PPM) equipment. The measuring area is 38 m × 40 m with 1599 measurement points and the distance between the points is 1 m. Total magnetic field anomaly values were obtained through the diurnal and International Geomagnetic Reference Field (IGRF) corrections. The maximum values of the total magnetic field anomaly are 71.0 nT and the minimum values are -99.5 nT. The maximum and minimum values are close to where the artifacts have been exposed. To obtain the distribution of anomalies, analysis signal processes were performed. The results succeeded in showing the existence of archaeological artifacts based on elongated and closed anomalies. Elongated anomalies were identified as a fence structure called diwai in Acehnese culture and the closure anomalies were identified as gravestones. The existence of these archaeological artifacts and their historical values need to be preserved so that they will be educational facilities and historical tourism objects for the community. [ABSTRACT FROM AUTHOR]
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- 2024
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9. Preliminary identification of candidate layer of 2004 Indian Ocean tsunami sediment deposited in Seungko Meulat village in Aceh Besar Regency, Indonesia.
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Mitaphonna, Rara, Ramli, Muliadi, Ismail, Nazli, and Idris, Nasrullah
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Investigation of sediments carried by tsunami 2004 was conducted in Seungko Meulat village, located in Lhoong subdistrict of Great Aceh, Aceh province, Indonesia. Seungko Meulat is directly opposite the Indian Ocean thus it is probable to be affected by the giant tsunami that has hit Aceh province. The deposit samples were taken at two points using a hand drill with a depth of over 1 meter. The collected samples have been further prepared in the laboratory including cleaning, refining, and sieving. Based on our visual observations, the 2004 tsunami candidate layer was found in our study. Tsunami deposits were identified at a depth of 4 cm with a thickness of 16-24 cm. The layers are characterized by light brown coarse to fine sand material located above a dark brown paleosoil layer with sharp erosion contacts. The tsunami deposits of coarse size at the bottom gradually turn into medium to fine sand at the upmost layer. The finer grain size of sand material reflects weakened tsunami waves in the pre-backwash deposition. Moreover, the lower part of the tsunami deposition layer is rich in plant roots, stems, and anthropogenic products. Based on the results obtained, the tsunami layers found in this study have characteristics that are almost similar to the tsunami layer found in other areas. [ABSTRACT FROM AUTHOR]
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- 2024
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10. The northernmost part of the Great Sumatran Fault map and images derived from gravity anomaly
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Yanis, Muhammad, Abdullah, Faisal, Zaini, Nasrullah, and Ismail, Nazli
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- 2021
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11. Numerical study of tides in the Malacca Strait with a 3-D model
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Haditiar, Yudi, Putri, Mutiara R., Ismail, Nazli, Muchlisin, Zainal A., Ikhwan, Muhammad, and Rizal, Syamsul
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- 2020
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12. Application of ERT, IP and VLF-EM Methods to Investigate Landslide-Prone Structures at Archaeological Sites in Lamreh, Aceh Besar, Indonesia.
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Ali, Bukhari, Nanda, Muhammad, Zainal, Muzakir, Yanis, Muhammad, Surbakti, Muhammad Syukri, Idris, Nasrullah, and Ismail, Nazli
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ARCHAEOLOGICAL excavations ,LANDSLIDES ,MIXING height (Atmospheric chemistry) ,CULTURAL property ,BRECCIA ,HAZARD mitigation - Abstract
Since the 21
st century, Lamreh, Aceh Besar Regency, Indonesia played an important role during the maritime silk route at the gate of the Malacca strait. This article investigates the subsurface structure of landslide-prone areas in cultural heritage based on 2D resistivity, chargeability and current density models of ERT, IP and VLF-EM methods, respectively. Field data measurements were carried out on 2 crossing profiles along the cliff suspected of experiencing landslides. The length of each profile is 220 with 4 m distance between stations. The 2D models reveal that the subsurface geological structure of Lamreh is composed of a mixed layer of clastic sediment and volcanic material at the top, followed by a layer of calcareous sandstone, and volcanic breccia at the bottom. The 3 layers are most easily distinguished in the resistivity model. The topmost layer is permeable but dry, i.e., characterized by a more resistive layer in the models. While the second layer is characterized by an intermediate conductivity and the bottom layer is highly conductive. The conductivity in these 2 layers is influenced by the degree of water content within the rocks. The chargeability models derived from IP data can distinguish between the dry layer on the surface and the saturated layer below. Meanwhile, the current density models obtained from VLF-EM data have proven the presence of fractures and faults along the profiles due to weathering as also seen in the resistivity models. [ABSTRACT FROM AUTHOR]- Published
- 2024
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13. Identification ratio of Si/Ti and Ca/Ti content by X-ray fluorescence in tsunami soil samples.
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LAHNA, KURNIA, MITAPHONNA, RARA, RAMLI, MULIADI, ISBAH, FALIQUL, YUSIBANI, ELIN, FAUZI, FAUZI, ISMAIL, NAZLI, and IDRIS, NASRULLAH
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X-ray fluorescence ,TSUNAMIS ,SOIL sampling ,SEDIMENTOLOGY ,PALEONTOLOGY - Abstract
Earthquakes and tsunamis natural disasters have repeatedly occurred on the coast of Aceh province, which lies between the confluence of two plates. The tsunami deposits in this area can provide important information regarding the reconstruction of marine attacks by past earthquakes and tsunamis. In general, tsunami deposits can be identified based on their geological, sedimentological, paleontological, and geochemical characteristics. In our research work, spectrometry X-ray fluorescence (XRF) has been utilized to investigate the geochemical signatures of tsunami-affected soil samples in Aceh province at three tsunami-impacted areas, namely Aceh Besar regency, Banda Aceh City, and Aceh Barat regency. The sampling point is located about a kilometer from the coastal line. Our findings indicate that tsunami-affected soils in Aceh Province after 10 years struck by tsunami contain terrestrial markers such as Fe and Ti, carbonate markers (Mg, Ca), and heavy metals elements (Cr, Ni, Cu, Zn, and Sr). On the other hand, in our study, the concentration ratios of several elements such as Si/Ti and Ca/Ti seem most suitable as a chemical signature for differentiating environmental conditions such as the 2004 Indian Ocean tsunami event. It could be noticed that geochemical analysis by XRF can be applied to characterize the tsunami-affected soils in several coastal areas of Aceh province. [ABSTRACT FROM AUTHOR]
- Published
- 2024
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14. The impact of Ming and Qing dynasty maritime bans on trade ceramics recovered from coastal settlements in northern Sumatra, Indonesia
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Tai, Yew Seng, Daly, Patrick, Mckinnon, E. Edwards, Parnell, Andrew, Feener, R. Michael, Majewski, Jedrzej, Ismail, Nazli, and Sieh, Kerry
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- 2020
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15. Archaeological evidence that a late 14th-century tsunami devastated the coast of northern Sumatra and redirected history
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Daly, Patrick, Sieh, Kerry, Seng, Tai Yew, McKinnon, Edmund Edwards, Parnell, Andrew C., Feener, R. Michael, Ismail, Nazli, and Majewski, Jedrzej
- Published
- 2019
16. The Historic Trading Port of Lamri on the North Sumatran Coast
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Daly, Patrick, McKinnon, Edmund Edwards, Feener, R. Michael, Seng, Tai Yew, Ardiansyah, Parnell, Andrew, Nizamuddin, Ismail, Nazli, Sieh, Kerry, and Majewski, Jedrzej
