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SAFER: Seismic eArly warning For EuRope SAFER Test - Site Report: Bucharest by Gh.Marmureanu, C.Ionescu, A.Marmureanu, C.O.Cioflan, B.Grecu, A.Danet POTSDAM,

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Presentation on theme: "SAFER: Seismic eArly warning For EuRope SAFER Test - Site Report: Bucharest by Gh.Marmureanu, C.Ionescu, A.Marmureanu, C.O.Cioflan, B.Grecu, A.Danet POTSDAM,"— Presentation transcript:

1 SAFER: Seismic eArly warning For EuRope SAFER Test - Site Report: Bucharest by Gh.Marmureanu, C.Ionescu, A.Marmureanu, C.O.Cioflan, B.Grecu, A.Danet POTSDAM, GERMANY, June 3-5, 2009

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3 The Tectonic of the Carpathian Arch - Vrancea Area

4 SAFER: Seismic eArly warning For EuRope Bucharest is one of the cities most affected by earthquakes in Europe. Situated at 150-170 km distance from Vrancea epicenter zone, Bucharest had suffered many damages due to high energy Vrancea intermediate-depth earthquakes. For example, the March 4, 1977 event (Mw =7.2) produced the collapse of 36 buildings with 8-12 levels,while more than 150 old buildings were seriously damaged. The ruptured area was at 140 km on Nov. 10,1940 Vrancea earthquake( Mw =7.7), 110 km on March 4,1977(Mw =7.4), 134 km on August 30,1986(Mw =7.1) and 85 km on May 30,1990(Mw =6.9) depth. The depth interval between 110 km and 130 km remains not ruptured since 1802, October 26, when it was the strongest earthquake occurred in this part of Central Europe. The magnitude is assumed to be Mw =7.9-8.0 and this depth interval is a natural candidate for the next strong Vrancea event. POTSDAM, GERMANY, June 3-5, 2009

5 SAFER: Seismic eArly warning For EuRope POTSDAM, GERMANY, June 3-5, 2009 Geological section through Quaternary layers from Vrancea to Danube river

6 SAFER: Seismic eArly warning For EuRope POTSDAM, GERMANY, June 3-5, 2009 Isobaths are generally oriented from east to west, with a slope of about 8 dipping from south to north.

7 SAFER: Seismic eArly warning For EuRope Bucharest site amplifications by using very hard rock(VHR) and joint source site determination(JSSD) methods. (i)- methods that calculate the site response with respect to a reference site located on a hard rock( VHR ) and, ( ii)- methods that calculate the site response with respect to a reference site( JSSD ), so called non-reference techniques. We used as reference site a site located in Bucharest (INCERC) for which the geotechnical characteristics are known from the borehole existing in that place (thickness of the layers, velocity of the P and S waves, density). The procedure for obtaining the local amplification functions was the following : (a)-selection of the S-wave windows of 10s length with good signal-to-noise ratio; (b)-computing the amplitude Fourier spectra for the horizontal components of the selected windows; (c)-modeling the amplitude Fourier spectra for the Very Hard Rock site; (d)-computing the ratio between the amplitude Fourier spectra of the horizontal components of earthquakes and the modeled amplitude Fourier spectra; (e)-computing the average ratio for each station. POTSDAM, GERMANY, June 3-5, 2009

8 SAFER: Seismic eArly warning For EuRope POTSDAM, GERMANY, June 3-5, 2009 Distribution of the K2 stations in Bucharest area ( 42 K2 units)

9 SAFER: Seismic eArly warning For EuRope POTSDAM, GERMANY, June 3-5, 2009 Station BMG (VHR Method) Station BTM (VHR Method) Station CIO (VHR Method) Station CNC (VHR Method)

10 SAFER: Seismic eArly warning For EuRope POTSDAM, GERMANY, June 3-5, 2009 Station INC(INCERC Bucharest)-only VHR Station BMG :JSSD & VHR Methods The amplification functions got by VHR and JSSD methods for K2 stations from Bucharest (The average- black color ;± 1 σ – red color)

11 SAFER: Seismic eArly warning For EuRope Result 1 : From the VHR and JSSD analysis:for the stations situated downtown Bucharest (BGM, BST, BTM, BVC) the amplification functions show a decreasing tendency from small to high frequency. At stations BGM and BTM a well defined peak can be observed between 3 and 5 Hz. This reaches 2.6 units of amplitude at station BGM and respectively, 3.8 units at BTM. Station BAP indicates a high level of amplification (> 4 units) which is about constant for the considered frequency domain. This characteristic can be also found at the K2 stations located in the vicinity of Bucharest city (CIO, CNC, MOG, POP, STF) except for the station BMG where an increasing level of amplification is noticed at intermediate frequencies with a maximum of 3.3 units at 5.2 Hz; POTSDAM, GERMANY, June 3-5, 2009

