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Surface deformation and its implications for land degradation after the 2021 Flores earthquake (M7.4) using differential interferometry synthetic aperture radar Purba, Joshua; Harisma, Harisma; Priadi, Ramadhan; Amelia, Rosa; Dwilyantari, Anak Agung Istri; Jaya, Laode Muhammad Golok; Restele, La Ode; Putra, I Made Wahyu Gana
Journal of Degraded and Mining Lands Management Vol. 12 No. 1 (2024)
Publisher : Brawijaya University

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.15243/jdmlm.2024.121.6819

On December 14, 2021, an earthquake with a magnitude of 7.4 originated from the Flores Sea, impacting Kalaotoa Island in Indonesia, resulting in significant structural damage. Macroseismic observations at the site classified that there were 120 buildings slightly damaged, 108 buildings moderately damaged, and 201 buildings heavily damaged. The shakemap shows that Kalaotoa Island experienced VI-VII MMI shaking. The results of the field survey showed many indications of subsidence as many fractures were found in Kalaotoa Island. This study employed Differential Interferometry Synthetic Aperture Radar (DInSAR) to quantify land subsidence and uplift in Kalaotoa Island before and after the earthquake. Sentinel-1A satellite radar data from December 2 and December 14, 2021, were analyzed. The results revealed subsidence of up to 12 cm in Garaupa Raya Village and uplift of up to ±10 cm in Lembang Mate’ne Village. Approximately 50.50% of Kalaotoa Island experienced subsidence (39.4 km²), primarily in Garaupa Village (18.85 km²), while 49.02% of the island experienced uplift (38.2 km²), mostly in Lembang Mate’ne Village (19.03 km²). This spatial analysis underscores the efficacy of DInSAR in detecting and mapping surface deformation, offering critical insights for earthquake preparedness, mitigation efforts for impacted landscape topography, stability soils, structure of ecosystems, and infrastructure resilience.

Expert System of Error Tracking Automated Weather Observing System Using Certainty Factor Method Based on Android Application M Djibran, Halis; Purba, Joshua; Saadia, Aprilia Ode; Restele, La Ode; Hasria, Hasria
Jurnal Informatika Vol 12, No 1 (2025): April
Publisher : Universitas Bina Sarana Informatika

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.31294/inf.v12i1.22536

The limited number of technicians at several BMKG UPT (Task Implementation Units) in Indonesia is the main background of this research. Especially in the field of Aviation Meteorology, which has a significant safety risk for equipment data users. This can be made easier with an expert system. The fault tracking expert system aims to provide information about the symptoms of damage that occur in the Automated Weather Observing System (AWOS) so that it can make it easier for BMKG technicians to repair and handle the equipment. This research stage begins with collecting information data through experts and literature sources regarding AWOS equipment, then calculating the certainty value of the information using the certainty factor method, and produce information that will be displayed through the application. The system uses a Certainty Factor calculation method that presents the calculation of the certainty value of information based on the percentage of information delivery by the source, this method is used in accordance with the type of research that utilizes information from sources or experts in the AWOS field. The resulting system is an android application consisting of several knowledge bases stored in the MySQL database on the server. The results of the data analysis show that the resulting system can be used on the user's smartphone, and users can consult AWOS equipment damage properly. In addition, users can also view the consultation history and damage list. The application user satisfaction questionnaire shows the system has worked and fulfilled the function for users by showing a value of 33.3% Very Good and 66.7% Good.

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

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.

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

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

Karakterisasi Spasial Struktur Bawah Permukaan Gunung Merapi dan Sekitarnya Menggunakan Tomografi Seismik Purba, Joshua; Yulinda, Riska
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.v26i3.987

