Receiver-Fault Variability and Depth-Dependent Coulomb Stress Changes in the 2019 Mw 7.2 Halmahera Earthquake Sequence
DOI:
https://doi.org/10.70561/geocelebes.v10i2.47046Keywords:
extensional area, receiver fault variability, seismic triggering, stress shadow, strike-slip kinematicsAbstract
This study investigates the relationship between fault geometry, Coulomb stress transfer, and aftershock distribution in the Halmahera region after the 2019 Mw 7.2 Halmahera Earthquake. Analysis of focal mechanism solutions reveals two distinct clusters: Cluster 1 is located southwest of the mainshock around Bacan Island and is dominated by normal faulting that suggests local extension, whereas Cluster 2 trends southeast of the mainshock along southern Halmahera and exhibits a mix of strike-slip and normal. Coulomb stress modeling shows that when only the maximum ΔCFS across the depth column is considered, aftershocks appear to occur within positive stress-change zones (ΔCFS ≥ ~0.1 bar). Evaluation at the actual hypocentral depths reveals that many aftershocks are concentrated within zones of apparent stress-reduction at shallow levels (0–10 km). This observation may be due to mismatches in receiver-fault geometry, spatial heterogeneity in the background stress/strength field, or processes that are not captured by static ΔCFS. By applying a fault-variability approach, we demonstrate that small variations in receiver-fault orientation can substantially alter ΔCFS outcomes and better reproduce the observed aftershock distribution. These results underscore the importance of receiver-fault geometry and segmentation specific to the Halmahera region in interpreting stress transfer.
References
Altunel, E., Kozacı, Ö., Yıldırım, C., Sbeinati, R. M., & Meghraoui, M. (2024). Potential domino effect of the 2023 Kahramanmaraş earthquake on the centuries-long seismic quiescence of the Dead Sea fault: Inferences from the North Anatolian fault. Scientific Reports, 14(1), 15440. https://doi.org/10.1038/s41598-024-65906-4
Álvarez-Gómez, J. A. (2019). FMC—Earthquake focal mechanisms data management, cluster and classification. SoftwareX, 9, 299–307. https://doi.org/10.1016/j.softx.2019.03.008
Dai, X., Liu, X., Liu, R., Song, M., Zhu, G., Chang, X., & Guo, J. (2024). Coseismic Slip Distribution and Coulomb Stress Change of the 2023 MW 7.8 Pazarcik and MW 7.5 Elbistan Earthquakes in Turkey. Remote Sensing, 16(2), 240. https://doi.org/10.3390/rs16020240
Durkin, W., Kachuck, S., & Pritchard, M. (2019). The Importance of the Inelastic and Elastic Structures of the Crust in Constraining Glacial Density, Mass Change, and Isostatic Adjustment From Geodetic Observations in Southeast Alaska. Journal of Geophysical Research: Solid Earth, 124(1), 1106–1119. https://doi.org/10.1029/2018JB016399
Ekström, G., Nettles, M., & Dziewoński, A. M. (2012). The global CMT project 2004–2010: Centroid-moment tensors for 13,017 earthquakes. Physics of the Earth and Planetary Interiors, 200–201, 1–9. https://doi.org/10.1016/j.pepi.2012.04.002
Gercek, H. (2007). Poisson’s ratio values for rocks. International Journal of Rock Mechanics and Mining Sciences, 44(1), 1–13. https://doi.org/10.1016/j.ijrmms.2006.04.011
Hardebeck, J. L., & Harris, R. A. (2022). Earthquakes in the shadows: Why aftershocks occur at surprising locations. The Seismic Record, 2(3), 207–216. https://doi.org/10.1785/0320220023
Heidarzadeh, M., Ishibe, T., Harada, T., Natawidjaja, D. H., Pranantyo, I. R., & Widyantoro, B. T. (2021). High potential for splay faulting in the Molucca Sea, Indonesia: November 2019 Mw 7.2 earthquake and tsunami. Geophysical Research Letters, 48(10), e2020GL083989. https://doi.org/10.1029/2020GL083989
