[S-EM15] Electric, magnetic and electromagnetic survey technologies and scientific achievements

[SEM15-P14] The significance of the high-amplitude magnetic anomaly belt in the seismotectonic of mid-west Taiwan

*Wen-Bin Doo¹、Yin-Sheng Huang¹、Hsueh-Fen Wang² (1.Center for Environmental Studies, National Central University, Taiwan、2.Department of Earth Sciences, National Central University, Taiwan)

キーワード：magnetic anomaly, earthquake, Taiwan, deformation front, compact inversion, wavelet spectrum

In mid-west Taiwan, there is a unique zone with high crustal magnetization called Lukang Magnetization High (LMH). This zone is interpreted to dominate earthquake occurrence in middle Taiwan. According to the magnetic anomaly feature in the Taiwan region, the LMH is the inversion result of the eastern part of the high-amplitude magnetic anomaly zone (NSCSMA) found in the northern South China Sea continental margin. To better understand the connection between this magnetic high (HMAZ) and background tectonic features, this study analyzes the magnetic data in mid-west Taiwan. We used wavelet spectrum analysis and compact inversion techniques to determine its causal source. Wavelet spectrum analysis results show that the wavelength of the major magnetic signal of the HMAZ is 180 km, indicating the source depth is approximately 25 km. The compact inversion results reveal high-susceptibility materials distributed around 20-30 km depth. P-wave velocity models suggest that the causal source of the HMAZ could be located in the lower crust and/or upper mantle and belong to the Eurasia plate. Based on the previous analysis results of the NSCSMA and our observation, we propose that the serpentinized materials may be the causal source of the HMAZ. Considering the characteristics of seismicity and our observation about the magnetic features, our study may not support the idea that the high-susceptibility materials (and/or the LMH) dominate earthquake occurrence in middle Taiwan. In particular, we emphasize that the deformation front is considered to play an important role in the seismotectonic of mid-west Taiwan.