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Nepal Hazard Risk Assessment
Figure 1.5. Precipitation index Tp1 for Nepal.
The precipitation trigger index, Tp, was obtained by the equation below:
Tp = Tp1 Ta (3)
The variation range for Tp is therefore 0.8 – 6.0.
1.2.6 SEISMIC TRIGGER FACTOR T S
The data set used for the classification of the seismic trigger factor was the expected peak ground
acceleration (PGA) with 475 to 500 years return period (10% probability of exceedance in 50 years).
The PGA map was developed on the basis of the site-specific data provided by Department of Mines and
Geology (DMG) in Nepal (Pandey et al., 2002) and an earlier study by NGI (2004).
The peak ground acceleration (PGA) with 500-year return period was used as the representative
triggering parameter for seismically-induced landslides in the present study,.
Figure 1.6. Seismic trigger factor Ts for Nepal.
The seismic trigger index, Ts, was evaluated from the PGA500 data according to the table below.
Table 1.8. The seismic trigger index, Ts
PGA500 (m/s 2 ) Ts
0.00 – 0.50 0.1
0.51 – 1.00 0.4
1.01 – 1.50 0.8
1.51 – 2.00 1.5
2.01 – 2.50 2.5
2.51 – 3.00 3.5
3.01 – 3.50 5
3.51 – 4.00 6
4.01 – 4.50 7.5
Greater than 4.50 10
97