Breaking the High-Frequency Barrier in Earthquake Source Imaging With a Network of Seismic Antennas

利用地震天线网络打破震源成像的高频障碍

• 批准号: 1015704
• 负责人: Jean-Paul Ampuero
• 金额: $ 8.4万
• 依托单位: California Institute of Technology
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-08-01 至 2012-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1015704&HistoricalAwards=false
• 关键词: Breaking; Frequency; Barrier; Earthquake; Source

Seismological insight into the physics of earthquakes is hampered by the limited spatio-temporal resolution of conventional source imaging techniques which, due to the heterogeneity of the Earth's crust, are incapable of assimilating the high-frequency wavefield. This project aims at enabling the development of a new generation of seismic networks specially designed for high-resolution imaging of large earthquake ruptures. Non-parametric source imaging can be achieved if an earthquake is recorded on a highly clustered strong motion network, composed of multiple small aperture arrays: processing array data with high resolution direction-of-arrival estimation techniques can provide the spatio-temporal distribution of "bright spots" of high-frequency source radiation, a direct insight on rupture complexity. The proposed research encompasses aspects of the system design and specifications that can be addressed through computational modeling of realistic earthquake scenarios, numerical solution of optimal experiment design problems, developments in array signal processing techniques and analysis of available datasets. The researchers will generate source dynamics and wave propagation in earthquake scenarios with realistic source complexity, crustal heterogeneities and topography to provide a proof of concept, to assess the robustness and resolution of imaging complex source processes with multiple arrays. These synthetic scenarios will also guide the definition of practical guidelines for array site selection, by quantifying the effect of scattering on waveform coherency as a function of frequency and inter-station distance and by identifying adequate geomorphological proxies for wavefield coherency. Optimization techniques will be employed to find the network and array geometries that maximize the source imaging resolution and robustness while minimizing the total number of sensors to be deployed.Many large urban areas around the world are exposed to earthquake hazard in close proximity to active faults, where the effects of the earthquake source complexity dominate the amplitude and variability of ground shaking. Improving our understanding of earthquake dynamics will consolidate the emerging trend of physics-based approaches for earthquake hazard assessment. This project aims at a transformative development of our capabilities to image the details of the rupture propagation of large earthquakes through the design of a new generation of seismic networks made of multiple clusters of strong motion sensors near active faults. This development aims at an order-of-magnitude improvement in the spatio-temporal resolution of earthquake rupture processes that will allow testing of competing hypothesis about the physics of earthquakes and hence will advance our quantitative understanding of earthquake hazards. The concept timely builds upon recent experience with single-array recordings of the 2004 Parkfield earthquake and takes advantage of recent technological developments, such as the increasing availability of low cost MEMS accelerometers and wireless communication. The proposed concept will be designed to allow contributions to multiple additional applications in earthquake engineering, analysis of conventional seismic networks and monitoring tectonic tremor.

传统震源成像技术的时空分辨率有限，由于地壳的不均匀性，无法同化高频波场，这阻碍了对地震物理的地震学见解。该项目旨在开发新一代地震网络，专门用于大地震破裂的高分辨率成像。如果地震记录在由多个小孔径阵列组成的高度集群的强震网络上，则可以实现非参数源成像：用高分辨率到达方向估计技术处理阵列数据可以提供高频源辐射的“亮点”的时空分布，直接洞察破裂的复杂性。拟议的研究包括系统设计和规格，可以通过计算模拟现实的地震场景，最佳实验设计问题的数值解，阵列信号处理技术的发展和可用数据集的分析来解决的方面。研究人员将在具有真实震源复杂性、地壳非均匀性和地形的地震场景中生成震源动态和波传播，以提供概念验证，评估使用多个阵列成像复杂震源过程的鲁棒性和分辨率。这些综合设想方案还将通过量化散射对波形相干性的影响作为频率和台站间距离的函数，并通过确定波场相干性的适当地貌代理，指导确定阵列选址的实用准则。优化技术将被用来寻找网络和阵列的几何形状，最大限度地提高源成像的分辨率和鲁棒性，同时最大限度地减少传感器的总数量被部署。世界各地的许多大城市地区都暴露在地震危险的活动断层附近，地震源的复杂性的影响占主导地位的振幅和变化的地面震动。提高我们对地震动力学的理解将巩固地震危险性评估的基于物理方法的新兴趋势。该项目旨在通过设计由活动断层附近的多个强震传感器集群组成的新一代地震网络，实现我们对大地震破裂传播细节进行成像的能力的变革性发展。这一发展的目的是在地震破裂过程的时空分辨率上取得数量级的提高，这将允许测试有关地震物理学的竞争性假设，从而促进我们对地震危害的定量理解。该概念及时地建立在2004年帕克菲尔德地震的单阵列记录的最新经验的基础上，并利用了最新的技术发展，例如低成本MEMS加速度计和无线通信的日益可用性。拟议的概念将被设计为允许在地震工程，分析传统的地震网络和监测构造震颤的多个额外的应用程序的贡献。