[S-SS16] [JJ] Crustal Structure

[SSS16-P01] Seismotectonic characteristics in the Yun-Chia-Nan area, Southwest Taiwan: Insight from seismic ambient noise

*Chih-Yin Lin¹ (1.Department of Earth and Environmental Sciences, National Chung Cheng University, Minhsiung, Chiayi, Taiwan)

Keywords:Ambient Noise, 1-D shear-wave velocity structure

The seismic ambient noise tomography (ANT) has been wildly used in regions lack of earthquake data to image subsurface seismic velocity as well as its spatial-temporal variations using surface wave type of Green's function extracted from cross correlation of seismic ambient noise. Due to vigorous collision of the Eurasian Plate and the Philippine Sea Plate, the deformation front of Taiwan composes complex folds and fault systems. The Yun-Chia-Nan area is suited in southwest segment of the deformation front, where includes southern portion of the Western Foothills and the Coastal Plain. The detailed physical properties for the above mentioned areas are not well known as a result of less seismicity. Thus, we had conducted a 2-year project to deploy a temporary broadband array with 14 stations. The project is not only to monitor seismic activities in the Yun-Chia-Nan area, but also to derive an average 1-D shear-wave velocity structure using seismic ambient noise.
By analyzing time domain empirical Green’s function (TDEGF) from the cross correlation of seismic ambient noise between station-pairs, we are able to obtain 1-D shear-wave velocity profile. Our results indicate that between the period of 1–10 s, shear-wave velocity shows prominent low value in the upper crust. We also compare time variant of shear-wave velocity profiles derived from a station pair (HNME-RELI) located in the east of the Chukuo fault. Interestingly, we find that, after 10-years, shear-wave velocity becomes greater as depth is beyond 2 km. This feature might imply crack closing due to intensive orogenic process in Taiwan.