Fast rupture of the 2009 Mw?6.9 Canal de Ballenas earthquake in the Gulf of California dynamically triggers seismicity in California
Fast rupture of the 2009 Mw?6.9 Canal de Ballenas earthquake in the Gulf of California dynamically triggers seismicity in California
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2009 年加利福尼亚湾 Mw?6.9 Canal de Ballenas 地震的快速破裂动态触发了加利福尼亚州的地震活动
DOI：
10.1093/gji/ggac059
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发表时间：
2022
影响因子：
2.8
通讯作者：
Cochran Elizabeth S
中科院分区：
文献类型：
--
作者：
Fan Wenyuan;Okuwaki Ryo;Barbour Andrew J;Huang Yihe;Lin Guoqing;Cochran Elizabeth S
在墨西哥加州湾，横跨北美-太平洋边界的相对运动由一系列海洋转换断层和扩张中心所调节。自1960年以来，该地区共发生了约40次6级以上地震。2009年8月3日，该地区的巴列纳斯运河附近发生了Mw6.9级地震。这次地震是一次走滑事件，震源较浅，可能接近海底。与邻近的7级地震相反，这次地震触发了一种基于地面运动的地震预警算法，该算法正在加州南部（约600公里外）进行测试。这一观测结果表明，这次地震观测到的异常大的地面运动和动态应变与其破裂性质有关。为了研究这种可能性，我们成像的破裂过程中，并解决了滑动分布的事件，使用P波反投影方法和一个可扩展的，有限故障反演方法。从这两个独立的分析结果表明，一个相对简单的，单向破裂的传播方向沿走向在北方向。然而，平均破裂速度估计约为4 km s-1，表明可能是超剪切破裂。超剪切速度也支持瑞利波马赫锥分析，虽然在当地的速度结构的不确定性排除了一个明确的结论。巴列纳斯运河地震在加州的多个地点动态触发地震活动，触发响应特征因地点而异。例如，加州的一些触发地震发生在24小时后，这表明非线性触发机制可能已经调制了它们的发生。
In the Gulf of California, Mexico, the relative motion across the North America–Pacific boundary is accommodated by a series of marine transform faults and spreading centres. About 40M> 6 earthquakes have occurred in the region since 1960. On 2009 August 3, anMw6.9 earthquake occurred near Canal de Ballenas in the region. The earthquake was a strike-slip event with a shallow hypocentre that is likely close to the seafloor. In contrast to an adjacentM7 earthquake, this earthquake triggered a ground-motion-based earthquake early warning algorithm being tested in southern California (∼600 km away). This observation suggests that the abnormally large ground motions and dynamic strains observed for this earthquake relate to its rupture properties. To investigate this possibility, we image the rupture process and resolve the slip distribution of the event using aP-wave backprojection approach and a teleseismic, finite-fault inversion method. Results from these two independent analyses indicate a relatively simple, unilateral rupture propagation directed along-strike in the northward direction. However, the average rupture speed is estimated around 4 km s−1, suggesting a possible supershear rupture. The supershear speed is also supported by a Rayleigh wave Mach cone analysis, although uncertainties in local velocity structure preclude a definitive conclusion. The Canal de Ballenas earthquake dynamically triggered seismicity at multiple sites in California, with triggering response characteristics varying from location-to-location. For instance, some of the triggered earthquakes in California occurred up to 24 hr later, suggesting that nonlinear triggering mechanisms likely have modulated their occurrence.