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Simultaneous rupture on conjugate faults during the 2018 Anchorage, Alaska, intraslab earthquake (MW 7.1) inverted from strong-motion waveforms
Earth, Planets and Space ( IF 3.0 ) Pub Date : 2020-11-23 , DOI: 10.1186/s40623-020-01315-x
Yujia Guo , Ken Miyakoshi , Masato Tsurugi

An M W 7.1 ~ 50-km-deep intraslab earthquake within the Pacific/Yakutat slab underlying the North American Plate struck Anchorage, southern Alaska, on November 30, 2018. The ground-motion records very close to the source region of the Anchorage earthquake provide an important opportunity to better understand the source characteristics of intraslab earthquakes in this subduction zone. We estimated the kinematic rupture process during this earthquake using a series of strong-motion waveform (0.05–0.4 Hz) inversions. Our inversions clearly indicate that the Anchorage earthquake was a rare intraslab event with simultaneous rupture on two conjugate faults, which are recognized sometimes for shallow crustal earthquakes but rarely for deep intraslab earthquakes. Interestingly, one of the conjugate faults had low aftershock productivity. This fault extends to great depth and may reflect a deep oceanic Moho or a local low-velocity and high- V P / V S zone within the oceanic mantle. Even though the Anchorage earthquake was a rare event due to the conjugate faults, we found that its kinematic source parameters such as the slip amplitude and large slip area nearly equal the global averages derived from source scaling relationships for intraslab earthquakes. Because the source parameters comparable to the global averages were also found for another large intraslab earthquake in the subducting Pacific/Yakutat slab, these source parameters are likely an important source characteristic common to this subduction zone.

中文翻译:

2018 年阿拉斯加安克雷奇板内地震(MW 7.1)期间共轭断层的同时破裂,从强运动波形反演

2018 年 11 月 30 日,北美板块下方的太平洋/雅库塔特板块内发生了 7.1 ~ 50 公里深的板块内地震,袭击了阿拉斯加南部的安克雷奇。 非常接近安克雷奇地震震源区的地面运动记录提供了这是更好地了解该俯冲带板内地震震源特征的重要机会。我们使用一系列强运动波形 (0.05–0.4 Hz) 反演估计了这次地震期间的运动破裂过程。我们的反演清楚地表明,安克雷奇地震是一个罕见的板内地震,在两个共轭断层上同时破裂,有时在浅地壳地震中被识别,但在深板内地震中很少被识别。有趣的是,共轭断层之一的余震发生率很低。该断层延伸到很深的地方,可能反映了深海莫霍面或大洋地幔内的局部低速高 VP / VS 带。尽管由于共轭断层,安克雷奇地震是一个罕见的事件,但我们发现其运动源参数,如滑动幅度和大滑动面积,几乎等于板内地震震源比例关系得出的全球平均值。由于在俯冲太平洋/雅库塔板块中的另一次大型板内地震也发现了与全球平均值相当的震源参数,因此这些震源参数可能是该俯冲带共有的重要震源特征。尽管由于共轭断层,安克雷奇地震是一个罕见的事件,但我们发现其运动源参数,如滑动幅度和大滑动面积,几乎等于板内地震震源比例关系得出的全球平均值。由于在俯冲太平洋/雅库塔板块中的另一次大型板内地震也发现了与全球平均值相当的震源参数,因此这些震源参数可能是该俯冲带共有的重要震源特征。尽管由于共轭断层,安克雷奇地震是一个罕见的事件,但我们发现其运动源参数,如滑动幅度和大滑动面积,几乎等于板内地震震源比例关系得出的全球平均值。由于在俯冲太平洋/雅库塔板块中的另一次大型板内地震也发现了与全球平均值相当的震源参数,因此这些震源参数可能是该俯冲带共有的重要震源特征。
更新日期:2020-11-23
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