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

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

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**Earthquake engineering and real-time early warning: the AMRA**perspective. Iunio Iervolino* and Gaetano Manfredi *Assistant Professor ofStructuralEngineering Department of Structural Engineering, University of Naples Federico II, Italy. SAFER Project Final Meeting – Potsdam 3-5 June 2009**RegionalEarthquake Early Warning Systems and the**ISNetIrpinia Seismic Network (Italy) Commonly used to give distributed estimates of the ground motion right after the event: SHAKEMAPS.**Structural/non-structural performance/loss**EDP (i.e. Maximum Interstory Drift Ratio) Source-to-site distance IM (i.e. PGA) Ground motion at the site Site-SpecificWarningbyRegionalNetworks: Hybrid EEWS Seismic network Epicenter Signal at the network stations BECAUSE OF REAL-TIME SEISMOLOGY!**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**RTS: Rapid estimationof 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**PDF of distance due to rapid localization method**Ordinary Attenuation relationship Negligible uncertainty Distribution of PGA at the site conditional on the measures of the seismic instruments PDF of magnitude conditional on the measures of the seismic instruments Real-Time ProbabilisticHazardAnalysis (RTPSHA) forHybrid EEWS Iervolino et al., 2006. Convertito et al., 2008.**Gutenberg-Richter**Measurements t[s] Magnitude Magnitude Magnitude’s distribution Iervolino et al., 2007. The mean of the tau network measurements is all we need to estimate the magnitude!**t = 6s**t = 9s t = 11s t = 5s t = 12s 23 stations 28 stations 30 stations 8 stations 2 stations M=6 R=110km Event Simulation**Simulazione Hazard M=6; R=110km**4 stazioni 27 stazioni 25 stazioni 11 stazioni 1 stazione**Real-Time ProbabilisticSeismicHazardAnalysis (RTPSHA) -**Summary Estimation of Magnitude Naples Estimation of PGA at the site Estimation of Distance**Is the Bayesianestimator appropriate**alsoifittendstounderestimate the magnitude? Iervolino et al., 2009.**False and Missed Alarm Probabilities**Iervolino et al., 2006.**When to activate security measures? Decisional Rules**ALARM ! Because the probability that PGA exceeds the limit value is too high Pc PGAc**Time-Dependent Uncertainty in Early Warning**Estimation of PGA at the site Iervolino et al., 2009.**Which uncertainty really matters in prediction of**engineering ground motion parameters? Estimation of PGA at the site Iervolino et al., 2009.**Design Targets**Lead Time Low Perception Impact(e.g. Elevator) Medium Perception Impact (e.g.TrasportationInterruption High Perception Impact (e.g. LifelinesInterruption ) False Alarm Probability Performances/ Consequences**EngineeringRequirementsof 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**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.**Developed with the group of Aldo Zollo**Operating since July 25 2008 http://143.225.72.209:5800/ - ID: “utente” PW: “ergo” Event Detection Real-Time estimation of Magnitude and Location Structure Specific Alert Regional alert Map**Let’s consider a simpleschoolclassequippedwith a ringer**and suppose that the students are trainedtoshelter under the deskswhen the alarmisissued. A schoolclassromequippedwithan EEWS terminal: howto set the alarmthreshold**Whatcauses loss?**• Structuralcollapse (DS) • No structuraldamage, butcollapseoflighting (NDS) • No structuraldamage, no lightingdamage (loss due to false alarm) Total expectaion theorem: The total expected loss is the summation of the expected losses corresonding to these three cases!**1. Loss probability depending on the alarming decision**2. Structural damage probability depending on building’s seismic response 3. Seismic response probability depending on hazard 4. Real-time hazard analysis 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.**Alarm loss (reduced because of security action)**1. Lossfunctions No sheltering Sheltering of students under desks No alarm loss**Expected Loss [€]**[s] Optimal Alarm threshold Expected loss as a functionof the seismicinstrumentsmeasures No alarm Alarm Iervolino et al., 2009.**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. EarlyWarning and StructuralControl**A structure equipped with a semi-active control device**activable by the EEWS: feasibility. This model may be used to study other systems…**Variable-Orifice Viscous Dampers**PASSIVE DEVICE**3. Seismic response probability depending on hazard**4. Real-time hazard analysis Real-Time performance analysis Expected Structural performance Iervolino et al., 2009b.**Benefit of The EEWS in terms of reduction of Drift Response**Iervolino et al., 2009b.**Benefit of The EEWS in terms of reduction of Peak Floor**Acceleration Iervolino et al., 2009b.**Response improvement in respect to the structure without the**EEWS**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; Design and Feasibilityissuesfor the engineeringuseof EEWS forstructural “control”**References**http://www.saferprojct.net/publications • 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, DOI:10.1029/2008GL036644, in press. • Convertito V., Iervolino I., Giorgio M., Manfredi G., Zollo A. (2008). Predictionofresponsespectra via real-time earthquake measurements. Soil Dyn Earthquake Eng, 28: 492–505. • Iervolino I., Convertito V., Giorgio M., Manfredi G., Zollo A. (2006). Real-time riskanalysisforhybrid earthquake early warning systems. Journal of earthquake Engineering, 10: 867–885. • Iervolino I., Giorgio M., Manfredi G. (2007). Expected loss-based alarm threshold set for earthquake early warning systems. Earthquake EngnStructDyn, 36: 1151–1168.**EarlyWarningSpecialIssue**• 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.