- Ground-motion model is:
where Y is in g, a = -7.9527, b = 1.4043, c = 19.82, d = -0.0682 and σ = 0.8243.
- Use two site classes:
S = 0
- Rock/stiff. Relatively compact Jurassic formations. Believe that V s,30 > 760m∕s.
S = 1
- Soil. Alluvium or fragile Tertiary and Quaternary formations. Believe that 250 ≤ V s,30 < 760m∕s.
Classify using geological information.
- Fault ruptures mainly less than 40km depth.
- Use data from engineering seismoscopes (SRR) from 2001 Mw7.7 Bhuj earthquake and from strong-motion
(20) and broadband (8) instruments of its aftershocks (3.1 ≤ Mw ≤ 5.6), which correct for instrument
response. Earthquakes recorded at 3 to 15 stations.
- All data from aftershocks from repi < 80km and all data from mainshock from rjb ≤ 44km.
- Relocate earthquakes using local 1D velocity model. Report average error of 1km in epicenter and 1.5km
in focal depth.
- Estimate seismic moments (from which compute Mw) and other source parameters, assuming Brune
spectra, using spectral analysis of SH waves from transverse components. Report uncertainty of 0.05–0.1
- Report that faults well mapped so believe rjbs are quite reliable.
- Plot residuals w.r.t. rjb. Find greater scatter in residuals for 0 ≤ rjb ≤ 30km, which could be related
to amplification/noise in data from stations in Kachchh sedimentary basin. Note lower scatter for range
100 ≤ rjb ≤ 300km is unreliable due to lack of data.
- State equation less reliable for 100 ≤ rjb ≤ 300km due to lack of data.
- Plot observations and predictions for Mw3.5, 4.1, 4.5, 5.6 and 7.7 and find fair match. Note that insufficient
data to judge relation between Mw5.6 and 7.7. Find reasonable match to six records from 29 March 1999
Chamoli earthquake (Mw6.5) but poor match (predictions lower than observations) to single record from
10 December 1967 Koyna earthquake (Mw6.3).