| dc.description.abstract |
Statistical quantification of observed seismicity is
important for understanding earthquake dynamics and future risk in
any seismic-prone region. In this paper, we implement the idea of
nowcasting (Rundle et al. in Earth and Space Science 3:480–486,
2016) to examine the current uncertain state of earthquake hazard
assessment in the seismically active Bay of Bengal (BoB) and
adjacent regions. First, we utilize the concept of ‘‘natural time’’
(Varostos et al. in Physical Review E 71:032102, 2005), rather than
clock time, to develop a statistical distribution of inter-event counts
of ‘‘small’’ earthquakes occurring between ‘‘large’’ earthquakes.
Using relevant statistics of natural time, we then calculate the
earthquake potential score (EPS) as the cumulative number of
small earthquakes since the last large event in the selected region.
The EPS, which provides the nowcast value for a region, reveals
the current state of earthquake hazard in that region. Therefore, by
indirect means, the EPS provides us with a simple yet transparent
estimation of the current level of seismic progress through the
regional earthquake cycle of recurring events in a geographical
area. To illustrate the nowcasting approach in the study region, we
computed EPS values for the two most seismically exposed
megacities, Dhaka and Kolkata, considering events of M 4 within
a radius of 250 km around their respective city centers. We found
that the current EPS values corresponding to MC6 events in
Dhaka and Kolkata were approximately 0.72 and 0.40, respec-
tively. The practical applicability of these values is discussed in
conjunction with sensitivity analysis of the threshold magnitudes. |
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