12 SAFER: Seismic eArly warning For EuRope Nonlinear Bucharest site amplifications by using spectral amplification factors (SAF) method. (SAF)a= S a max /a max ; (SAF)v = S v max /v max ; (SAF)d = S d max /d max a max =ÿ(t)max ; v max =x˙(t)max and d max = x(t)max POTSDAM, GERMANY, June 3-5, 2009 Vrancea-epicenter Bucharest-site

13 SAFER: Seismic eArly warning For EuRope POTSDAM, GERMANY, June 3-5, 2009 Non - filtered 0.005-1.0 Hz

14 SAFER: Seismic eArly warning For EuRope 0.05 - 2 Hz 0.05 - 5 Hz Space distribution/dispersion of the SAF values in Bucharest area from Vrancea earthquake on August 30,1986 (Mw =7.2) POTSDAM, GERMANY, June 3-5, 2009

15 SAFER: Seismic eArly warning For EuRope Result 2: There is a strong nonlinear dependence of the spectral amplification factors of earthquake magnitude and site conditions (Marmureanu et al,2005). Dispersion of the SAF values for strong motion records in Bucharest (Mw>6) shows a certain stability of SAF values for each frequency domain discussed (0.005 - 1Hz: 3.5- 4.6; 0.005- 2Hz: 2.8 - 3.8 ) which can be used in rapid estimation of the seismic response on the city area (Figure 5). The innovation is the nonlinear of SAF of magnitude POTSDAM, GERMANY, June 3-5, 2009

16 SAFER: Seismic eArly warning For EuRope Bucharest site amplification by using down-hole seismic measurements: Case A: Acceleration response spectra by using as input the accelerogrames recorded at -100m depth to the surface during of Vrancea earthquake on October 27, 2004, Mw =6.00) –Bucharest City Mean weighted seismic velocities for the seven main types of Quaternary layers Geologic layer Depth of the Density Mean weighted Vp Mean weighted Vs upper limit (m) (g/cm3) seismic velocity (m/s) seismic velocity (m/S) 1. Backfill 0.00 1.10 370 167 2.Upper clay layer 0.50-5.00 1.75 687 244 3.Colentina aquifer 5.00-12.00 1.99 1044 274 (sand+ gravel) 4.Intermediate layer 10.00-20.00 2.07 1488 327 5.Mostistea aquifer 15.00-35.00 2.00 1563 340 6.Lacustrine layer 35.00-50.00 2.14 1753 397 7.Fratesti aquifer 100.00-185.0 2.05 1740 545 (sand +gravel) POTSDAM, GERMANY, June 3-5, 2009 The depths of the boreholes : Basilescu:- 172m ; Foradex :- 81m ; Grivita:- 110m ; Iorga:- 170m ; Policolor:- 100m ;Buciumeni:- 150m ;Otopeni:- 200m ;Politehnica:- 200m; IMGB: - 155m ; Magurele:- 112m ;Centura 1:- 80m and Centura 2:- 60m.

17 SAFER: Seismic eArly warning For EuRope Case B:The amplification of the seismic signals in Bucharest by using as input at -52m the signal recorded at - 52m deep,at City Hall Bucharest,during on Oct. 27.2004 Vrancea earthquake (Mw =6.00) Mean weighted Vs, Vs-30 and Vs-50 seismic velocities in the first Quaternary layers Layer 1 Layer 2 Layer 3 Layer 4 Layer 5 Layer 6 Vs-30 Vs-50 1.Tineret Park 140 220 299 - 398 - 263 340 2.Ecology Univ. 120 220 241 354 390 401 286 326 3.Astronomy Inst. 120 260 330 350 390 433 283 320 4.Titan 2 Park 160 250 250 350 381 450 299 341 5.Metrodrom Park 200 200 320 393 410 410 288 327 6.Student Park 210 210 342 270 375 400 295 319 7.Basilescu Park 160 160 317 390 408 - 294 334 8.Rom. Shooting Fed. 210 330 350 400 400 - 327 347 9.Geological Museum 180 310 322 - 376 - 320 328 10.NIEP site 250 350 320 337 410 410 326 338 Mean weighted Vs (m/s) 169 252 320 367 386 417 POTSDAM, GERMANY, June 3-5, 2009

