Earthquake doublets have been described in fault systems around the world but have not yet been confidently resolved in paleoseismic records. Our current knowledge is limited to historical occurrences, preventing researchers from uncovering potential patterns or recognizing common fault behavior. Identification of prehistoric doublets is thus of crucial importance for adequate seismic hazard assessment and risk mitigation. We developed a new methodology to reveal the sedimentary imprint of earthquake doublets in lacustrine paleoseismic records based on flow direction analysis in multipulsed turbidites, because the delayed arrival of turbidity currents originating from the same source location demonstrates the occurrence of individual triggering mechanisms. As grains tend to align in the presence of a flow, we analyzed flow directions by determining the dominant orientation of elongated grains using a combination of grain size, paleomagnetism, and high-resolution X-ray computed tomography. This methodology was applied to a turbidite deposited by the 2007 CE earthquakes in West Sumatra (Mw 6.4 and 6.3, 2 h apart), and it provides the first unmistakable sedimentary evidence for an earthquake doublet. We argue that this methodology has great potential to be applied to multipulsed turbidites in various subaquatic paleoseismic records and can reveal the occurrence of unknown earthquake sequences.

中文翻译：

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湖相地震浊积岩中多次脉冲揭示的地震双峰

世界各地的断层系统中都描述了双震，但尚未在古地震记录中得到可靠的解决。我们目前的知识仅限于历史事件，阻止研究人员发现潜在模式或识别常见故障行为。因此，识别史前双峰对于充分的地震灾害评估和风险缓解至关重要。我们开发了一种基于多脉冲浊积岩流向分析揭示湖相古地震记录中地震双峰沉积印记的新方法，因为源自同一震源位置的浊流的延迟到达证明了个别触发机制的发生。由于颗粒在流动的情况下倾向于排列，我们通过结合晶粒尺寸、古地磁和高分辨率 X 射线计算机断层扫描确定细长晶粒的主要取向来分析流动方向。这种方法被应用于西苏门答腊 2007 年 CE 地震沉积的浊积岩（Mw 6.4 和 6.3，相隔 2 小时），它为地震双峰提供了第一个明确无误的沉积证据。我们认为，这种方法有很大的潜力应用于各种水下古地震记录中的多脉冲浊积岩，并可以揭示未知地震序列的发生。2 小时），它为地震双峰提供了第一个明确无误的沉积证据。我们认为，这种方法有很大的潜力应用于各种水下古地震记录中的多脉冲浊积岩，并可以揭示未知地震序列的发生。2 小时），它为地震双峰提供了第一个明确无误的沉积证据。我们认为，这种方法有很大的潜力应用于各种水下古地震记录中的多脉冲浊积岩，并可以揭示未知地震序列的发生。