Earthquake engineering and real-time early warning: the AMRA perspective.

1
Earthquake engineering and real-time early
warning the AMRA perspective.
Iunio Iervolino and Gaetano Manfredi Assistant
Professor of Structural Engineering Department of
Structural Engineering, University of Naples
Federico II, Italy.
SAFER Project Final Meeting Potsdam 3-5 June
2009
2
Regional Earthquake Early Warning Systems and the
ISNet Irpinia Seismic Network (Italy)
Commonly used to give distributed estimates of
the ground motion right after the event
SHAKEMAPS.
3
Site-Specific Warning by Regional Networks
Hybrid EEWS
Seismic network
BECAUSE OF REAL-TIME SEISMOLOGY!
4
RTS Rapid estimation of event magnitude
MT
Seismologists (i.e. Allen Kanamori, 2003) claim
it is possible to estimate the magnitude from the
predominant period (?) of the first 4 sec of the
P-wave velocity recording
5
RTS Rapid estimation of event location
Epicenter
Triggered Stations
Other seismologists (i.e. Zollo et al., 2007)
claim it is possible to locate the hypocenter
with negligible uncertainty within 4 sec from the
event origin time
6
Real-Time Probabilistic Hazard Analysis (RTPSHA)
for Hybrid EEWS
Iervolino et al., 2006. Convertito et al., 2008.
7
Magnitudes distribution
Iervolino et al., 2007.
The mean of the tau network measurements is all
we need to estimate the magnitude!
8
M6 R110km Event Simulation
9
Simulazione Hazard M6 R110km
10
Real-Time Probabilistic Seismic Hazard Analysis
(RTPSHA) - Summary
11
Is the Bayesian estimator appropriate also if it
tends to underestimate the magnitude?
Iervolino et al., 2009.
12
False and Missed Alarm Probabilities
Iervolino et al., 2006.
13
When to activate security measures? Decisional
Rules
14
Time-Dependent Uncertainty in Early Warning
Iervolino et al., 2009.
15
Which uncertainty really matters in prediction of
engineering ground motion parameters?
Iervolino et al., 2009.
16
Design Targets
Lead Time
Low Perception Impact (e.g. Elevator)
Medium Perception Impact (e.g.Trasportation
Interruption
High Perception Impact (e.g. Lifelines
Interruption )
False Alarm Probability
Performances/ Consequences
17
Engineering Requirements of EEWS

• Quantitative real-time assessment of seismic risk
  (losses for specific application)
• Time dependent decision making (quantification of
  trade-off between lead-time and costs of
  missed/false alarms)
• Automated decision for structural control system

Consequence-based approach
18
Lead-time maps for the case-study region can be
superimposed to real-time risk reduction actions
for specific structural systems. These security
measures can be classified according to the time
required to be carried out.
19
Application of RTPSHA on our school of engineering
20
Developed with the group of Aldo Zollo Operating
since July 25 2008 http//143.225.72.2095800/ -
ID utente PW ergo
Event Detection
Real-Time estimation of Magnitude and Location
Structure Specific Alert
Regional alert Map
21
Event detected on 19/11/2008 8.17 PM
22
A school classrom equipped with an EEWS terminal
how to set the alarm threshold

• Lets consider a simple school class equipped
  with a ringer and suppose that the students are
  trained to shelter under the desks when the alarm
  is issued.

23
What causes loss?

• Structural collapse (DS)
• No structural damage, but collapse of lighting
  (NDS)
• No structural damage, no lighting damage (loss
  due to false alarm)

Total expectaion theorem The total expected loss
is the summation of the expected losses
corresonding to these three cases!
24
Real-Time loss assessment

• Extending the hazard approach it is possible to
  determine the expected losses condiotioned to the
  measurements of the seismic network in the case
  of alarming or not

Expected Loss
Iervolino et al., 2009.
25
1. Loss functions
No sheltering
Sheltering of students under desks
No alarm loss
26
Expected loss as a function of the seismic
instruments measures
No alarm
Alarm
Iervolino et al., 2009.
27
Early Warning and Structural Control

• Passive Control
• to modify, the stiffnes and/or the damping so as
  to achieve a better structural response
• Semi-Active Control
• to modify just-in-time the dynamic
  characteristics of
• the structure as to achieve the optimal
  response
• Active Control
• based on the availability of large force
  actuators able to
• counterbalance inertial forces due to seismic
  excitation.

28
A structure equipped with a semi-active control
device activable by the EEWS feasibility.
This model may be used to study other systems
29
Variable-Orifice Viscous Dampers
? PASSIVE DEVICE
30
Real-Time performance analysis
Expected Structural performance
Iervolino et al., 2009b.
31
Benefit of The EEWS in terms of reduction of
Drift Response
Iervolino et al., 2009b.
32
Benefit of The EEWS in terms of reduction of Peak
Floor Acceleration
Iervolino et al., 2009b.
33
Response improvement in respect to the structure
without the EEWS
34
Design and Feasibility issues for the engineering
use of EEWS for structural control

• Maximization of the lead time is not the only
  design target, in some case it is not even the
  principal design objective
• The uncertainties related to the real-time
  estimations of earthquake features have to be
  integrated with the models of seismic response of
  facilities to protect
• False and missed alarm probabilities have to be
  optimized
• The alarm thresholds have to be set on the basis
  of expected losses

35
References http//www.saferprojct.net/publication
s

• Iervolino I., Giorgio M., Galasso C., Manfredi G.
  (2009) Uncertainty in early warning predictions
  of engineering ground motion parameters what
  really matters? Geophysical Research Letters,
  DOI10.1029/2008GL036644, in press.
• Convertito V., Iervolino I., Giorgio M., Manfredi
  G., Zollo A. (2008). Prediction of response
  spectra via real-time earthquake measurements.
  Soil Dyn Earthquake Eng, 28 492505.
• Iervolino I., Convertito V., Giorgio M., Manfredi
  G., Zollo A. (2006). Real-time risk analysis for
  hybrid earthquake early warning systems. Journal
  of earthquake Engineering, 10 867885.
• Iervolino I., Giorgio M., Manfredi G. (2007).
  Expected loss-based alarm threshold set for
  earthquake early warning systems. Earthquake Engn
  Struct Dyn, 36 11511168.

36
Early Warning Special Issue

• Tentative Title Prospects and applications of
  earthquake early warning, real-time risk
  management, rapid response and loss mitigation
• Topics Risk analysis, system performance
  evaluation and feasibility studies, design of
  earthquake engineering applications of EEW, civil
  protection via EEW
• SDEE Editor in chief Mustafa Erdik Guest
  editors Iunio Iervolino and Aldo Zollo
• Expected publication date Jan 2010.