Aktivitas vulkanik intensif di kawasan Gunung Merapi memerlukan pemahaman mendalam terhadap struktur bawah permukaan, terutama dalam konteks mitigasi bahaya erupsi dan analisis sistem magmatik. Namun, keterbatasan resolusi spasial pada studi tomografi sebelumnya menyulitkan identifikasi detail struktur seperti reservoir magma dangkal, zona rekahan, dan sesar aktif yang berperan dalam suplai magma. Oleh karena itu, penelitian ini bertujuan untuk mengidentifikasi dan mengkarakterisasi struktur bawah permukaan Gunung Merapi dan wilayah sekitarnya secara spasial melalui tomografi seismik berbasis kecepatan gelombang P (Vp), gelombang S (Vs), dan rasio Vp/Vs. Data seismik lokal yang digunakan berasal dari jaringan broadband DOMERAPI dan BMKG, yang diolah menggunakan perangkat lunak LOTOS-13 dengan pemodelan inversi non-linier. Hasil inversi menunjukkan adanya zona anomali kecepatan rendah dengan rasio Vp/Vs tinggi pada kedalaman <6 km di bawah Merapi, yang diinterpretasikan sebagai reservoir magma dangkal yang kaya fluida. Zona transisi dan reservoir magma menengah teridentifikasi masing-masing pada kedalaman 6–12 km dan 13–16 km. Di bawah Gunung Merbabu, anomali kecepatan lebih lemah tanpa indikasi aktivitas magmatik signifikan, mencerminkan sistem vulkanik yang relatif tidak aktif. Selain itu, zona kecepatan rendah dan rasio Vp/Vs tinggi pada kedalaman 15–18 km di selatan Merapi dikaitkan dengan keberadaan Sesar Opak. Hasil studi ini memperkuat pemahaman mengenai dinamika sistem magmatik serta potensi seismotektonik di kawasan vulkanik Jawa Tengah. Kata Kunci: Tomografi seismik, Gunung Merapi, Struktur bawah permukaan, rasio Vp/Vs, Reservoir Magma Abstract Intense volcanic activity in the Mount Merapi region necessitates a thorough understanding of its subsurface structure, particularly for eruption hazard mitigation and magmatic system analysis. However, limitations in spatial resolution from previous tomography studies have hindered detailed identification of features such as shallow magma reservoirs, fracture zones, and active faults responsible for magma transport. Therefore, this study aims to identify and spatially characterize the subsurface structure beneath Mount Merapi and its surroundings using seismic tomography based on P-wave velocity (Vp), S-wave velocity (Vs), and Vp/Vs ratio data. Local seismic data were obtained from the DOMERAPI and BMKG broadband networks and processed using the LOTOS-13 software with a non-linear inversion model. The results reveal a low-velocity anomaly zone with a high Vp/Vs ratio at depths of less than 6 km beneath Merapi, interpreted as a shallow, fluid-rich magma reservoir. A transition zone and an intermediate magma reservoir were identified at depths of 6–12 km and 13–16 km, respectively. Beneath Mount Merbabu, weaker velocity anomalies without significant magmatic signals indicate a relatively inactive volcanic system. Additionally, low-velocity and high Vp/Vs ratio zones at depths of 15–18 km south of Merapi are associated with the Opak Fault. These findings enhance our understanding of magmatic dynamics and seismotectonic potential in the Central Java volcanic region. Keywords: Seismic tomography, Mount Merapi, Subsurface structure, Vp/Vs ratio, Magma reservoir

Hypocenter relocation to identify hidden faults and their environmental implications in the karst region of Maros-Pangkep, South Sulawesi Wulur, Kevin Hanyu Clinton; Junaedi, Subaer; Susanto, Agus; Purba, Joshua; Priadi, Ramadhan
Journal of Degraded and Mining Lands Management Vol. 12 No. 5 (2025)
Publisher : Brawijaya University

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.15243/jdmlm.2025.125.8663

The Maros-Pangkep region in South Sulawesi is a tropical karst landscape not officially mapped as an active fault zone, yet it has exhibited increasing micro-seismic activity in recent years. This study investigates the potential existence of hidden faults through hypocenter relocation using the double-difference method. A total of 191 earthquake events with magnitudes of 1-2.6 were successfully relocated using BMKG catalog data and the IASP91 global velocity model. The resulting hypocenters form a northwest–southeast-trending cluster, with fault plane geometry of 333°–346° strike, 8°–9° dip, and ~11 km length. These events cluster along boundaries of the Tonasa, Camba, and intrusive rocks, where competence contrast and karstification localize deformation. To complement the spatial analysis, magnitude–frequency characteristics were evaluated using the Gutenberg–Richter relationship. The estimated b-value of 1.34 indicates a low-stress regime dominated by small-magnitude seismicity, consistent with distributed deformation in brittle, heterogeneous lithologies. Although micro-seismic in scale, the spatial and statistical patterns suggest the presence of a structurally weak and potentially seismogenic zone that is not reflected in current tectonic maps. These findings underscore the importance of including the Maros–Pangkep region of South Sulawesi in seismic hazard assessments and land management efforts. The integration of relocation techniques and seismicity statistics proves effective for detecting latent fault structures in complex karst settings. In addition to seismic risks, such activity may accelerate land degradation through sinkholes, aquifer disruption, and ground instability, highlighting the value of geophysical assessments in managing vulnerable karst environments.

