https://jgsm.geologi.esdm.go.id/index.php/JGSM <p><strong>Jurnal Geologi dan Sumberdaya Mineral (Journal of Geology and Mineral Resources)</strong> is an Indonesian scientific journal published by the Center for Geological Survey, Geological Agency, Ministry of Energy and Mineral Resources. The journal receives Indonesian or English articles. Those articles are selected and reviewed by our professional editors and peer reviewers.</p> <p>JGSM has been assigned as an Accredited Scientific Periodical Magazine by the Indonesian Institute of Sciences (LIPI) No. 596/Akred/P2MI-LIPI/03/2015 in 2015, followed by Kementerian Riset dan Teknologi / Badan Riset dan Inovasi Nasional No. 200/M/KPT/2020 in 2020. The journal is indexed in <a title="portal_garuda_IPI" href="http://id.portalgaruda.org/?ref=browse&amp;mod=viewjournal&amp;journal=10104" target="_blank" rel="noopener">Indonesian Publication Index (IPI)</a>, <a title="isjd" href="http://isjd.pdii.lipi.go.id/index.php/public_no_login/index_direktori" target="_blank" rel="noopener">Indonesian Scientific Journal Database (ISJD)</a>, <a href="http://dx.doi.org/10.33332">Digital Object Identifier (DOI)</a> and <a title="google_scholar" href="https://scholar.google.co.id/citations?user=nXMHIYUAAAAJ&amp;hl=en" target="_blank" rel="noopener">Google Scholar</a>, the contents are freely available in electronic version. JGSM is published quarterly in February, May, August, and November.</p> <p><a title="issn" href="http://issn.pdii.lipi.go.id/issn.cgi?daftar&amp;1402376294&amp;1&amp;&amp;" target="_blank" rel="noopener"><strong>ISSN : 0853-9634 (print)</strong></a></p> <p><a title="eissn" href="http://issn.pdii.lipi.go.id/issn.cgi?daftar&amp;1485227549&amp;1&amp;&amp;" target="_blank" rel="noopener"><strong>e-ISSN : 2549-4759 (online)</strong></a></p> <p><strong><em><strong>DOI Prefix: </strong></em><a title="JGSM" href="https://doi.org/10.33332">https://doi.org/10.33332</a><br /></strong></p> Pusat Survei Geologi en-US Jurnal Geologi dan Sumberdaya Mineral 0853-9634 <p>Authors who publish articles in <strong>Jurnal Geologi dan Sumberdaya Mineral (JGSM.Geologi)</strong> agree to the following terms:</p><ol><li>Authors retain copyright of the article and grant the journal right of first publication with the work simultaneously licensed under a <strong>CC-BY-NC</strong> or <strong>The Creative Commons Attribution–ShareAlike License.</strong></li><li>Authors are able to enter into separate, additional contractual arrangements for the non-exclusive distribution of the journal's published version of the work (e.g., post it to an institutional repository or publish it in a book), with an acknowledgment of its initial publication in this journal.</li><li>Authors are permitted and encouraged to post their work online (e.g., in institutional repositories or on their website) prior to and during the submission process, as it can lead to productive exchanges, as well as earlier and greater citation of published work (See <a href="http://opcit.eprints.org/oacitation-biblio.html" target="_blank">The Effect of Open Access</a>)</li></ol> https://jgsm.geologi.esdm.go.id/index.php/JGSM/article/view/987 <p>Aktivitas vulkanik intensif di kawasan Gunung <br />Merapi memerlukan pemahaman mendalam terhadap <br />struktur bawah permukaan, terutama dalam konteks <br />mitigasi bahaya erupsi dan analisis sistem magmatik. <br />Namun, keterbatasan resolusi spasial pada studi tomografi <br />sebelumnya menyulitkan identifikasi detail struktur seperti <br />reservoir magma dangkal, zona rekahan, dan sesar aktif yang <br />berperan dalam suplai magma. Oleh karena itu, penelitian <br />ini bertujuan untuk mengidentifikasi dan mengkarakterisasi <br />struktur bawah permukaan Gunung Merapi dan wilayah <br />sekitarnya secara spasial melalui tomografi seismik berbasis <br />kecepatan gelombang P (Vp), gelombang S (Vs), dan <br />rasio Vp/Vs. Data seismik lokal yang digunakan berasal <br />dari jaringan broadband DOMERAPI dan BMKG, yang <br />diolah menggunakan perangkat lunak LOTOS-13 dengan <br />pemodelan inversi non-linier. Hasil inversi menunjukkan <br />adanya zona anomali kecepatan rendah dengan rasio Vp/<br />Vs tinggi pada kedalaman &lt;6 km di bawah Merapi, yang <br />diinterpretasikan sebagai reservoir magma dangkal yang <br />kaya fluida. Zona transisi dan reservoir magma menengah <br />teridentifikasi masing-masing pada kedalaman 6–12 km dan <br />13–16 km. Di bawah Gunung Merbabu, anomali kecepatan <br />lebih lemah tanpa indikasi aktivitas magmatik signifikan, <br />mencerminkan sistem vulkanik yang relatif tidak aktif. <br />Selain itu, zona kecepatan rendah dan rasio Vp/Vs tinggi <br />pada kedalaman 15–18 km di selatan Merapi dikaitkan <br />dengan keberadaan Sesar Opak. Hasil studi ini memperkuat <br />pemahaman mengenai dinamika sistem magmatik serta <br />potensi seismotektonik di kawasan vulkanik Jawa Tengah.