doi: 10.3319/TAO.2017.11.27.01 * Corresponding author E-mail: songlin@moeacgs.gov.tw Introduction to the special issue on submarine geohazard records and potential seafloor instability Song-Chuen Chen 1, * and Jia-Jyun Dong 2 1 Central Geological Survey, Ministry of Economic Affairs, New Taipei City, Taiwan 2 Graduate Institute of Applied Geology, National Central University, Taoyuan City, Taiwan Received 21 November 2017, Accepted 27 November 2017 Keywords: Submarine landslide, Kaoping Canyon, Southwest Taiwan, Northeast Taiwan Citation: Chen, S.-C. and J.-J. Dong, 2018: Introduction to the special issue on submarine geohazard records and potential seafloor instability. Terr. Atmos. Ocean. Sci., 29, 1-6, doi: 10.3319/TAO.2017.11.27.01 Submarine landslides frequently occur in passive con- tinental margins or active margins (Hampton et al. 1996; Wynn et al. 2000; Mienert et al. 2002; Korup et al. 2007; Twichell et al. 2009; Cukur et al. 2016). Submarine land- slides have been studied extensively not only for scientific research but also for submarine geohazards. Submarine landslides could jeopardize marine infrastructures, such as offshore drilling platforms or submarine telecommuni- cation cables, and could even trigger disastrous tsunamis (Bondevik et al. 2005; Harbitz et al. 2006; Hornbach et al. 2007, 2008; Hsu et al. 2008; Su et al. 2012; Tappin et al. 2014; Li et al. 2015). For instance, one disastrous tsunami hitting the coastal area of southwestern Taiwan in 1781 or 1782 was reported (Chen 1830; Hsu 1983); the tsunami event was probably generated by submarine landslides in the offshore area of southwestern Taiwan (Li et al. 2015). Moreover, several submarine landslides triggered by the 2006 Pingtung earthquake have induced turbidity currents off southwest Taiwan and destroyed about 14 submarine telecommunication cables off SW Taiwan (Hsu et al. 2008). The area of southwest Taiwan currently has a dense popula- tion (more than 3 million people in total), one deep-water Kaohsiung Port, several tanks of liquefied natural gas and a nuclear power plant on the coast (Fig. 1). Numerous sub- marine telecommunication cables exist off SW Taiwan. If a considerable tsunami event would hit again the costal area of SW Taiwan, the damage could very serious. Likewise, there are two nuclear power plants on the coast of northern Taiwan (Fig. 2), and the population in northern Taiwan has more than 10 million people. Submarine telecommunication cables also exist off northern Taiwan. In any case, it is im- portant to understand the status of seafloor stability in the offshore areas of SW and NE Taiwan. For that, this special issue of submarine geohazard records and potential seafloor instability is aimed to provide some research results, hop- ing to have a general reconnaissance of submarine landslide potential off Taiwan. In the offshore area of SW Taiwan, the deformation front is the main tectonic feature and the Kaoping subma- rine canyon is the most profound canyon (Fig. 1). The de- formation front represents the northward continuation of the Manila Trench, separating the fold-and-thrust structures of the active convergent margin to the east and the horst- and-graben structures of the passive South China Sea conti- nental margin to the west. The Kaoping submarine canyon provides a main sediment dispersal system, transporting lots of sediments from land to the offshore area of SW Taiwan (Huh et al. 2009; Yu et al. 2009). Associated with active mud volcanoes, numerous gas emissions are distributed between the Kaoping and Fangliao submarine canyons, while few gas emissions are distributed in the vicinity of the deformation front (Fig. 1). In this special issue, Hsu et al. (2018b) have examined the gas emissions distribution and further evaluated the seafloor stability between the Kaoping and Fangliao canyons area. Chen et al. (2018a) have dis- covered and delineated a large submarine landslide (named Fangliao Slide) to the west of the Fangliao submarine can- yon; they have also discussed the possible mechanisms of the slope failure. Cheng et al. (2018) and Lin et al. (2018) have used ocean bottom seismometer data to study the seis- mic site response and velocity structures of P- and S-waves in sedimentary layers, respectively. Su et al. (2018) have used a large amount of cored sediments to characterize the geological and geochemical characters and to study the pro- cesses of sedimentation, sediments properties and to discuss the seabed stability off SW Taiwan. Hsu et al. (2018a) have used triaxial tests to obtain the effective strength parameters of the cored sediments taken at a landslide, which occurred in the 2006 Pingtung earthquake. The southernmost part of the Okinawa Trough back-arc Terr. Atmos. Ocean. Sci., Vol. 29, No. 1, 1-6, February 2018