- Published
- 2019
17. Application of VLF-EM method for archaeological mapping on an ancient Graveyard in Banda Aceh.
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Ismail, Nazli, Yanis, Muhammad, and Alfarabi, Syauqi
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CEMETERIES , *RADIO transmitters & transmission , *GEOPHYSICAL surveys , *CULTURAL property , *ARCHAEOLOGICAL excavations - Abstract
Gampong Pande is an ancient village from the first millennium, the area is known as zero km of Banda Aceh Municipality today. Many cultural heritages are found around the area including a complex of ancient graveyards known as diwai by Acehnese. Physically the structure has been destroyed and buried by aging and natural hazards processes, archaeological investigation is needed for conservation. Before archaeological excavation, a geophysical survey of the very low frequency electromagnetic (VLF-EM) method has been applied to image subsurface structures of the ancient graveyard. The VLF-EM data were measured using the GEM-systems console, namely, GSM-19 T. Data measurement was carried out on 20 profiles with a 1 m distance between stations. The length of each profile is 45 meters so that the measurement covered the graveyard area. Magnetic fields in terms of in-phase and out-phase data were measured with frequencies 19.8 kHz and 21.4 kHz propagated by VLF radio transmitters. Based on the data, the area with the graveyard structure is shown by lower in-phase and out-phase values than the area outside the structure. The first derivative of VLF-EM data (i.e., Fraser filter) analysis indicated some elongated buried structures in the subsurface. The structures were further clarified by 2D modeling of the Karous Hjelt filter as the wall of the graveyard was 1 meter to 4 meters. [ABSTRACT FROM AUTHOR]
- Published
- 2023
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18. Investigation of possible Paleo tsunami deposit in Seubadeh Village in the Southern part of Aceh.
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Prasetyo, Aditya Vethra, Sukman, Muhammad Mirda, Vahreza, Anshar, Mitaphonna, Rara, Fauzi, Rajibussalim, Ismail, Nazli, Lahna, Kurnia, and Idris, Nasrullah
- Subjects
TSUNAMIS ,LASER-induced breakdown spectroscopy ,SOIL sampling ,COASTS - Abstract
A study to locate the paleotsunami deposition was carried out in Seubadeh Village situated in East Bakongan Timur sub-district of South Aceh, which is a part of the province of Aceh, Indonesia. Seubadeh Village is located on the coast and faces directly to Indian Ocean, thus possibly affected by historic tsunamis occured in the past. this area has been identified geologically as one of the areas that has the potential to store paleotsunami deposition. The sample collection was carried out by drilling the ground using coring at several points with depth of up to 3 meters. The collected soil samples have been processed in the laboratory, dried and sifted. Visual observation of the soil and sediment samples taken showed that it mainly consits of sand and ordinary soil. However, it was found that there were parts of the deposited layer that show geological characteristics fit to characteristics of a paleo-tsunami deposition layer. Thus, the excavated deposition layer is a very potential candidate for the paleotsunami layer. The paleotsunami candidate layer was found at at a depth of 2.5 meters below ground level. The deposition layer considered as the candidate paleotsunami deposition consists of 2 separate layers with different thickness. The first deposition layer has a thickness of more than 30 cm, while the second layer has a thickness of more than 9 cm. The paleotsunami deposition layer found will be further characterized by geological methods and optical analytical tools, namely laser induced breakdown spectroscopy (LIBS). This study implies that the south west coast of Aceh holds records of past tsunami events, and Seubadeh Village could be an appropriate area to study paleotsunami further. [ABSTRACT FROM AUTHOR]
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- 2023
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19. X-Ray fluorescence (XRF) investigation of soil sample from 2004 Indian Ocean tsunami affected region in Aceh of Indonesia.
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Mitaphonna, Rara, Ramli, Muliadi, Ismail, Nazli, Lahna, Kurnia, and Idris, Nasrullah
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INDIAN Ocean Tsunami, 2004 ,TRANSITION metals ,TRACE elements ,X-ray fluorescence ,SOIL sampling ,ALKALI metals - Abstract
Investigation of affected soils by the massive Indian Ocean tsunami 2004 in Banda Aceh city was carried out utilizing X-Ray Fluorescence (XRF) technique for analyzing and identifying its chemical component. Based on this preliminary study, the XRF investigation demonstrated that the affected soil samples in Banda Aceh city 10 years after the tsunami disaster were still contaminated by alkali metal elements identified as salt content (Ca and K) and transition metal elements involving Al, Si, P, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, and Sr. On the other hand, this research also revealed that Fe element dominantly appeared in the tsunami-affected soils in more than 35% of collected samples, then it followed by Si and Ca elements. It could be noticed that almost all of the chemical elements that appeared in the soil 10 years after the tsunami event were higher than the similar experiment held 1.5 and 3 years after the Indian Ocean tsunami 2004 in Aceh province. This work found that the concentration ratio of Fe/Ti and Si/Ti is far higher than other elements, thus the ratio is potential chemical signature to characterize the soil samples impacted by 2004 Indian Ocean tsunami in Banda Aceh city. [ABSTRACT FROM AUTHOR]
- Published
- 2023
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- View/download PDF
20. Characteristics of plasma produced from tsunami impacted soil sample using a transversely excited atmospheric pressure-carbon dioxide (TEA-CO2) laser.