18 SAFER: Seismic eArly warning For EuRope POTSDAM, GERMANY, June 3-5, 2009 The variation of the peak acceleration from - 52 m depth to the surface at site Ecology Univ. for the two input horizontal ground motions: PRI_EW (PGA=0.022g) and PRI_NS (PGA=0.013g) recorded at - 52 m in borehole during of Vrancea earthquake on October 27,2004 (Mw =6.0) Case C: The amplifications of PGA during of Vrancea earthquake on Oct. 27, 2004(MW =6.00) in other 6 boreholes made in Bucharest City. The Vrancea earth- quake on Oct.27,2004(Mw=6.00) was recorded in 6 boreholes in depths between free field level and -153m

19 SAFER: Seismic eArly warning For EuRope Station Deep sensor Shallow sensor Surface sensor (free filed ) Depth PGA(g) Depth PGA(g) PGA(g) The amplification (1) (2) (3) 3: 1 3 : 2 1.UTCB NS 0.0165 0.0285 0.0349 2.115 1.225 EW -78 m 0.0231 -28 m 0.0146 0.0584 2.528 4.000 V 0.0098 0.0111 0.0344 3.510 3.099 2.UTCB NS 0.0156 0.0216 0.0416 2.667 1.926 EW -66 m 0.0235 -28 m 0.0168 0.0409 1.740 2.435 V 0.0070 0.0115 0.0248 3.543 2.157 3.NCSRR/ NS 0.0113 0.0139 0.0297 2.628 2.137 INCERC EW -153m 0.0114 -24 m 0.0125 0.0296 2.596 2.365 V 0.0067 0.0083 0.0249 3.716 3.000 4.Civil Prot. NS 0.0127 0.0203 0.0290 2.283 1.283 Hdq. EW -68 m 0.0194 -28 m 0.0131 0.0492 2.536 3.756 V 0.0088 0.0112 0.0340 3.864 3.036 5.City Hall NS 0.0132 0.0166 0.0298 2.258 1.795 EW -52 m 0.0222 -28 m 0.0377 0.0790 3.559 2.095 V 0.0096 0.0118 0.0331 3.448 2.805 6.Municipal NS 0.0126 0.0116 0.0546 2.459 4.707 Hospital EW -70 m 0.0181 -30 m 0.0185 0.0445 2.459 2.405 V 0.0089 0.0082 0.0508 5.708 6.195 POTSDAM, GERMANY, June 3-5, 2009

20 SAFER: Seismic eArly warning For EuRope Result 3. The variation of the peak acceleration from - 52 m depth to the surface at site Ecology Univ. for the two input horizontal ground motions ( PGA= 0.022g) recorded at -52 m in borehole during of Vrancea earthquake on Oct.27, 2004(Mw=6.0) is between 0.06 g and 0.10 g. This is consistent with the maximum values recorded in Bucharest for the earthquake on 27.Oct. 2004 whose borehole recordings were used as input. We didnt use amplification factors similar to those of Borcherdt; Result 4: The scattering of the amplifications between PGA recorded by deep,shallow and surface/free field K2 sensors in Bucharest site was made obvious by measurements made in 6 boreholes with real data for last Vrancea earthquake on Oct.2004(M W =6.0). The ratio between surface sensors and deep ones is between 2.115 and 5.708. The average is 3.912. The innovation: for the first time we can see the nonlinear quantitative amplification between sensors placed at: -153 m, -78 m, -70 m, -68 m, -66 m and -52 m and surface sensors; POTSDAM, GERMANY, June 3-5, 2009

21 SAFER: Seismic eArly warning For EuRope Frequency dependent PGA/PGV amplification analysis POTSDAM, GERMANY, June 3-5, 2009 Observed distribution of macroseismic intensity during the large Vrancea earthquakes (November 10,1940, Mw = 7.7 and March 4,1977, Mw = 7.4).

22 SAFER: Seismic eArly warning For EuRope POTSDAM, GERMANY, June 3-5, 2009 Distribution of maximum accelerations for last significant Vrancea earthquake on Oct.27,2004(Mw=6.0;h=98 km).(Grecu et al)

23 SAFER: Seismic eArly warning For EuRope The earthquakes affects very large area with a predominant NE-SW orientation ( banana shape),characteristic response spectra with large periods of 1.5-1.6 seconds, no significant attenuations on Romanian territory, large amplifications away etc. POTSDAM, GERMANY, June 3-5, 2009 Functions of amplification dependent on region (Sokolov,Grecu etc.)

