Collaborative Research: High-resolution imaging of the Elgin-Lugoff earthquake swarm sequence and subsurface structures in South Carolina using a dense seismic nodal array

合作研究：使用密集地震节点阵列对南卡罗来纳州埃尔金-卢戈夫地震群序列和地下结构进行高分辨率成像

• 批准号: 2321095
• 负责人: Daniel Frost
• 金额: $ 16.84万
• 依托单位: University of South Carolina at Columbia
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-08-01 至 2025-07-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2321095&HistoricalAwards=false
• 关键词: Collaborative; Research; resolution; imaging; Elgin

A prolonged earthquake swarm sequence started on December 27, 2021, beginning with a magnitude 3.3 earthquake between Elgin and Lugoff in South Carolina, a region with very low prior seismic activity. More than 90 small earthquakes have been reported in this region since then, with the largest magnitude of 3.6 occurring on June 29, 2022. These earthquakes have continued until at least summer of 2023, making this highly unusual for the region. This swarm has had no clear main shock and has no obvious tectonic or anthropogenic causes. So far, standard earthquake locations do not reveal a clear relationship with the pre-existing Eastern Piedmont Fault System. This project will analyze seismic data from a set of instruments deployed by the researchers in October 2022 to better image the fault structure hosting the swarm and the underlying driving force. This project will naturally provide opportunities for public engagement with the impacted community in Elgin-Lugoff, and the broader midlands of South Carolina, where many residents have felt earthquakes for the first time in their lives. This project also provides inclusion and STEM workforce development opportunities, by funding research by undergraduate students from the local South Carolina community to perform research in their own state. Students on this grant will participate in outreach to build STEM literacy through knowledge transfer and further broaden participation in geoscience. This project will also provide funding to support summer internships at both institutions.In October 2022, 85 seismic nodes were deployed for 4 months by the research team over the Elgin-Lugoff swarm to record further earthquakes. These instruments were complemented by one broadband station and one nearby strong motion station operated by the South Carolina Seismic Network. The rich dataset can be used to identify additional smaller earthquakes, which will better image fault structures hosting this swarm sequence and elucidate the driving forces. The work will attempt to reveal small earthquakes during the nodal deployment period, below the detection threshold before this deployment, by using both machine learning and template matching techniques. The team will then relocate these newly detected events with waveform-based techniques, followed by focal mechanism determinations. This information will be used to construct a new model of the seismic velocities beneath Elgin. Using both the more complete catalog and the improved velocity model, the earthquakes earlier in this swarm can be relocated relative to the later ones thus improving the accuracy of the whole catalogue. Results from this project will answer the following questions: 1) does the swarm occur in a diffuse or well-defined region, 2) how the swarm evolved in space and time, and 3) what is the likely process that drives this swarm. The information gained from the analysis will inform on the ongoing tectonic processes in South Carolina, and on East coast seismicity and tectonics generally.This project is jointly funded by the Geophysics program and the Established Program to Stimulate Competitive Research (EPSCoR).This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

长时间的地震群序列始于2021年12月27日，从埃尔金（Elgin）和卢戈夫（Lugoff）在南卡罗来纳州的地震中发生3.3地震开始，这是一个先前的地震活性。从那以后，该地区已有90多个小地震报道，最大的3.6级发生在2022年6月29日。这些地震持续到至少2023年夏季，这对于该地区来说是非常不寻常的。该群没有明显的主要冲击，也没有明显的构造或人为原因。到目前为止，标准地震位置尚未揭示与现有东部皮埃蒙特故障系统的明确关系。该项目将分析研究人员在2022年10月部署的一组工具中的地震数据，以更好地想象主持群体和基础驱动力的故障结构。该项目自然会为与埃尔金·卢格夫（Elgin-Lugoff）的受影响社区以及南卡罗来纳州的更广泛的中部地区提供公众参与的机会，那里许多居民在他们的生活中首次感受到地震。该项目还通过资助来自当地南卡罗来纳州当地社区的本科生的研究来提供纳入和STEM劳动力发展机会，以在自己的州进行研究。这项赠款的学生将参加宣传，通过知识转移并进一步扩大对地球科学的参与来建立STEM识字。该项目还将提供资金来支持这两个机构的暑期实习。在2022年10月，研究小组在Elgin-Lugoff群体上部署了4个月的85个地震节点，以记录进一步的地震。这些仪器是由一个宽带站和附近的强大运动站进行补充，由南卡罗来纳州地震网络运营。丰富的数据集可用于识别额外的较小地震，这将更好地图像托管该群序列并阐明驱动力的故障结构。这项工作将尝试通过使用机器学习和模板匹配技术来揭示节点部署期间的小地震，低于该部署前的检测阈值。然后，团队将使用基于波形的技术重新定位这些新检测到的事件，然后进行焦点机制确定。此信息将用于构建埃尔金下面的地震速度的新模型。使用更完整的目录和改进的速度模型，可以将群的早期地震转移到后来的地震中，从而提高整个目录的准确性。该项目的结果将回答以下问题：1）群体是否发生在弥漫性或定义明确的区域中，2）群体在时空中如何发展，以及3）3）可能会驱动这一群的过程。从分析中获得的信息将告知南卡罗来纳州正在进行的构造过程，以及东海岸的地震性和构造学的一般性。该项目由地球物理计划和既定计划共同资助，旨在刺激竞争研究（EPSCOR）的既定计划（EPSCOR）。这项奖项通过NSF的法规和审查的范围来审查，以反映了构成群体的范围。