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Mitaphonna, Rara, Ramli, Muliadi, Lahna, Kurnia, Ismail, Nazli, Kurihara, Kazuyoshi, and Idris, Nasrullah
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LASER plasmas ,SOIL sampling ,PLASMA temperature ,PLASMA density ,TSUNAMIS ,MAXWELL-Boltzmann distribution law - Abstract
In this work, plasma characteristics in terms of temperature and electron density of a plasma of the tsunami impacted soil sample induced by a transversely excited atmospheric carbon dioxide (TEA-CO
2 ) LIBS was studied. Practically, the tsunami impacted soil samples was taken from at the worst affected area by the giant tsunami, Banda Aceh city, Aceh province, Indonesia. The generated plasma has been produced after TEA-CO2 pulses laser was targeted onto sample placed on a sample holder in air surrounding gas. The emission spectral lines emitted from the plasma region collected using system of an optical multichannel analyser (OMA) allowed atomic emission lines could be clearly identified. The temperature of plasma was estimateed through the method of Boltzmann plot, while the plasma electron density has been obtained by method of Saha-Boltzmann using spectral lines of calcium both atomic and ionic spectral lines. As results, the plasma temperature and electron density produced were T = 8691 K and 5,2 × 1015 cm−3 , respectively. Generally, the plasma temperature and density electron obtained are fit to the Maxwell distribution criteria kT <50,000 and Mcwhriter's criteria (Ne >1.6×1012 T½ (ΔE)3 ) for plasma laser in state of local thermal equilibrium LTE). [ABSTRACT FROM AUTHOR]- Published
- 2023
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21. Co-seismic offsets due to two earthquakes (M w 6.1) along the Sumatran fault system derived from GNSS measurements
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Ito, Takeo, Gunawan, Endra, Kimata, Fumiaki, Tabei, Takao, Meilano, Irwan, Agustan, Ohta, Yusaku, Ismail, Nazli, Nurdin, Irwandi, and Sugiyanto, Didik
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- 2016
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22. Empirical model for the estimation of global solar radiation in the Aceh Besar Regency, Aceh.
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ISLAMI, MUHAMMAD IRFAN, ISMAIL, NAZLI, ISMAIL, ISMAIL, and RIMASILANA, DEA
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SOLAR radiation , *SOLAR energy , *SUNSHINE , *CLIMATOLOGY , *DATA analysis - Abstract
Solar energy plays an important role in the temperature distribution on the Earth's surface and essential energy that sustains life for human. In the calculation of solar energy, the limitation of solar radiation data is a major obstacle. Solar radiation data is very limited at some observation stations due to the costly procurement of measuring instruments and complicated techniques. Estimation of global solar radiation using empirical models is one way to overcome the limitations of global solar radiation data at various locations. This study built the Angstrom-Prescott model to estimate global solar radiation based on the sunshine duration's parameter in Aceh Besar Regency. Two years (2019-2020) global solar radiation and sunshine duration data from Aceh Climatological Station were used to estimate global solar radiation in 2021. Data for 2021 was using to evaluate the equation H/H0=0.28+0.22 (n/N), the results showed good model accuracy with an RMSE value of 0.052 and a MAPE of 11% (good forecasting). The model equation has been reliable to calculate solar radiation in four locations in Aceh Besar Regency. [ABSTRACT FROM AUTHOR]
- Published
- 2023
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23. Identification of changes in sediment provenance by mid-infrared spectroscopy and sediment source fingerprinting in two Holocene river deltas: Albegna, Italy, and Aceh, Indonesia
- Author
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Chapkanski, Stoil, Brocard, Gilles, Lavigne, Franck, Vittori, Cécile, Meilianda, Ella, Ismail, Nazli, Darusman, Darusman, Goiran, Jean-Philippe, Chapkanski, Stoil, Laboratoire de géographie physique : Environnements Quaternaires et Actuels (LGP), Université Paris 1 Panthéon-Sorbonne (UP1)-Université Paris-Est Créteil Val-de-Marne - Paris 12 (UPEC UP12)-Centre National de la Recherche Scientifique (CNRS), ARCHEORIENT - Environnements et sociétés de l'Orient ancien (Archéorient), Université Lumière - Lyon 2 (UL2)-Centre National de la Recherche Scientifique (CNRS), Tsunami and Disaster Mitigation Research Center (TDMRC), Department of Geophysics, Syiah Kuala University. (UNSYIAH), and Post-Graduate School, Universitas Syiah Kuala (UNSYIAH)
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[SDE.MCG] Environmental Sciences/Global Changes ,[SHS.ENVIR] Humanities and Social Sciences/Environmental studies ,[SDE.MCG]Environmental Sciences/Global Changes ,[SHS.ENVIR]Humanities and Social Sciences/Environmental studies ,[SHS.GEO] Humanities and Social Sciences/Geography ,[SDU.STU] Sciences of the Universe [physics]/Earth Sciences ,[SDU.STU]Sciences of the Universe [physics]/Earth Sciences ,[SHS.GEO]Humanities and Social Sciences/Geography ,ComputingMilieux_MISCELLANEOUS - Abstract
International audience
- Published
- 2022
24. Distribution of landforms and buried sedimentary deposits during the growth of the Aceh River delta (Sumatra, Indonesia).
- Author
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Chapkanski, Stoil, Le Doaré, Maureen, Brocard, Gilles, Steuer, Annika, Siemon, Bernhard, Lavigne, Franck, Ismail, Nazli, Meilianda, Ella, Virmoux, Clément, Darusman, Darusman, and Goiran, Jean-Philippe
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BEACH ridges ,LANDFORMS ,COASTS ,GEOMORPHOLOGICAL mapping ,ROGUE waves ,RIVER channels ,TIDAL flats ,FLUVIAL geomorphology - Abstract
Fluvial and coastal landforms are indicative of landscape river delta evolution over time and provide clues for understanding coastal adjustments to sea-level and fluvial dynamics fluctuations, tectonic displacements, and extreme waves. We have mapped the surface and sub-surface footprints of fluvial and coastal geomorphological features in the Aceh River delta, northern Sumatra, using imagery dataset, vertical facies logging and helicopter electromagnetic surveys. The result is a geomorphological map at the scale of 1:75.000 which outlines the main features of the deltaic plain, including rivers, tidal and buried channels, fluvial levees, beach ridges, swales, tidal flats and lagoons. We compare their spatial distribution to the geometry of buried sediment bodies, revealed by boreholes and resistivity maps. Buried channel belts and floodplain deposits document the former locations of the distributary channels of the Aceh River. Coastal-parallel beach ridges evidence 7–8 km of asymmetric delta progradation since the mid-Holocene sea-level high stand. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
25. Investigation of groundwater resources using controlled-source radio magnetotellurics (CSRMT) in glacial deposits in Heby, Sweden
- Author
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Ismail, Nazli, Schwarz, Gerhard, and Pedersen, Laust B.
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- 2011
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26. SUBSURFACE MAPPING OF FAULT STRUCTURE IN THE WEH ISLAND BY USING A 3D DENSITY OF GLOBAL GRAVITY.
