- Ground-motion model is:
- Response parameter is acceleration for 5% damping.
- Use two site classes:
S = 1
- Rock. 69 records.
S = 0
- Soil. 132 records.
- Focal depths between 5 and 33km for Iranian events and 19 and 50km for Indian earthquakes.
- Use two fault mechanisms:
H = 0
- Reverse. 8 earthquakes and 123 records.
H = 1
- Strike-slip. 8 earthquakes and 78 records.
- Seek to develop model for Indian Himalayas. Due to lack of near-source data from India include data
from the Zagros region of Iran, which has comparable seismotectonics (continental compression). Note that
some differences, in particular the higher dip angles of reverse events in the Zagros compared to those in
- Use data from three strong-motion arrays in Indian Himalayas: Kangra array in Himachal Pradesh, Uttar
Pradesh and Shillong array in Meghalaya and Assam, and from Iran Strong-Motion Network. Note that
records from at least three significant Himalayan earthquakes have not yet been digitized.
- Use some non-Zagros data from Iran because of similar focal mechanisms and since no significant difference
in ground motions between these events are those in the Zagros was observed.
- Note that data seems to be adequate between Mw5 and 7 and up to 100km.
- To exclude data from earthquakes that show anomalous behaviour, the PGAs for each earthquake
individually were plotted against distance. Find that decay rates for 6/2/1988 and 14/3/1998 earthquakes
were different than rest so data from these events were excluded.
- Also exclude data from two earthquakes (6/8/1988, 10/1/1990 and 6/5/1995) due to their great hypocentral
depths (> 90km).
- Also exclude data from eight earthquakes (9/1/1990, 24/3/1995, 14/12/2005, 29/11/2006, 10/12/2006,
9/6/2007, 18/10/2007 and 25/11/2007) because no focal mechanisms published.
- Prefer rjb partly because of lack of reliable depths for most Himalayan earthquakes.
- Estimate rjb for some earthquakes by using reported focal mechanism and relationships of Wells and
- Use explicit weighting method of Campbell (1981) with equal weights given to records falling into three
ranges: ≤ 10km, 10–100km and more than 100km.
- Note that high standard deviations partly due to low quality of site information, large uncertainties in
source-to-site distances and simple functional form.