Abstract Database


Wahyudi Nasrul Pratama
Supervisor: Saeko KITA
Country: Indonesia

Determination of the stress field is essential to understanding the stress source and earthquake mechanism. However, the stress field study has been rarely conducted in the Indonesia region. We constructed the stress map in Indonesia derived from the Global Centroid Moment Tensor (GCMT) and the National Research Institute for Earth Science and Disaster Prevention (NIED) focal mechanism data from 1990 until 2021, where the Agency for Meteorology, Climatology, and Geophysics, Indonesia (BMKG)’s stations were also used for determining focal mechanisms in the NIED catalog. Overall, we used 3,756 earthquake focal mechanism data with a depth of ≤30 km. We applied two methodologies in this study; firstly, we created a mesh size of 75 km x 75 km of spatial mean of maximum horizontal compression stress (SHmax) and fault type. Then, we also performed the stress tensor inversion method to confirm the spatial mean of SHmax orientations. We got very declivous plunges of 𝜎1 in the northern North Maluku, southern North Maluku, and Batu-Mentawai-Pagai subduction segments. Meanwhile, the West and Central Java, the East Java, and the Sumba subduction segments have relatively steeper plunge angles than other regions. We found that the two methodologies we used yielded the same results in general. In our stress map, the orientations of SHmax are commonly perpendicular to the trench in the subduction zone and subparallel to the plate motion. This stress map also revealed the fault type distribution, which is generally consistent with the tectonic setting and focal mechanisms of large earthquakes. We confirmed that the normal faulting associated with SHmax parallel to the trench is intense near the trench of Java and Sumba subduction segments, indicating this area as the uncouple subduction zone. Stress field map in this study has possibility to assess the potential slip of faults in Indonesia for future prospects.

Keywords: Stress Map, Stress Tensor Inversion, SHmax, Focal Mechanisms.