feasibility study on earthquake early warning for schools in
TRANSCRIPT
FEASIBILITY STUDY ON EARTHQUAKE EARLY WARNING FOR SCHOOLS IN SOUTHERN ITALY Antonio EMOLO1, Ma.eo PICOZZI1, Aldo ZOLLO1, Gerardo VERDERAME1, Claudio MARTINO1, Luca ELIA1, Simona COLOMBELLI1, Ortensia AMOROSO1,2, Maria Teresa DE RISI1, Dino BINDI3,
Stefano PAROLAI3, Tobias BOXBERG3, Nicola MIRANDA4, Lilly BUONAIUTO4, Angelo AMELIA4
(1) AMRA-‐University of Naples, Italy , (2) IsQtuto Nazionale di Geofisica e Vulcanologia, Osservatorio Vesuviano, Italy -‐ University of Naples, Italy, (3) Helmholtz-‐Zentrum Potsdam Deutsches GeoForschungsZentrum, Germany, (4) ITIS ‘E. Majorana’, Somma Vesuviana, Italy
Monitoring system
PRESToPlus System with Early Warning SenFnel
EvaluaQng the effecQveness of Earthquake Early Warning Systems (EEWS) and real-‐Qme risk assessment procedures in reducing seismic risk for various industrial partners and end-‐users is one of the main objecQve of the WP7 (Strategic ApplicaQons and Capacity Building) in the framework of the REAKT-‐Strategies and tools for Real Time Earthquake RisK ReducTion FP7 European project. In this context our group is engaged in a feasibility study on the applicaFon of earthquake early-‐warning procedures in two high schools (Liceo ‘F. de SancQs’, S. Angelo dei Lombardi, SALI and ITIS ‘E. Majorana’, Somma Vesuviana, MAJI) located in the Irpinia region (Southern Italy). The area has been interested by large earthquakes both in historic and recent Qme. The last destrucQve earthquake was the 23 November 1980, M 6.9, Irpinia earthquake, which caused more than 3000 casualQes and produced huge and widespread damage. Here we present a summary of the acQviQes carried out and the results obtained so far at the MAJI School.
A high quality accelerometric staQon consisQng of a 24-‐bit ADC (Sigma/Delta) Agecodagis Kefren data-‐logger and a Guralp CMG-‐5TC accelerometer with a 0.25g full-‐scale has been installed. In order to perform a conQnuous seismic monitoring of the site, a total of five accelerometric staQons have been installed in different parts of the school building. In parQcular, besides the Guralp CMG-‐5TC accelerometer in the school courtyard, four SOSEWIN sensors have been deployed at different locaQons within the building. Commercial ADSL lines provide transmission of real-‐Qme data to the EEW centre. Data streams are now acquired in real-‐Qme in the PRESToPlus (regional and on-‐site, threshold-‐based early-‐warning) sojware plakorm (Satriano et al, 2010)*.
IntroducFon
PRESTo (PRobabilisQc and EvoluQonary early warning SysTem) is a sojware plakorm for Earthquake Early Warning, that integrates a regional, network-‐based approach with an on-‐site, single staFon approach. The sojware processes the real-‐Qme 3-‐Component acceleraQon data streams from seismic staQons of the Irpinia Seismic Network (ISNet) in Southern Italy and from schools involved in the NERA and REAKT European Projects. Once a P-‐waves arrival has been detected at a staQon and three seconds of signal are available, PRESTo measures the peak displacement and predominant period of P-‐waves. These values are compared to thresholds, set for a minimum magnitude 6 and instrumental intensity VII, based on the empirical regression analyses of strong moQon data. If thresholds are exceeded and damage is expected, a first rough but robust alert level to the site / school is issued. The data streams and alert levels from all the staQons are also gathered and processed at regional scale, contribuQng at improving the earthquake locaQon and magnitude esQmaQons, peak ground moQon predicQons at target sites and regional PotenQal Damage Zone. Whenever an alert message is released, independently from the EEWS source (i.e. On-‐site, Regional, or even from both of them cooperaQng), it is received and taken in charge by a EEW SenFnel (i.e. Arduino®). Arduino is a low cost programmable actuator that we set-‐up to keep listening and interpreFng the messages and alert levels from PRESToPlus. Hence, in the case of an event, this EEW senFnel is able to provide to the school users a real-‐Fme P-‐wave based predicFon of the ground moFon severity expected at the target site.
