Abstract. A large earthquake of 8.0 magnitude occurred on 12 May 2008, 14:28 UTC, with the epicentre in Wenchuan. To investigate the pre-earthquake anomalous strain changes, negentropy is introduced to borehole strain data for three locations, approximated by skewness and kurtosis, revealing the non-Gaussianity of recorded fluctuations. We separate the negentropy anomalies from the background by Otsu's method and accumulate the anomaly frequency on different scales. The results show that the long-term cumulative frequency of negentropy anomalies follows a sigmoid behaviour, while the inflection point of the fitting curve is close to the occurrence of the earthquake. For the short-term analysis before the earthquake, there are two cumulative acceleration phases. To further verify the correlation with the earthquake, we compare our findings for different time periods and stations and rule out the possible influence of meteorological factors. We consider the negentropy analysis to exhibit potential for studying pre-earthquake anomalies.

中文翻译：

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汶川8.0级地震钻孔应变的负熵异常分析

摘要。2008 年 5 月 12 日 14:28 UTC，发生 8.0 级大地震，震中在汶川。为了研究震前异常应变变化，将负熵引入三个位置的钻孔应变数据中，通过偏度和峰度近似，揭示记录波动的非高斯性。我们通过 Otsu 的方法将负熵异常与背景分离，并在不同尺度上累积异常频率。结果表明，负熵异常的长期累积频率遵循S形曲线，拟合曲线的拐点接近地震发生的位置。对于震前的短期分析，有两个累积加速度阶段。为进一步验证与地震的相关性，我们比较了不同时间段和站点的发现，并排除了气象因素的可能影响。我们认为负熵分析具有研究震前异常的潜力。