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Sediment thickness mapping and soil classification using ellipticity inversion of Rayleigh wave in the eastern part of Mataram City, Indonesia

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Journal of Physics: Conference Series 2021年第1期1763卷

作者： I U Meidji M Rusydi Asrafil H Jayadi N Safitri Geology Engineering Study Program Tadulako University Indonesia Geophysical Engineering Study Program Tadulako University Indonesia

A soil's dynamic characteristics greatly influence earthquake potential damage inland. Subsurface investigations to determine the dynamic characteristics of the soil can minimize the risk of such damage. The sediment layer thickness is one of the parameters to assess the local geological character in response to an earthquake. Another parameter is Vs30 value, which is used to classify soil types as an indicator of soil response, which generally dominates ground motion amplification. In this study, the two parameters are analyzed to determine the potential for local damage in the event of an earthquake in the eastern area of Mataram City using the rayleigh wave inversion from microtremor data. The research area covers 3 districts, including Selaparang, Cakranegara, and Sandubaya Districts. The results showed that the value of the sediment thickness in the entire study area ranged from 12.78 m to 57.20 m. The value of Vs30 varies between 286 m/s to 866 m/s with the classification of rigid soils, very dense soils, and soft rocks and rocks. These results indicate that the study area in general experiences a large potential for damage if an earthquake occurs. This research is expected to be a reference for the spatial plan of Mataram City.

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Analysis of the Groundwater Table of Theis's Formula Through the Analytical and Numerical Methods Combination for Time-Lapse Microgravity Modeling

SSRN

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SSRN 2024年

作者： Lestari, Mutia Dyah Dahrin, Darharta Abdurrahman, Dadi Azhari, Naila Yuni Faculty of Mining and Petroleum Engineering Institut Teknologi Bandung Jalan Ganesa 10 Bandung40132 Indonesia Geophysical Engineering Study Program Institut Teknologi Sumatera Jalan Terusan Ryacudu Desa Way Hui Lampung Selatan Kecamatan Jatiagung 35365 Indonesia

Massive and continuous well pumping can result in significant groundwater table decline, potentially leading to groundwater depletion and land subsidence over the long term. The timelapse microgravity method, an innovation in gravity measurement techniques, is currently widely used in hydrological applications, including groundwater table monitoring. Groundwater pumping induces changes in subsurface mass distribution, resulting in subsurface mass anomalies that can be detected using gravity method. Many previous studies have employed the slab Bouguer approach to estimate gravity anomalies due to groundwater table changes. This method has significant error for detail anomaly value of groundwater table, which is high decline near production wells. According to Theis formula, the groundwater table decline model as drawdown cone (inverted cone), which gravitational field is calculated. Therefore, calculated gravity anomaly must account for the drawdown cone shape. In this study, gravity anomaly calculations for groundwater drawdown cones are resolved by integrating triple integrals using cylindrical coordinates both analytical and numerical methods. The analytical calculation of integrating triple integrals can only be resolved for two variables (variable z and [[EQUATION]]), and for [[EQUATION]] variable is calculated using numerical methods with the trapezoidal rule. By making the trapezoidal step smaller for closer the well, it is expected this calculation has smaller errors. This study aims to provide more accurate gravity anomaly calculations in accordance with the conceptual model of groundwater table changes. This technique can be used to help groundwater management where monitoring wells is insufficient. © 2024, The Authors. All rights reserved.

关键词： Microgravity

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Landslide investigation through surface geological study and photogrammetry methods in Poi area, Sigi Regency Central Sulawesi

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AIP Conference Proceedings 2023年第1期2719卷

作者： Asrafil Asrafil Muhammad Fuad Afdal Mauludin Kurniawan Geological Engineering Study Program Tadulako University Palu 94118 Indonesia Geophysical Engineering Study Program Tadulako University Palu 94118 Indonesia

The earthquake that occurred on September 28, 2018 with a magnitude of 7.4 Mw at Central Sulawesi, caused damage to the extraordinary areas of Donggala, Palu, Sigi, and surrounding areas. The shock caused by the earthquake-triggered landslide in Poi Village, South Dolo District, Sigi Regency, with large dimensions on the hillsides and resulted in the formation of piles of material and closed the water flow to the west of the Poi Village settlement (Geological Agency 2018). Investigations through surface geological studies and photogrammetry were carried out to identify surface geological conditions and potential landslide susceptibility in the study area. Based on the results of the geological review and analysis, it is known that the geology of the research area is composed of 3 rock units, namely the granite intrusion unit, the conglomerate unit, and the alluvial deposit unit. The photogrammetry results show that the structural activity acting on the study area is proven by the presence of two shear faults with opposite displacement directions. The landslide control factor in the study area lies in the structural conditions, slope, and geohydrological conditions as well as the level of weathering that occurs in rocks in the study area.

