Abstract
ABSTRACTThis work concentrates on the distribution of earthquake interevent times in northwest Himalaya and its adjacent regions. We consider 12 time-dependent probability distributions for analysis. The maximum likelihood estimation and Fisher information matrix-based methods are used to estimate model parameters and their respective uncertainties. Results from three model selection criteria suggest that the best fit arises from exponentiated Weibull, exponentiated exponential, Weibull and gamma distributions. An intermediate fit comes from exponentiated Rayleigh, and lognormal distributions, whereas the remaining distributions exhibit a poor fit to the seismic interoccurrence times of present catalogue. Using exponentiated Weibull model, it is observed that the estimated cumulative probability of magnitude 6.0 or higher event in the northwest Himalaya reaches 0.92–0.95 after about 20–23 (2019–2022) years since the last event in 1999. The conditional probability, for an elapsed time of 19 years (i.e. 2018), reaches 0.90–0.95 after about 20–25 (2038–2043) years from now. A series of conditional probability curves is also presented to understand the recent and future earthquake hazard in the study region. This temporal evolution of seismic interevent times may provide important clues to the underlying physical mechanism of earthquake genesis in the northwest Himalaya region.
Highlights
Occurrence of earthquakes has been known to be a natural phenomenon in the northwest Himalaya and its adjoining regions since colonial times
This work concentrates on the distribution of earthquake interevent times in northwest Himalaya and its adjacent regions
In view of the above discussion, the present study considers 12 probability models from timedependent and heavy-tailed distributions to provide a comprehensive statistical analysis of earthquake interoccurrence times in the northwest Himalaya
Summary
Occurrence of earthquakes has been known to be a natural phenomenon in the northwest Himalaya and its adjoining regions since colonial times. Historical record of these earthquakes started with the settlement of people and their gradual involvement in understanding the process. Interactions among different spatial network of fault systems and temporal processes govern this nonlinear threshold dynamics. Despite this complex behaviour, one may consider earthquakes as a simple point process in time and space, by ignoring its temporal effect due to event duration and spatial effect due to GEOMATICS, NATURAL HAZARDS AND RISK rupture zones. Apart from an immediate empirical earthquake hazard estimation of the study area, the best-fit statistical models may provide important insights to the long-term earthquake generation process involving loading and stressing condition of the fault system, deep fault creeping, post-seismic relaxation of fault-zone material properties, and earthquake interactions between low-frequency (slow-slip) and regular events (Hainzl et al 2006; Shelly et al 2007; Wu et al 2013)
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