HR: 0800h
AN: T41B-1295    [Abstracts]
TI: Focal Mechanisms of Recent Earthquakes in the Southern Korean Peninsula
AU: * Park, J
EM: jcpark@kma.go.kr
AF: Department of Earth and Environmental Sciences, Gyeongsang National University, Gajwa-dong, Jinju, 660-701 Korea, Republic of
AU: Kim, W
EM: wookim@gsnu.ac.kr
AF: Department of Earth and Environmental Sciences, Gyeongsang National University, Gajwa-dong, Jinju, 660-701 Korea, Republic of
AU: Chung, T
EM: chungtw@sejong.ac.kr
AF: Department of Earth Environments, Sejong University, Gunja-dong, Seoul, 143-747 Korea, Republic of
AU: Baag, C
EM: baagce@snu.ac.kr
AF: School of Earth and Environmental, Seoul National University, Sinlim-dong, Seoul, 151-742 Korea, Republic of
AU: Ree, J
EM: reejh@korea.ac.kr
AF: Department of Earth and Environmental Sciences, Korea University, Anam-dong, Seoul, 136-701 Korea, Republic of
AB: There has been a lack of seismic data in the Korean Peninsula mainly because it is in a seismically stable area within the Eurasian plate (or Amurian microplate) and because a network of seismic stations has been poor until recently. Consequently, first motion studies on the peninsula showed a large uncertainty or covered only local areas. Also, a tectonic province map constructed based on pre-Cenozoic tectonic events in Korea has been used for a seismic zonation. To solve these problems, we made focal mechanism solutions for 71 earthquakes (M_L = 1.9 to 5.2) occurred in and around the peninsula from 1999 to 2004 and collected by a new dense seismic network established since 1995. For this, we relocated the hypocenters and obtained fault plane solutions with errors of fault parameter less than 15° from the data set of 1,270 clear P-wave polarities and from 46 SH/P amplitude ratios. The focal mechanism solutions show that subhorizontal ENE P- and subhorizontal NNW T-axes are predominant, representing the common direction of P- and T-axes within the Amurian plate. The faulting mechanisms are mostly strike-slip faulting or strike-slip-dominant-oblique-slip faulting with a reverse-slip component, although normal-slip-dominant-oblique-slip faultings occur locally probably due to a local reorientation of stress. These results incorporated with those from the kinematic studies of the Quaternary faults imply that NNE-striking faults (dextral strike-slip or oblique-slip with a reverse-slip component) are highly likely to generate earthquakes in South Korea. The spatial distribution of the maximum horizontal stress direction and faulting types does not correlate with the preexisting tectonic province map of Korea, and a new construction of seismic zonation map is required for a better seismic evaluation.
DE: 7215 Earthquake source observations (1240)
DE: 8002 Continental neotectonics (8107)
DE: 8036 Paleoseismology (7221)
DE: 8164 Stresses: crust and lithosphere
SC: Tectonophysics [T]
MN: Fall Meeting 2005