Detecting Earthquake-Related Anomalies of a Borehole Strain Network Based on Multi-Channel Singular Spectrum Analysis.

Zining Yu,Kaiguang Zhu,Xiaodan He,Mengxuan Fan,Katsumi Hattori,Chengquan Chi

doi:10.3390/e22101086

Zining Yu, Kaiguang Zhu + Show 4 more

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https://doi.org/10.3390/e22101086

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Journal: Entropy	Publication Date: Sep 27, 2020
Citations: 5	License type: CC BY 4.0

Affiliation: Chiba University, Jilin University

Abstract

To investigate the nonlinear spatio-temporal behavior of earthquakes, a complex network has been built using borehole strain data from the southwestern endpoint of the Longmenshan fault zone, Sichuan-Yunnan region of China, and the topological structural properties of the network have been investigated based on data from 2011–2014. Herein, six observation sites were defined as nodes and their edges as the connections between them. We introduced Multi-channel Singular Spectrum Analysis (MSSA) to analyze periodic oscillations, earthquake-related strain, and noise in multi-site observations, and then defined the edges of the network by calculating the correlations between sites. The results of the daily degree centrality of the borehole strain network indicated that the strain network anomalies were correlatable with local seismicity associate with the earthquake energy in the strain network. Further investigation showed that strain network anomalies were more likely to appear before major earthquakes rather than after them, particularly within 30 days before an event. Anomaly acceleration rates were also found to be related to earthquake energy. This study has revealed the self-organizing pre-earthquake phenomena and verified the construction of borehole networks is a powerful tool for providing information on earthquake precursors and the dynamics of complex fault systems.

Highlights

Strain measurements play an essential role in analyzing geodynamic processes, such as those used to study slow earthquakes [1,2], volcanic activities [3], and preparation processes that occur prior to earthquakes [4,5,6,7]
We found that the weight of degree anomalies increased as the local earthquake energy increased for energy values greater than 105
In order to verify the existence of recognizable strain changes preceding major earthquakes, network analysis was conducted using borehole strain data from the southwestern endpoint of the Longmenshan fault zone, China, for the period 2011 to 2014

Summary

Introduction

Strain measurements play an essential role in analyzing geodynamic processes, such as those used to study slow earthquakes [1,2], volcanic activities [3], and preparation processes that occur prior to earthquakes [4,5,6,7]. In an effort to monitor the crustal activities associated with earthquakes, numerous geodetic monitoring systems have been established around the world, which provide an opportunity to investigate complex tectonic structures [8,9,10,11], short- and medium-term earthquake prediction [12,13,14], etc The development of such monitoring systems has facilitated intensive studies on crustal deformations associated with earthquake preparation, their occurrence, and post-earthquake phases [9,15,16,17,18], such as those from the 2011 Tohoku earthquake in Japan [19,20,21] and the 2008 Wenchuan earthquake in China [22,23].

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