Kinematic fault slip evolution source models of the 2008 M7.9 Wenchuan earthquake in China from SAR interferometry, GPS and teleseismic analysis and implications for Longmen Shan tectonics
Kinematic fault slip evolution source models of the 2008 M7.9 Wenchuan earthquake in China from SAR interferometry, GPS and teleseismic analysis and implications for Longmen Shan tectonics
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DOI：
10.1093/gji/ggt155
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发表时间：
2013-08-01
影响因子：
2.8
通讯作者：
Ryder, Isabelle
中科院分区：
文献类型：
--
作者：
Fielding, Eric J.;Sladen, Anthony;Ryder, Isabelle
2008年汶川7.9级地震使位于青藏高原东部边缘的中国四川省龙门山约280公里的断层破裂。我们使用地震波形与全球定位系统，合成孔径雷达干涉测量和图像振幅相关的大地测量数据，以产生一个源模型的地震。该模型描述了地震过程中断层滑动的演化。大地测量资料制约断层滑动的空间分布，地震波形主要制约滑动的时间演化。我们发现，地震开始于龙门山中部下方的叠瓦状断层系统，包括北川断层和彭官断层，断层滑动深度延伸至山前西北50公里。断层沿沿着北川断裂继续向北东方向破裂，龙门山北方斜滑（右旋和逆冲）活动增强，侧向运动比例增加。最北的断层段有一个更陡的倾角，与几乎纯粹的走滑运动相一致。震源运动学模型表明，破裂以2.5-3.0 km/s的速度向东北方向传播，产生了一系列持续时间约110 s的子事件。复杂的断层破裂导致龙门山中部极度陡峭的缩短和隆起，这支持了高原陡峭边缘是由四川盆地的坚固地壳逆冲形成的模型。
The M-w 7.9 2008 Wenchuan earthquake ruptured about 280 km of faults in the Longmen Shan of Sichuan province, China, at the eastern edge of the Tibetan Plateau. We use teleseismic waveforms with geodetic data from Global Positioning System, synthetic aperture radar interferometry and image amplitude correlation to produce a source model of this earthquake. The model describes evolution of fault slip during the earthquake. The geodetic data constrains the spatial distribution of fault slip and the seismic waveforms constrain mostly the time evolution of slip. We find that the earthquake started with largely thrust motion on an imbricate system of faults beneath the central Longmen Shan, including the Beichuan Fault and Pengguan Fault, with fault slip at depth extending up to 50 km northwest of the mountain front. The fault ruptures continued northeast along the Beichuan Fault with more oblique slip (right-lateral and thrust) and the proportion of lateral motion increasing in the northern Longmen Shan. The northernmost fault segment has a much steeper dip, consistent with nearly pure strike-slip motion. The kinematic source model shows that the rupture propagated to the northeast at about 2.5-3.0 km s(-1), producing a cascade of subevents with a total duration of about 110 s. The complex fault ruptures caused shortening and uplift of the extremely steep central Longmen Shan, which supports models where the steep edge of the plateau is formed by thrusting over the strong crust of the Sichuan Basin.