Fractal Dimension of the 1999 Chamoli Earthquake from Aftershock Studies in Garhwal Himalaya

The Aftershock sequence of Chamoli earthquake (Mw 6.4) of 29 March 1999 is analyzed to study the fractal structure in space, time and magnitude distribution. The b value is found to be 0.63 less than which is usually observed worldwide and in the Himalayas. This indicates that the numbers of smaller earthquakes are relatively less than the larger ones. The spatial correlation is 1.64, indicating that events are approaching a two-dimensional region meaning that the aftershocks are uniformly distributed along the trend of the aftershock zone. Temporal correlation is 0.86 for aftershocks of M ‡ 1, indicating a nearly continuous aftershock activity. However, it is 0.5 for aftershocks of M ‡ 1.75, indicating a non continuous aftershock activity. From the assessment of slip on different faults it is inferred that 70% displacement is accommodated on the primary fault and the remainder on secondary faults