Revealing the Subsurface Geometry of the 2023 Sumedang Earthquake Sequence Using Double-Difference Relocation and Cross-Section Analysis
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Abstract
The Sumedang Regency experienced a significant tectonic earthquake sequence beginning on December 31, 2023, which raised concerns regarding active fault structures in the region. Identifying the precise causative fault geometry was essential for seismic hazard mitigation but remained challenging due to the complex local geology and potential location errors in preliminary data. This study investigated the source mechanism and subsurface geometry of the aftershocks recorded between December 31, 2023, and January 8, 2024. The Double-Difference (HypoDD) method was applied to relocate earthquake hypocenters by minimizing travel-time residuals, utilizing a 1-D velocity model with a variable Vp/Vs ratio. Subsequently, vertical cross-section analysis was conducted to interpret the dip patterns and fault orientation perpendicular to the seismicity trend. The results revealed a significant transformation in the spatial distribution pattern; while initial data exhibited a linear north-south trend, the relocated hypocenters formed a distinct curved cluster extending from the south toward the west. The seismic activity was concentrated at shallow depths ranging from 3 km to 17 km. Cross-section interpretations suggested two potential fault geometries: a near-vertical alignment indicating a strike-slip mechanism potentially associated with the Subang Segment of the Baribis Fault, or an inclined, slab-like structure indicative of a thrust fault system. These findings provided critical constraints for future moment tensor inversion studies.
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[1] R. Meilani, Rosida Tiurma Manurung, Maria Yuni Megarini, Tessalonika Sembiring, and Karthy Priyathy Mastovani, “Penanganan psikologis pasca gempa bumi Sumedang,” BEGAWE J. Pengabdi. Masy., vol. 2, no. 1, pp. 59–62, 2024.
[2] P. Supendi, A. D. Nugraha, N. T. Puspito, S. Widiyantoro, and D. Daryono, “Identification of active faults in West Java , Indonesia , based on earthquake hypocenter determination , relocation , and focal mechanism analysis,” Geosci. Lett., vol. 31, pp. 4–10, 2018, doi: 10.1186/s40562-018-0130-y.
[3] D. Purwanto, D. D. Permadi, U. S. Saputri, U. Aditiawarman, D. O. D. Handayani, and D. A. Dewi, “Kajian tentang bencana dan dampak gempa bumi di cianjur bersama mahasiswa teknik sipil nusaputra,” J. Pengabdi. Kpd. Masy. Abdi Nusa, vol. 3, no. 1, pp. 36–39, 2023.
[4] M. Aritonang, A. F. T. Parera, and N. Nasution, “Relokasi Hiposenter Gempabumi Di Segmen ( Toru , Angkola , Barumun ) Dengan Menggunakan Metode Double Difference ( Hypo-DD ),” Pendidik. Fis. dan Sains, vol. 4, no. 2, pp. 24–29, 2021.
[5] F. Waldhauser and W. L. Ellsworth, “A Double-difference Earthquake location algorithm: Method and application to the Northern Hayward Fault, California,” Bull. Seismol. Soc. Am., vol. 90, no. 6, pp. 1353–1368, 2000, doi: 10.1785/0120000006.
[6] S. Wulandari, A. F. T. Parera, and L. H. Lubis, “Relokasi Gempabumi di Sesar Renun A, B, Dan C dengan Menggunakan Metode Double Difference (Hypo-DD),” GRAVITASI J. …, vol. 4, no. 2, pp. 30–35, 2021, [Online]. Available: https://ejurnalunsam.id/index.php/JPFS/article/view/4560
[7] W. T. Baskoro, I. G. A. Kasmawan, I. K. Putra, N. N. Ratini, and Sismanto, “Metode Double-Difference Untuk Merelokasi Hiposenter Gempabumi Susulan Seririt Singaraja,” Kappa J., vol. 8, no. 1, pp. 28–33, 2024, doi: 10.29408/kpj.v8i1.24434.
[8] F. Waldhauser, hypoDD: A computer program to compute double-difference earthquake locations (2001). 2001.
[9] M. P. Lestari, Budiarta, Darsono, and Y. H. Perdana, “Penggunaan Software GMT 6 Dan Python Untuk Menampilkan Peta Seismisitas Dan Menghitung Besar Sudut Subduksi Di Pulau Jawa,” J. Stasiun Geofis. Sleman, vol. 1, no. 2, p. 19, 2023.
[10] A. Arimuko, B. M. T. F. Nanda, and Rasmid, “Identifikasi Struktur Bawah Permukaan Berdasarkan Pemodelan Kecepatan 1D Hasil Relokasi Hiposentrum Gempa di Pulau Lombok, Gunung Sinabung, dan Jailolo,” J. Geofis., vol. 18, no. 02, pp. 40–48, 2021.
[11] P. Wessel et al., “The Generic Mapping Tools Version 6,” Geochemistry, Geophys. Geosystems, vol. 20, no. 11, pp. 5556–5564, 2019, doi: 10.1029/2019GC008515.
[12] B. E. B. Nurhandoko et al., “Subsurface Characterization and Revealing Geometry of the Baribis Fault in the Eastern Part of West Java Using Long-Offset Resistivity Tomography,” J. Earthq. Tsunami, vol. 19, no. 2, pp. 1–25, 2025, doi: 10.1142/S1793431124500313.
[13] A. Koulali et al., “Crustal strain partitioning and the associated earthquake hazard in the eastern Sunda-Banda Arc,” Geophys. Res. Lett., vol. 43, no. 5, pp. 1943–1949, 2016, doi: 10.1002/2016GL067941.
[14] V. I. C. Sinaga, M. A. F. Aolindar, M. A. N. Pramudita, P. Supendi, K. H. Kirana, and M. U. Hasanah, “Relocation of Earthquake Hypocenter Using Double-Difference Method in Western Part of Sumatera,” J. Phys. Conf. Ser., vol. 2582, no. 1, pp. 1–8, 2023, doi: 10.1088/1742-6596/2582/1/012004.
[15] A. D. Nugraha et al., “Hypocenter Relocation of Earthquake Swarm in West Halmahera, North Molucca Region, Indonesia by using Double-Difference Method and 3D Seismic Velocity Structure,” in IOP Conference Series: Earth and Environmental Science, 2017. doi: 10.1088/1755-1315/62/1/012053.
[16] D. H. Natawidjaja, B. Sapiie, G. I. Marliyani, and M. R. Daryono, “Baribis-Kendeng Thrust-Fold Zone of Java , Indonesia : New Evidences of Active Back- Arc Tectonics and Their Implications to Seismic Hazards,” Proc. Jt. Conv. MALANG 2017, no. Jcm, 2017.
[17] L. Ye et al., “The 22 December 2018 tsunami from flank collapse of Anak Krakatau volcano during eruption,” Sci. Adv., vol. 6, no. 3, pp. 1–9, 2020, doi: 10.1126/sciadv.aaz1377.
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