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Characteristics of Earthquakes Recorded Around the High Dam Lake with Comparison to Natural Earthquakes Using Waveform Inversion and Source Spectra
Pure and Applied Geophysics ( IF 1.9 ) Pub Date : 2020-05-20 , DOI: 10.1007/s00024-020-02490-4
Hamada Saadalla , Abdel-Aziz Khairy Abdel–aal , Abdelnasser Mohamed , K. El-Faragawy

To determine whether recent seismicity around the High Dam Lake (Lake Nasser) in the Aswan region is induced or triggered by the lake reservoir or is of natural origin, we analyzed moment tensor solutions and source spectra of recent recorded earthquakes in the area. The earthquakes' focal mechanisms, including source mechanism parameters and source spectra, can give important information to assist in discriminating between triggered and natural seismic events. In the current work, we computed moment tensors and stress drop values for six recently triggered earthquakes recorded by the Egyptian National Seismic Network (ENSN) around Lake Nasser, Aswan area, with local magnitudes between 3.0 and 4.6, as well as 40 nearby earthquakes in and around Egypt with local magnitudes ranging from 4.0 to 5.5, that are known as natural events. We performed full waveform inversion for the studied seismic events, including the dominant double-couple (DC) signature, and also completed moment tensor solutions. Our results show that most triggered events demonstrated significant non-double-couple components. The focal depths of most Aswan seismic events calculated in the current study are significantly shallower than the estimated focal depths for inter-plate and intraplate earthquakes in and around the area under investigation. The focal depths of 80% of the triggered events are shallower than 10 km, while 80% of the tectonic earthquakes are deeper than 15 km. On the other hand, stress and source spectra of the studied events are used as another key to deeply study the source mechanics and physics of natural and triggered events in this area.

中文翻译:

使用波形反演和震源谱将高坝湖周围记录的地震特征与自然地震进行比较

为了确定阿斯旺地区高坝湖(纳赛尔湖)周围最近的地震活动是由湖水库诱发或触发还是自然起源,我们分析了该地区最近记录地震的矩张量解和震源谱。地震的震源机制,包括震源机制参数和震源谱,可以提供重要信息,有助于区分触发和自然地震事件。在目前的工作中,我们计算了埃及国家地震网 (ENSN) 在阿斯旺地区纳赛尔湖附近记录的 6 次最近触发的地震的矩张量和应力降值,当地震级在 3.0 到 4.6 之间,以及附近的 40 次地震在埃及周围,当地震级在 4.0 到 5.5 之间,被称为自然事件。我们对所研究的地震事件进行了全波形反演,包括主要的双偶 (DC) 特征,并且还完成了矩张量解。我们的结果表明,大多数触发事件表现出显着的非双偶组件。当前研究中计算的大多数阿斯旺地震事件的震源深度明显小于所调查区域内和周围板间和板内地震的估计震源深度。80%的触发事件震源深度小于10公里,而80%的构造地震深度大于15公里。另一方面,利用所研究事件的应力谱和源谱作为深入研究该领域自然和触发事件的源力学和物理的又一关键。
更新日期:2020-05-20
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