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All Journal Geoplanning : Journal of Geomatics and Planning Journal of Geoscience, Engineering, Environment, and Technology Jurnal Geologi dan Sumberdaya Mineral (Journal of Geology and Mineral Resources) Jurnal Geosaintek
Imanuela Indah Pertiwi
BMKG Balai Besar Wilayah IV Makassar
Chemistry Earth & Planetary Sciences Energy Engineering Environmental Science 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.
Post-Seismic Surface Deformation of The Tarakan Earthquake in 2015 Using The DInSAR Technique Pertiwi, Imanuela Indah; Trismahargyono, Trismahargyono; Marniati, Marniati; Purba, Joshua
Geoplanning: Journal of Geomatics and Planning Vol 12, No 1 (2025)
Publisher : Department of Urban and Regional Planning, Diponegoro University

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.14710/geoplanning.12.1.79-94

Abstract

Deformation can help predict the presence and severity of an earthquake. SAR image data can be used to calculate post-seismic surface deformation using the InSAR and DInSAR methods. DInSAR (Differential Interferometric Synthetic Aperture Radar) is a well-established technology for monitoring subsidence and uplift with millimeter precision. This study uses SAR imagery to detect surface deformation caused by a magnitude M 6.1 earthquake on December 21, 2015, at 01:47:37 WIB in Tarakan Regency, North Borneo. The data used is Sentinel-1 satellite imagery in SLC (single-look complex) format, with a master image from December 18, 2015 (3 days before the earthquake), and a slave image from January 11, 2016 (21 days after). The interferogram generated by the Tarakan earthquake shows deformation patterns radiating in three directions: northeast, southeast-southwest, and southwest-northwest. Tarakan City, located south-southwest of the epicenter, experienced the highest subsidence deformation of 0.001–0.035 meters. On December 21, 2015, the Tana Tidung I Regency area, 33 kilometers southwest of the epicenter, showed the highest uplift deformation (0.019–0.079 meters). The largest uplift in Tana Tidung II Regency (0.069 meters), about 10 kilometers north of the epicenter, occurred near the fault zone. Surface deformation due to the Tarakan earthquake contributes to seismic hazard assessment in North Borneo and indicates other locally active faults. Uplift to the east and subsidence to the west of the epicenter suggest an oblique-normal fault, with dominant strike-slip motion and normal (downward) fault blocks to the west.
Identifikasi Kualitas Site Seismik di Sulawesi Tenggara Berdasarkan Analisis Spektrum Noise Seismik Trismahargyono, Trismahargyono; Pertiwi, Imanuela Indah
Jurnal Geosaintek Vol. 9 No. 1 (2023)
Publisher : Institut Teknologi Sepuluh Nopember

Show Abstract | Download Original | Original Source | Check in Google Scholar

Abstract

Seismic stations are usually located in bedrock areas and stored in boreholes with the aim of protecting the seismometer from temperature and vibration due to weather changes. In general, the most widely used seismometers are broadband seismometers which have a wide frequency range so they record a lot of noise. PSD and PDF analysis were used to evaluate the noise characteristics of seismic stations. The standardization of high and low seismic noise refers to the Peterson Model. This research was conducted with the aim of knowing the quality of seismic stations in Southeast Sulawesi through analysis of the level of seismic noise sources that affect the quality of seismic data. The evaluation of the seismic site quality is based on the PSD value percentage parameter by calculating the PSD value of the signal recorded on June 17 to June 20, 2022. Various kinds of seismic noise in the resulting spectrum will be seen whether it is still within the limits of the Peterson Model or not. Based on the signal spectrum images obtained, there are 9 seismic sites in Southeast Sulawesi with ideal site quality, which can record seismic signal data and seismic noise sources activity well, namely BBSI, KKSI, PKCI, RKCM, WKCM, UKCM, WWCI, and KDI. Meanwhile, one seismic site with poor site quality cannot record seismic signal data and seismic noise sources activity, namely the LKCI seismic site. The seismic noise level at a frequency of 5-10 Hz originating from human activities and vehicles is the highest indicated by the LKUCM seismic site.
Analisis Deformasi Permukaan akibat Gempabumi pada 28 September 2018 di Kota Palu menggunakan Metode DInSAR dan Hubungannya dengan Sebaran Vs30 Saadia, Aprilia Ode; Purba, Joshua; Hasria, Hasria; Jaya, LM. Golok; Pertiwi, Imanuela Indah; Djibran, Halis M.
Jurnal Geologi dan Sumberdaya Mineral Vol. 26 No. 3 (2025): JURNAL GEOLOGI DAN SUMBERDAYA MINERAL
Publisher : Pusat Survei Geologi

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.33332/jgsm.geologi.v26i3.967

