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All Journal JGE (Jurnal Geofisika Eksplorasi) JOURNAL ONLINE OF PHYSICS JITEK (Jurnal Ilmiah Teknosains) Spektra: Jurnal Fisika dan Aplikasinya Journal of Multidisciplinary Academic Eksakta : Berkala Ilmiah Bidang MIPA Jurnal Pendidikan, Sains, Geologi, dan Geofisika (GeoScienceEd Journal) Jurnal Geosaintek
Yudha Styawan
Institut Teknologi Sumatera (ITERA)
Aerospace Engineering Agriculture, Biological Sciences & Forestry Astronomy Biochemistry, Genetics & Molecular Biology Chemical Engineering, Chemistry & Bioengineering Chemistry Civil Engineering, Building, Construction & Architecture Computer Science & IT Earth & Planetary Sciences Education Electrical & Electronics Engineering Energy Engineering Environmental Science Materials Science & Nanotechnology Mathematics Mechanical Engineering Physics Social Sciences Veterinary

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ANALISIS SPASIAL BERBASIS SISTEM INFORMASI GEOGRAFIS (SIG) UNTUK PEMETAAN BAHAYA DAN RISIKO TANAH LONGSOR DI KABUPATEN LAMPUNG UTARA Efriyanti, Annisa; Farduwin, Alhada; Styawan, Yudha
JOURNAL ONLINE OF PHYSICS Vol. 11 No. 1 (2025): JOP (Journal Online of Physics) Vol 11 No 1
Publisher : Prodi Fisika FST UNJA

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.22437/jop.v11i1.49284

Abstract

Kabupaten Lampung Utara termasuk daerah rawan tanah longsor yang telah mengalami kejadian dalam beberapa tahun terakhir. Penelitian dilakukan untuk menganalisis tingkat risiko tanah longsor melalui pendekatan Sistem Informasi Geografis (SIG) melalui komponen ancaman (hazard), kerenatan (vulnerability), dan kapasitas (capacity). Setiap  komponen dibentuk berdasarkan parameter fisik dan social seperti curah hujan, kemiringan lereng, jenis tanah, tutupan lahan, geologi, kepadatan penduduk, serta ketersediaan sarana dan prasarana umum. Parameter tersebut diberikan skor dan bobot sesuai tingkat pengaruhnya, kemudian diolah menggunakan metode overlay spasial. Hasil analisis menunjukkan bahwa nilai indeks risiko tanah longsor berkisar antara 0,933-2,3 dan terbagi menjadi tiga kelas yaitu risiko rendah seluas 1.664,436 km², risiko sedang 754,743 km², dan risiko tinggi 39,820 km². Wilayah dengan risiko tinggi terindentifikasi di Kecamatan Tanjung Raja, Bukit Kemuning, dan sebagian Abung Tengah, sedangkan risiko rendah umumnya berada di bagian timur dan utara Kabupaten Lampung Utara. Secara umum, semakin tinggi tingkat ancaman dan kerentanan serta rendahnya kapasitas masyarakat di suatu daerah, maka semakin besar tingkat risiko tanah longsor yang berpotensi terjadi.  
Analisis Bahaya Gempa Bumi Berdasarkan Nilai Peak Ground Acceleration (PGA) Menggunakan Metode Probabilistic Seismic Hazard Analysis (PSHA) di Wilayah Bali dan Nusa Tenggara Hafeezul, Muhammad; Styawan, Yudha; Wulandari, Rizki
Jurnal Pendidikan, Sains, Geologi, dan Geofisika (GeoScienceEd Journal) Vol. 7 No. 1 (2026): Februari
Publisher : Mataram University

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.29303/goescienceed.v7i1.1621

