Endra Gunawan, Sri Widiyantoro, Nikmah Ramadani Fitri, Lila Nurrohmah, Genesia Shielvy Reyna, Nuraini Rahma Hanifa, Moh. Fifik Syafiudin, Sidik Tri Wibowo, Fitri Rahmafitria, Rizanna Rosemary, Achmad Choiruddin, Suryanto
The southern coast of Java, Indonesia, is a high-risk region characterized by intense seismic activity where the 17 July 2006 Mw 7.7 Java tsunami earthquake occurred and generated devastating tsunami. This study investigates the prolonged crustal deformation following this event by analyzing over a decade (2010–2022) of Global Navigation Satellite System (GNSS) data from stations along the southern coast of West Java. We quantify the contributions of two primary postseismic mechanisms—viscoelastic relaxation and afterslip—alongside ongoing interseismic coupling on the megathrust. Our results indicate that surface deformation was dominated by postseismic processes in the immediate years after the earthquake, with velocities of 2–3 mm/yr directed southward. Over time, the influence of postseismic deformation decayed significantly; viscoelastic relaxation diminished by 79% by 2019–2022. Afterslip distribution and moment release increased then decreased over the studied periods, releasing seismic moments equivalent to Mw 6.4–6.6. Concurrently, the deformation pattern gradually transitioned, revealing the increasing dominance of interseismic coupling as postseismic deformation progressively diminishes. The study highlights a transitional phase between postseismic and interseismic deformation along the Java subduction zone. These findings underscore the critical importance of long-term geodetic monitoring for refining seismic hazard assessments in subduction zones. © 2026 Royal Society of New Zealand Te Apārangi.
Global Geophysics Research Group, Faculty of Mining and Petroleum Engineering, Institut Teknologi Bandung, Bandung, Indonesia; Geophysical Engineering, Faculty of Mining and Petroleum Engineering, Institut Teknologi Bandung, Bandung, Indonesia; Research Center for Geological Disaster, National Research and Innovation Agency, Bandung, Indonesia; Geospatial Information Agency, Cibinong, Indonesia; Resort and Leisure Management, Faculty of Social Science Education, Universitas Pendidikan Indonesia, Bandung, Indonesia; Department of Communication Studies, Faculty of Social and Political Sciences, Universitas Syiah Kuala, Aceh, Indonesia; Tsunami Disaster Mitigation Research Center, Universitas Syiah Kuala, Aceh, Indonesia; Department of Statistics, Faculty of Science and Data Analytics, Institut Teknologi Sepuluh Nopember, Surabaya, Indonesia; Faculty of Economics and Business, Universitas Sebelas Maret, Surakarta, Indonesia
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