Seismological Investigations of Earthquakes and Deep Earth Structure

地震和地球深层结构的地震学研究

基本信息

批准号：
2123529
负责人：
Peter Shearer
金额：
$ 57.96万
依托单位：
University of California-San Diego Scripps Inst of Oceanography
依托单位国家：
美国
项目类别：
Continuing Grant
财政年份：
2021
资助国家：
美国
起止时间：
2021-08-01 至 2024-07-31
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=2123529&HistoricalAwards=false
关键词：
Seismological Investigations Earthquakes Deep Earth

项目摘要

This project will use decades of records of seismic waves generated by thousands of earthquakes all over the world to learn about both earthquakes and deep Earth structure. Analyses of earthquakes will focus on the high-frequency components of the seismograms, which provide key constraints on the energy radiated by earthquakes and information about the speed and complexity of fault ruptures. These results should help improve forecasts of damaging ground motions produced by strong earthquakes. Planned analyses for Earth structure will examine sharp changes in seismic wave velocities that occur at depths of 50 to 400 miles below the surface that are related to changes in crystal structure or the presence of fluids, such as water or magma. A related project will examine scattering of seismic waves, which provides clues regarding small-scale variability in rock properties at depths extending from the surface to Earth's liquid core. These results will help in understanding the internal composition of the Earth and its relation to tectonic processes. The project will support undergraduate, graduate, and postgraduate students and involve them in research. Educational components include graduate student and postdoc support, as well as sponsoring an undergraduate summer intern in a long-standing and successful SIO program designed to increase student diversity. Systematic analyses of large datasets recorded by both permanent and temporary seismic stations all over the world provide rich opportunities to study problems concerning earthquakes and Earth structure. Planned research includes innovative investigations of upper-mantle discontinuity structure within and near the transition zone and the lithosphere-asthenosphere boundary, observing and modeling of seismic scattering to characterize small-scale compositional heterogeneity in the mantle, and spectral analyses of earthquake radiation to constrain earthquake rupture dimensions and dynamics. Some key questions this project plans to examine include: (1) What is the role of the low-velocity layer (LVL) above the 410-km discontinuity in mantle convection and water recycling? (2) What causes the mid-lithospheric discontinuity (MLD) observed under many continental cratons? (3) How variable is the sharpness and roughness of the 660-km discontinuity and what does that imply for mantle composition? (4) What is the strength of small-scale heterogeneity in the mid- to lower mantle and does it vary laterally? (5) What causes the large scatter in earthquake stress drop estimates, i.e., how much is due to modeling uncertainties versus real differences in earthquake dynamics? (6) Does earthquake stress drop vary systematically with tectonic region? (7) How do improved global high-frequency body-wave attenuation models compare to tomographic models and to surface-wave attenuation models?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.

该项目将利用世界各地数千次地震产生的数十年地震波记录来了解地震和地球深层结构。地震分析将重点关注地震图的高频分量，它提供了地震辐射能量的关键约束以及有关断层破裂速度和复杂性的信息。这些结果应该有助于改进对强地震产生的破坏性地面运动的预测。计划中的地球结构分析将检查地表以下 50 至 400 英里深度处发生的地震波速度的急剧变化，这些变化与晶体结构的变化或水或岩浆等流体的存在有关。一个相关项目将检查地震波的散射，这提供了有关从地表到地球液体核心的深度岩石特性小规模变化的线索。这些结果将有助于了解地球的内部组成及其与构造过程的关系。该项目将支持本科生、研究生和研究生，并让他们参与研究。教育内容包括研究生和博士后支持，以及资助一名本科生暑期实习生参加一项长期且成功的 SIO 项目，该项目旨在提高学生多样性。对世界各地永久和临时地震台记录的大型数据集的系统分析为研究地震和地球结构问题提供了丰富的机会。计划的研究包括对过渡带和岩石圈-软流圈边界内部和附近的上地幔不连续结构进行创新研究，对地震散射进行观测和建模以表征地幔中的小尺度成分不均匀性，以及对地震辐射进行频谱分析以限制地震破裂尺寸和动力学。该项目计划研究的一些关键问题包括：（1）410公里间断面上方的低速层（LVL）在地幔对流和水循环中的作用是什么？ (2) 是什么原因导致许多大陆克拉通下观察到的岩石圈中部不连续面（MLD）？ (3) 660 公里不连续面的锐度和粗糙度变化有多大？这对地幔成分意味着什么？（4）中下地幔小尺度非均质性的强度是多少，横向上有变化吗？ (5) 是什么导致地震应力降估计值出现较大的分散性，即，模型不确定性与地震动力学的实际差异有多少是由于模型不确定性造成的？ (6) 地震应力降是否随构造区域存在系统变化？ (7) 改进的全球高频体波衰减模型与断层扫描模型和表面波衰减模型相比如何？该奖项反映了 NSF 的法定使命，并通过利用基金会的智力价值和更广泛的影响进行评估，认为值得支持审查标准。