EAR-PF: Are large earthquakes like small earthquakes? Using synthetic earthquakes to resolve discrepancies in observations of earthquake stress drop magnitude-invariance

EAR-PF：大地震和小地震一样吗？

• 批准号: 2204102
• 负责人: James Neely
• 金额: $ 18万
• 依托单位: Neely, James Scott
• 依托单位国家: 美国
• 项目类别: Fellowship Award
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-09-01 至 2024-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2204102&HistoricalAwards=false
• 关键词: EAR; PF; large; earthquakes; like

Dr. James Neely has been awarded an NSF EAR Postdoctoral Fellowship to assess whether small and large earthquakes release energy in the same way. This work will be conducted at the University of Chicago in collaboration with Dr. Sunny Park and Dr. Annemarie Baltay of the U.S. Geological Survey. Larger earthquakes release more energy than smaller earthquakes, but how earthquakes release that energy is not as well understood, despite having important implications for seismologists’ understanding of earthquake processes and, crucially, the seismic hazards that earthquakes pose. Specifically, the way that a given earthquake releases energy determines, at least in part, how strong the shaking will be (which should, in turn, inform building safety standards, etc.). Using computer simulations, Dr. Neely will examine assumptions about how earthquakes release energy and assess whether insights from small earthquakes can help us better understand the hazards posed by rarer, large earthquakes. Additionally, Dr. Neely will work on an initiative to foster knowledge-sharing relationships between Illinois state legislators and researchers within the state.In this project, Dr. Neely will examine the question of whether earthquake stress drop—the decrease in stress along a fault due to an earthquake—is magnitude-invariant. Earthquake stress drop is thought to control the levels of high-frequency shaking that damages buildings, and it may provide insight into earthquake rupture dynamics. Some studies suggest that earthquake stress drop is constant with earthquake magnitude, while others indicate that it varies systematically with magnitude. Because seismologists cannot directly measure stress drop, they cannot compare estimates to the true value, so it is not known which methods are most accurate. Dr. Neely will overcome this issue by generating a large dataset of synthetic earthquakes with known stress drops and then apply four commonly used stress drop estimation methods to this dataset. To simulate real earthquake data, Dr. Neely will generate earthquakes that differ from the simple earthquake models assumed by the stress drop methods and examine how well the stress drop estimates match the true values. Dr. Neely will identity which stress drop method is most accurate and then examine a large dataset of real earthquakes to determine whether stress drop is or is not magnitude-invariant. If stress drop magnitude-invariance is true, seismologists can measure the stress drops of a region’s past small earthquakes to gain insight into the stress drops, and potential shaking levels, of future large earthquakes. But if stress drop magnitude-invariance is false, then seismological models—and as a result policy preparations, including building codes—for this future shaking may be wrong and need major revisions. In addition to this stress drop analysis, Dr. Neely will work to expand the Science One-Pager Initiative (SOPI), an Illinois-based program where graduate students and post-doctoral researchers provide short analyses of scientific topics to state legislators.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.

詹姆斯·尼利（James Neely）博士被授予NSF耳朵博士后奖学金，以评估小地震是否以相同的方式释放能量。这项工作将在芝加哥大学与Sunny Park博士和美国地质调查局的Annemarie Baltay博士合作进行。较大的地震比较小的地震释放更多的能量，但是地震如何释放该能量的理解并不那么理解，尽管对地震学家对地震过程的理解具有重要意义，并且至关重要的是，地震构成地震构成的地震危害。具体而言，给定的地震释放能量的方式至少部分决定了摇动的强度（反过来又应为建筑安全标准等提供信息）。使用计算机模拟，Neely博士将研究地震如何释放能量和评估小地震的见解是否可以帮助我们更好地了解稀有，大地震的危害姿势的假设。此外，Neely博士将努力促进该州伊利诺伊州立法者和该州研究人员之间的知识共享关系。在本项目中，Neely博士将研究地震压力下降（由于地震而导致的压力下降）是否下降的问题 - 是否不变。人们认为地震应力下降可以控制损害建筑物的高频摇动的水平，并且可以洞悉地震破裂动态。一些研究表明，地震应力下降是恒定的，而地震幅度却是恒定的，而其他研究则表明它随着幅度而变化。由于地震学家无法直接测量应力下降，因此他们无法将估计值与真实值进行比较，因此尚不清楚哪种方法最准确。 Neely博士将通过在已知应力下降的大量合成地质地震来克服此问题，然后将四种常用的应力下降估计方法应用于该数据集。为了模拟真实的地质数据，Neely博士将产生与应力下降方法假设的简单地质地震模型不同的地质地震，并检查应力下降估计值与真实值的匹配程度。 Neely博士将要确定应力下降方法最准确，然后检查一个真实地震的大数据集，以确定应力下降是否不变。如果应力下降幅度不变性是正确的，那么地震学家可以测量一个地区过去的小地震的应力下降，以深入了解未来大地地震的应力下降和潜在的震动水平。但是，如果压力下降的幅度不变性是错误的，那么地震学模型（因此，包括建筑物代码在内的政策准备）可能是错误的，并且需要进行重大修改。除了这种压力下降分析外，Neely博士还将努力扩展一项基于伊利诺伊州的计划（SOPI），该计划是一项基于伊利诺伊州的计划，该计划在该计划中，研究生和博士后研究人员对州立法者提供了科学主题的简短分析。该奖项反映了NSF的立法使命，并被认为是通过基金会的智力综述和广泛的评估来评估的，并值得通过评估来进行评估。