Abstract

Penelitian ini dilatarbelakangi oleh kejadian deformasi yang terjadi akibat gempabumi pada 28 September 2018 di Kota Palu. Penelitian ini bertujuan untuk mengetahui nilai deformasi akibat gempa M 7,4 di Kota Palu 2018 dan mengetahui hubungan deformasi dengan Vs30. Penggunaan metode DInSAR digunakan untuk mengetahui perubahan deformasi yang terjadi akibat gempa tersebut dengan menggunakan data sentinel 1A pada tanggal 07 Juni 2018 (sebelum gempa) dan 22 November 2018 (sesudah gempa). Hasil penelitian menunjukkan adanya penurunan (subsidence) hingga 23 cm dan pengangkatan (uplift) hingga 13 cm di wilayah Kota Palu. Wilayah dengan nilai Vs30 rendah cenderung mengalami penurunan akibat tanah lunak, sedangkan wilayah dengan nilai Vs30 tinggi cenderung mengalami kenaikan akibat tanah keras. Namun demikian, terjadi anomali pada wilayah Kecamatan Ulujadi dan Kecamatan Palu Selatan. Penggunaan data Vs30 menunjukkan bahwa nilai Vs30 dapat digunakan sebagai indikator awal untuk memprediksi area dengan potensi deformasi akibat gempa. Hal tersebut penting untuk pengembangan strategi mitigasi bencana, misalnya dalam penentuan zona aman untuk pembangunan. Kata Kunci: Deformasi, Metode DInSAR, Sentinel 1A, Vs30Kota Palu Abstract This research is motivated by the deformation event that occurred due to the earthquake on September 28, 2018 in Palu City. This research aims to determine the value of deformation due to the M 7.4 earthquake in Palu City in 2018, and to determine the relationship between deformation and Vs30. The DInSAR method was used to determine the deformation changes due to the earthquake using Sentinel 1A data on June 07, 2018 (pre-earthquake) and November 22, 2018 (post-earthquake). The analysis results showed subsidence of up to 23 cm and uplift of up to 13 cm in the city of Palu. Areas with low Vs30 values tend to experience subsidence due to soft soils, whereas areas with high Vs30values tend to experience uplift due to hard soil. However, anomalies occurred in Ulujadi and South Palu subdistricts. The use of Vs30data shows that Vs30valuescan be used as an early indicator to predict areas with potential earthquake-induced deformation. It is important for the development of disaster mitigation strategies, such as determining safe zones for development. Keywords: Deformation, DInSAR method, Sentinel 1A, Vs30, Palu City
IDENTIFICATION OF LOCAL ACTIVE FAULTS IN MAINLAND GORONTALO REGION BASED ON FOCAL MECHANISM ANALYSIS Pertiwi, Imanuela Indah; Rifai, Listya Dewi
Jurnal Geosaintek Vol. 10 No. 3 (2024)
Publisher : Institut Teknologi Sepuluh Nopember

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.12962/j25023659.v10i3.2217

Abstract

One of the nations that experiences devastating earthquakes frequently is Indonesia. Local active faults on land are one of the causes of these earthquakes. New information on the purported presence of local active faults can be obtained from the quantity of small-magnitude earthquake occurrences. By analyzing the focal sphere mechanism, small-scale earthquake data are used to identify local active faults in the Gorontalo area. The minor magnitude earthquakes (M<5) that struck the Gorontalo region in February 2023 and were recorded eleven events at the BMKG- Gorontalo Geophysical Station that were used in this investigation. he resulting focus sphere diagram can be used to ascertain the faults or strike direction propensity. The focal mechanism of the earthquake in the Pohuwato region demonstrates the Oblique Thrust Fault's inclination toward a northeastern-southern strike orientation. The tendency of the strike orientation of the east-west-oriented Oblique Thrust Fault, which is the focal mechanism of the earthquake that happened in Buol, also demonstrates the same thing. According to the Gorontalo Fault diagram provided by the National Earthquake Study Center, the focal mechanism of the earthquake in Cluster A (earthquake numbers 1,6,9), the Gorontalo region, also demonstrates the strike direction of the Northwest-Southeast-oriented Oblique Thrust Fault. The earthquake occurrences in cluster B (Pohuwato area), earthquake numbers 2,3,8, and cluster C (Buol area), earthquake numbers 4, 5,7, raise the possibility of a new local active fault on the Gorontalo region's mainland. The Gorontalo region's suspicion of the existence of local active faults is strengthened by the monitoring of earthquake intensity based on occurrences that occurred between March 2023 and March 2024. Over the course of a year, there are nine to twenty-seven earthquakes with a magnitude of less than five (M<5). These seismic occurrences provide credence to the theory that Pohuwato and Buol, Gorontalo, have local active faults.
Co-Authors Chahyani, Rani Djibran, Halis M. Hasria Hasria, Hasria Irawati Jaya, LM. Golok Listya Dewi Rifai Marniati Marniati, Marniati Purba, Joshua Puspitafuri, Cindy Saadia, Aprilia Ode Siti Helmyati Trismahargyono, Trismahargyono