SPATIAL STUDY OF SEISMIC HAZARD USING CLASSICAL PROBABILISTIC SEISMIC HAZARD ANALYSIS (PSHA) METHOD IN THE KENDARI CITY AREA Purba, Joshua; Restele, La Ode; Hadini, La Ode; Usman, Ida; Hasria, Hasria; Harisma, Harisma
Indonesian Physical Review Vol. 7 No. 3 (2024)
Publisher : Universitas Mataram

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.29303/ipr.v7i3.325

Kendari City is an area prone to earthquakes because it is in a seismic zone dominated by local faults such as the Lawanopo Fault, Kendari Fault, Buton Fault, Tolo Thrust and Matano Fault, as evidenced by significant seismic events like those in 2011 and 2022. The earthquake in 2011, with a magnitude of 6.0, struck Kolono District, South Konawe Regency, while the 2022 earthquake, registering a magnitude of 5.2, occurred in the sea approximately 5 km north of Soropia, Konawe Regency. With seismic activity such as the 2011 and 2022 earthquakes causing significant damage, understanding seismic hazards is critical. The research stage starts from Hazard Analysis using the Classical Probabilistic Seismic Hazard Analysis (PSHA) method to produce a hazard map that presents the distribution of peak ground acceleration on the surface, at periods 0 seconds (PGA), SA (T= 0.2 seconds) and SA (T= 1.0 seconds) for probabilities of exceedance 10% and 2% in 50 years, respectively. Classical Probabilistic Seismic Hazard Analysis (PSHA) processing uses OpenQuake Engine software. The analysis results show that the PGA value in Kendari City on the surface ranged from (0.49 - 0.68 g and 0.79 - 1.17 g), SA at T= 0.2 seconds (1.10 - 1.53 g and 1.74 - 2.09 g), and SA at T= 1 second (0.64 - 0.93 g and 1.35 - 1.91 g). This result indicates the potential for significant damage and shocks.

Pengembangan Sistem Pelaporan Data Pos Hujan Berbasis Web di Sulawesi Tenggara sebagai Upaya Digitalisasi di Era Revolusi 4.0: Development of a Web-Based Rain Post Data Reporting System in Southeast Sulawesi as a Digitalization in the Era of Revolution 4.0 Saadia, Aprilia Ode; Purba, Joshua; Wicaksono, Satriyo Unggul; Djibran, Halis M
Jurnal Stasiun Geofisika Sleman Vol. 3 No. 1 (2025): Jurnal Stasiun Geofisika Sleman (JSGS) - Juni 2025
Publisher : Stasiun Geofisika Kelas I Sleman

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

Sistem pelaporan data pos hujan di Sulawesi Tenggara masih dilakukan secara manual, menggunakan pencatatan manual dan pengiriman data melalui jasa pos atau layanan pengiriman lainnya. Penelitian ini bertujuan untuk merancang dan mengimplementasikan sistem pelaporan data pos hujan berbasis web yang dapat mempersingkat alur pengiriman data ke Stasiun Klimatologi Sulawesi Tenggara. Sistem ini diharapkan dapat memudahkan pelaporan data pengamatan pos hujan dengan menyediakan peta persebaran pos hujan dan fitur live chat untuk bantuan langsung kepada pengamat. Pengembangan sistem menggunakan prototype model dengan alat bantu perancangan sistem yaitu Unified Modeling Language (UML). Hasil penelitian menunjukkan bahwa sistem ini dapat mempercepat proses pengumpulan dan pengolahan data, serta mengurangi risiko kehilangan data. Berdasarkan pengujian User Acceptance Test (UAT), 87,5% pengguna menyatakan bahwa situs web ini user-friendly. Digitalisasi dalam pengelolaan data klimatologi ini merupakan langkah maju dalam menghadapi tantangan di era revolusi industri 4.0, yang menawarkan solusi yang lebih efisien dan akurat dibandingkan metode manual sebelumnya.

