EGU22-3794, updated on 27 Mar 2022
EGU General Assembly 2022
© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

Preliminary results of investigation of “unidentified fault” associated with the Mw 7.3 Flores Sea earthquake

Pepen Supendi1,2, Nicholas Rawlinson1, Bambang Setiyo Prayitno2, Sri Widiyantoro3,4, Kadek Hendrawan Palgunadi5, Andrean Simanjuntak2, Andri Kurniawan6, Gayatri Indah Marliyani7, Andri Dian Nugraha3, Daryono Daryono2, Iman Fatchurochman2, Muhammad Sadly2, Suko Prayitno Adi2, Dwikorita Karnawati2, Mohammad Taufik Gunawan2, and Abraham Arimuko2
Pepen Supendi et al.
  • 1Department of Earth Sciences – Bullard Labs, University of Cambridge, Cambridge CB30EZ, United Kingdom (
  • 2Agency for Meteorology, Climatology, and Geophysics, Jakarta 10720, Indonesia
  • 3Global Geophysics Research Group, Faculty of Mining and Petroleum Engineering, Institut Teknologi Bandung, Bandung 40132, Indonesia
  • 4Faculty of Engineering, Maranatha Christian University, Bandung 40164, Indonesia
  • 5Physical Science and Engineering, King Abdullah University of Science and Technology, Thuwal, Saudi Arabia
  • 6Geophysical Engineering Study Program, Faculty of Mining and Petroleum Engineering, Institut Teknologi Bandung, Bandung, 40132, Indonesia
  • 7Geological Engineering Department, Gadjah Mada University, Yogyakarta 55281, Indonesia

On December 14, 2021, the Mw 7.3 Flores Sea earthquake occurred approximately 100 km to the north of Flores Island, one of the most complex tectonic settings in Indonesia. The existence of the causative fault that generated this earthquake was not been previously known, therefore making further analysis crucial for assessing future seismic hazard in the region. In this study, we relocated the hypocenter of the mainshock and aftershocks using a double-difference method, determine focal mechanisms using waveform inversion, and then analyse stress changes to estimate the fault type and stress transfer caused by this earthquake. Our relocated hypocenters show that this earthquake sequence ruptured on at least three segments: the source mechanism of the mainshock exhibits dextral strike-slip motion (strike N288oW and dip 78o) that occurred on a West-East trending fault which we call the Kalaotoa Fault, while rupture of the other two segments located to the west and east of the mainshock (WSW-ESE directions, respectively) may have been triggered by this earthquake. The Coulomb stress change of the mainshock shows that areas to the northwest and southeast experienced an increase in stress, which is consistent with the observed aftershock pattern.

How to cite: Supendi, P., Rawlinson, N., Prayitno, B. S., Widiyantoro, S., Palgunadi, K. H., Simanjuntak, A., Kurniawan, A., Marliyani, G. I., Nugraha, A. D., Daryono, D., Fatchurochman, I., Sadly, M., Adi, S. P., Karnawati, D., Gunawan, M. T., and Arimuko, A.: Preliminary results of investigation of “unidentified fault” associated with the Mw 7.3 Flores Sea earthquake, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3794,, 2022.