- Author
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Abdullah, Faisal, Yanis, Muhammad, Razi, Muhammad Haikal, Zainal, Muzakir, and Ismail, Nazli
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EARTHQUAKE hazard analysis ,BRECCIA ,SINGULAR value decomposition ,GRAVITY ,VOLCANIC ash, tuff, etc. ,ISLANDS - Abstract
Indonesia's Aceh Province is an earthquake-prone area due to its location on the Great Sumatran Fault (GSF). Currently, earthquake mitigation by the local government constantly refers to the regional seismic hazard maps. However, some sources of an earthquake in the province which had caused damage to buildings and loss of human life were not easily traced to the fault on the surface. Currently, the mapping activities related to the Sumatra fault lines are only focused on the mainland. In contrast, the continuity of the GSF fault in the area of the sea and surrounding islands is very rarely studied. Weh Island is inhabited by many communities and has become a popular tourism area. This study aims to map the regional and local fault structure on the Weh Island using the gravity model plus (GGMPlus) data. We used the GGMPlus data with a resolution of 200 m for detailed mapping of regional and local faults. The 3D inversion of the GGMPlus data was carried out to obtain density parameters using two models, namely Singular Value Decomposition (SVD) and Occam optimization. The 3D inversion describes the presence of high-density rock blocks. A density value ranging between 2.72 - 2.96 gr/cm³ is interpreted as rocks with andesite-basaltic lava composition and lava or pyroclastic breccias resulting from local volcanic products as the rocks creating the island. Therefore, the zone interpreted as a local fault had a smaller density value (2.5 - 2.65 gr/cm³) than the surrounding. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
27. Geophysics and geomorphic observation for near-surface structures mapping of Seulimeum Fault on Lamtamot area, Northern Sumatra.
- Author
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YANIS, MUHAMMAD, ISLAMI, GOZIAN, and ISMAIL, NAZLI
- Subjects
GEOPHYSICAL observations ,ELECTRICAL resistivity ,MAGNETOTELLURICS ,GEOPHYSICAL surveys ,GEOPHYSICS ,NEAR-surface geophysics ,ELECTRONIC data processing - Abstract
In the northern part of Sumatra Island, Indonesia, the Great Sumatran Fault, which can cause an earthquake, was divided into two segments: the Aceh and Seulimeum. An effort to reduce the risk is mapping the fault area, especially in the region that does not clearly show the sign on the surface, e.g., in the Lamtamot area, Indonesia. Electrical resistivity is widely used to study shallow structures, but the method requires more time when applied in a large area. This research explores the potential of an extremely low frequency (very low frequency-electromagnetic; VLF-EM) method to investigate the shallow fault of the Seulimeum segment. Here, the VLF-EM is compared with other geophysical methods such as resistivity and magnetic methods. For comprehensive results, the geomorphic observation that was conducted covered outcrops of the fault and trenching sites in the geophysical study for validating the model. A similar pattern of the VLFEM and electrical resistivity data has been shown in a two-dimensional profile using data processing. The fault structure can be mapped at a distance of 20-24 m from the profile measurement, which is demonstrated by the low current density associated with the conductive zone from the VLF-EM, and low resistive anomaly in electrical resistivity. The fault can also be confirmed via magnetic intensity, which significantly increases at the same distance (20-25 m) of the VLF-EM and electrical resistivity. The geomorphic observation shows outcrops of fault activity, such as fault scarp, fractures, and faults, in the same direction as the Seulimeum segment, while scrap extends in the northwest direction up to ~20 m around the geophysical surveys. As revealed by the results, the VLF-EM method combined with other geophysical surveys and geomorphic observation can be used as a technique to image the fault that shows the shallow structure of the Seulimeum fault at 20-32 m along the profile. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
28. Fluvial and coastal landform changes in the Aceh River delta (northern Sumatra) during the century leading to the 2004 Indian Ocean tsunami.
- Author
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Chapkanski, Stoil, Brocard, Gilles, Lavigne, Franck, Tricot, Camille, Meilianda, Ella, Ismail, Nazli, Majewski, Jedrzej, Goiran, Jean‐Philippe, Alfian, Dedy, Daly, Patrick, Horton, Benjamin, Switzer, Adam, Degroot, Veronique, Steuer, Annika, Siemon, Bernhard, Cavero, Julien, Virmoux, Clement, and Darusman, Darusman
- Subjects
INDIAN Ocean Tsunami, 2004 ,COASTS ,FLUVIAL geomorphology ,RIVER channels ,BEACH ridges ,GLACIAL landforms ,AERIAL photographs ,REMOTE-sensing images - Abstract
River deltas are strongly affected by demographic growth and by the intensification of land use. The migration of deltaic coastlines is often rapid, threatening urban settlements, coastal farming, and coastal biotopes. Some deltas benefit from centuries of monitoring, such that the evolution of their coastline is well documented. For most deltas, however, such long records do not exist. The study of their geomorphological evolution can benefit from overlapping maps drafted over time, combined with aerial photographs and satellite images, to track the evolution of fluvial and coastal landforms. Both fluvial and coastal landforms are sensitive to variations in water and sediment supply, such that covariations in the evolution of these landforms, or the lack thereof, provide clues on the contribution of water and sediment supply to delta evolution. We document the evolution of river channels and coastlines in the delta of the Aceh River in northwest Sumatra, by overlying maps, ortho‐rectified aerial photographs, and satellite images covering the past 130 years. We assess the accuracy of the overlays, and then use multivariate statistics to analyze the co‐evolution of fluvial and coastal landforms. We propose that a progressive decrease in sediment supply spurred river channel lengthening and narrowing, landward migration of the shoreline, and narrowing of beach ridges. The 2004 Indian Ocean tsunami generated an instantaneous retreat of the coastline that amounts to ∼53% of the coastal retreat from 1884 to 2019 ce. Post‐tsunami evolution is marked by an irreversible acceleration of previous trends. Beach ridges located up‐drift of rivers and tidal channel mouths are more sensitive to long‐term landward retreat and tsunamigenic erosion. [ABSTRACT FROM AUTHOR]
- Published
- 2022
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29. Islamisation and the formation of vernacular Muslim material culture in 15th-century northern Sumatra.
