Civil Insight: A Technical Magazine Volume 3 | Page 55
Shrestha P. et al.
Civil Insight (2019) 51-56
Fig. 4. Earthquake epicenter data around Nepal (declustered data)
3.2) Seismicity parameters
The earthquake catalog was further divided into two parts for the study: the first part consisted of data from
1800 to 1963 AD, and the second part consisted of data from 1964 to 2017 AD (Thapa & Wang, 2013).
Source zones will produce earthquakes of different sizes – earthquake events up to the maximum
earthquake, with smaller earthquakes occurring more frequently than that of the larger size events. The
magnitude of completeness was obtained. Using Eqn (8) and Eqn (9), the ߚ-value and the activity rate ߣ
are determined. From the value ofߣ, the -value can be calculated using Gutenberg-Richter recurrence
relationship Eqn (7), for a minimum magnitude value. The various seismicity parameters obtained for the
sources are shown in Table 2.
Table 2. Seismic parameters of all seismic zones
Source Model
1
SM
SZ1
SZ2
SZ3
SZ4
SZ5
SZ6
2
SZ7
SZ8
SZ9
SZ10
SZ11
SZ12
ࢼ
1.92
1.92
1.92
1.92
1.92
1.92
1.92
1.92
1.92
1.92
1.92
1.92
1.92
ࣅ
1.40
2.41
2.89
2.41
2.29
1.27
0.87
2.41
1.55
1.49
2.11
2.59
1.22
0.83
0.83
0.83
0.83
0.83
0.83
0.83
0.83
0.83
0.83
0.83
0.83
0.83
3.48
3.72
3.80
3.72
3.69
3.44
3.27
3.72
3.53
3.51
3.66
3.75
3.42
8.1
5.2
6.3
7.0
5.1
5.9
7.8
5.5
6.8
8.1
5.6
6.0
5.7
4) Conclusions
The dam site of Upper Seti Hydropower Project was selected and all the available data on past earthquake
events from 1255 to 2018 AD around Nepal were collected from various sources. For consistency, the
earthquakes including main events and aftershock events were converted into a moment magnitude. The
aftershocks were then decluttered using MATLAB (MATLAB, 2015) and referring to Gardner and Knopoff
(1974) window algorithm. A basic assumption of seismic hazard analysis is that the recurrence law obtained
from past seismicity is appropriate for the prediction of future seismicity. Thus, using Gutenberg-Richter
recurrence law (1944), the seismicity parameters, and , were obtained. From this research, for Upper
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