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All Journal Komunikasi Fisika Indonesia Jurnal Geocelebes Journal of Geoscience, Engineering, Environment, and Technology
Chahyani, Rani
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Earth & Planetary Sciences Electrical & Electronics Engineering Energy Engineering Environmental Science Materials Science & Nanotechnology Physics

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Identification Of Shear Strain On The Surface Ground Of Wangi-Wangi Island, Southeast Sulawesi, Indonesia, Using Nakamura’s Technique and The Possibility Of Its Impacts Manan, Abdul; Puspitafuri, Cindy; Chahyani, Rani; Irawati; Pertiwi, Imanuela Indah
Journal of Geoscience, Engineering, Environment, and Technology Vol. 8 No. 4 (2023): JGEET Vol 08 No 04 : December (2023)
Publisher : UIR PRESS

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.25299/jgeet.2023.8.4.11780

Abstract

This research was conducted to determine the possible impact of an earthquake on the mainland of Wangi-Wangi Island based on the presence of shear strain on the surface ground (γ). The size of γ is obtained by multiplying the ground susceptibility index and the acceleration of basement ground or PGA using Nakamura’s technique. The data used are microtremor data and earthquake data from 1920 to 2020 sourced from the USGS. Microtremor data are obtained from the results of filtering ground vibration signals using a Band Pass Filter in the frequency range between 0.5 to 25 Hz. Ground vibration signals were recorded at 47 measurement points spread over the surface of Wangi-Wangi Island within 29.25 to 48.16 minutes. Furthermore, the microtremor data were processed using the HVSR (Horizontal to Vertical Spectral Ratio) method. The use of earthquake data must meet the requirements for a surface magnitude (MS) ≥ 5.0 SR and an earthquake epicenter depth (h) ≤ 45 km. The results obtained are the γ sizes of Wangi-Wangi Island in the order of 10-06 to 10-03. Based on the size distribution, it is known that the majority of the Wangi-Wangi Island area has the potential to experience cracks and land subsidence due to settlements if an earthquake occurs, and only a portion of the area is vibrating. In addition, it is also known that the mainland of Wangi-Wangi Island is not prone to landslides and liquefaction because γ<10-2.
Identification of subsurface structure using the pseudo-gravity method of magnetic data at the geothermal area of Sonai Village and its surroundings, Puriala, Konawe Regency Ratu, Misbayanti Dian; Manan, Abdul; Bahdad, Bahdad; Chahyani, Rani
Indonesian Physics Communication Vol 22, No 2 (2025)
Publisher : Universitas Riau

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.31258/jkfi.22.2.73-84

Abstract

It has been conducted a geomagnetic research in the geothermal area of Sonai Village and its surroundings, Puriala, Konawe Regency, which aims to identify the structure of the subsurface using the pseudo-gravity method. After performing diurnal and IGRF corrections on the measurement data, the residual magnetic field anomaly is obtained around -150 to 90 nT. Furthermore, transformation process using the pseudo-gravity method is carried out, and the anomaly contour density is obtained around -0.07 to 0.06 mGal. The results of 2D modeling of 2 slices on the residual magnetic anomaly map that have undergone pseudo-gravity transformation show that the subsurface layers of the research area are composed of 3 formations. Layers with density values of 1.5 and 2.5 g/cm3 are thought to be Alluvium Deposits in the form of sand and clay, layers with density values of 2.6 and 2.78 g/cm3 are sandstone and conglomerate in the Alangga Formation, and a layer with a density value of 2.84 g/cm3 is peridotite in the Ultramafic Complex (bedrock layer). In addition, several minor faults were also found, and among them 2 minor faults adjacent to geothermal manifestation are located at coordinates of approximately 4o1’16.149” South Latitude dan 122o7’9.609” East Longitude with a distance of ±15 meters, and at coordinates of approximately 4o1’23.388” South Latitude dan 122o7’24.326” East Longitude which is ±28 meters from the manifestation. These minor faults cut through the peridotite layer and the conglomerate layer, and are thought to be the migration path of hot fluids towards the surface.
Estimation of Subsurface Structure Using Euler Deconvolution Method of Magnetic Data at the Geothermal Area of Sonai Village and its Surroundings, Konawe Regency Sariani, Sariani; Manan, Abdul; Bahdad, Bahdad; Chahyani, Rani
JURNAL GEOCELEBES Vol. 8 No. 2: October 2024
Publisher : Departemen Geofisika, FMIPA - Universitas Hasanuddin, Makassar

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.70561/geocelebes.v8i2.36380

Abstract

It has been carried out research with the aim of determining the subsurface structure at the geothermal area of Sonai Village and its surroundings, Konawe Regency. The data used are magnetic data obtained through field measurements at 126 points in the N180oS direction. After the data were subjected to diurnal and IGRF corrections, a residual (local) magnetic field anomaly of around -150 nT to 90 nT was obtained. On the residual magnetic anomaly map which has been reduced to the Pole (RTP), the Euler Deconvolution (ED) method is applied to the Index Structure N=0 to estimate the subsurface structure in the form of the presence of minor faults, and it is known that there are 5 minor faults at a depth of around 9 to 38 meters. Information on the existence of these faults is then used in 2D modeling. Modeling results show that these minor faults cut through two rock layers, which are the layers composed of conglomerate rocks from the Alangga Formation and peridotites as bedrock from the Ultramafic Complex. One of the minor faults closest to the manifestation area (hot spring) is at coordinates around 4o1’12.412” S and 122o7’24.263” E to 4o1’15.532” S and 122o7’19.561” E with a distance of ±15 meters. The existence of these minor faults is thought to be the migration routes for heat flow or conduction to the surface at the geothermal area of Sonai Village and its surroundings.
Co-Authors Abdul Manan Bahdad, Bahdad Imanuela Indah Pertiwi Irawati Puspitafuri, Cindy Ratu, Misbayanti Dian Sariani, Sariani Siti Helmyati