- Author
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Feener, R. Michael, Daly, Patrick, Edwards McKinnon, E., En-Ci, Luca Lum, Ardiansyah, Nizamuddin, Ismail, Nazli, Seng, Tai Yew, Rahardjo, Jessica, and Sieh, Kerry
- Subjects
MATERIAL culture ,FIFTEENTH century ,SUMATRA Earthquake, 2004 ,SEPULCHRAL monuments - Abstract
This study presents a distinctive type of Muslim gravestone found on the northern coast of Sumatra, Indonesia, that dates to the 15th century. These grave markers, locally known as plang-pleng, provide evidence for the formation and disappearance of an early form of vernacular Muslim material culture in Southeast Asia. We documented over 200 of these gravestones during a large-scale archaeological landscape survey. In this article, we present a typology of these gravestones based upon shape, morphology and ornamentation. We then discuss their geographical distribution and periodisation based on examples with dated Arabic inscriptions. Our results show that these gravestones were initially a cultural product of the historic trading settlement of Lamri dating from the early 15th century. By the middle of the 15th century, variations of these stones started to appear widely near the Aceh river. The plang-pleng tradition was displaced in the early 16th century by the batu Aceh gravestones associated with the Aceh sultanate, which became a standardised part of Muslim material culture in the region for the next two centuries. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
30. Physical Model of Discontinuity Response in Landslide Application Using Geometry Normalized Electromagnetic System (GNES).
- Author
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Surbakti, Muhammad Syukri, Bukhari, Ismail, Nazli, Idris, Nasrullah, Isa, Muhammad, Yusibani, Elin, Zakaria, Nurman, Muhammad, and Jafri, MohdZubir Mat
- Subjects
ALUMINUM plates ,LANDSLIDES ,ELECTROMAGNETIC fields ,METAL defects ,GEOMETRY ,EDDIES - Abstract
The discontinuity in a fractured land in landslide application could be represented by the metal defects in the physical modeling that will usually reduce the mass of the metal. The scale factor n is important for interpreting the field data using the physical model data. In this physical modeling (n=100), the anomaly targets are aluminum plates and aluminum plates with the discontinuities. It is assumed the nonconductive environment. In the free-air condition which has zero conductivity is become representative of this environment. In the zero conductivity, the secondary field from the medium is not presence. In this condition, there are no phase differences between transmitted electromagnetic fields and that was received by the receiver. The discontinuity in this term is any treatment or defect that causes disruption or leads to a reduction in response triggered by the eddy currents. The discontinuities used on the thin plates and flaws will interrupt or reduce the eddy current flow on the plate, thereby reducing the induced voltage on the receiving coil and increasing its effective impedance. This is the basis of eddy current measurement. The electromagnetic field response to a metal that has discontinuities will change the eddy current portion. The eddy current that changes, therefore, will change the second field so that the percent response (% Response) of the receiver in the Geometry Normalized Electromagnetic System (GNES) instrument will also change. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
31. MAPPING FAULTS DISTRIBUTION BASED ON DEM DATA FOR REGIONAL SPATIAL PLAN ASSESSMENT OF SABANG MUNICIPALITY, INDONESIA.
- Author
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Nanda, Muhammad, Rizal, Syamsul, Abdullah, Faisal, Idroes, Rinaldi, and Ismail, Nazli
- Subjects
REGIONAL planning ,DIGITAL elevation models ,GEOLOGICAL maps ,CITIES & towns ,DATABASES - Abstract
Sabang Municipality is located on Weh Island. As a maritime gateway to Indonesia, the island has been inaugurated as an Integrated Economic Development Zone by the Government. A complete infrastructure has been planned and built to support the manufacturing and tourism industries in the region. On the other hand, the island is potentially affected by geological hazards. Tectonically, the island is crossed by the Great Sumatran Fault (GSF), but few studies have shown the fault trace on the island. To ensure sustainable development, such potential geological hazards have to be incorporated into the Regional Spatial Plan (RSP) of the city. In this study, fault distribution on the island were mapped using shaded relief, slope, lineament extraction, orientation, and Fault Fracture Density (FFD) distribution extracted from the National Digital Elevation Model (DEMNAS) data. The map shows that the island is crossed by several fault lines, but the one located along the eastern with northwest-southeast direction is considered tectonically active. However, according to the RSP, the eastern Weh Island is the most developed area. The city center, airport, seaports, dam, sewerage treatment plan, landfills, and diesel power electricity generator for the city are situated along this fault line. It seems that the RSP of Sabang Municipality was issued without taking into account potential geological hazard maps in it. Some recommendations have been proposed to reduce the impact of losses in the future. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
32. 2D INVERSION AND STATIC SHIFT OF MT AND TEM DATA FOR IMAGING THE GEOTHERMAL RESOURCES OF SEULAWAH AGAM VOLCANO, INDONESIA.
- Author
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Marwan, Yanis, M., Idroes, Rinaldi, and Ismail, Nazli
- Subjects
GEOTHERMAL resources ,GEOTHERMAL ecology ,TRANSMISSION electron microscopy ,VOLCANOES ,CAP rock ,SURFACE topography - Abstract
In order to increase the geothermal exploration, the magnetotelluric (MT) method has been used to study the subsurface of the Seulawah Agam volcano, Aceh Province, Indonesia. Similar to all resistivity methods that are based on measuring the electric field on the surface, the MT commonly contains a static shift problem, which is caused by the heterogeneities near the surface and the different topography of the volcano. The static effect can be expressed as a vertical shift from the apparent resistivity curve. In this study, the apparent resistivity data from the 1D inversion of the Transient Electromagnetic (TEM) method were used to correct the static shift problem in the MT data. Both methods were acquired in the same site at ten stations along with a 12 km distance profile that crosses the Seulawah Agam volcano. The north-south profile of the volcano area appeared to host a geothermal system. The 1D inversion in the TEM data shows a low resistivity layer that indicated a cap rock with a thickness up to 1000 m. The area below the cap rock is estimated to be a reservoir zone while the 2D inversion of MT shows that the deep conductor below 2000 m could be the heat source for the Seulawah Agam geothermal system. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
33. Penultimate predecessors of the 2004 Indian Ocean tsunami in Aceh, Sumatra: stratigraphic, archeological, and historical evidence
- Author
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Horton, Benjamin P., Vane, Christopher H., Feener, R. Michael, Rubin, Charles M., Shen, Chuan-Chou, Ismail, Nazli, Sieh, Kerry, Daly, Patrick, McKinnon, E. Edwards, Pilarczyk, Jessica E., Chiang, Hong-Wei, and Earth Observatory of Singapore
- Subjects
Social sciences::Geography::Physical geography [DRNTU] - Abstract
We present stratigraphic, archeological and historical evidence for two closely timed predecessors of the giant 2004 tsunami on the northern coast of Aceh, northern Sumatra. This is the first direct evidence that a tsunami played a role in a fifteenth century cultural hiatus along the northern Sumatran portion of the maritime silk route. One seacliff exposure on the eastern side of the Lambaro headlands reveals two beds of tsunamigenic coral rubble within a small alluvial fan. Radiocarbon and Uranium-Thorium disequilibrium dates indicate emplacement of the coral rubble after 1344 ± 3 C.E. Another seacliff exposure, on the western side of the peninsula, contains evidence of nearly continuous settlement from ~1240 C.E. to soon after 1366 ± 3 C.E., terminated by tsunami destruction. At both sites, the tsunamis are likely coincident with sudden uplift of coral reefs above the Sunda megathrust 1394 ± 2 C.E., evidence for which has been published previously. The tsunami (or tsunami pair) appears to have destroyed a vibrant port community and led to the temporary recentering of marine trade dominance to more protected locations farther east. The reestablishment of vibrant communities along the devastated coast by about 1500 CE set the stage for the 2004 disaster. Published version
