Deformation features and history of the Yangsan Fault Zone in the Eonyang-Gyeongju area, SE Korea

The Quaternary slip rate of the Yangsan Fault offshore the SE Korean Peninsula and implications for seismic hazard assessment

“…That is, it is likely that the dextral activity of the Yangsan Fault did not occur during backarc extension. Kinematic and paleostress analysis suggested that the dextral displacement along the Yangsan Fault continued to 25 Ma (Cheon et al 2017), which is in reasonable agreement with the above interpretation.…”

Long‐Term Weakening Processes and Short‐Term Seismic Slip Behavior of an Intraplate Mature Fault Zone: A Case Study of the Yangsan Fault, SE Korea

“…The Yangsan Fault, the most prominent fault of the system, can be traced for ∼200 km on land and shows over 20–30 km dextral offset (e.g., Chang et al., 1990; Hwang, Lee, et al., 2007; Hwang, McWilliams, et al., 2007). The widths of the main fault core and damage zone measure several decameters and a few kilometers, respectively, although variations in the width of the fault zone and its internal structures are commonly observed along fault traces (e.g., Cheon, Choi, Choi, et al., 2020; Cheon et al., 2017, 2019; Choi et al., 2009; C.‐M. Kim et al., 2020; N. Kim et al., 2021; C.‐M.…”

“…Multiple stages of deformation of the Yangsan Fault have been suggested by various structural observations and radiometric age determinations of transected rocks (e.g., Chang, 2002;Chang & Chang, 1998;Cheon et al, 2019;Cho et al, 2007Cho et al, , 2016Kim, 1992), as well as by K-Ar illite ages (Sim et al, 2017;Song et al, 2016Song et al, , 2019 and electron spin resonance ages Lee & Schwarcz, 2001;Yang, 2006;Yang & Lee, 2012 of fault gouge. Recently, based on a compilation of previous results, Cheon et al (2019) proposed the tectonic evolution of the fault and age constraints, including the following: (a) Late Cretaceous sinistral movement with a component of extensional deformation (e.g., NW-SE-striking extensional structures, and the Dadaepo pull-apart basin between the Yangsan and Dongnae faults; Cheon et al, 2017;Cho et al, 2007Cho et al, , 2016Ha et al, 2016); (2) late Paleogene (∼43-23 Ma) dextral movement, which was the most intense phase of deformation on the fault, with 20-30 km of dextral offset being inferred from the distribution of several piercing points, such as A-type granite bodies (see Figure 1c; Chang et al, 1990;Hwang, Lee, et al, 2007;; and (c) subsequent reactivations along some segments during the late Miocene associated with sinistral kinematics (Chang, 2002;Chang & Chang, 1998;Choi et al, 2009). Gu et al (2021) suggested that the structural maturity of the fault appears to fit the intermediate class (Class 2) following the criteria of Manighetti et al (2007) based on the minimum values of fault length on land (∼200 km), fault initiation age (>70 Ma), maximum long-term slip rate (∼0.4 cm/yr), and finite dextral offset (>20-30 km).…”

“…Recently, based on a compilation of previous results, Cheon et al. (2019) proposed the tectonic evolution of the fault and age constraints, including the following: (a) Late Cretaceous sinistral movement with a component of extensional deformation (e.g., NW–SE‐striking extensional structures, and the Dadaepo pull‐apart basin between the Yangsan and Dongnae faults; Cheon et al., 2017; Cho et al., 2007, 2016; Ha et al., 2016); (2) late Paleogene (∼43–23 Ma) dextral movement, which was the most intense phase of deformation on the fault, with 20–30 km of dextral offset being inferred from the distribution of several piercing points, such as A‐type granite bodies (see Figure 1c; Chang et al., 1990; Hwang, Lee, et al., 2007; Hwang, McWilliams, et al., 2007); and (c) subsequent reactivations along some segments during the late Miocene associated with sinistral kinematics (Chang, 2002; Chang & Chang, 1998; Choi et al., 2009). Gu et al.…”