Seismo-tectonic structure of the Aysén Region, Southern Chile, inferred from the 2007 Mw= 6.2 Aysén earthquake sequence 2007 Aysén Fjord seismic sequence
Seismo-tectonic structure of the Aysén Region, Southern Chile, inferred from the 2007 Mw= 6.2 Aysén earthquake sequence 2007 Aysén Fjord seismic sequence
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智利南部艾森地区的地震构造结构，根据 2007 年 Mw= 6.2 艾森地震序列推断 2007 年艾森峡湾地震序列
DOI：
10.1111/j.1365-246x.2012.05507.x
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发表时间：
2012
影响因子：
2.8
通讯作者：
Agurto H
中科院分区：
文献类型：
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作者：
Agurto H
2007年4月21日，智利南部的ays<s:1>峡湾发生了里氏6.2级地震，这是该地区地震活度较低的地区前所未有的一次地震。该地区与Liquiñe-Ofqui断层系统（LOFS）相交，这是一条长1000公里的走滑断层，吸收了纳斯卡和南美板块之间的部分斜辐合运动。为了研究这次主震的余震序列，我们在该地区安装了一个由15个台站组成的地震台网，历时近7个月。我们通过计算最小1-D局部速度模型，利用非线性概率方法获得精确的震源坐标和不确定性估计，对该区的孕震结构进行了表征。我们还得到了基于首次运动极性和sv / p振幅比的断层平面解。速度模型显示，该区域的平均evp / vs1为1.76，地壳上3 km处的横波速度值较低。余震地震活动主要位于4 ~ 10 km深度之间，分布在(1)沿LOFS轨迹的~ N-S走向和(2)主断层东部的E-W走向。此外，我们重新分析了之前公布的前震和早期余震活动，包括四个最大的事件，大大改善了之前的位置估计。选定的震源机制显示出强烈的走滑成分，这与LOFS的性质相一致。根据我们的新分析，我们得出结论，2007年的ays<s:1>地震序列有一个与LOFS南端的活动有关的构造起源，但不排除流体对余震活动的存在和潜在作用。
On 2007 April 21, aMw= 6.2 earthquake shook the Aysén Fjord, Southern Chile in an unprecedented episode for this region characterized by low seismicity. The area is intersected by the Liquiñe-Ofqui Fault System (LOFS), a +1000-km-long strike-slip fault that absorbs part of the oblique convergence motion between Nazca and South America plates. To study the aftershock sequence of this main event, we installed a seismic network of 15 stations in the area for a period of nearly 7 months. We characterized the seismogenic structure of the zone by calculating a minimum 1-D local velocity model and obtaining precise hypocentral coordinates and uncertainty estimates by using a non-linear probabilistic approach. We also obtained fault plane solutions based on first motion polarities andSV/Pamplitude ratios. The velocity model shows an averageVp/Vsratio of 1.76 for the area and low shear wave velocity values for the upper 3 km of crust. The aftershock seismicity was located mainly between 4 and 10 km depth and disposed in (1) an ∼N—S trending alignment that follows the trace of the LOFS and (2) an E—W alignment at the East of the main fault. Furthermore, we re-analysed the previously published foreshock and early aftershock activity of the sequence including four of its largest events, improving considerably previous location estimates. Selected focal mechanisms show a strong strike-slip component that coincides with the nature of the LOFS. Based on our new analysis we conclude that the 2007 Aysén seismic sequence had a tectonic origin related to activity on the southern end of the LOFS, however not discarding the presence and potential action of fluids on the aftershock activity.