- Published
- 2015
- Full Text
- View/download PDF
34. The Designing Of E-Learning Model for Disaster Risk Reduction In Serambi Mekkah University Banda Aceh.
- Author
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Musliyadi, Samsuddin, Jalil, Zulkarnain, and Ismail, Nazli
- Subjects
HAZARD mitigation ,EARTHQUAKES ,TSUNAMIS ,MOBILE learning ,UNIVERSITIES & colleges ,INTERNET in education - Abstract
Disaster Risk Reduction (DRR) is one of the important point to reduce the victim in a disaster. Aceh is the one of province in Indonesia that was hit by the earthquake and tsunami on 2004 that there are so many victims. The education of DRR was to be a reference for the university to implementation the DRR modules. This research was conducted in Serambi Mekkah University with the populations among the students and the lecturer. In Sendai Framework mentioned that the education of disaster modules was one of the factor to influence the DRR programs to achive the community for resilient disaster (ISDR, 2015). The elearning was designed using online media to publish that use internet facilities through a website, and the content of website such as text, images, videos and others that will help to aim the DRR programs. This research was used research and development approach, where are in these research are was doing several models and methods to get the suit models and methods in develop to be a models that can be use for the long periods. The populations are 50 individuals and the technique of sample using saturated sampling that means all of the populations use as the sample. The result of the research show that the students and the lecturers are very support in DRR programs in the university and they hope that can be soon to be design, develop and implementation in Serambi Mekkah University. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
35. Evaluation of the 2012 Indian Ocean Coseismic Fault Model in 3-D Heterogeneous Structure based on Vertical and Horizontal GNSS Observation.
- Author
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Cecep Pratama, Takeo Ito, Takao Tabei, Fumiaki Kimata, Gunawan, Endra, Yusaku Ohta, Tadashi Yamashina, Nurdin, Irwandi, Sugiyanto, Didik, Muksin, Umar, Ismail, Nazli, and Meilano, Irwan
- Subjects
METEOROLOGICAL observations ,EARTHQUAKES ,GEOLOGIC faults ,SEISMIC migration ,TOPOGRAPHY ,BATHYMETRY - Abstract
Lack of observation network in the vicinity of oceanic intraplate earthquake lead the estimation of coseismic fault slip with high uncertainty. Satriano et al. [2] and Wei et al. [3] found NNE trending left-lateral slip as the primary features. In another hand, Yue et al. [4] and Hill et al. [5] proposed WNW trending right-lateral faults structure as the main characteristic. Here, we investigate the coseismic fault model that could explain the coseismic offset both vertical and horizontal in a 3-D heterogeneous earth structure. We constructed finite element model that include threedimensional velocity structure, topography/bathymetry, spherical-earth and subducting slab. In this study, we employed scaling slip to adjust slip amount and total seismic moment. Instead of original slip amount, we preserve seismic moment as a basis comparison. Based on vertical and horizontal observation data, WNW trending right-lateral fault could fit better than NNE trending left-lateral fault. The present study demonstrates best-fit calculation using scaling slip optimized to the horizontal or vertical observation lead the both fault model worsen the misfit of vertical or horizontal component, respectively. This result analysis indicates a trade-off between vertical and horizontal component and reflects the importance of revisiting the fault slip modeling incorporating vertical and horizontal data equally. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
36. DEEP AND SHALLOW STRUCTURES OF GEOTHERMAL SEULAWAH AGAM BASED ON ELECTROMAGNETIC AND MAGNETIC DATA.
- Author
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Marwan, Syukri, Muhammad, Idroes, Rinaldi, and Ismail, Nazli
- Subjects
ELECTROMAGNETIC devices ,MAGNETOTELLURIC prospecting ,VLF emissions - Abstract
Indonesia is a country with the largest geothermal reserves in the world, but exploration and utilization of geothermal energy are still low. As an effort in increasing exploration process, an integrated geophysical method to image the subsurface structure of the geothermal system has been done at Seulawah Agam Geothermal Field, Aceh Province, Indonesia. Very low frequency (VLF-R) method was used for shallow and magnetotellurics method for deep structures studies in the area. The magnetic method was used for a complementary of the electromagnetic methods. Magnetotelluric data were acquired at ten stations along a 30 km distance profile crossing the Seulawah Agam volcano in a north-south direction. The VLV-R and Magnetic stations were measured on the Ie Ju manifestation area only, located at the northern slope of the volcano. The magnetic and VLF-R methods have been able to investigate the local structure, while the regional structure of subsurface is described by the magnetotelluric method. 2D resistivity model of magnetotelluric data shows a conceptual model of the geothermal system based on resistivity variation. The model also reveals two local faults crossing the volcano in a northwest-southeast direction. Most of the geothermal manifestations in Seulawah Agam are controlled these faults. Application of VLF-R and magnetic methods on the Ie Ju manifestation area has shown clearly near surface structures of the area. The inverted models have strong agreement with a reduction to the pole of total magnetic field anomalies. Presence of the conductors in the resistivity models coincides with low total magnetic field anomalies. In addition, the total magnetic field anomalies map can be also used to locate the presence of geothermal manifestation with or without their appearance on the surface [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
