Evidence of large prehistoric offshore earthquakes deduced from uplifted Holocene marine terraces in Pangasinan Province, Luzon Island, Philippines
Evidence of large prehistoric offshore earthquakes deduced from uplifted Holocene marine terraces in Pangasinan Province, Luzon Island, Philippines
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菲律宾吕宋岛邦阿西楠省全新世海洋阶地隆起推断出史前近海大地震的证据
DOI：
10.1016/j.tecto.2010.08.007
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发表时间：
2010
期刊：
影响因子：
2.9
通讯作者：
H. Tsutsumi
中科院分区：
文献类型：
--
作者：
N. Ramos;H. Tsutsumi
本文首次报道了菲律宾吕宋岛最西端的潘加西南省全新世隆起的海洋阶地，作为史前近海大地震的地貌证据。我们发现了多达三个全新世阶地台阶。海岸线角的高程为TI：1至5米，TII：2至7米，TIII：4至11米。阶地台阶高程的横向变化表明沿着有差异抬升。阶梯状地形，其特征是水平的磨损平台，米级阶地的裂缝，和波切凹口，表明这些地貌特征是由大的同震隆升事件。阶地形态和放射性碳年龄进一步表明，自6000年前冰后期海平面上升达到顶峰以来，至少发生了三次同震海岸抬升事件。TIII为全新世海侵面（~6000 yBP），最大抬升速率为1.7mm/yr，与晚更新世的1.3mm/yr基本一致。我们推断，近海地震源的接近促成了全新世阶地的变形模式和阶地台阶数的变化。海洋阶地的隆起模式也表明，史前地震的震级和位置可能在个别同震隆起事件之间有所不同。我们进行了简单的弹性位错模拟，以评估源参数的成因断层。我们的初步模型表明，位于分离弧前盆地和大陆架的陡坡底部的向陆倾斜的离岸逆断层可能是沿着西部潘加西南半岛海岸隆起的原因。
Uplifted Holocene marine terraces in Pangasinan Province, westernmost Luzon Island, Philippines are reported here for the first time as geomorphic evidence of large prehistoric offshore earthquakes. We recognized up to three Holocene terrace steps. Elevations of shoreline angles are TI: 1 to 5m, TII: 2 to 7m, and TIII: 4 to 11m above mean sea level (amsl). The lateral variation in the elevation of terrace steps indicates differential uplift along the coast. The staircase topography, characterized by horizontal abrasion platforms, meter-scale terrace risers, and wave-cut notches, suggests that these geomorphic features were formed by large coseismic uplift events. Terrace morphology and radiocarbon ages further suggest that at least three coseismic coastal uplift events have occurred since the culmination of the post-glacial sea level rise ~6000years ago. We interpret TIII to be the Holocene transgressive surface (~6000 yBP) and estimated a maximum uplift rate of 1.7mm/yr which is almost the same as the Late Pleistocene uplift rate of 1.3mm/yr. We infer that proximity to offshore seismic sources has contributed to the deformation pattern of Holocene terraces and variation in the number of terrace steps. Uplift patterns of marine terraces also suggest that the magnitude and location of prehistoric earthquakes may have varied between individual coseismic uplift events. We conducted simple elastic dislocation modeling to evaluate the source parameters of the causative faults. Our preliminary models show that a landward-dipping offshore reverse fault located at the base of a steep slope separating the fore arc basin and continental shelf could be responsible for coastal uplift along the western Pangasinan peninsula.
影响因子：
3
作者：
Y. Okada
通讯作者：
Y. Okada
影响因子：
8.3
作者：
Hughen, KA;Baillie, MGL;Weyhenmeyer, CE
通讯作者：
Weyhenmeyer, CE