  Seismic wave amplification due to localized site conditions is an important
aspect of regional seismic hazard assessment. Without systematic studies of
frequency-dependent site-effects during strong Icelandic earthquakes, various
local site proxies of large-scale studies in other seismic regions have been
used in Iceland. Recently, earthquake site-effects were rigorously quantified
for 34 stations in Southwest Iceland for the first time and correlated to
distinct Icelandic geological units of hard rock, rock, lava rock, and
sedimentary soil. These units are prevalent throughout Iceland and herein we
present 1) nationwide maps of proxies (slope, Vs30, geological units) that may
contribute to a better estimation of site effects and associated, 2)
frequency-dependent site-amplification maps of Iceland. The frequency-dependent
site factors for each geological unit are presented at 1-30 Hz and PGA.
Finally, we generate site amplification maps based on recent large-scale models
developed in other seismic regions (ESRM20) and various site proxies they are
based on (geology- and slope-based inferred Vs30, geomorphological sedimentary
thickness). We compare site-proxy maps and amplification maps from both
Icelandic and large-scale, non-Icelandic, models. Neither spatial patterns nor
amplification levels in either proxy or amplification maps from large-scale
non-Icelandic studies resemble those observed from local quantitative
strong-motion research as presented in this study. We attribute the discrepancy
primarily to the young geology of Iceland and its formation history.
Additionally, we compare model performance across frequencies by assessing the
bias of model predictions against empirical site amplifications in the South
Iceland Seismic Zone, accounting for site-to-site variability of residuals
indicating the superior performance of the local amplification model.
