台灣北部山脈抬升與板塊斷裂模式的地體動力模擬

Mountain Building and Slab Breakoff in Northern Taiwan: Insights from Numerical Modeling

曹景皓(Jing-Hao Tsao)

指導教授 ： 王維豪

國立中正大學/理學院/地球與環境科學系地震研究所/碩士(2014年)

摘要

我們針對北臺灣山脈快速抬升的模式進行數值模擬，並探討其與歐亞大陸板塊斷裂之間的關係。根據前人研究顯示，在最近一百萬年間，雪山山脈南段水平方向聚合速率低於垂直方向的抬升速率。另外，地震層析成像也顯示歐亞大陸板塊在北台灣極可能已經撕裂，我們懷疑此處撕裂與菲律賓海板向南退縮有關，而在大陸板塊撕裂的過程中，可能造成雪山山脈劇烈的垂直運動。
我們初步模擬結果顯示，歐亞大陸板塊可能不是自發性斷裂，而是在沖繩海槽張裂時後，因菲律賓海板塊下沉並且向南回捲形成額外施加在向東隱沒的歐亞大陸板塊上的壓力，此力量最後切斷歐亞大陸板塊使之斷裂，而大陸也隨之下沉。模擬解果也顯示在大陸板塊撕裂之前，因菲律賓海板塊下沉的壓力使韌性大陸地殼受擠壓而快速向上隆起，形成地殼尺度的逆斷層，因此台灣雪山山脈南段區域反而有向上抬升的趨勢。

關鍵字

雪山山脈 ； 板塊斷裂 ； 地體動力模擬

並列摘要

We have conducted numerical modeling to test the hypothesis of Eurasian slab breakoff in response to the fast uplift in Northern Taiwan. Previous studies suggested that the southern part of the Hsuehshan Range had a low horizontal shortening rate yet a high uplift rate during last 1Ma. Recent seismic tomography studies also implied part of the Eurasian plate may have been torn apart in this area. We suspect the southward rollback of the Philippine Sea Plate is responsible for the slab breakoff. Our preliminary simulation results show that slab breakoff in this area might not be spontaneous. Instead, it may be induced by southward rollback of the Philippine Sea Plate corresponding to the opening of the Okinawa Trough. The retreating Philippine slab exerts an additional force upon the underlying Eurasian Plate. This additional force has been tearing the Eurasian Plate apart and resulting in subsidence of the northern part of the Hsuehshan Range. However, before the slab breakoff, our models show that the loading by the rollback of the Philippine Sea Plate would compress the Eurasian continental lower crust to form crustal-scale reverse faults, which leads to fast uplift analogous to what observed at the southern part of the Hsuehshan Range.

並列關鍵字

Hsuehshan Range ； slab breakoff ； geodynamic modeling

參考文獻

An, M., and Y. Shi (2006), Lithospheric thickness of the Chinese continent, Physics of the Earth and Planetary Interiors, 159(3-4), 257-266, doi:10.1016/j.pepi.2006.08.002.

Aoki, I., and E. Takahashi (2004), Density of MORB eclogite in the upper mantle, Physics of the Earth and Planetary Interiors, 143-144, 129-143, doi:10.1016/j.pepi.2003.10.007.

Baumann, C., T. V. Gerya, and J. A. D. Connolly (2010), Numerical modelling of spontaneous slab breakoff dynamics during continental collision, Geological Society, London, Special Publications, 332(1), 99-114, doi:10.1144/sp332.7.

Brown, E. H. (1977), Phase quilibria among pumpellyite, lawsonit,epidote and associated minerals in low grade metamorphic rock, Contributions to Mineralogy and Petrology, 64, 123-136.

Carena, S., J. Suppe, and H. Kao (2002), Active detachment of Taiwan illuminated by small earthquakes and its control of first-order topography, Geology, 30(10), 935-938, doi:Doi 10.1130/0091-7613(2002)030<0935:Adotib>2.0.Co;2.