Civil Engineering Reference
In-Depth Information
inelastic analyses for given structure types. The differences could be larger
in case of the ultimate displacement
S
du
, which is more diffi cult to estimate
(given the structural model-specifi c assumptions involved) during inelastic
analysis. Nonetheless, signifi cant progress has been made in compiling the
requisite data for non-US building types to be used within the operational
PAGER system.
31.5
Earthquake impact scale
For all signifi cant earthquakes around the world, the NEIC locates, assesses
and disseminates earthquake information through a variety of means. Its
user-subscribed Earthquake Notifi cations Service (ENS; Wald
et al.
, 2008b)
presents fundamental improvements for USGS earthquake alerting in that
users can customize their alerting levels based on magnitude, hypocenter,
and time of day, and they can receive messages on multiple devices or
electronic addresses (each with, potentially, different triggering criteria) in
near-real time. ENS alerts are sent to over 345 000 subscribed users includ-
ing critical responders, non-governmental organizations (NGOs), govern-
ments, the media, as well as individuals (see Wald
et al.
, 2008b).
Despite the benefi t of ENS over earlier list-servers, the alerting criteria
are currently limited to magnitude- and location-based triggers. While expe-
rienced users can take advantage of earthquake magnitude, depth, and
location to make informed decisions, most users do not have suffi cient
expertise to tie these parameters to population exposure and region-specifi c
vulnerability in order to confi dently assess the potential impact. In addition,
users must either set a low magnitude trigger level not to miss signifi cant
events (and potentially get many more alerts than desired), or risk missing
an important event by setting a higher threshold.
PAGER employs a new earthquake impact scale (EIS) that is based on
two complementary criteria. The fi rst criterion is the estimated cost of
damage; this is most suitable for domestic events and those in earthquake-
resistant communities. The second criterion, representing the estimated
ranges of fatalities, is generally more appropriate for global events, particu-
larly in developing countries. Simple thresholds, derived from the system-
atic analysis of past earthquake impacts and associated response levels,
turn out to be quite effective in communicating predicted impact and
response needed after an event, characterized by alerts of green (little or
no impact), yellow (regional impact and response), orange (national-scale
impact and response), and red (international response). Corresponding
fatality thresholds for yellow, orange, and red alert levels are 1, 100, and
1000, respectively. For damage impact, yellow, orange, and red thresholds
are triggered by estimated losses reaching $1 M, $100 M, and $1 B,
respectively.
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