- Ground-motion model is:
_{h}= 7.0; a_{1}= 0.44780, a_{2}= 0.24582, a_{3}= -0.14444, a_{4}= 0.49645, b_{1}= -1.17792, b_{2}= 0.04959, b_{3}= 0.00000, h = 4.52478, c_{1}= 0.68185, c_{2}= -0.10727, Δb_{3,Alborz}= 0.00000, Δb_{3,Zagros}= 0.00000, Δ_{3,Others}= 0.00000, τ = 0.20592 (inter-event), ϕ_{S2S}= 0.20338 (site-to-site), ϕ_{0}= 0.45542 and σ = 0.53961 (total) for horizontal PGA; and a_{1}= -0.32176, a_{2}= 0.00795, a_{3}= -0.14011, a_{4}= 0.32612, b_{1}= -1.60377, b_{2}= 0.12555, b_{3}= -0.00223, h = 4.90710, c_{1}= -0.01229, c_{2}= 0.00132, Δb_{3,Alborz}= 0.00000, Δb_{3,Zagros}= 0.00000, Δ_{3,Others}= 0.00000, τ = 0.21104 (inter-event), ϕ_{S2S}= 0.16597 (site-to-site), ϕ_{0}= 0.50317 and σ = 0.57032 (total) for vertical PGA. - Characterise sites using V
_{s,30}. Data from 321 different stations. Data has 155 ≤ V_{s,30}≤ 1564m∕s but only recommend use for 300 ≤ V_{s,30}≤ 1000m∕s. - Use data from Iranian Strong Motion Network from 1979 to 2013. Data from SMA-1 and SSA-2 instruments. Visually inspect data and remove poor-quality records. Baseline correct records. Remove instrument response. Individually bandpass filter zero-padded records using phaseless 8-pole filter using cut-off frequencies determined for when signal-to-noise ratio is < 3.
- Exclude data that:
- 1.
- Lack all 3 components;
- 2.
- Have a focal depth ≥ 35km;
- 3.
- Have a r
_{jb}≥ 250km; - 4.
- Do not have known V
_{s,30}(30% of original data have no V_{s,30});

- 46 earthquakes have only a single record. Note that this may mean τ and ϕ
_{S2S}are slightly underestimated. - Note that few data from r
_{jb}< 10km so model not well constrained for short distances. - Include terms to account for potential differences in anelastic attenuation between: Alborz (132 records), Zagros (262 records) and other (e.g. central and eastern Iran) regions (294 records).
- Use nonparametric plots of data against, e.g., r
_{jb}, Akaike and Bayesian information criteria and try various trial functional forms to choose final functional form. - Allow for oversaturation of ground motions for large magnitudes within functional form.
- Constrain b
_{3}to be zero or negative to avoid unrealistic distance scaling and because of trade-off between geometric and anelastic terms. - Do not account for nonlinear site effects because dataset is deficient in records with high M
_{w}, short r_{jb}and low V_{s,30}. - Originally try to model regionality in c
_{1}and c_{2}but effect is not significant. - Do not include fault mechanism in model because total σ reduced by 10% by removing this term and effect of inclusion of these terms is statistically insignificant.
- Regress to obtain source and path coefficients and then regress again to find site coefficients.
- Examine residuals (unbinned and binned: using 0.25M
_{w}, 100m∕s and 25km intervals, computing mean and 95% confidence intervals when ≥ 3 records). Find no trends.