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Optimalization of ultrasonic tomography method using robotic instrument

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Journal of Physics: Conference Series 2019年第1期1204卷

作者： Tedy Setiawan Fatkhan Fernando Lawrens Albertus Ariel Rahadi Geophysical Engineering of Study Program Faculty of Mining and Petroleum Engineering Institut Teknologi Bandung Indonesia

Ultrasonic tomography is one of many non-destructive methods to image a rock by measuring wave velocities (P or S-wave). Some applications of ultrasonic tomography include research for seismic anisotropy, rock physics, shale gas etc. The objective of this study is to assess the ability of the robotic instrument to measure rock samples using ultrasonic tomography method. As we know that a conventional method are still employed to measure wave velocities in ultrasonic tomography. The conventional method measures a rock manually that it is often difficult and sometime takes quite long time. One of alternatives to cope with the problem is to design a robotic instrument. The robotic instrument is made of microcontroller and stepper motor. The microcontroller and stepper motor control the position of ultrasonic transducers while measuring the rock sample. The robotic instrument is not only able to measure but also have feedback controls. As a result, measured data can be more accurate and precise than those of the conventional method. Several rock samples are used for testing measurements using a MSIRT (Modified Simultaneous Iterative Reconstruction Technique) method. Results show that using the robotic instrument can enhance quality of data and reduce error up to 50%.

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Geoelectrical Method for Detecting the Limit of Liquid Waste Flowing Below the Surface at Piyungan Landfill

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Journal of Physics: Conference Series 2021年第1期1763卷

作者： H Jayadi M R Muin Sabhan I U Meidji Geological Engineering Study Program University of Tadulako Indonesia Geophysical Engineering Study Program University of Tadulako Indonesia Departement of Physics University of Tadulako Indonesia

Increasingly limited residential land in urban areas results in residents looking for and making settlements around landfills. This affects people's lives in fulfilling their daily needs, clean water. To meet the demand for clean water, some residents use well water as the primary drinking water source. Judging from the condition of the residential areas located in the landfill area, there may be an effect of waste, especially liquid waste, on well water sources. For this reason, research is carried out using the geoelectric method by combining two configurations, namely Schlumberger and dipole-dipole. So that it can provide an overview of the boundaries of liquid waste contaminants in the soil, which are associated with conductive fluids that affect the quality of clean water from residential areas around the landfill. In this study, it was found that the fluid flow associated with liquid waste has a lateral movement to the right with a depth of 24.5 meters.

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Geological hazards that occurred on September 28, 2018 in Sirenja sub-district Donggala Regency, Central Sulawesi Province, Indonesia

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AIP Conference Proceedings 2023年第1期2719卷

作者： Abdullah Abdullah Ahmad Imam Abdullah Fitrawati A. Marhum Ajeng Listianti Muslimin Umar Botjing Muhammad Rusli Muhammad Dahlan Th Musa Abdul Rahman I. Kadek Sulendra Sandra Sandra Geophysical Engineering Study Program Tadulako University Palu Indonesia Geological Engineering Study Program Tadulako University Palu Indonesia Physics Study Program Tadulako University Palu Indonesia Civil Engineering Study Program Tadulako University Palu Indonesia

The location of the Mw 7.5 earthquake on September 28, 2018, was in the Sirenja District of Donggala Regency or about 75 km to the north of Palu City. We present this paper to complete information on disaster data in the northern part, especially for the Sirenja area as an epicenter location. The scope of this research is to present the types of geological hazards, including the area coverage that influenced them. Starting with studying the geological conditions of the Sirenja area, then identifying and mapping the types of hazards that occur. Five types of geological hazards hit the Sirenja area at that time, namely due to surface rupture faults, earthquake shocks, liquefaction effects, tidal flood inundation, and tsunami. Thus, September 28, 2018, is a time that marks the Sirenja area is prone to several geological hazards, and at any time or without knowing when a natural disaster like this will occur again. Based on the results of this study, the local government and the people of Sirenja District are expected to immediately relocate and make a risk reduction strategy or action plan, where the information from this paper can contribute to this.

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Application of tomography seismic for subsurface modeling of Kelud Mountain

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AIP Conference Proceedings 2016年第1期1730卷

作者： R. Destawan A. Bernando M. Aziz I. R. Palupi Geophysical Engineering Study Program Faculty of Mineral Technology UPN “Veteran” Yogyakarta Indonesia

Kelud is a Quaternary volcano formed by the collision between the Indo-Australian plate with the Eurasian plate, exactly in the south of Java. This volcano is included in stratovolcanoes type explosive eruption characteristics. In order observation of subsurface conditions, performed imaging tomography. The research used data recordings from the 4 point observation in 2007. The data processing started from the initial velocity modeling, ray tracing calculations using the method of bending and tomographic velocity model Vp, Vs and Vp/Vs using inversion techniques delay time. Based on the research activities carried out, were resulted velocity structure models Vp, Vs, Vp/Vs and the hypocenter distribution of volcanic earthquakes occurring in Kelud. Velocity structures of Vp and Vs with variations of negative values between -60 to 0% and the value of Vp / Vs positive indicating the presence of hot fluid Kelud from top to sea level. While the positive values of Vs velocity structure between 0 to 20%, which dominate the east and south peaks interpreted as the rest of the frozen magma from previous volcanic activity.

