Source Complexity of the 2021 MW 4.9 Offshore Jeju Island, Korea, Earthquake
Abstract
The 14 December 2021 MW 4.9 Offshore Jeju Island, Korea, earthquake, is a significant event that occurred in close proximity to the intraplate volcano on the continental shelf south of the Korean Peninsula. This earthquake offers a unique window into understanding source complexities of moderate-sized earthquakes in stable continental regions. To better probe slip distribution of the mainshock exhibiting complex rupture growth, we used a method of preserving relative arrival time between the rupture time of mainshock and empirical Green's function when calculating relative source time functions. This method enabled to determine the relative location between four distinct subevents constituting the mainshock (two large subevents followed by two small ones) and aftershocks. During the rupture initiation period of ~1.5 s, the two small subevents preceded immediately before the rupture of the first large subevent as the nucleation started from the deeper depth, and the second large subevent occurred ~1 km west of the hypocenter of the first one after ~0.7 s. We further constrained rupture properties of the two large subevents using local and regional seismic stations that provided a limited azimuth coverage of 140 degrees. Both subevents show higher stress drops but with different rupture velocities. Our results show that the MW 4.9 offshore Jeju earthquake consists of well-separated slip asperities, commonly appearing in immature faults in low deformation regions, cascading each other sequentially.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2022
- Bibcode:
- 2022AGUFM.S14A..11H