Expert System of Error Tracking Automated Weather Observing System Using Certainty Factor Method Based on Android Application Djibran, Halis M; Purba, Joshua; Saadia, Aprilia Ode; Restele, La Ode; Hasria, Hasria
Jurnal Informatika Vol. 12 No. 1 (2025): April
Publisher : Universitas Bina Sarana Informatika

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.31294/informatika.v12i1.12254

The limited number of technicians at several BMKG UPT (Task Implementation Units) in Indonesia is the main background of this research. Especially in the field of Aviation Meteorology, which has a significant safety risk for equipment data users. This can be made easier with an expert system. The fault tracking expert system aims to provide information about the symptoms of damage that occur in the Automated Weather Observing System (AWOS) so that it can make it easier for BMKG technicians to repair and handle the equipment. This research stage begins with collecting information data through experts and literature sources regarding AWOS equipment, then calculating the certainty value of the information using the certainty factor method, and produce information that will be displayed through the application. The system uses a Certainty Factor calculation method that presents the calculation of the certainty value of information based on the percentage of information delivery by the source, this method is used in accordance with the type of research that utilizes information from sources or experts in the AWOS field. The resulting system is an android application consisting of several knowledge bases stored in the MySQL database on the server. The results of the data analysis show that the resulting system can be used on the user's smartphone, and users can consult AWOS equipment damage properly. In addition, users can also view the consultation history and damage list. The application user satisfaction questionnaire shows the system has worked and fulfilled the function for users by showing a value of 33.3% Very Good and 66.7% Good.

Sekolah Lapang Gempa Bumi dan Tsunami sebagai Strategi Mewujudkan Komunitas Siaga Bencana Tsunami Purba, Joshua; Priadi, Ramadhan; Wahyuddin, Muhamad Rizky Noor; Hiola, Muhamad Fikri Hayqal; Nurfitriani, Nurfitriani; Wulur, Kevin Hanyu Clinton; Firmansyah, Hendi; Susanto, Erwan
Amal Ilmiah: Jurnal Pengabdian Kepada Masyarakat Vol. 7 No. 2 (2026): Edisi Juli 2026
Publisher : FKIP Universitas Halu Oleo

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.36709/amalilmiah.v7i2.669

Kawasan pesisir Indonesia memiliki tingkat kerentanan tinggi terhadap ancaman gempa bumi dan tsunami akibat aktivitas tektonik yang intens. Oleh karena itu, peningkatan kesiapsiagaan masyarakat berbasis edukasi menjadi langkah penting dalam upaya pengurangan risiko bencana. Kegiatan ini bertujuan untuk meningkatkan pemahaman dan kesiapsiagaan masyarakat terhadap ancaman gempa bumi dan tsunami melalui implementasi Sekolah Lapang Gempa bumi dan Tsunami (SLGT) berbasis data ilmiah. Kegiatan dilaksanakan dengan melibatkan BMKG, BPBD, pemerintah desa, sekolah, dan masyarakat setempat. Metode yang digunakan meliputi penyampaian materi, simulasi, Table Top Exercise (TTX), serta susur jalur evakuasi. Materi edukasi didukung oleh peta sebaran seismisitas historis (2009–2024) dan peta bahaya tsunami hasil pemodelan Comcot sebagai media visual pembelajaran. Hasil kegiatan menunjukkan peningkatan pemahaman masyarakat sebesar 35–45% berdasarkan perbandingan nilai pre-test dan post-test. Selain itu, penggunaan peta berbasis pemodelan terbukti membantu masyarakat dalam memahami risiko secara spasial dan meningkatkan kemampuan dalam pengambilan keputusan saat kondisi darurat. Integrasi data ilmiah dengan metode pembelajaran partisipatif juga memperkuat kesadaran risiko dan keterampilan tanggap bencana masyarakat. Dengan demikian, kegiatan ini menunjukkan bahwa pendekatan edukasi berbasis pemodelan dan partisipatif efektif dalam mendukung terwujudnya komunitas siaga tsunami sebagai bagian dari upaya menuju Tsunami Ready Community di wilayah pesisir.

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