Abstract

The Bali, West Nusa Tenggara (NTB), and East Nusa Tenggara (NTT) regions are located within an active tectonic zone influenced by the transition subduction of the Sunda–Banda arc and the presence of surrounding active faults, resulting in a high potential for earthquake hazards. This study was conducted to evaluate seismic hazard through the estimation of Peak Ground Acceleration (PGA) using the Probabilistic Seismic Hazard Analysis (PSHA) method. The analysis is based on an earthquake catalog covering the period 1964–2024 and considers various seismic sources, including shallow background, deep background, active faults, and megathrust sources. Earthquake occurrence models for fault and subduction sources were represented using a truncated exponential model. Ground motion predictions were calculated using several Ground Motion Prediction Equations (GMPEs), which were combined through a logic tree approach. The calculations were performed at bedrock conditions with a Vₛ30 value of 760 m/s, for exceedance probabilities of 10% and 2% within a 50-year period. The results indicate that PGA values for a 10% probability of exceedance range from 0.30 to 1.18 g, while those for a 2% probability of exceedance range from 0.62 to 1.75 g. High PGA values are distributed in the southern and eastern regions, which are adjacent to megathrust segments and active faults with high slip rates, whereas the northern regions exhibit lower PGA values. These results are important for public awareness in earthquake disaster mitigation efforts and for earthquake-resistant building planning.
Integrating Time-Dependent and Time-Independent Earthquake Recurrence Models for Fault-Based Seismic Hazard Assessment in the Lampung Region, Southern Sumatra Wulandari, Rizki; Styawan, Yudha; Prabowo, Satria Bagus
Spektra: Jurnal Fisika dan Aplikasinya Vol. 11 No. 1 (2026): SPEKTRA: Jurnal Fisika dan Aplikasinya, Volume 11 Issue 1, April 2026
Publisher : Program Studi Fisika Universitas Negeri Jakarta

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.21009/SPEKTRA.111.05

Abstract

The Lampung region in southern Sumatra is exposed to significant seismic hazard due to its proximity to the Sunda megathrust and multiple active crustal faults. This study integrates time-independent (Poissonian) and time-dependent (Brownian Passage Time/BPT) earthquake recurrence models to evaluate fault-specific rupture probabilities and their implications for probabilistic seismic hazard assessment (PSHA). This approach systematically bridges the gap between traditional stationary models and the physical reality of seismic cycles, ensuring that the resulting hazard estimates reflect the current elapsed time since the last major rupture. Earthquake catalogs from USGS, BMKG, and historical sources were compiled for shallow events ( 50 km) between 1900–2023, and fault parameters were derived from national hazard maps and published geological studies. Recurrence intervals were estimated for 28 major fault segments across Sumatra, the Sunda Strait, and western Java. Results show strong temporal variability in seismic potential, with the Kumering South segment exhibiting the highest 50-year rupture probability (>50%) due to its elapsed time nearing the estimated recurrence interval. In contrast, segments such as Semangko West-A show markedly reduced short-term probability under the BPT model. PSHA simulations using OpenQuake reveal peak ground acceleration (PGA) values of 0.6–1.5 g for 2% exceedance in 50 years, indicating very high hazard levels in areas adjacent to the Sumatra Fault System. Incorporating time-dependent recurrence provides a more cycle-consistent spatial pattern compared to Poissonian results, reducing overestimation in early-cycle segments and enhancing hazard representation in late-cycle faults. While this study is constrained by uncertainties in historical recurrence intervals and fault slip-rates, these findings provide a more refined academic contribution to regional hazard characterization, supporting more robust risk mitigation strategies in Lampung Province.
Pemetaan Ancaman dan Risiko Bencana Tanah Longsor Menggunakan Sistem Informasi Geografis di Kabupaten Lampung Barat Maisyaroh, Siti; Farduwin, Alhada; Styawan, Yudha
(JITEK)Jurnal Ilmiah Teknosains Vol 12, No 1/Now (2026): Vol.12 No. 1 Mei 2026
Publisher : Universitas PGRI Semarang

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.26877/jitek.v12i1/Now.27319

Abstract

Kabupaten Lampung Barat termasuk daerah yang memiliki kondisi topografi berbukit hingga pegunungan dengan kemiringan lereng bervariasi dari datar hingga sangat curam, sehingga berpotensi tinggi terhadap kejadian tanah longsor ketika terjadi hujan. Penelitian ini bertujuan untuk memetakan tingkat ancaman dan risiko bencana tanah longsor di Kabupaten Lampung Barat menggunakan pendekatan Sistem Informasi Geografis (SIG). Analisis dilakuka dengan metode weighted overlay terhadap beberapa parameter yaitu curah hujan, kemiringan lereng, jenis batuan, tutupan lahan, jenis tanah dan keberadaan sesar. Masing-masing parameter diklasifikasikan, diberi skor dan bobot sesuai pengaruhnya terhadap terjadinya bencana tanah longsor.Pemetaan ancaman dilakukan dengan mengintegrasikan seluruh parameter melalui proses overlay yang kemudian diklasifikasikan menjadi tiga kelas yaitu rendah, sedang, dan tinggi. Analisis risiko dilakukan melalui integrasi peta ancaman dengan peta kerentanan dan kapasitas. Hasil penelitian menunjukkan bahwa tingkat ancaman longsor didominasi oleh kelas sedang dengan indeks (2,72-3,38) hingga tinggi dengan indeks (3,38-4,05). Sementara itu tingkat risiko longsor diperoleh indeks rendah (1,3-2,6), sedang (2,6-4), dan tinggi (4-5,3).kata kunci: ancaman; longsor; overlay; risiko; SIG
Spatial-Temporal Analysis of b-value Before and After the 2018 Lombok Earthquake Using OK1993 Based on Voronoi in the Bali-NTB Region Tata Dwi Hardi Yanti; Yudha Styawan; Rizki Wulandari
EKSAKTA: Berkala Ilmiah Bidang MIPA Vol. 27 No. 03 (2026): Eksakta : Berkala Ilmiah Bidang MIPA (E-ISSN : 2549-7464) In Progress
Publisher : Faculty of Mathematics and Natural Sciences (FMIPA), Universitas Negeri Padang, Indonesia

