Crustal-scale fault systems in the Korean Peninsula unraveled by
reflection seismic data
Abstract
An approximately 40-km long high-resolution reflection seismic profile
(P3) was acquired in the metropolitan area of Seoul in South Korea for
the purpose of fault system imaging in a highly noisy and challenging
urban environment. Two 12t seismic vibrators (mini-vibs) were used as
the seismic source. Data were recorded using a dual element seismic
spread; 20 m spaced 421 wireless seismic recorders connected to 10 Hz
geophones and 20 micro-electro-mechanical (MEMS-based) landstreamer
sensors (2 m sensor spacing) attached to one of the vibrators. The
purpose of the dual spread employed was to delineate both near-surface
and deep structures. The processing results show good quality and the
processing work was complemented by different analysis to further
constraints the geological interpretation. The survey results provide
evidence for the 3D geometry of three fault systems, including
Chugaryeong, Pocheon and Wangsukcheon faults. A gently westerly-dipping
set of reflectivity underlying a domed-shaped package of reflectivity is
interpreted as a fault, and could project to the known surface position
of the Pocheon fault. The domed-shaped reflectivity is interpreted as
folded and faulted dyke or sill systems. Downward continuation of the
interpreted fault intersects the sub-vertical Chugaryeong fault in a
zone where the current seismicity is observed, suggesting that these two
major fault systems may have jointly evolved in the form of splay
faults. Reflections from the Wangsukcheon fault are also present in the
data and interpreted to dip approximately 60 degrees to the east, in an
opposite direction to the two other faults.