International Seismological Centre. (2026). On-line Bulletin. https://doi.org/10.31905/D808B830
Kusumawati, D., Sahara, D. P., Nugraha, A. D., & Puspito, N. T. (2019). Sensitivity of static Coulomb stress change in relation to source fault geometry and regional stress magnitude: case study of the 2016 Pidie Jaya, Aceh earthquake (Mw = 6.5), Indonesia. Journal of Seismology, 23, 1391–1403. https://doi.org/10.1007/s10950-019-09878-3
Lentas, K., Di Giacomo, D., Harris, J., & Storchak, D. A. (2019). The ISC Bulletin as a comprehensive source of earthquake source mechanisms. Earth System Science Data, 11, 565–578, https://doi.org/10.5194/essd-11-565-2019
Liu, C., Lay, T., Wang, R., Taymaz, T., Xie, Z., Xiong, X., Irmak, T. S., Kahraman, M., & Erman, C. (2023). Complex multi-fault rupture and triggering during the 2023 earthquake doublet in southeastern Türkiye. Nature Communications, 14(1), 5564. https://doi.org/10.1038/s41467-023-41404-5
Muzli, M., Umar, M., Nugraha, A. D., Bradley, K. E., Widiyantoro, S., Erbas, K., Jousset, P., Rohadi, S., Nurdin, I., & Wei, S. (2018). The 2016 Mw 6.5 Pidie Jaya, Aceh, North Sumatra, Earthquake: Reactivation of an unidentified sinistral fault in a region of distributed deformation. Seismological Research Letters, 89(5), 1761-1772. https://doi.org/10.1785/0220180068
Provost, F., Karabacak, V., Malet, J.-P., Van der Woerd, J., Meghraoui, M., Masson, F., Ferry, M., Michéa, D., & Pointal, E. (2024). High-resolution co-seismic fault offsets of the 2023 Türkiye earthquake ruptures using satellite imagery. Scientific Reports, 14(1), 6834. https://doi.org/10.1038/s41598-024-55009-5
Pusat Studi Gempa Nasional (PuSGeN). (2017). Peta Sumber dan Bahaya Gempa Indonesia Tahun 2017. Bandung: Pusat Penelitian dan Pengembangan Perumahan dan Permukiman, Kementerian Pekerjaan Umum dan Perumahan Rakyat.
Ramdhan, M., Palgunadi, K. H., Mukti, M. M., Librian, V., Daniarsyad, G., Muttaqy, F., Hidayat, E., Syuhada, S., Hanif, M., Mursitantyo, A., Lühr, B.-G., Nugraha, A. D., Widiyantoro, S., Setyonegoro, W., & Febriani, F. (2025). Aftershock sequence of the Yogyakarta earthquake 2006 (Mw ~ 6.4), Indonesia, based on analysis of hypocenter relocation, static, and dynamic stress. Natural Hazards, 121, 16559–16579. https://doi.org/10.1007/s11069-025-07440-8
Reasenberg, P. A., & Simpson, R. W. (1992). Response of regional seismicity to the static stress change produced by the Loma Prieta earthquake. Science, 255(5052), 1687-1690. https://doi.org/10.1126/science.255.5052.1687
Rohadi, S., Perdana, Y. H., Herayndoko, N., Sunardi, B., Prakoso, T. A., Suliyanti, S., Sunardi, S., Florida, N., Edison, R., & Karnawati, D. (2021). The M 6.5 Ambon earthquake 26 September 2019: the source mechanism and the aftershock sequence characteristics. IOP Conference Series: Earth and Environmental Science, 873(1), 012013. https://doi.org/10.1088/1755-1315/873/1/012013
Sharma, S., Hainzl, S., Zöeller, G., & Holschneider, M. (2020). Is coulomb stress the best choice for aftershock forecasting? Journal of Geophysical Research: Solid Earth, 125(9), e2020JB019553. https://doi.org/10.1029/2020JB019553
Sinaga, G. H. D., Zarlis, M., Sitepu, M., Prasetyo, R. A., & Simanullang, A. (2021). Coulomb stress analysis of West Halmahera earthquake Mw=7.2 to Mount Soputan and Gamalama volcanic activities. IOP Conference Series: Earth and Environmental Science, 56(1), 012005. https://doi.org/10.1088/1755-1315/56/1/012005
Siwi, P. W., Sriyanto, S. P. D., Rondonuwu, A. T., & Silangen, P. M. (2020). Perubahan Coulomb Stress Akibat Gempa Bumi Laut Maluku 7 Januari 2019. Jurnal Geosaintek, 6(3), 137–142. https://doi.org/10.12962/j25023659.v6i3.7030
