In the present work we investigated changes in the extent of regularity (randomness) of seismic process in fixed time span windows. A comparison with a set of randomized catalogues was accomplished basing on spatial, temporal and energetic characteristics of a seismic process. Increments of cumulative times, increments of cumulative distances and increments of cumulative seismic energies have been calculated from the southern California earthquake catalogue, 1980 to 2020.

The multivariate Mahalanobis' distance calculation, combined with the surrogate data testing procedure, was chosen as the analysis method. An analysis of variability in the extent of regularity of a seismic process has been accomplished for different completeness magnitude thresholds and sliding windows of different time spans.

Analysing the features of temporal, spatial and energetic variability, in periods of supposedly aftershock activity, we found that the original seismic process is significantly different from a random process. Such periods, containing windows with nonrandom seismicity, are always ended by a series of windows in which a seismic process is indistinguishable from a random one. This was shown at different magnitude thresholds, comparing the original catalogue with the set of randomized catalogues.

It was also found that at small magnitude thresholds (M2.6 and M3.0), the fixed time span windows with a seismic process significantly different from the random process might have occurred also prior to four large (M > 7.0) earthquakes in the considered catalogue. The amount of the released seismic energy in these windows is essentially smaller than in the ones after strong earthquakes of smaller magnitudes. Relying on our results we suggest that causes of regularity in the seismic process prior and after large earthquakes are probably different.

At larger-magnitude thresholds, the total number of fixed time windows with a seismic process different from the random one gradually decreases. Moreover, at M3.8 and M4.2 thresholds there are practically no windows with regular seismic process prior to four large catalogue earthquakes. In the periods between strong earthquakes, mostly in the periods of relatively small earthquakes generation, the percentage of windows in which the seismic process is indistinguishable from the random one essentially increases with increasing magnitude threshold.

在目前的工作中，我们研究了固定时间跨度窗口中地震过程的规律性（随机性）程度的变化。根据地震过程的空间、时间和能量特征，完成了与一组随机目录的比较。累积时间的增量、累积距离的增量和累积地震能量的增量已从 1980 年至 2020 年的南加州地震目录中计算出来。

选择多元马氏距离计算，结合代理数据检验程序作为分析方法。已经完成了对不同时间跨度的不同完整性幅度阈值和滑动窗口的地震过程规律性程度的可变性的分析。

通过分析时间、空间和能量变化的特征，在所谓的余震活动期间，我们发现原始地震过程与随机过程有显着差异。这些包含非随机地震活动窗口的周期总是以一系列窗口结束，在这些窗口中，地震过程与随机过程无法区分。这是在不同的幅度阈值下显示的，将原始目录与随机目录集进行比较。

还发现，在较小的震级阈值（M2.6 和 M3.0）下，地震过程与随机过程显着不同的固定时间跨度窗口也可能发生在 4 次大（M > 7.0）地震之前。考虑目录。这些窗口释放的地震能量基本上小于较小震级强震后的地震能量。根据我们的结果，我们认为大地震前后地震过程规律性的原因可能不同。

在较大的阈值处，具有不同于随机过程的地震过程的固定时间窗的总数逐渐减少。此外，在 M3.8 和 M4.2 阈值处，在四次大目录地震之前，实际上没有具有规则地震过程的窗口。在两次强震之间，主要是在相对较小地震发生的时期，随着震级阈值的增加，地震过程与随机过程无法区分的窗口的百分比本质上增加。