Characterizing spatial heterogeneity based on the b-value and fractal analyses of the 2015 Nepal earthquake sequence

The multi-fractal nature of spatial distribution of heterogeneities of the 2015 Nepal earthquake is investigated. While explaining the multi-fractal spectrum (D2 = 1.66 to D22 = 0.11) of the aftershocks, more attention is paid on testing the reliability of the results for any data set with finite number of points by carrying out the fractal analysis of both the real data and their surrogates through simulations. The similarity in their spectra suggests the lack of long-range correlation, with an only weakly multi-fractal (D2 to D22) or a mono-fractal (only D2) nature of data. Within the error limit, we tested for a possible correlation between changes in D2 and energy released during the earthquakes. The values of D2 rise during the two largest earthquakes (M > 7.0) in the sequence (Figure 1). Our results provide useful constraints on the spatial distribution of fractal dimension, especially for finite earthquake catalogs, which should be interpreted with care (Subhadra et al., 2018).

Figure 1. Correlation between energy released (gray shaded area) and correlation dimension D₂ (black dashed line). The errors (1-σ) in D₂ are shown. Note the change (rise) in D₂ during the two major energy peaks, corresponding to the earthquakes  of magnitude 7.8 and 7.3 in the sequence, as shown by arrows.

Citation:

Nampally, Subhadra; Padhy, Simanchal; Dimri, Vijay P (2018), Characterizing spatial heterogeneity based on the b-value and fractal analyses of the 2015 Nepal earthquake sequence, TECTONOPHYSICS, 722, 154-162. DOI: 10.1016/j.tecto.2017.11.004