37. Coseismic Slip Distribution of the 2 July 2013 Mw 6.1 Aceh, Indonesia, Earthquake and Its Tectonic Implications.
- Author
-
Gunawan, Endra, Widiyantoro, Sri, Rosalia, Shindy, Daryono, Mudrik Rahmawan, Meilano, Irwan, Supendi, Pepen, Takeo Ito, Takao Tabei, Fumiaki Kimata, Yusaku Ohta, and Ismail, Nazli
- Abstract
This study investigates the coseismic slip distribution of the 2 July 2013 M
w 6.1 Aceh earthquake using Global Positioning System (GPS) data, measured geological surface offsets, and an aftershock distribution for a period of four days after the mainshock. We use the aftershock distribution to constrain the fault-plane strike of a right-lateral fault identified as the Pantan Terong segment. We estimate the coseismic slip distribution with dip angle information from the Global Centroid Moment Tensor (CMT) (model 1) and U.S. Geological Survey (USGS) (model 2) catalogs. We also estimate the coseismic slip distribution using another two fault models. Model 3 is constructed on a left-lateral fault, the Celala segment, which is perpendicular to the Aceh segment of the Sumatran fault, and model 4 is constructed using the multiple faults in models 2 and 3. We further estimate the coseismic slip distribution of this earthquake by employing an elastic dislocation model, inverting only the GPS displacements for model 3 and jointly inverting GPS displacements and geological surface offsets for models 1, 2, and 4. Minimum misfit between data and model is obtained with model 3, suggesting that the earthquake slip occurred along a left-lateral fault. Analysis of stress transfer caused by the 2013 earthquake indicates that the stress level along the Pantan Terong segment is >0.4 bar and the southeast part of Aceh segment was brought ~0.3 bar closer to failure, suggesting a possible earthquake occurrence in the future. This work demonstrates that the seismicity-derived fault plane fails to predict the surface displacement, and that the inferred Celala segment produces positive stress on Pantan Terong segment and potentially triggered all the aftershocks. [ABSTRACT FROM AUTHOR]- Published
- 2018
- Full Text
- View/download PDF
38. Geodetic and Geomorphic Evaluations of Earthquake Generation Potential of the Northern Sumatran Fault, Indonesia.
- Author
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Tabei, Takao, Kimata, Fumiaki, Ito, Takeo, Gunawan, Endra, Tsutsumi, Hiroyuki, Ohta, Yusaku, Yamashina, Tadashi, Soeda, Yoshio, Ismail, Nazli, Nurdin, Irwandi, Sugiyanto, Didik, and Meilano, Irwan
- Published
- 2017
- Full Text
- View/download PDF
39. Controlled Source Radiomagnetotelluric (CSRMT) Applications in Environmental and Resource Exploration
- Author
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Ismail, Nazli
- Subjects
Magnetotelluric ,radio magnetotelluric ,Geofysik ,fracture zone ,resolution ,plane wave ,two-dimensional model ,three-dimensional model ,near surface geophysics ,controlled-source tensor magnetotelluric ,inversion ,Geophysics ,sediment ,near field effect ,forward modelling - Abstract
An integrated use of radio magnetotelluric (RMT) and controlled source tensor magnetotelluric (CSTMT) measurements, the so-called CSRMT method, has been employed in environmental and resource exploration studies. A number of case histories, including a groundwater investigation in glacial deposits, a study of fracture zones for geotechnical purposes and a mining exploration study of a copper deposit, are presented in this thesis in order to illustrate the usefulness and capability of the CSRMT method. The resolutions of the estimated models using various types of data are studied. Magnetotelluric transfer functions are used to analyze the dimensionality, the near surface resistivity distortions and the near field effects in the case of CSTMT data analysis. The near field effects in CSTMT data have also been identified by performing 2½D forward modelling. Data analysis, dimensionality tests and forward modelling show that at the lowest frequencies used the CSTMT transfer functions are generally distorted by source effects, except when the source-receiver distances are sufficient large compared with the penetration depth. Regarding CSTMT transfer functions, apparent resistivities are generally less distorted than phases. TM mode transfer functions are more affected by the sources than TE mode, while tipper vectors generally contain source signatures at all frequencies. Based on the analysis of dimensionality and source effects 2D inverse modelling of CSTMT and RMT data, as well as their combination, have been performed under the plane wave assumption. The RMT method proved to be a powerful tool for imaging the upper 50 m near-surface, but their penetration depth reduces as a conductive layer structures cover the targets at depth. The penetration depth can be increased by including the CSTMT data in the modelling if the measurements are in the far field range. The resolution of the deeper parts of the models may be improved by performing a joint inversion of TE and TM modes, if the strike direction is well-defined. Alternatively, inversion of determinant data can be performed, since the determinant data are less affected by 3D structures and source effects. However the resolution of the determinant models is somewhat degraded compared to the models inverted from combined TE and TM modes.
- Published
- 2009
40. Co-seismic offsets due to two earthquakes ( M 6.1) along the Sumatran fault system derived from GNSS measurements.
- Author
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Ito, Takeo, Gunawan, Endra, Kimata, Fumiaki, Tabei, Takao, Meilano, Irwan, Agustan, Ohta, Yusaku, Ismail, Nazli, Nurdin, Irwandi, and Sugiyanto, Didik
- Subjects
SUMATRA Earthquake, 2004 ,EARTHQUAKE hazard analysis ,GLOBAL Positioning System ,INDIAN Ocean Tsunami, 2004 ,MARKOV chain Monte Carlo ,DENSITY functionals ,COULOMB functions - Abstract
Since the 2004 Sumatra-Andaman earthquake ( M 9.2), the northwestern part of the Sumatran island has been a high seismicity region. To evaluate the seismic hazard along the Great Sumatran fault (GSF), we installed the Aceh GNSS network for the Sumatran fault system (AGNeSS) in March 2005. The AGNeSS observed co-seismic offsets due to the April 11, 2012 Indian Ocean earthquake ( M 8.6), which is the largest intraplate earthquake recorded in history. The largest offset at the AGNeSS site was approximately 14.9 cm. Two M 6.1 earthquakes occurred within AGNeSS in 2013, one on January 21 and the other on July 2. We estimated the fault parameters of the two events using a Markov chain Monte Carlo method. The estimated fault parameter of the first event was a right-lateral strike-slip where the strike was oriented in approximately the same direction as the surface trace of the GSF. The estimated peak value of the probability density function for the static stress drop was approximately 0.7 MPa. On the other hand, the co-seismic displacement fields of the second event from nearby GNSS sites clearly showed a left-lateral motion on a northeast-southwest trending fault plane and supported the contention that the July 2 event broke at the conjugate fault of the GSF. We also calculated the Coulomb failure function ΔCFF caused by the first event to evaluate its effect on the second event. The results showed that the July 2 event was likely brought 0.1 MPa closer to failure by the January 21 event. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
41. Penultimate predecessors of the 2004 Indian Ocean tsunami in Aceh, Sumatra: Stratigraphic, archeological, and historical evidence.
- Author
-
Sieh, Kerry, Daly, Patrick, Edwards McKinnon, E., Pilarczyk, Jessica E., Chiang, Hong-Wei, Horton, Benjamin, Rubin, Charles M., Shen, Chuan-Chou, Ismail, Nazli, Vane, Christopher H., and Feener, R. Michael
- Published
- 2015
- Full Text
- View/download PDF
42. Delineating hydrothermal stockwork copper deposits using controlled-source and radio-magnetotelluric methods: A case study from northeast Iran.