Smith, S. A. F., & Faulkner, D. R. (2010). Laboratory measurements of the frictional properties of the Zuccale low‐angle normal fault, Elba Island, Italy. Journal of Geophysical Research: Solid Earth, 115(B2), 2008JB006274. https://doi.org/10.1029/2008JB006274
Souisa, M., & Sapulete, S. M. (2021). Analysis of the Impact of Coulomb Stress Changes of Tehoru Earthquake, Central Maluku Regency, Maluku Province. Jurnal Penelitian Pendidikan IPA, 7(4), 593–600. https://doi.org/10.29303/jppipa.v7i4.975
Storchak, D. A., Harris, J., Brown, L., Lieser, K., Shumba, B., & Di Giacomo, D. (2020). Rebuild of the Bulletin of the International Seismological Centre (ISC)—part 2: 1980–2010. Geoscience Letters, 7(1), 18. https://doi.org/10.1186/s40562-020-00164-6
Supendi, P., Nugraha, A. D., Widiyantoro, S., Pesicek, J. D., Thurber, C. H., Abdullah, C. I., Daryono, D., Shiddiqi, H. A., & Rosalia, S. (2020). Relocated aftershocks and background seismicity in eastern Indonesia shed light on the 2018 Lombok and Palu earthquake sequences. Geophysical Journal International, 221(3), 1845-1855. https://doi.org/10.1093/gji/ggaa118
Supendi, P., Rawlinson, N., Prayitno, B. S., Sianipar, D., Simanjuntak, A., Widiyantoro, S., Palgunadi, K. H., Kurniawan, A., Ash Shiddiqi, H., Nugraha, A. D., Sahara, D. P., Daryono, D., Triyono, R., Adi, S. P., Karnawati, D., Daniarsyad, G., Ahadi, S., Fatchurohman, I., Anugrah, S. D., Heryandoko, N., & Sudrajat, A. (2023). A previously unidentified fault revealed by the February 25, 2022 (Mw 6.1) Pasaman earthquake, West Sumatra, Indonesia. Physics of the Earth and Planetary Interiors, 334, 106973. https://doi.org/10.1016/j.pepi.2022.106973
Toda, S., Stein, R. S., Sevilgen, V., & Lin, J. (2011). Coulomb 3.3 Graphic-rich deformation and stress-change software for earthquake, tectonic, and volcano research and teaching-user guide (2011–1060). U.S. Geological Survey. https://doi.org/10.3133/ofr20111060
USGS. (2019). Finite fault model for the M 7.2 earthquake 155 km SSE of Sofifi, Indonesia (2019-07-14 09:10:51 UTC). U.S. Geological Survey. https://earthquake.usgs.gov/earthquakes/eventpage/us70004jyv/finite-fault
Wajedy, M. F., Saaduddin, S., Massinai, M. A., Fahruddin, F., & Thariq, A. (2026). Seismic hazard and tectonic stress in Halmahera, Indonesia based on b-value and apparent stress analyses. Physics of the Earth and Planetary Interiors, 372, 107512. https://doi.org/10.1016/j.pepi.2026.107512
Watkinson, I. M., & Hall, R. (2017). Fault systems of the eastern Indonesian triple junction: evaluation of Quaternary activity and implications for seismic hazards. Geological Society, London, Special Publications, 441(1), 71–120. https://doi.org/10.1144/SP441.8
Wu, J., Cai, Y., Li, W., & Feng, Q. (2017). Strong Aftershock Study Based on Coulomb Stress Triggering—A Case Study on the 2016 Ecuador Mw 7.8 Earthquake. Applied Sciences, 7(1), 88. https://doi.org/10.3390/app7010088
Wulandari, R., Chan, C.-H., & Wibowo, A. (2023). The 2022 Mw6.2 Pasaman, Indonesia, earthquake sequence and its implication of seismic hazard in central-west Sumatra. Geoscience Letters, 10(1), 25. https://doi.org/10.1186/s40562-023-00279-6
Downloads
Published
Issue
Section
License
Copyright (c) 2026 JURNAL GEOCELEBES
This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.
Authors who publish with this journal agree to the following terms:
- Authors retain copyright and grant the journal right of first publication with the work simultaneously licensed under a Creative Commons Attribution License that allows others to share the work with an acknowledgement of the work's authorship and initial publication in this journal.
- 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 acknowledgement of its initial publication in this journal.
- 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 The Effect of Open Access).
