基于云计算的九分量噪声互相关函数计算及其在China Array密集台阵数据的应用

Speeding the Nine-component Cross Correlation Function Calculation Using Cloud-computing and Its Application on the Dataset of China Array-NE Tibet

摘要:

提出一种基于云计算的九分量噪声互相关函数的计算方法，可以利用弹性的云计算服务，实现海量噪声互相关函数计算的分解和加速。本文将此技术应用于“中国地震科学台阵探测——南北地震带北段”674个宽频带台站2014～2015年的三分量连续记录，获取了所有台站间的九分量噪声互相关函数。总体计算共完成了约22万条台站对路径上近14.9亿条单天互相关函数的计算，整体平均耗时约为10.2h，完成等量计算，传统计算模式需要耗时近6个月，基于云计算的NCF计算技术实现了近400倍的加速，并可以弹性地扩充。分析了所得九分量噪声互相关函数中瑞利面波的ZH振幅比，并与天然地震中瑞利面波的振幅比进行了比较，验证了计算结果的可靠性。基于云计算的噪声互相关函数计算方法，为利用现代计算技术处理海量数据提供了重要参考。

Abstract:

The nine-component cross-correlation function(NCF)has been paid more and more attention to with the development of research based on ambient noise cross-correlation. However,with the development of large aperture and dense arrays,it is challenging to quickly calculate the cross-correlation function from large-amount dataset in traditional high performance workstations,especially for the nine-component cross-correlation functions which will roughly take nine times longer compared to the vertical-vertical component alone. In present paper we propose one possible solution to speed the calculation of nine-component cross-correlation functions for large dataset using the cloud computing. The cloud computing can provide scalable computation power and storage which is suitable for data intensive computing tasks,while calculating NCFs from large amount data is exactly one data intensive computation. Based on the cloud services provided by Aliyun,we have developed one framework which could factorize the entire computation into small pieces and execute each piece in one single virtual server evoked at the cloud end. Since all those virtual servers can run simultaneously,the time cost to obtain NCFs from large dataset could be highly reduced,which is roughly inversely proportional to the number of evoked virtual servers. We apply this technique to obtain the nine-component NCFs based on the continuous three component records of China Array from 2014 to 2015,which consists of 674 broadband stations and covers a ten by ten degree area in northeast Tibet. Our results show that the entail computation can be finished in eleven hours,which is about 400 times faster compared to that on one single traditional server. We further validated the resulting NCFs by calculating the Rayleigh wave ZH ratios from both the stacked nine-component NCFs and earthquake results and the results suggest our computation method is fast and reliable. Seismology is developing in an era of big data and our study suggests that by utilizing the techniques from computing science of mass data,we can benefit from the advances in observational capabilities.