[S12-P] Poster

[S12-P-01] Characterizing the nature of spatial heterogeneities based on multi-fractal and seismic b-value analysis of the 2015 Nepal earthquake sequence

^○Vijay Prasad Dimri, Nampally Subhadra, Simanchal Padhy (CSIR-National Geophysical Research Institute, Hyderabad)

The multi-scaling nature of the spatial heterogeneities of the medium in the source region of the 2015 Nepal earthquake is investigated based on the multi-fractal and seismic b-value analyses of the aftershock sequence of the 2015 earthquake. The aftershock sequence exhibits an apparent multi-fractal structure, characterized by a spectrum of generalized dimension Dq varying from D2 = 1.61 to D22 = 0.1. We estimated the bias in Dq that may arise due to finite numbers of data points and limited size of study volume by comparing the true estimates with those obtained with uniform random distribution of point sets using the same numbers of events as for the real data. In addition, samples from the real data are randomly extracted and dimension spectra for these are examined as well. We also discussed the possibility of the apparent multi-fractality that may arise in case of finite data sets. Our results show that the spectrum for the uniform random generation is weakly multi-fractal by comparing the results from real data and simulated points sets that may help distinguish between true and apparent multifractality,that is expected for a data set with finite number of samples. Next, temporal correlation between the correlation dimension D2 and energy released shows a significant drop in D2 before the major events in the sequence, which tries to come back to the background value. The multi-fractal structure of Dq and their temporal variation suggest that the spatial distribution of aftershocks is not a random phenomenon, but it self-organizes on a spatio-temporal scale into a critical state, exhibiting a scale-independent structure governed by a power-law scaling. We also studied the frequency-size distribution of the sequence, characterized by the Gutenberg-Richter law with an average seismic b-value of 1.11±0.08. Our results are useful for seismic hazard assessment in the near field due to the subduction zone earthquake in the region.