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.24036/eksakta/vol27-iss03/678

Abstract

This study is motivated by the tectonic complexity of the Bali-NTB region, which results in a heterogeneous seismic distribution and active stress dynamics. The objective is to analyze the spatiotemporal evolution of the b-value using the Ogata-Katsura maximum likelihood estimation (OK1993), combined with Voronoi tessellation as an adaptive spatial partition and the Bayesian Information Criterion (BIC) for ensemble model optimization. Spatial analysis prior to the 2018 event revealed a contradiction in the form of high b-value (>1.0) in Lombok. However, the spatiotemporal analysis successfully explains the condition by identifying a zone of low b-value (<1.0) that developed following the 2007 intermediate sized earthquake through the 2018 mainshock distinct from the 2004 local anomaly that did not progress into a major earthquake. This indicates that the persistence of low b-values is a key indicator of high stress accumulation. Following the 2018 earthquake, the high stress zone expanded across Lombok and West Nusa Tenggara (NTB). This study emphasizes the importance of evaluating statistical reliability, such as N(b) and Median Absolute Deviation (MAD), to avoid misinterpretations due to data limitations, thereby providing a more reliable framework for regional seismic hazard assessment.
Peak Ground Acceleration Mapping of Indonesia Using Complementary Area Source and Smoothed Seismicity Approaches Eka Nioisa Br Surbakti; Rizki Wulandari; Yudha Styawan
EKSAKTA: Berkala Ilmiah Bidang MIPA Vol. 27 No. 03 (2026): Eksakta : Berkala Ilmiah Bidang MIPA (E-ISSN : 2549-7464) In Progress
Publisher : Faculty of Mathematics and Natural Sciences (FMIPA), Universitas Negeri Padang, Indonesia

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.24036/eksakta/vol27-iss03/684

Abstract

 In Indonesia, the choice between area source and smoothed seismicity approaches has been driven by data availability rather than scientific evaluation, and no systematic comparison of both methods at the national scale has been conducted. This study compared both approaches across Indonesia to evaluate their differences in PGA estimation and assess the forecasting skill of the smoothed seismicity model. Both models were applied to the same declustered earthquake catalog with a Magnitude of Completeness of 4.7, b-value of 0.89, and a-value of 8.753, using identical Ground Motion Prediction Equations within a probabilistic seismic hazard analysis framework. Both models consistently identified North Sulawesi as the highest hazard region and Kalimantan as the lowest. The smoothed seismicity model produced higher maximum PGA values of 2.13 g compared to 1.1597 g and 1.5901 g from the area source model at 10% and 2% probability of exceedance in 50 years, respectively. Molchan Diagram validation yielded an Area Skill Score of 0.88 and R-score of 0.656, confirming strong forecasting skill. The two methods are complementary, and their integration within a logic tree framework is recommended for future national-scale PSHA in Indonesia.
Co-Authors Agus Ariyanto Antosia, Risky Martin Efriyanti, Annisa Eka Nioisa Br Surbakti Farduwin, Alhada Fattah, Erlangga Ibrahim Hafeezul, Muhammad Junian, Wahyu Eko Lestari, Eka Yunita Purnama Maisyaroh, Siti Nugraha, Purwaditya Nugraha Nurwijayanti Pinem, Junita Cintia Dewi Br Prabowo, Satria Bagus Prasetyo, Nugroho Putri, Intan Andriani Reza Rizki Reza Rizki Rizki Wulandari Rizki Wulandari Rizki Wulandari Rizki, Reza Sillak Hasiany Tata Dwi Hardi Yanti TR, Dina Puspita Julyanti Zakhra, Vera Meysya