A seismological reassessment of the source of the 1946 Aleutian 'tsunami' earthquake
A seismological reassessment of the source of the 1946 Aleutian 'tsunami' earthquake
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DOI：
10.1111/j.1365-246x.2006.02899.x
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发表时间：
2006-06-01
影响因子：
2.8
通讯作者：
Okal, Emile A.
中科院分区：
文献类型：
--
作者：
Lopez, Alberto M.;Okal, Emile A.
我们对1946年4月1日阿留申“海啸地震”的地震学性质进行了重新评估，考虑到它在近场和远场的灾难性海啸，其特征是具有欺骗性的低常规震级(7.4级)。对40次余震的重新定位表明，断裂带沿着阿留申海沟至少延伸了181公里，其几何形状需要从震中原始形核的两侧破裂。它们的空间和时间分布是典型的大地震余震模式，排除了不包括错动的滑坡震源模式。对地幔波谱的分析支持大震源模型，静态矩为8.5x10(28)dyn-cm，使这次地震成为有记录以来十次最大地震之一(因此发生了远场破坏性海啸)，以及平均速度仅为1.12公里的缓慢双侧破裂S(-1)，因此除最长的地幔波外，所有方位都存在破坏性干扰。地震异常缓慢的特征被辐射地震能量的不足所证实，辐射地震能量由迄今测得的能量与力矩比的最低值表示。这场地震似乎是“海啸地震”家族的最后一员，它是由异常但并非史无前例的参数组合而成的，例如低应力降和破裂速度。
We present a re-evaluation of the seismological properties of the Aleutian 'tsunami earthquake' of 1946 April 1, characterized by a deceptively low conventional magnitude (7.4) in view of its catastrophic tsunami, both in the near and far fields. Relocation of 40 aftershocks show that the fault zone extends a minimum of 181 km along the Aleutian trench, in a geometry requiring a bilateral rupture from the original nucleation at the epicentre. Their spatial and temporal distribution are typical of the aftershock patterns of a large earthquake, and rule out the model of a landslide source exclusive of a dislocation. The analysis of the spectra of mantle waves favours the model of a large seismic source, with a static moment of 8.5 x 10(28) dyn-cm, making the event one of the ten largest earthquakes ever recorded (hence the destructive tsunami in the far field), and of a slow bilateral rupture, at an average velocity of only 1.12 km s(-1), hence the destructive interference in all azimuths for all but the longest mantle waves. The exceptionally slow character of the earthquake is confirmed by a deficiency in radiated seismic energy expressed by the lowest value measured to date of the energy-to-moment ratio. The earthquake appears as an end member in the family of 'tsunami earthquakes', resulting from the combination of anomalous, but not unprecedented, parameters, such as low stress drop and rupture velocity.