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All Journal PROSIDING : Seminar Nasional Fisika dan Pendidikan Fisika Indonesian Physical Review Kasuari: Physics Education Journal (KPEJ)
Richard Lewerissa
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Education Physics

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Pemetaan Daerah Rawan Gempabumi di Wilayah Sorong Provinsi Papua Barat berdasarkan Metode Probabilistic Seimic Hazard Analysis (PSHA) Lewerissa, Richard; Manobi, Theresia
PROSIDING : Seminar Nasional Fisika dan Pendidikan Fisika Vol 1, No 4 (2013)
Publisher : PROSIDING : Seminar Nasional Fisika dan Pendidikan Fisika

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (1666.209 KB)

Abstract

Pemetaan daerah rawan gempabumi di wiayah Sorong Provinsi Papua Barat telah dilakukan berdasarkan analisis data sekunder sejarah gempabumi wilayah Sorong bersumber dari ANSS Catalog. Pemetaan wilayah ini didasarkan pada distribusi nilai percepatan tanah maksimum (Peak Ground Acceleration) menggunakan pendekatan Probability Seismic Hazard Analysis (PSHA) dengan probability of excedance 2% terkomputasi pada program komputer EQRISK dan analisis pohon logika. Hasil penelitian menunjukkan bahwa nilai percepatan tanah maksimum wilayah Sorong yang diperoleh mengikuti model seismisitas sumber seismik dan faktor geologi berkisar antara 300 – 1700 Gal atau 0.3 – 0.7 g dan dipetakan menggunakan program komputer ArcGIS 9.2, nilai kisaran ini dibagi kedalam beberapa kategori tingkat kerawanan gempabumi. Berdasarkan distribusi nilai percepatan tanah maksimum, wilayah Sorong dikategorikan kedalam daerah dengan tingkat kerawanan besar satu dan besar dua. Nilai tingkat kerawanan gempabumi besar satu berkisar antara 300 – 600 Gal meliputi daerah distrik Seget, distrik Beraur, sebagian distik Makbon dan Kota Sorong sedangkan tingkat kerawanan gempabumi besar dua berkisar antara > 600 Gal meliputi distrik Samate, distrik Sausapor, distrik Sorbar dan sebagian kecil distrik Makbon. Wilayah Sorong di Provinsi Papua Barat termasuk daerah dengan tingkat kerawanan gempabumi yang tinggi hal ini disebabkan karena wilayah Sorong merupakan daerah dengan banyaknya kejadian gempabumi  ≥ 5 SR dengan kedalaman dangkal ≥ 30 km serta keberadaan jalur Sesar aktif gempabumi Sorong-Yapen akibat pertemuan lempeng Eiruasia, lempeng Indo-Australia dan lempeng samudera Pasifik. Kata Kunci : Percepatan tanah maksimum, PSHA, Sorong, gempabumi
Overview of Geothermal Potential in Momiwaren, South Manokwari Regency using Earth Gravity Field Analysis Lewerissa, Richard
Kasuari: Physics Education Journal (KPEJ) Vol. 3 No. 2 (2020): December 2020
Publisher : Universitas Papua, Jurusan Pendidikan Fisika FKIP Unipa

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.37891/kpej.v3i2.142

Abstract

West Papua province has a geothermal resource that can be established as renewable electricity energy or tourism. One of the locations for geothermal prospects is in the Momiwaren district of South Manokwari regency. A preliminary study in form of a qualitative interpretation has been conducted through the analysis of high-resolution of earth gravity fields from the Global Gravity Map developed by Curtin University, Australia. This research was performed to increase the boundary of the geological structure which indicates the existence of a source of manifestation of hotsprings and the fault structures that control it. The study begins with the reduction of the gravity field data to obtain a complete Bouguer anomaly based on the SRTM2gravity terrain model correction. Furthermore, regional and residual gravity anomalies are separated, and vertical and horizontal gravitational gradient analysis using 2-D fast Fourier transform. Qualitative interpretation produces models and boundaries of the main structure and the corresponding Demini and Gaya Baru faults and the distribution of the geological rock formations in the study area. This interpretation provides useful information as a constraint for quantitative interpretation through subsurface inversion modeling to obtain detailed geothermal models in Momiwaren.
GROUNDWATER RESOURCE ESTIMATION USING VERTICAL ELECTRICAL SOUNDING AND RESISTIVITY TOMOGRAPHY IN WEST MANOKWARI, WEST PAPUA, INDONESIA Kammarudin, Kammarudin; Wahyudi, Wahyudi; Lewerissa, Richard; Afkril, Baina; Erari, Ishak
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.v7i3.340