T0 Origin Time
2013-‐12-‐29 17:08:45 17:08:56
DetecQon Time
Lead Time: 7s M:4,3
Mmin:3,9 Mmax:4,6
PGV: 0,09 cm/s
2° Alert Sent to Target
3° Alert Sent to Target
1° Alert Sent to Target
17:08:57
Lead Time: 6s M:4,5
Mmin:4,3 Mmax:4,8
PGV: 0,13 cm/s
17:08:59
Lead Time: 4s M:4,7
Mmin:4,5 Mmax:4,9
PGV: 0,19 cm/s
1° Alert
2° Alert
3° Alert4
Weak– II°-‐III°
Weak– II°-‐III°
Weak– II°-‐III°
Green Light
No Siren
I.T.I.S. Majorana School Somma Vesuviana (Naples)
Off-‐line analyses at the school ITIS ‘E. Majorana’
The first tests were performed on 24-‐hour long waveforms recorded by the five staQons, during four different days, with school acQvity but no nearby earthquakes. The aim of these analyses was to verify the rate of false events detected by the EEW On-‐site system due to the anthropic acQviQes. The P-‐wave picking was performed using the same picker used in PRESTo (FilterPicker5, Lomax et al, 2012)*. Due to the high noise level incorrect and false phase pickings can be automaQcally declared, up to 1 pick every 5 minutes for the most sensiQve staQon. This suggests that the single staQon EEW approaches require a specific tuning of parameters, to avoid the repeated occurrence of false alarms. Conversely, when an almost simultaneous pick at a minimum number of 4 staQons is required before declaring an event, the rate of false alerts is significantly reduced. To account for Qme differences in the picks due to the low signal-‐to-‐noise raQo, we chose a 0.5 sec Qme window for coincidence. We observed that when 3-‐staQons are considered only 1-‐2 events per day are detected, while there was never a coincidence of picks within 0.5 seconds, and thus no early warning procedure would have been triggered, when 4-‐ or 5-‐staQons are considered.
The second test was carried out considering the only relevant earthquake recorded so far by the system, that is the Matese earthquake (2013/12/29 17:08:43, ML 4.9), for which only 4 staQons were available. The distance from the school to the hypocenter was about 55 km. On-‐site Alert (Leh): we applied a low-‐pass filter (10 Hz) to the waveforms to reduce the high frequency noise contaminaQon and we verified that the seismic staQons correctly picked the P-‐wave onset of the event. For the less sensiQve SOSEWIN staQons, that use an internal MEMS sensor, it was also necessary to decrease the threshold parameter of the picker. All the staQons picked within 0.5 seconds from the arrival of the P-‐wave. The accelerometric records have been double integrated to get displacement waveforms and a high-‐pass filter with cut-‐off frequency of 0.075 Hz has been applied to reduce the noise introduced by the double integraQon operaQon, as it is usually done in Early Warning applicaQons. Then, the iniQal peak displacement and dominant period have been measured at each staQon, on 3 seconds of signal ajer the P-‐wave detecQon, corresponding to the correct alert level of 0 (No Local Damage, M < 6). Integrated Regional / On-‐site Alert (Right): The playback in PRESToPlus of the waveforms of MAJI and of all the ISNet staQons was performed fixing the epicenter since the earthquakes is external to the network. PRESToPlus predicts a magnitude within 0.5 points to the real value, and the expected on-‐site alert level of 0 at all staQons, including MAJI. The SenQnel then outputs non-‐criQcal visual and audio signals based on the correctly predicted Intensity (II-‐III) at MAJI.
Concerning the EEW On-‐Site approach, the basic idea is to use a stand-‐alone operaQng system for the rapid esQmate of the local damage at the school. In this system, the early porQon of the recorded P-‐wave signal is used to predict the Peak Ground Velocity (PGV) and Instrumental Intensity (IMM) expected at the site We performed off-‐line analyses to test the feasibility of such an on-‐site early warning procedure at the school ITIS ‘E. Majorana’.
*Satriano C, Elia L, MarQno C, Lancieri M, Zollo A, Iannaccone G (2010) " PRESTo, the earthquake early warning system for Southern Italy: concepts, capabiliQes and future perspecQves" , Soil Dyn Earthq Eng ,doi: 10.1016/j.soildyn.2010.06.008
*Lomax A, Satriano C, Vassallo M (2012) “AutomaQc picker developments and opQmizaQon: FilterPicker – a robust, broadband picker for real-‐Qme seismic monitoring and earthquake early-‐warning” Seism. Res. Le.. , 83, 531-‐540, doi: 10.1785/gssrl.83.3.531
ON-‐SITE ALERT LEVEL ZERO: • No Local Damage • M < 6
The ML 4.9 Matese earthquake@MAJI Noise analysis on 24-‐hour waveforms
REGIONAL ALERT: • No Local Damage • 4.5 ≤ M ≤ 4.9