where y is in cm∕s2, c1= 9.6231, c2= 1.4232, c3= -0.1555, c4= -1.1316, c5= -0.0114, c6= -0.0024,
c7= -0.0007, c8= -0.0835, c9= 0.1589, c10= 0.0488, τ = 0.406 (inter-event), σ = 0.568 (intra-event)
and σT= 0.698 (total).
Use 3 site classes (2 are based on Eurocode 8):
360 < Vs,30≤ 800m∕s. Includes a few class A (Vs,30> 800m∕s) sites, which are included here because
of scarcity of data. Sb= 1 and Sc= Ss= 0.
180 < Vs,30≤ 360m∕s. Sc= 1 and Sb= Ss= 0.
Sites that could not be assigned into B or C. Generally stations in Mexico, India and Martinique.
Ss= 1 and Sb= Sc= 0. B, C and soil sites are grouped within regression to find c10.
Classify records into 2 classes on location w.r.t. arc:
For Romania this is based on location w.r.t. Carpathian Mountains.
Focal depths, h, between 87 and 151km for Vrancea events and 60 and 173km for others.
Investigate the impact of the fore-arc and back-arc regions on ground motions, in particular w.r.t. the
Vrancea intermediate-depth source. Aim to improve model of Vacareanu et al. (2014) (see Section 2.385).
Use data from NIEP, INCERC, CNRRS and GEOTEC analogue and digital networks. Use some
already-processed records so processing procedures are not uniform. Filter raw analogue records using
Ormsby bandpass filter with cut-offs 0.15–0.25 and 25–28Hz. Filter raw digital records using 4th-order
Butterworth bandpass with cut-offs 0.05 and 50Hz.
Include data from foreign intermediate-depth in-slab earthquakes in Japan (fore-arc data with repi≤ 80km
to limit number of records), New Zealand, Mexico, Chile, India, Martinique (France) and Peru to fill in
gap in magnitude-depth-distance distribution.
Fore-arc data from 8 countries. Back-arc data from only Romania and Japan.
Limited Romanian data for repi≤ 80km and larger number for 100 ≤ repi≤ 200km.
Try fixing c4 to -1 but find that this is not valid at all periods.
Find average misfits (offset) (using total residuals) for entire set is around 5%, with peaks of 10%, and for
Vrancea records only it is around 10%, with peaks of 18%.
Derive model without site terms but based on analysis of variance and the F test on intra-event residuals
w.r.t. site classes find that site effects are significant at the 5% level for all periods except 0.1s.
Examine inter- and intra-event residuals and the average misfits. Find that ground motions from Vrancea
and foreign events are similar and justifies inclusion of foreign data.
Find that by examining inter-event residuals w.r.t. Mw that obtained magnitude scaling is appropriate
and that there is no difference between Vrancea and foreign data.
Examine inter-event residuals w.r.t. number of records per event. Find weak correlations (correlation
coefficient in range 0.1 to 0.2) and hence conclude that no undue influence from well-recorded events.
Examine intra-event residuals classified by site category w.r.t. repi. Find no trends in residuals and hence
conclude that distance scaling is appropriate, at least for B, C and average soil classes (there are insufficient
records from Eurocode 8 A and D classes to conclude).
Examine intra-event residuals grouped into back-arc and fore-arc classes w.r.t. repi. Find no clear trends.
Compare observed (corrected to soil class) and predicted motions for the Mw6 27/10/2004 Vrancea
earthquake. Find good match for both fore-arc and back-arc.
Do not advise using model for soil classes A or D because of lack of data from these categories and hence
model is not calibrated for these classes.