The Idea of the Early Warning

Transcription

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2 The Idea of the Early Warning

3 P S R P Wave - Comes first at the surface point, being harmless. S Wave - Comes second, and it's distructive upon buildings. RWave- Comes third, being as devastative as the second.

4 Israel Seismic Network Station MMLI 83 km from the Source Dead Sea Earthquake M= September 2004

5 M=5.1 BB Station MMLI R=83 km P S 11 sec Sec

6 M=5.1 BB Station MMLI R=83 km P S R 25 sec Origin 0 sec 11 sec Sec

7 M=5.1 BB Station MMLI R=83 km DRGI 20 km 5 sec Early warning 20 sec P S R 25 sec Origin 0 sec Sec

8 Purpose of EWS Clean-up personal as they work on unstable debris Slow and stop trains Abort airplane landings Prevent cars from entering the free-way Industry shut-down process to prevent c ascade failures Developing of buildings with active response systems (Japan). The buildings are changing their mechanical properties within few seconds to better withstand ground motion

9 Early Warning Systems International experience

10 Which parameters are measured first? 1. Hypocenter 2. Magnitude

11 1. Single-station method 2. Network method

12 Single-station method Single-station method JMA experience

13 Single-station method JMA experience Japan EWS for the Railroads

14 Example of recursive magnitude Recursively measured magnitudes time

15 Rapid Magnitude estimation M=F(frequency content of the Pwave arrival) (Japan experience)

16 Existing EWS Mexico City: Front detection system: 300 km ~ 70 sec Taiwan: 22 sec for location and magnitude ~ 75 warning for areas > 75 km Japan UrEDAS system Earthquake Alarm System (ELARMS) California

17 California Earthquake Alarm System (ElarmS) with TriNet instrumentation

18 REASONING Event magnitude is proportional to the size of slip => proportional to the predominant frequency of seismic waveforms.

19 RECURSIVE FORMULATIONS Predominant real-time period, as function of time i T = 2π X / i i D Smoothed ground velocity squared. (α smoothing parameter) X + i 2 = αx i 1 xi Smoothed ground acceleration squared D i = αd i 1 + ( dx / dt) i i 2

20 CONCLUSIONS Longer period is measurable within the longer time period. Magnitude estimate may increase after 2, 3, 4 sec of measurements

21 Predominant period vs Magnitude Low magnitude earthquakes P P m = 6.3log( Tmax ) m h = 7.0 log( Tmax ) l High magnitude earthquakes Predominant period, sec average magnitude per event Measured after 2 sec Measured after 4 sec

22 Real-time Source Location Horiuchi S. et al. 2005

23 Using not-arrival information Using not-arrival Information together with arrival time make It possible real-time location within first seconds after originating the event. now { T T arive now TT TT = = R R a n = 0 > 0

24 Network methods

25 Early Warning Systems. Approach of Geophysical Institute of Israel Responsible: Vladimir Pinsky V. Avraam Hofstetter

26 Using arrival and not-arrival information Horiuchi S. et al For Real-time Source Location We are developing robust algorithms for real-time accurate location using uncertainty of travel-time model

27 Model free method of pairs of stations Model free method of pairs of stations Epicentral location using arrival time order, AOL algorithm Andersen, BSSA, 1981 t 4 R 1 t 1 Find all points, which belong, to maximum number of half-planes t 3 R 2 t 2 Find maxσω[ R kj (X)] Ω={ 1, R > 0 0, R < 0

28 Using not arrival information will additionally increase accuracy of location t 4 R 1 t 1 t 3 R 2 t 2

29 GII Alarm system. Automatic on-set

30 Automatic location procedure S(X,Y,H) = Σ exp (- (X, Y, H) 2 / σ 2 ) The final solution is a grid point (x,y,h,t) that provides maximum to the sum

31 Automatic location procedure -seismic Network -main shock manual -main shock automatic --aftershocks

32 3 km

33 Real-time detection and on-set estimation procedures are realized in the GII Earthquake alarm system.

34 11/02/04 08:15 X Y Lat Lon NP NS Array Dead Sea Mw=5.1 Automatic location Manual picking Explosions 2 km

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37 70 km רשת סייסמומטרים של ישראל

38 רשת מדי תאוצה

39 30 תחנות סייסמיות מותקנות לאורך העתק ים המלח במרחק של 10 ק"מ