**1. Introduction**

In addition to gravimetric and magnetic data, the reflection seismic data are powerful tools to understand the subsurface geological features and to determine the nature of the sedimentary

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2017 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

basins. In terms of regional stratigraphy, they provide not only the thickness and the distribution of the sedimentary sequences but also the contact relationships between the sedimentary sequences, representing stratigraphic lap-out and geological unconformities. In addition to sea level change, tectonic events are generally accepted as a general cause for these seismic unconformities, indicating the basin formation mechanisms directly. In this study, we aim at analyzing the dominant tectonic events and the present-day tectonic setting of northern offshore Taiwan based on newly collected marine reflection seismic data, which reveal the subsurface stratigraphic features.

The northern offshore Taiwan is located at the junction among the southernmost part of the East China Sea, the south-western extension of Okinawa Trough and the northern tip of the Taiwan orogenic belt (**Figure 1**). The northern offshore area of Taiwan is surrounded by different geological units highlighting that several basins have influenced its tectono-sedimentary evolution. It could be the part of the post-rift stage of the Paleogene rift basin in the East China Sea [1, 2]. It may also be proposed that it is dominated by relict back-arc basins, which were controlled by a progressive eastward migrating subduction of the Pacific plate and ended up in the present Okinawa Trough [3–5]. The progressive southward migration of the Taiwan orogenic belt could be a practical mechanism for basin formation as well [6–9]. Recently, strike-slip motion along the East Asia continental margin is considered to play a role on the basin evolution of the East China Sea [10]. A re-appraisal of which basin formation mechanism is more dominant for the Neogene basin development in the northern offshore Taiwan is thus required.

This chapter provides new seismic stratigraphic information on the Neogene tectonic setting in the northern offshore Taiwan through seismic interpretation. The stratigraphic architecture of the Neogene sedimentary sequences in the northern offshore Taiwan has been reconstructed through the geological interpretation of high-resolution seismic profiles. Here, we examine two high-resolution reflection seismic profiles of different orientations northern offshore Taiwan (**Figure 2**). One of the profiles runs in NE-SW direction, showing a northward dipping sequence. The other one, on the other hand, runs in NW-SE direction, showing a series of tilted fault blocks. Most significantly, both profiles feature obvious, angular unconformities. The geological and tectonic significance of these unconformities is discussed in this study.