- Author
-
Bastani, Mehrdad, Malehmir, Alireza, Ismail, Nazli, Pedersen, Laust B., and Hedjazi, Farhang
- Subjects
MAGNETOTELLURIC prospecting ,HYDROTHERMAL deposits ,COPPER mining ,EARTH resistance (Geophysics) - Abstract
Radio- and controlled-source-tensor magnetotelluric (RMT and CSTMT) methods are used to target hydrothermal veins of copper mineralization. The data were acquired along six eastwest- and three north-south-trending profiles, covering an area of about 500 x 400 m². The tensor RMT data were collected in the 10-250-kHz frequency band. A double horizontal magnetic dipole transmitter in the 4-12.5-kHz frequency range allowed us to constrain the deeper parts of the resistivity models better. To obtain optimum field parameters, ground magnetic profiling was conducted prior to the RMT and CSTMT surveys. Although the study area (in Iran) is remote, a number of radio transmitters with acceptable signal-to-noise ratio were utilized. The 2D inversion of RMT data led to unstable resistivity models with large data misfits. Thus, the RMT data were used to complement and analyze the near-surface resistivity anomalies observed in the 2D CSTMT models. Analyses of strike and dimensionality from the CSTMT data suggests that the low-resistivity structures are mainly three dimensional; therefore, 2D inversion of determinant data is chosen. Independent 2D inversion models of the determinant CSTMT data along crossing profiles are in good agreement. Known copper mineralization is imaged well in the CSTMT models. The thinning of the conductive overburden correlates very well with magnetic highs, indicating the bedrock is resistive and magnetic. In this sense, the magnetic and electromagnetic fields complement each other. Analysis of the 2D resistivity models indicates the volcanic rock deepens at the center of the study area. This zone is associated with a magnetic low and therefore is recommended for detailed exploration work. [ABSTRACT FROM AUTHOR]
- Published
- 2009
- Full Text
- View/download PDF
43. Highly variable recurrence of tsunamis in the 7,400 years before the 2004 Indian Ocean tsunami.
- Author
-
Rubin, Charles M., Horton, Benjamin P., Sieh, Kerry, Pilarczyk, Jessica E., Daly, Patrick, Ismail, Nazli, and Parnell, Andrew C.
- Abstract
The devastating 2004 Indian Ocean tsunami caught millions of coastal residents and the scientific community off-guard. Subsequent research in the Indian Ocean basin has identified prehistoric tsunamis, but the timing and recurrence intervals of such events are uncertain. Here we present an extraordinary 7,400 year stratigraphic sequence of prehistoric tsunami deposits from a coastal cave in Aceh, Indonesia. This record demonstrates that at least 11 prehistoric tsunamis struck the Aceh coast between 7,400 and 2,900 years ago. The average time period between tsunamis is about 450 years with intervals ranging from a long, dormant period of over 2,000 years, to multiple tsunamis within the span of a century. Although there is evidence that the likelihood of another tsunamigenic earthquake in Aceh province is high, these variable recurrence intervals suggest that long dormant periods may follow Sunda megathrust ruptures as large as that of the 2004 Indian Ocean tsunami. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
44. Transient rheology of the oceanic asthenosphere following the 2012 Indian Ocean Earthquake inferred from geodetic data.
- Author
-
Pratama, Cecep, Ito, Takeo, Sasajima, Ryohei, Tabei, Takao, Kimata, Fumiaki, Gunawan, Endra, Ohta, Yusaku, Yamashina, Tadashi, Ismail, Nazli, Nurdin, Irwandi, Sugiyanto, Didik, Muksin, Umar, and Meilano, Irwan
- Subjects
- *
RHEOLOGY , *GEODESY , *ROCK deformation , *LITHOSPHERE , *THICKNESS measurement - Abstract
Postseismic motion in the middle-field (100–500 km from the epicenter) geodetic data resulting from the 2012 Indian Ocean earthquake exhibited rapid change during the two months following the rupture. This pattern probably indicates multiple postseismic deformation mechanisms and might have been controlled by transient rheology. Therefore, the relative contribution of transient rheology in the oceanic asthenosphere and afterslip in the oceanic lithosphere should be incorporated to explain short- and long-term transitional features of postseismic signals. In this study, using two years of post-earthquake geodetic data from northern Sumatra, a three-dimensional spherical-earth finite-element model was constructed based on a heterogeneous structure and incorporating transient rheology. A rheology model combined with stress-driven afterslip was estimated. Our best-fit model suggests an oceanic lithosphere thickness of 75 km with oceanic asthenosphere viscosity values of 1 × 10 17 Pa s and 2 × 10 18 Pa s for the Kelvin and Maxwell viscosity models, respectively. The model results indicate that horizontal landward motion and vertical uplift in northern Sumatra require viscoelastic relaxation of the oceanic asthenosphere coupled with afterslip in the lithosphere. The present study demonstrates that transient rheology is essential for reproducing the rapidly changing motion of postseismic deformation in the middle-field area. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
45. Accommodation space, relative sea level, and the archiving of paleo-earthquakes along subduction zones.
- Author
-
Kelsey, Harvey M., Engelhart, Simon E., Pilarczyk, Jessica E., Horton, Benjamin P., Rubin, Charles M., Daryono, Mudrik R., Ismail, Nazli, Hawkes, Andrea D., Bernhardt, Christopher E., and Cahill, Niamh
- Subjects
- *
SEISMOLOGICAL research , *SUBDUCTION zones , *SEA level , *SEDIMENTATION & deposition research , *PALEOENVIRONMENTAL studies - Abstract
The spatial variability of Holocene relative sea-level (RSL) change influences the capacities of coastal environments to accommodate a sedimentary record of paleoenvironmental change. In this study we couch a specific investigation in more general terms in order to demonstrate the applicability of the relative sea-level history approach to paleoseismic investigations. Using subsidence stratigraphy, we trace the different modes of coastal sedimentation over the course of time in the eastern Indian Ocean where RSL change evolved from rapidly rising to static from 8000 yr ago to present. Initially, the coastal sites from the Aceh, Sumatra, coastal plain, which are subject to repeated great earthquakes and tsunamis, built up a sedimentary sequence in response to a RSL rise of 1.4 mm/yr. The sequence found at 2 sites 8 km apart contained 3 soils of a mangrove origin (Rhizophora, Bruguiera/Ceriops, Avicennia pollen, and/or intertidal foraminifera) buried by sudden submergence related to coseismic subsidence and 6 tsunami sands that contain pristine subtidal and planktic foraminifera. After 3800 cal yr B.P. (years before A.D. 1950), sea level stabilized and remained such to the present. The stable relative sea level reduced accommodation space in the late Holocene, suggesting that the continued aggradation of the coastal plain was a consequence of periodic coastal inundation by tsunamis. [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
- View/download PDF
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