</p> <p><strong>Kata Kunci: </strong>Tomografi seismik, Gunung Merapi, Struktur <br />bawah permukaan, rasio Vp/Vs, Reservoir Magma</p> <p> </p> <p><em><strong> Abstract</strong></em></p> <p><em>Intense volcanic activity in the Mount Merapi </em><br /><em>region necessitates a thorough understanding of its </em><br /><em>subsurface structure, particularly for eruption hazard </em><br /><em>mitigation and magmatic system analysis. However, </em><br /><em>limitations in spatial resolution from previous tomography </em><br /><em>studies have hindered detailed identification of features </em><br /><em>such as shallow magma reservoirs, fracture zones, and </em><br /><em>active faults responsible for magma transport. Therefore, </em><br /><em>this study aims to identify and spatially characterize </em><br /><em>the subsurface structure beneath Mount Merapi and its </em><br /><em>surroundings using seismic tomography based on P-wave </em><br /><em>velocity (Vp), S-wave velocity (Vs), and Vp/Vs ratio data. </em><br /><em>Local seismic data were obtained from the DOMERAPI </em><br /><em>and BMKG broadband networks and processed using the </em><br /><em>LOTOS-13 software with a non-linear inversion model. The </em><br /><em>results reveal a low-velocity anomaly zone with a high Vp/Vs </em><br /><em>ratio at depths of less than 6 km beneath Merapi, interpreted </em><br /><em>as a shallow, fluid-rich magma reservoir. A transition zone </em><br /><em>and an intermediate magma reservoir were identified at </em><br /><em>depths of 6–12 km and 13–16 km, respectively. Beneath </em><br /><em>Mount Merbabu, weaker velocity anomalies without </em><br /><em>significant magmatic signals indicate a relatively inactive </em><br /><em>volcanic system. Additionally, low-velocity and high Vp/</em><br /><em>Vs ratio zones at depths of 15–18 km south of Merapi are </em><br /><em>associated with the Opak Fault. These findings enhance our </em><br /><em>understanding of magmatic dynamics and seismotectonic </em><br /><em>potential in the Central Java volcanic region.</em></p> <p><em><strong>Keywords:</strong> Seismic tomography, Mount Merapi, Subsurface </em><br /><em>structure, Vp/Vs ratio, Magma reservoir</em></p> Joshua Purba Riska Yulinda Copyright (c) 2025 Joshua Purba, Riska Yulinda http://creativecommons.org/licenses/by-nc/4.0 2025-08-18 2025-08-18 26 3 139 155 10.33332/jgsm.geologi.v26i3.987 https://jgsm.geologi.esdm.go.id/index.php/JGSM/article/view/967 <p><span style="font-weight: 400;">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 Vs</span><span style="font-weight: 400;">30</span><span style="font-weight: 400;">. 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 (</span><em><span style="font-weight: 400;">subsidence</span></em><span style="font-weight: 400;">) hingga 23 cm dan pengangkatan (</span><em><span style="font-weight: 400;">uplift</span></em><span style="font-weight: 400;">) hingga 13 cm di wilayah Kota Palu. Wilayah dengan nilai Vs</span><span style="font-weight: 400;">30</span><span style="font-weight: 400;"> rendah cenderung mengalami penurunan akibat tanah lunak, sedangkan wilayah dengan nilai Vs</span><span style="font-weight: 400;">30</span><span style="font-weight: 400;"> tinggi cenderung mengalami kenaikan akibat tanah keras. Namun demikian, terjadi anomali pada wilayah Kecamatan Ulujadi dan Kecamatan Palu Selatan. Penggunaan data Vs</span><span style="font-weight: 400;">30</span><span style="font-weight: 400;"> menunjukkan bahwa nilai Vs</span><span style="font-weight: 400;">30</span><span style="font-weight: 400;"> 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.</span></p> <p><span style="font-weight: 400;"><strong> Kata Kunci:</strong><em> Deformasi, Metode DInSAR, Sentinel 1A, Vs30</em><br /><em>Kota Palu</em></span></p> <p><strong><em>Abstract</em></strong></p> <p><em>This research is motivated by the deformation </em><br /><em>event that occurred due to the earthquake on September </em><br /><em>28, 2018 in Palu City. This research aims to determine the </em><br /><em>value of deformation due to the M 7.4 earthquake in Palu </em><br /><em>City in 2018, and to determine the relationship between </em><br /><em>deformation and Vs30. The DInSAR method was used to </em><br /><em>determine the deformation changes due to the earthquake </em><br /><em>using Sentinel 1A data on June 07, 2018 (pre-earthquake) </em><br /><em>and November 22, 2018 (post-earthquake). The analysis </em><br /><em>results showed subsidence of up to 23 cm and uplift of up to </em><br /><em>13 cm in the city of Palu. Areas with low Vs30 values tend to </em><br /><em>experience subsidence due to soft soils, whereas areas with high Vs30values tend to experience uplift due to hard soil. </em><br /><em>However, anomalies occurred in Ulujadi and South Palu subdistricts. The use of Vs30data shows that Vs30</em><br /><em>valuescan be used as an early indicator to predict areas with </em><br /><em>potential earthquake-induced deformation. It is important </em><br /><em>for the development of disaster mitigation strategies, such </em><br /><em>as determining safe zones for development.</em></p> <p><em><strong>Keywords:</strong> Deformation, DInSAR method, Sentinel 1A, Vs30, Palu City</em></p> Aprilia Ode Saadia Joshua Purba Hasria Hasria LM. Golok Jaya Imanuela Indah Pertiwi Halis M. Djibran Copyright (c) 2025 Aprilia Ode Saadia, Joshua Purba, Hasria Hasria, LM. Golok Jaya, Imanuela Indah Pertiwi, Halis M. Djibran http://creativecommons.org/licenses/by-nc/4.0 2025-08-21 2025-08-21 26 3 157 168 10.33332/jgsm.geologi.v26i3.967