In this study, a detail tomography was taken in order to understand the seismogenic structures, earthquake and volcanic activities in Northern Taiwan region especially in Taipei Basin and TVG regions. According to the analysis and discussion several results are obtained as follows:
(1) A significant half-graben shape is depicted in the tomography image with low Vp/Vs ratio through entire region. The feature might reflect the hard rock site relative to the upper soft sedimentary.
(2) The earthquakes occurred in the TVG region may correlate to local hydrothermal activity rather than Chinshan fault base on results from tomography, seismicity and focal mechanism, especially a considerable variation in focal mechanisms solutions.
(3) Two seismogenic zones beneath TVG are coincident with the surface hydrothermal regions. The unobstructed conduits may exist beneath the Matsao, Tayukeng and Chishing mountain regions.
(4) Because of no connection between these two seismogenic zones beneath the TVG. It may imply that there are two different hydrothermal sources.
The accurate earthquake location is very important to recognize the conduits beneath TVG. So, the tomography algorithm including calculating the difference of absolute travel-time between neighboring event pairs such as tomoDD (Zhang and
Thurber, 2003) should be an appropriate tool to study this region. Besides, because of the abundant seismogram recordings due to combining the data from different networks, it is worthy to more detail analyze the waveform information in the future.
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