Fractal characteristics of the seismic swarm succeeding the 2015 gorkha earthquake, Nepal
- Vol.53(4), Aug
- USA Springer 2023
- 789-804p.
This study discusses the regional distribution of the b-value, box counting fractal dimension (D0) and correlation fractal dimension (D2) of the 2017–2019 seismic swarm. The location of swarm was about 30 km north of the epicenter of 2015 Gorkha earthquakes in high topography of the Manaslu-Himalchuli range. The b-values are estimated from the maximum likelihood approach, while fractal dimensions are estimated from the generalized fractal dimension approach. The b-value estimated was 1.82 ± 0.02 for the swarm sequence, while its maximum value was 2.97 ± 0.14 and minimum value was 1.81 ± 0.07 for different temporal windows. D0 values range from 0.55 ± 0.02 to 1.68 ± 0.08 for different temporal windows and correlation fractal dimension ranges from 0.27 ± 0.07 to 0.78 ± 0.02 for the same windows. Positive correlation between fractal dimensions D0 and D2 and a negative correlation between fractal dimensions and b-value were observed from the study. The seismic moment released during the 2017–2019 swarm was around Nm. The large b-value (1.82) obtained for the whole sequence signifies the typical characteristic of swarm earthquakes. The variation in b and fractal dimensions can be related to the highly heterogeneous environment caused by the thermal cracking of the weak zone. Furthermore, reduced value of effective stress might have caused the failure of isolated and small asperities and consequently the earthquakes occurred in clusters. The occurrence of swarms may be associated with the formation of new fractures in the region.