Source parameters of the 2011 Yellow Sea earthquake (ML 5.3): Different features from earthquakes on the Korean Peninsula

摘要

A moderate earthquake of magnitude ML 5.3 occurred in the Yellow Sea on January 12, 2011. We estimated the source parameters and found that the quake was a shallow strike-slip fault event with a moment magnitude of 4.6. The stress drop of this event, 1.2-2.0 MPa, is lower than that of moderate earthquakes inland and at the eastern offshore of the Korean Peninsula, and also that of the typical value for shallow intraplate earthquakes. A stronger event (M ～ 6) in the southern Yellow Sea in 1984 was previously reported to have a low stress drop. Therefore the low stress drop is probably characteristic of earthquakes in the Yellow Sea region. We found that aftershocks of the 2011 Yellow Sea event, with magnitudes greater than 2, occurred for about 5 days, while similar-sized aftershocks of some inland earthquakes of the Korean Peninsula continued for several hours only. The lower stress drop and greater active aftershocks in the Yellow Sea region might reflect a different tectonic setting from that on the Korean Peninsula.