A Study on the Extension of Fault Zones in Yellow Sea and its Adjacent Areas Based on Gravity Data

Abstract

In light with Bouguer gravity data, various information on faults were obtained by means of analytical continuation, target field extraction, arbitrary horizontal direction derivative processing and discrete wavelet transform processing. According to synthetic analyses with geologic data, the 123°E longitude was chosen as a typical profile, then initial models were established based on seismic data to perform gravitational inverse iterative fitting, and finally density parameters of various modules and their distribution were given. Based upon which the geologic and geophysical properties of the principal faults of the study area were analyzed, resulting in fault zone and block binding distribution maps. The paper focuses on the discussion of west marginal fault zone of the Korean Peninsula and Wulian– Qingdao–Rongcheng fault zone in the study area and points out that Wulian–Qingdao– Rongcheng fault zone did not intrude Korean Peninsula to connect with Imjinhang fault zone. It also holds that northward translational movement of the portion belonging to the Yangtze Plate at the west side of west marginal fault zone of the Korean Peninsula once occurred under the action of northward stress. Only the fault zones consisting of Wulian– Qingdao–Rongcheng fault zone along with northern fault zone of South Yellow Sea, west marginal fault zone of the Korean Peninsula, and south marginal fault zone of Cheju Island should be the binding site of Sino‐Korean and Yangtze Plates.

East Marginal Fault of the Yellow Sea: a part of the conjunction zone between Sino‐Korea and Yangtze Blocks?

“…Along the western margin of the Korean Peninsula a narrow low-velocity belt corresponds to the location of the EMFYS. Its strike direction and length are consistent with the result from gravity data (Hao et al 2002). The velocity profile crossing the southern end of the Korean Peninsula ( Fig.…”

“…4). In addition, the P-wave velocity profile along 388N (Hao et al 2002) reveals velocity structure differences on the two sides of the EMFYS, and confirms that this fault penetrates to a great depth. Because of the limited resolution in depth of the velocity inversion, the character of the EMFYS in the upper mantle cannot be well defined.…”

“…By analytical continuation, wavelet transformation and other processing techniques we extracted linear structural information on the Yellow Sea area, and defined the location of a nearly north-south-trending dextral strike-slip fault in the eastern margin of the Yellow Sea (Hao et al 2002). This fault belt is named the EMFYS.…”

“…Choi et al (2006) suggested that the suture zone continues in an ENE direction to the region of the Imjingang Belt and Hongseong in the western Korean Peninsula, based on interpretation of the GRACE satellite gravity dataset. On the basis of gravity and seismic tomography, Hao et al (2002) proposed that there is a dextral strike-slip fault in the eastern margin of the Yellow Sea. In that study, the gravity data used were taken from the Bouguer gravity database (Liu 1992), and the 5 km  5 km grid data were obtained through Mercator projection and interpolation.…”

“…Hao et al believed that the dextral strikeslip fault in the eastern margin of Yellow Sea is connected with the Wulian-Qingdao-Rongcheng collision zone in the north, and extends southward to the southern margin of Jeju Island, where it joins the south. In our Marginal Fault of Jeju Island (SMFJI) earlier papers (Hao et al 2002(Hao et al , 2003a this fault was called the West Margin Fault of the Korean Peninsula. However, in a later study on deep structures of the Yellow Sea and East China Sea , we renamed it the East Marginal Fault of the Yellow Sea (EMFYS), which tallies better with the actual situation.…”