Comprehensive high-precision relocation of global seismicity

区域和全球地震台网每年探测和记录数十万次地震。地震台网运营商经常分析他们的地震记录，以估计各种参数，包括时间、位置和每次新地震的震级，从而增加了快速增长的数字地震数据档案。地震地点目录是地震学和一般地球科学数据的基本来源。然而，这些个别地点的空间分辨率非常低，这限制了它们解决有关地球结构和组成的基本问题的潜力。地震的性质，以及地震对我们的社会和建筑环境造成的危害。该项目的主要目标是通过应用高阶地震定位方法，利用不断增加的地震档案数量和质量以及可负担得起的计算能力，显著提高全球范围内数百万次地震的定位精度。该项目将重点利用丰富的高精度数据，以比较的方式更好地了解控制全球俯冲带的孕震结构和过程。预计该项目的成果将在地球科学中得到许多应用，并在自然灾害和《全面禁止核试验条约》的地震核查领域产生社会影响。在过去的几十年里，全球地震档案的巨大增长，计算成本的持续下降，以及地震重新定位方法的进步，为大幅度提高标准全球地震目录的空间分辨率提供了一个独特的机会。这些震源目录中的震源位置通常是根据全球地震台站观测到的相位到达时间来估计一次一个事件的，其准确性非常低，这不仅阻碍了地震学的研究，而且阻碍了地球科学的广泛研究领域。这个正在进行的项目建立在先前工作的基础上，该工作开发了高效的波形相互关联和双差（DD）算法，以重新定位国际地震中心（ISC）和NEIC？s地震数据报告，跨越1964-2012年。这些工具通过利用新的程序来处理这种大规模工程的计算负荷，从而提高了地震位置的精度。基于相互关联的相位延迟时间是在数十亿对波形上测量的，有效的远震双差算法将这些数据与报告的相位到达时间相结合。使用这种方法的初步结果已经揭示了时间和空间上的特征地震活动模式，并提供了新的数据，有助于以前所未有的分辨率深入了解地震发生过程。本项目将重点研究Wadati-Benioff带俯冲带地震活动性的精细结构和窄双地震带的性质，并分析与近期大俯冲地震相关的重新定位地震活动性，以更好地了解其结构和运动学行为。全球DD目录可能会在地球科学中找到许多应用，并可能有助于提高我们对控制地震的物理过程的理解，以及我们对地球结构和组成的成像能力。以及我们估计大地震造成的危害的能力。

Hundreds of thousands of earthquakes are detected and recorded each year by regional and global seismic networks. Seismic network operators routinely analyze their seismograms to estimate various parameters, including time, location, and magnitude of each new earthquake, adding to a rapidly growing archive of digital seismic data. Catalogs of earthquake locations are a fundamental source of data in seismology, and in the Earth sciences in general. Yet these individual locations have had notoriously low spatial resolution, which limits their potential to address fundamental questions concerning the structure and composition of the Earth?s interior, the nature of earthquakes, and the seismic hazards they impose on our society and the built environment. The main goal of this project is to significantly improve the location precision of millions of earthquakes on a global scale by applying higher-order earthquake location methods that take advantage of the increasing quantity and quality of seismic archives and the availability of affordable computing power. This project will focus on using the wealth of high-precision data to better understand, in a comparative way, the seismogenic structure and processes that control subduction zones worldwide. Results from this project are expected to find many applications in the Earth Sciences, and to have social impact in the areas of natural hazards and seismic verification of the Comprehensive Nuclear-Test Ban Treaty (CTBT).The tremendous growth in global seismic archives over the last several decades, the continuous fall in computing costs, and advances in earthquake relocation methods provide a unique opportunity to substantially improve the spatial resolution of standard global earthquake catalogs. The locations of hypocenters in these catalogs, typically estimated one event at a time from phase arrival times observed at global seismic stations, have notoriously low accuracy that hamper studies in a wide range of research areas, not only in Seismology, but in the Geosciences in general. This continuing project builds on previous work that developed high-efficiency waveform cross-correlation and double-difference (DD) algorithms to relocate more than 3 million earthquakes listed in the combined bulletins of the International Seismological Centre (ISC) and NEIC?s Earthquake Data Report, spanning the years 1964-2012. These tools increase the precision of the earthquake locations by harnessing new procedures that can cope with the computational load of this massive-scale undertaking. Cross-correlation based phase delay times are measured on billions of pairs of waveforms, and efficient teleseismic double-difference algorithms invert these data in combination with reported phase arrival times. Initial results using this approach already reveal characteristic seismicity patterns in time and space, and provide new data that help gain insight into seismogenic processes at unprecedented resolution. This project will focus on the fine-scale structure of Wadati-Benioff zone seismicity at subduction zones and the nature of narrow double-seismic zones, and analyze the relocated seismicity associated with recent great subduction earthquakes to better understand their structural and kinematic behavior. A global DD catalog will likely find many applications in the Earth Sciences, and may help improve our understanding of the physical processes controlling earthquakes, our ability to image the structure and composition of the Earth?s interior, and our capability to estimate the hazards imposed by large earthquakes.