| 摘要: | 研究期間：10106~10207;The Taiwan arc-continent collision is one of the most challenged tectonic problems in the world. Both ‘thin-skinned model’ and ‘lithospheric collision model’ have been invoked to explain the geologic and geophysical observations. The thin-skinned tectonics model was proposed by Suppe (1987), which calls for the buildup of a 15-km thick wedge during subduction of the Asian lithosphere. With the improved Taiwan seismic network in 1991, the local earthquake data became adequate for more detailed seismic tomography. The imaged crust under the Central Range can be as deep as 50 km and the general velocity structures under the Central Range are found inconsistent with those of an accretionary wedge. Wu et al. (1997) considered all these data and proposed that a continuous lithospheric deformation model (Molnar et al., 1999), which predicts the deformation extending not only into the lower crust but also into the upper mantle. The integrated research plan TAIGER has been carried out during 2007~2009, including: 1) passive earthquake source broadband seismometer observation, 2) land thousand-kg dynamite explosion, 3) sea-land airgun shooting, 4) MT profile, 5) rock property analysis and dating, 6) theoretical plate collision modeling. At the present time, the data processing is actively undertaken. The preliminary results show that the Moho is deeper in the north (> 40km) than in the south. The thin-skin model could be appropriate for the middle and south Taiwan, but the lithosphere collision model may prevail in the north. The present proposal is an extension of the 2008 experiment. At 2009, the Fujan earthquake administration created a long-term project making a sequence of big explosions (1000~3000kg) to detect crust structures. To catch the explosion signals, we organize the ‘Across Taiwan Strait Explosion Experiment (ATSEE)’ to deploy sea-land instruments to receive the precious signals from the mainland. In ATSEE2010 project, we found very promising Pn signals from the Moho directly under the Central-mountain range using the explosion signals from the mainland (FJ3 line). The largest Moho depth is found to be less than 44 km. In ATSEE2011, five big explosions were set off along the N–line direction (FJ 1 line). Two lines N and NN were deployed on northern Taiwan. A Moho (largest 43km) is detected under the N-line, but it reduced to 40km under the NN-line. In this 2012 proposal, two shot lines, total 10 explosions, will be ignited (FJ2 and FJ4) at the same time. We plan to deploy all three lines (N, M, and S) along previous TAIGER’s lines. Twenty OBS’s will also be deployed in both Taiwan-Strait and the eastern Taiwan offshore to cover a wider Pn range. |
