- Ground-motion model is:
where A is in cm∕s2, a = -0.987, b = 0.7521, c = -0.00475, σ = 0.914 (without site correction) and σ =
0.716 (with site correction)
- Compute site corrections (absolute factors between 0.34 and 5.72) based on mean residuals w.r.t. each
station. Relate site terms to variations in soil conditions.
- Records from portable broadband network of 14 different stations (3 STS-2 and 11 Trillium 40 instruments)
operated by Institute of Geophysics (Vietnamese Academy of Science and Technology, Vietnam) and
Institute of Earth Sciences (Academia Sinica, Taiwan). Data from 01/2006 to 12/2009
- Focal depths between 0.5 and 28km.
- Only use good-quality records, records with repi < 500km and events recored by ≥ 3 stations.
- Check signal-to-noise ratios for the weakest records and find ratios > 1.5 for frequencies < 15Hz and hence
conclude that data are suitable.
- Try using quadratic M term and using rhypo rather than repi and find similar coefficients but higher σ,
which relate to poor focal depths or PGAs being associated with surface waves.
- Do not consider faulting mechanism because no estimates for selected events and major faults in Vietnam
- Compare predicted and observed (grouped by magnitude) PGAs w.r.t. repi for used data and independent
data (SSA-1 instruments) from period 04/1997 to 08/1999 (3.2 ≤ Mw ≤ 4.3) and 19/02/2001 to
05/03/2001 [Dien Bien, Mw5.3 and aftershocks (3 ≤ Mw ≤ 4.8) recorded at Dien Bien and Tuan Giao].
Find good match for both sets.