| Penulis/Author |
AYU KRISNO EKARSTI (1) ; Prof. Dr. Ir. Subagyo Pramumijoyo, DEA., IPU. (2); Ir. Gayatri Indah Marliyani, S.T., M.Sc., Ph.D., IPM (3); Dr.Eng. Ir. Agung Setianto, S.T., M.Si., IPM. (4); Prof. Ir. Dwikorita Karnawati, M.Sc., Ph.D. (5) |
| Abstrak/Abstract |
On May 26, 2006, a devastating Mw 6.4 earthquake struck Yogyakarta, causing significant loss of life and widespread damage. Despite extensive studies, discrepancies remain regarding the earthquake’s epicenter, faulting mechanism, and causative structures. In this study, we revisit the 2006 Yogyakarta earthquake sequence to develop a more refined understanding of its source characteristics. Our analysis involved recalculating mainshock parameters using expanded regional seismic data, detecting and relocating aftershocks, and modeling the mainshock focal mechanism. The mainshock is re-estimated at Mw 6.3 with a left-lateral strike-slip mechanism. Seismicity clustered approximately 12 km east of the Opak Fault, forming a 21 km-long zone oriented N45°E, which bends westward at its southern end, extending an additional 9 km along N40°W. This pattern suggests activation of a concealed fault segment, likely an ancient extension of the Opak Fault predating the Miocene. The spatial distribution of aftershocks, the modeled focal mechanism, and the overlying Wonosari Depression support the interpretation of a negative flower structure. These findings highlight the structural complexity of the Opak Fault System, shaped by deep-seated tectonic processes associated with the evolution of the southern mountain zone since the Cretaceous. |
