Neotectonics of the Southern Hengchun Peninsula (Taiwan): Inputs from high resolution UAS Digital Terrain Model, updated geological mapping and PSInSAR techniques

Abstract What is the neotectonics of the Southern Hengchun Peninsula (Taiwan), which corresponds to the accretionary prism of the Manila subduction? In such an area structural geology is difficult due to the soft and muddy turbiditic outcropping formations. Consequently different geological maps had been settled with contrasting lithological boundaries as well as various structural-wise incompatible interpretations. To resolve these questions, we acquired numerous aerial photographs using UAS surveys and photogrammetric processing to acquire a new high resolution UAS Digital Terrain Model (DTM). We update the lithological boundaries by taking into consideration both the information of the existing geological maps and a detailed morphostructural interpretation of our high resolution UAS DTM. This leads us to propose a new structural scheme of the Southern Hengchun Peninsula. The major tectonic structures (folds and faults) that affect the Hengchun Peninsula are located. Furthermore, 13 SAR images were processed through PSInSAR techniques during the 2007–2011 monitoring time-period in order to get the mean line of sight (LOS) surface velocities. Consequently, we are able to characterize and quantify the active interseismic tectonic structures (active folds and faults) during the SAR monitoring time-period. Finally, we reveal that the southern Hengchun Peninsula is composed of two west-verging active ramp structures (duplex), situated above the Kenting Melange. The Kenting Melange is actively uplifting and it acts as the frontal, lateral and basement “muddy mega-fault breccia”. The active Hengchun and Kenting Faults are situated on the West and East side of the Kenting Melange of the western ramp. As we monitor only four (4) years with the PSInSAR technique, the whole earthquake cycle of both Hengchun and Kenting Faults needs to be better constrained as the still in use Nuclear Power Plant N°3 is located close to the Hengchun Fault.