Seismic Structure in Eastern Taiwan: Integrated from Reflection Seismic Method, Seismicity, and Seismic Travel-Time and Ambient Noise Tomography(2/3)

The Coastal Range, east of the suture zone, is an important geological feature in Taiwan, which is composed of the tectonic blocks of the deformed forearc block, arc, and sediments. Those tectonic blocks are the clues for the mountain building process of Taiwan. In previous studies, based on the data from geological survey, GPS, and InSAR, etc., the geological structures and active faults at surface have been mapped and studies in details. However, the information of the sub-surface is still limited. For example, the depth resolution (<7-800 m) of the seismic survey was restricted in the past seismic surveys due to the weak seismic sources, 550 lbs. weight dropper, used. Currently, supported by Ministry of Science and Technology, two seismic vibrators (minivib) with 13,000 lbs. energy for each vibrator can be used together as seismic sources to improve the depth resolution (up to 3,000 m) significantly. The complex background seismicity in the eastern Taiwan has shown that the tectonic features of the Coastal Range from south to north are very different, but how those features change in terms of the evolution of the Coastal Range is un-resolved. Therefore, the comprehensive study of the seismic fault zones is key for understanding the sub-structures of the Coastal Range. Moreover, in order to image the crustal structures, the seismic tomography is one of the most important tools to be used.In this research proposal, to resolve the sub-surface from shallow to deep depths for the whole Coastal Range, we propose a three-years seismic field experiment to integrate the seismic survey, monitoring earthquakes (especially for small earthquakes), and high-resolution seismic travel-time tomography and ambient noise tomography. The experiment is designed to be benefited from the different resolution of each method. The expected results are (1) the subsurface geometry of the active fault zones from seismic survey, (2) the seismic fault zones related to the surface structures from monitoring small earthquakes, (3) high resolution of the seismic travel-time and ambient noise tomography, (4) regional tomography (the Coastal Range to the Huatung basin) from integrating this research field experiment and the existed seismic data sets, and (5) understanding the evolution of the Coastal Range.