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3D Geothermal Modelling Using Gravity Survey on Dolok Marawa, Simalungun District, North Sumatera

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IOP Conference Series: Earth and Environmental Science 2016年第1期29卷

作者： A Rivandi R Destawan Z R Fajri W Hidayat Geophysical Engineering Study Program Faculty of Mineral Technology UPN 'Veteran' Yogyakarta Indonesia

In North Sumatera, gravity method is applied to identify the geothermal model. This method measured the earth gravitational field. This research has 160 measurement points covering 9 square kilometers. We obtained complete Bouguer anomaly values ranging 85 mGal - 130.68 mGal interpreted as a heat source of andesitic igneous rocks that are affected by the presence of Mount Bahtopu magma chamber. We interpreted the values between 40 mGal - 80 mGal as reservoir and caprock. The 3D gravity inverse modelling conducted using Gravblox, and identifying the following lithologies; Toba Pyroclastic Fall (Qjt) with density 1.92 g/cm3, Toba Pyroclastic Flow (Qjt) with density 2.00 g/cm3, Mount Bahtopu Andesite (Qlb) with density 2.4 g/cm3, and 2.6 g/cm3 which is interpreted as heat source in form of andesitic rock and Mount Bahtopu magma chamber. This heat source is estimated to be at a depth of 1.45 km to 3.78 km below the surface.

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Response of Gravity, Magnetic, and Geoelectrical Resistivity Methods on Ngeni Southern Blitar Mineralization Zone

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Journal of Physics: Conference Series 2018年第1期979卷

作者： Sunaryo Geophysical Engineering Program Study Physics Department Sciences Faculty University of Brawijaya Malang Indonesia

The research with entitle response of gravity, magnetic, and geoelectrical resistivity methods on Ngeni Southern Blitar mineralization zone has been done. This study aims to find the response of several geophysical methods of gravity, magnetic, and geoelectrical resistivity in an integrated manner. Gravity data acquisition was acquired 224 data which covers the whole region of Blitar district by using Gravity Meter La Coste & Romberg Model 'G', and magnetic data acquisition were acquired 195 data which covers the southern Blitar district only by using Proton Precession Magnetometer G-856. Meanwhile geoelectrical resistivity data only done in Ngeni village which is the location of phyropilite mining with the composition content of Fe, Si, Ca, S, Cu, and Mn by using ABEM Terrameter SAS 300C. Gravity data processing was performed to obtain the Bouguer anomaly value, which included unit conversion, tidal correction, drift correction, correction of tie point, base station correction, free air correction, and Bouguer correction. Magnetic data processing has been done by some corrections i.e daily, drift, and IGRF(International Geomagnetic Refference Field) to obtain the total magnetic anomaly. From gravity data processing has been obtained the simple Bouguer anomaly value in range from -10mGal until 115mGal. From this data processing has been obtained the total magnetic anomaly value in range from -650nT until 800nT. Meanwhile from geoelectrical resistivity 3.03Ωm until 11249.91 Ωm. There is a correlation between gravity anomaly, magnetic anomaly, and geoelectrical resistivity anomaly that are associated with deep anomaly, middle anomaly, and shallow anomaly.

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A field test and performance evaluation of accelerated weight drop (awd250 v1.0) for shallow seismic survey

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IOP Conference Series: Earth and Environmental Science 2019年第1期311卷

作者： Alfian Bahar Fatkhan M. Rachmat Sule Geophysical Engineering Study Program Institut Teknologi Bandung Jalan Ganesha 10 Bandung 40132 Indonesia

The acquisition of seismic reflection involves generating and recording seismic wave field on/near the surface of the earth. Success of producing high quality seismic data depend on choice of seismic sources. There are commonly seismic sources for land seismic surveys such as explosive sources, vibrators and Accelerated Weight Drop (AWD). In some cases, the use of explosive sources often faces many problems, especially related to the costs, permission and environmental issues. The use of vibrators is also similar, facing problems such as the availability of access roads, permits and the environment impact. The use of AWD seems to be a solution as an alternative seismic sources when explosive or vibroseis cannot be used for some reasons. In this research, we have designed and built a mechanical seismic source named AWD250V1.0. This hand-made AWD prototype was developed for shallow seismic surveys. To evaluate the performance of this tool and to improve the design of the prototype, a field tests have been carried out. The test was conducted in Ciparay village, Bandung Regency, West Java. The survey area is mostly paddy field with the near surface covered by clay and highly seismic attenuation. The purposes is simply whether AWD can work properly or not while maintaining data quality and safety standards. In addition, the test is intended to find out how deep penetration of seismic waves using this source. Seismic recorders used were 96 channels with interval between receivers was 10 meters. Findings showed that the deepest reflection can be seen around 450 millisecond or approximately 400 meters. To sum up, the device is work well and is able to produce good quality of seismic sources. The prototype can also meet design criteria that are repeatability, portability, economical and environmetal friendly.

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