Coseismic displacement fields and the slip mechanism of the 2021 Mw 6.7 Hovsgol earthquake in Mongolia constrained by Sentinel-1 and ALOS-2 InSAR

ABSTRACT

On 11 January 2021, an Mw 6.7 earthquake, which involved a complex rupture mechanism, occurred in Lake Hovsgol, Mongolia. This study measured the earthquake’s 3-D coseismic surface displacement fields using interferometric synthetic aperture radar (InSAR) pairs of three radar look directions: Sentinel-1B from the descending path and Advanced Land Observing Satellite-2 from the ascending and descending paths. The three DInSARs showed that the maximum coseismic surface displacement appeared east of the Northern Hovsgol Fault (NHF), where the displacement components were 18 cm, 5 cm, and 33 cm in the east–west, north–south, and up–down directions, respectively (precision: 1.7 cm, 20.4 cm, and 5.2 cm). However, the 3-D displacements indicated that although the earthquake induced a combination of normal faulting with strike slip motions, the displacements in the north–south direction had very large uncertainty owing to the similar geometry of the InSARs in the descending path. Later, we performed inversions of the DInSAR-measured coseismic surface displacement fields in the line-of-sight direction, which assumes a fault plane’s uniform and distributed slips in analyzing the slip mechanism. We conducted slip distribution estimations on the ruptured fault plane in accordance with the optimal fault geometry and source parameters determined by the uniform slip model. Investigations revealed that, with a correlation of 95.3%, the simulated displacements from the best-fitted distributed slip model were consistent with the observed displacements from DInSARs. Besides, our slip distribution model showed two distinctive slip patches, which include differences in their magnitudes and directions on the fault plane. We also observed ruptured faults experiencing a predominant right-lateral strike slip with a significant dip slip, according to the slip distribution, which caused two distinct slips due to the dramatic bending of the fault strike. Then, by analyzing the Coulomb stress change, our findings proposed that the seismic risk potential of active faults in the Hovsgol Basin increased after the earthquake. Overall, the great potential of multi-track DInSAR observations in the identification of complex slip mechanisms was demonstrated.

KEYWORDS:

• Hovsgol earthquake
• InSAR
• surface displacement
• slip distribution
• Sentinel-1
• ALOS-2

Acknowledgments

This study was supported by the National Research Foundation of Korea (NRF-2021R1C1C1009621 and No. 2019R1A6A1A03033167) and Ministry of the Interior and Safety as Earthquake Disaster Prevention Human resource development Project. This study was also supported by the Japanese Aerospace Agency (JAXA), under the 2^nd Earth Observation-Research Announcement (EO-RA2) collaboration with PI number of PER2A2N144 to obtain PALSAR-2 data. The authors would like to thank the European Space Agency (ESA) for providing Sentinel-1 SAR data and GLO-30 DEM and Centre for the Observation and Modelling of Earthquakes, Volcanoes and Tectonics (COMET) for sharing Geodetic Bayesian Inversion Software (GBIS).

Disclosure statement

No potential conflict of interest was reported by the authors.

Data availability statement

The data that support the findings of this study are available upon request from the corresponding author (H.H.), upon reasonable request.

Additional information

Funding

This study was funded by the National Research Foundation of Korea (NRF-2021R1C1C1009621 and No. 2019R1A6A1A03033167) and Ministry of the Interior and Safety as Earthquake Disaster Prevention Human resource development Project.