- Ground-motion model is for repi:
where y is in g, a = -2.487, b = 0.534, c = -1.280, h = 3.94, e1 = 0, e2 = 0.365, e3 = 0.065, e4 = 0.053,
σevent = 0.117 and σrecord = 0.241 (or alternatively σstation = 0.145 and σrecord = 0.232). For rhypo:
where y is in g, a = -2.500, b = 0.544, c = -1.284 and σ = 0.292 (do not report site coefficients for rhypo).
- Use four site classes:
- Lacustrine and alluvial deposits with thickness > 30m (180 ≤ V s,30 < 360m∕s). Sites in largest
lacustrine plains in Umbria region. S4 = 1 and others are zero.
- Lacustrine and alluvial deposits with thickness 10–30m (180 ≤ V s,30 < 360m∕s). Sites in narrow
alluvial plains or shallow basins. S3 = 1 and others are zero.
- Shallow debris or colluvial deposits (3–10m) overlaying rock (surface layer with V s < 360m∕s). Sites
located on shallow colluvial covers or slope debris (maximum depth 10m) on gentle slopes. S2 = 1
and others are zero.
- Rock (V s,30 > 800m∕s). Sites on outcropping rock, or related morphologic features, such as rock
crests and cliffs. S1 = 1 and others are zero.
Base classifications on recently collected detailed site information from site investigations, census data,
topographic maps, data from previous reports on depth of bedrock, and data from public and private
companies. Subscripts correspond to classification in Eurocode 8.
- Focal depths between 1.1 and 8.7km except for one earthquake with depth 47.7km.
- Nearly all earthquakes have normal mechanism, with a few strike-slip earthquakes.
- Select earthquakes with ML ≥ 4.0 and d < 100km.
- Use ML since available for all events.
- Fault geometries only available for three events so use repi and rhypo rather than rjb. Note that except for
a few records differences between repi and rjb are small.
- Correct for baseline and instrument response and filter analogue records to remove high- and low-frequency
noise by visually selecting a suitable frequency interval: average range was 0.5–25Hz. Filter digital records
with bandpass of, on average, 0.3–40Hz.
- For ML < 5 no records from de > 50km.
- Use maximum-likelihood regression with event and record σs and also one with station and record σs.
Perform each regression twice: once including site coefficients and once without to investigate reduction in
σs when site information is included.
- Investigate difference in residuals for different stations when site coefficients are included or not. Find
significant reductions in residuals for some sites, particularly for class CE.
- Note that some stations seem to display site-specific amplifications different than the general trend of sites
within one site class. For these sites the residuals increase when site coefficients are introduced.
- Find large negative residuals for records from the deep earthquake.
- Find similar residuals for the four earthquakes not from the 1997–1998 Umbria-Marche sequence.