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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

Abstract

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.
PENENTUAN DISTRIBUSI SLIP DAN ASPERITAS GEMPABUMI MENGGUNAKAN METODE INVERSI GELOMBANG BADAN TELESEISMIK STUDI KASUS: GEMPABUMI LOMBOK Mw 6,9 (9 AGUSTUS 2018) Priadi, Ramadhan; Julius, Admiral Musa; Suardi, Iman
Bulletin of Scientific Contribution Vol 17, No 3 (2019): Bulletin of Scientific Contribution : GEOLOGY
Publisher : Fakultas Teknik Geologi Universitas Padjadjaran

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (3.715 KB) | DOI: 10.24198/bsc.v17i3.24181

Abstract

Pada tanggal 9 agustus 2018 terjadi gempa signifikan dengan magnitude  6,9 (14:56:28 UTC). Gempa bumi tersebut merupakan salah satu gempa dari rangkaian gempabumi Lombok pada periode bulan Juli-Agustus 2019.  Diduga jika gempabumi Lombok disebabkan oleh adanya aktivitas back-arc thrust namun masih sulit untuk menginterpretasikan penyebab utamanya. Salah satu cara yang dapat dilakukan untuk mengetahui apa yang terjadi disumber dengan melakukan inversi moment tensor. Inversi moment tensor dilakukan untuk memisahkan waveform yang tercatat di seismogram dari fungsi raypath dan instrument sehingga diperoleh waveform di sumber. Metode yang digunakan dalam melakukan inversi moment tensor adalah metode teleseismic body wave inversion. Gelombang teleseismik dipilih karena gelombang teleseismic memiliki frekuensi gelombang rendah akibat dari penjalaran yang jauh sehingga frekuensi tinggi sudah teratenuasi selama penjalaran gelombang gempabumi. Komponen BHZ digunakan karena gelombang P terekam jelas di komponen Z. Stasiun seismik yang digunakan merupakan stasiun seismik dengan jarak antara stasiun ke sumber berkisar antara - sehingga diperoleh rekaman sinyal gelombang teleseismik. Dari hasil pengolahan diperoleh parameter sesar yaitu strike , dip , dan rake . Perbandingan antara sinyal observasi dan sinyal sintesis menghasilkan varian sebesar 0,1687. Luasan bidang sesar dari hasil inversi diestimasikan sebesar strike 48 km × dip 42 km. Pada gempabumi ini diperoleh momen seismik sebesar  0.428E+20 Nm. Magnitudo moment yang dihasilkan dari proses inversi adalah  7,02 dengan kedalaman 28 km. Dari hasil inversi diperoleh jika jenis patahan yang terjadi merupakan merupakan jenih patahan reverse (naik) dengan source duration selama 45 s. Slip maksimum yang dihasilkan dari proses inversi adalah 1,05 m. Dari hasil slip diketahui jika pada gempabumi Lombok  6,9 terjadi desakan dari arah selatan ke utara. Hal tersebut juga diperkuat dengan adanya asperitas tinggi di wilayah utara Lombok. Wilayah sekitar gunung Agung memiliki daerah-daerah dengan asperitas tinggi. Daerah dengan asperitas tinggi mengindikasikan jika wilayah tersebut merupakan wilayah dengan zona kuncian yang tinggi. Zona kuncian tersebut memiliki energi yang besar ketika release. Karena zona asperitas terbesar berada di utara Lombok dan menerima desakan dari arah selatan maka diindikasikan jika memang back-arc thrust merupakan penyebab utama gempa bumi Lombok.
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

Abstract

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.