Abstract

West Manokwari district in Manokwari Regency, West Papua province, Indonesia, is an area that continues to develop as part of the provincial capital region. Geologically, this area is located in three main formations: the Manokwari Formation, the Befoor Formation, and the Alluvium-littoral Formation at a depth radius between 0 and 500 meters. These formations comprise permeable sedimentary rocks that allow aquifer layers to develop. This study employed the geoelectric resistivity method, using both the Wenner and Schlumberger configurations, to identify the potential of groundwater in the West Manokwari district and address the scarcity of clean water sources for the local community. Subsurface interpretation was conducted on three measurement lines using forward modeling and inversion techniques, such as earth resistivity tomography and vertical electric sounding. The results of this interpretation indicate that the subsurface rock resistivity for the three lines is generally consistent and supports each other. The subsurface can be divided into four main layers: topsoil, limestone, sandstone, and bedrock. At the surface, rock resistivity is dominated by high values up to a depth of 6 m, after which it decreases to a depth of 30 m, which is considered a potential aquifer layer for exploration with medium to low resistivity. A bedrock layer with a resistivity of over 2000 Ωm is estimated to be at depths greater than 30 m. This study is expected to serve as a valuable resource for groundwater exploration in the West Manokwari district of West Papua Province.
INTEGRATING HIGH-RESOLUTION GRAVITY GRADIENTS AND 3D INVERSION MODELING TO DELINEATE MINERAL RESOURCES IN THE LEWA DISTRICT, EAST SUMBA, INDONESIA Raja, Aprianus; Tanesib, Jehunias; Lapono, Laura A. S.; Lewerissa, Richard
Indonesian Physical Review Vol. 8 No. 3 (2025)
Publisher : Universitas Mataram

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.29303/ipr.v8i3.501

Abstract

Research in Lewa District, East Sumba Regency, Indonesia, aimed to identify mineral potential and clarify subsurface geological structures through gravity gradient analysis and 3D inversion modeling. This approach addresses the limitations of field gravity data in the study area. The gravity gradient method was chosen to delineate geological structure boundaries (such as formation contacts and faults) compared to conventional gravity methods and for processing global satellite data (GGMplus and EGM2008 derivatives of ERTM 2160) with limited measured data. Gravity gradient analysis, including vertical, horizontal gradient, and tilt angle, was applied to Complete Bouguer Anomaly data using 2D Fourier transformation. Gravity field correction in Lewa showed positive anomalies from volcanic basement rocks. The gradient analysis sharpened boundaries of anomalies linked to geological structures. Zero contours of vertical gradient and tilt angle defined structural boundaries, while peaks of horizontal gradient and tilt angle indicated metallic mineral sources. 3D gravity inversion modeling (density 2.22–2.97 g/cm³) showed rock intrusions at 215 meters depth, interpreted as key to mineralization formation. The 2D sections (A-A', B-B', C-C') contain Masu Formation volcanic rocks, with fault zones filled by Waikabubak Formation sedimentary rocks and silicified rocks from magma intrusion alteration. Fault systems were identified through vertical gradient extremes, representing contact formation. Highly positive contour values on the tilt angle map confirm the influence of the volcanic basement rock. Metal mineralization is closely related to tectonic activity and alteration from massive igneous intrusion. The integration of gravity gradient analysis and 3D inversion modeling has proven to be effective in mapping geological structures and identifying mineral prospects using limited data. These findings provide insights into the subsurface geology of Lewa and provide a basis for further mineral exploration in East Sumba.
Co-Authors Afkril, Baina Erari, Ishak Kammarudin, Kammarudin Lapono, Laura A. S. Raja, Aprianus Tanesib, Jehunias Theresia Manobi Wahyudi Wahyudi