Characterizing variations in magnitude-frequency distribution and b-value using relative magnitudes

使用相对幅度表征幅度频率分布和 b 值的变化

• 批准号: 2315814
• 负责人: Yihe Huang
• 金额: $ 25.92万
• 依托单位: Regents of the University of Michigan - Ann Arbor
• 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: 2023-09-01 至 2026-08-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2315814&HistoricalAwards=false
• 关键词: Characterizing; variations; magnitude; frequency; distribution

The “magnitude-frequency distribution” (MFD) of earthquakes describes how often earthquakes of different magnitudes occur in a particular region, with large earthquakes being far less frequent than small ones. The proportion of small to large earthquakes, which scientists obtain from the MFD, is represented using the “b-value”. This quantity is used to infer from recordings of frequent, small earthquakes how often rarer, large earthquakes are expected, and to flag regions that may be at risk for major earthquakes. Robust estimates of b-value require enormous collections (or ‘catalogues’) of earthquake data, in which all magnitudes were estimated the same way. Dr. Huang and her team will characterize the variations in MFD and b-value by recalculating earthquake magnitudes for two catalogs: one from southern California (where most earthquakes occur naturally) and one from Oklahoma (where most earthquakes are triggered by injection of wastewater from oil and gas production). Using the new MFDs, she and her team will assess how b-values may vary in these two regions during foreshocks, large earthquakes, and aftershocks; and (where applicable) operation of nearby wastewater injection wells. This project will provide vital information for quantitative seismic hazard analysis, which is required for updating building codes and other public safety measures; and will advance scientific understanding of earthquake physics. The PI and her group will also develop and share a free online educational tool that will enable students, teachers, and the general public to access and analyze seismograph data, and estimate earthquake magnitudes.Current MFD and b-value analyses are strongly affected by magnitude uncertainties of small earthquakes and mixed magnitude types in earthquake catalogs. Recent studies have shown that MFDs can deviate from exponential distribution at low-magnitude ranges and b-value can vary considerably with the magnitude of completeness due to the discontinuity of MFDs in high-resolution catalogs. The project will produce earthquake catalogs with consistent magnitudes for small and large earthquakes using recalculated magnitude differences, which will enable a systematic analysis of the spatial-temporal variations in MFDs and b-value in Southern California and Oklahoma. After the magnitudes are recalculated, the project will investigate the possible deviations of MFDs from exponential distribution and their effects on the estimation of b-value. The project will also quantify whether there are significant changes of b-values during foreshocks, mainshocks, and aftershocks as well as the operation of injection wells for induced seismicity. The systematic MFD and b-value analysis together will produce more robust parameters for seismic hazard analysis and unveil whether b-value variations manifest changes in fault stress state.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.

地震的“大小频率分布”（MFD）描述了在特定地区发生不同幅度的地震的频率，大地震远比小地震频率要小得多。科学家从MFD获得的小到大地震的比例是使用“ B值”代表的。该数量用于从经常发生的，小地震的录音中推断出来，预计稀有多久，大地震，以及可能面临重大地震风险的旗帜区域。 B值的稳健估计需要地震数据的巨大收集（或“目录”），其中所有磁化率的估计方式相同。黄博士和她的团队将通过重新计算两个目录的地震幅度来表征MFD和B值的变化：一个来自南加州（大多数地震发生自然发生）和俄克拉荷马州（大多数地震发生）（大多数地震是通过从油气和天然气中向废水触发的大多数地震而触发的）。使用新的MFD，她和她的团队将评估B值在前壳，大地震和余震期间的这两个区域如何变化； （如果适用）近废水注入井的操作。该项目将为定量地震危害分析提供重要信息，这是更新建筑法规和其他公共安全指标所必需的；并将提高对地震物理学的科学理解。 PI和她的小组还将开发和共享一个免费的在线教育工具，这将使学生，老师和公众能够访问和分析地震仪数据，并估算地震幅度。电流MFD和B-Value分析受到地震小地震和地震中的混合级类型的巨大不确定性的强烈影响。最近的研究表明，由于高分辨率目录中MFD的不连续性，MFD可以偏离低速度范围和B值的指数分布很容易变化。该项目将使用重新计算的幅度差异生产具有一致和大地震的一致地震目录，这将使南加州和俄克拉荷马州的MFDS和B-Value的时空变化进行系统分析。重新计算幅度后，该项目将调查MFD与指数分布的可能偏离及其对B值估计的影响。该项目还将量化前壳，主震动和余震过程中B值的重大变化，以及用于诱导地震性的注入井的操作。系统的MFD和B值分析将共同产生更强大的参数，以进行地震危险分析，并揭示B值变化是否在断层压力状态中发生变化。该奖项反映了NSF的法定任务，并通过使用基金会的智力和更广泛的影响来审查Criteria来诚实地通过评估来诚实地通过评估来支持。