24 SAFER: Seismic eArly warning For EuRope POTSDAM, GERMANY, June 3-5, 2009 The observed macroseismic map and the modeled distribution of ground motion parameters (MSK intensity,PGA,PGV) for the major Vrancea earthquake on March 4,1977(Mw =7.4 ; h= 95 km).

25 SAFER: Seismic eArly warning For EuRope Result 5: The maps outline the following features: the general orientation of the isoaccelerations on the NE-SW direction, small value of accelerations in epicenter areas ( 0.1626 g ) and areas with large values of accelerations situated far from the epicenter (0.314 g at 32 km,in Focsani, August 30,1986,Mw =7.2) (Grecu,2008); Result 6: The average values of amplification can vary signifi- cantly from one region to another depending on the frequency range. The region South-West (Bucharest ) the highest amplifications are in the range of 0.6 to 4 Hz (Grecu et al, 2004). The region South shows almost the same amplification for frequencies greater than 1.0 Hz. The increase of amplification toward low frequencies ( region South-West) may be explained by the influence of the surface waves generated within the deep sediments of the Moesian platform. POTSDAM, GERMANY, June 3-5, 2009

26 SAFER: Seismic eArly warning For EuRope Attenuation laws to Bucharest by using different models (Joyner-Boore, Crouse etc.) PGA in epicenter area (Vrancioaia) during of August 30,1986 Vrancea earthquake(Mw =7.0) was 0.1626 cm/s 2, in the north of Bucharest was 0.156 cm/s 2 while in the south-est of it was only 0.0763 cm/s 2. Ln(a max ) = c 1 + c 2 M GR + c 3 ln R +c 4 h + σ ln a max.P Ln(a max )= 4.726 + 0.976 M GR -1.146 ln R - 0.0066 h + 0.353 P Earthquake M GR Depth (h,km) (km) R (km) a max ( recorded ) a max ( computed) 1.March 4,1977 7.2 110 100.37 148.91 198.00 cm/s2 199.00 cm/s 2 2.August 30,1986 7.0 143 123.25 188.78 95.30 cm/s2 95.55 cm/s 2 3.May 30,1990 6.7 90 173.53 195.48 98.70 cm/s2 102.05 cm/s 2 POTSDAM, GERMANY, June 3-5, 2009 Result 7: Each parameter for each zone(i) is obtained from reference station INCERC Bucharest: I zone i = ( I )INCERC ± Δ I (MMI scale); ( a max )zone i = ( a max )INCERC ± Δ a in (cm/s 2 ) ( T, s )zone i =( T, s )INCERC ± Δ T,s in seconds,i=1...14 The base is the seismic hazard map( microzoning ) of Bucharest

27 SAFER: Seismic eArly warning For EuRope POTSDAM, GERMANY, June 3-5, 2009 The innovation: Reference station concept: I zone i = ( I )INCERC ± Δ I (MMI scale); (a max )zone i = (a max ) INCERC ± Δ a in (cm/s 2 ) (T,s )zone i = ( T,s)INCERC ± ΔT,s in seconds i=1…14 zones

28 SAFER: Seismic eArly warning For EuRope Attenuation laws and intensity map by using the azimuths and the concept of etalon earthquake to get so-called banana shape It was observed that all epicenters are on the same line NE-SV (direction AB) and also for maxim macroseimic intensity I 0 -direction AB which is parallel to epicenter line AB at distance D 0 of 23 km. POTSDAM, GERMANY, June 3-5, 2009 Epicentres E(line AB) and I 0 (line AB) points corresponding to the four strong and major earthquakes (M GR 6.7) occurred in the last 69 years

29 SAFER: Seismic eArly warning For EuRope The earthquake on August 30,1986 is used by us control earthquake concept in all studies as it fulfils the following states: (i)-it was strong (Mw =7.2); (i)-it was recorded in a lot of seismic stations on Romanian territory; (iii)-the fall plan solutions are very closed (almost identically) to other Vrancea stronger earthquakes(Nov. 10, 1940; Mw =7.7 and March 4,1977;Mw =7.4) and with majority of earthquakes with moderate magnitudes (6.9 < Mw <7.2); (iv)-the depth of oh hypocenter (h131-143 km) is very close to medium value of all strong Vrancea earthquakes. Log I (X,Az) =Log I 0X +Log ( I e / I oe ) Az +b( Az )Log[Re /f ( he )/R X / f(x) ]Az +[c log δ ]Az where: I OX is the maximum intensity of an earthquake at a depth h=x ; δ is the directivity factor of the rupture propagation in the focus ; c is the way how the directivity factor may influence the directivity of the seismic source ; Re = (Δ 2 +he 2 ) 1/2 ; R X =(Δ 2 +x 2 ) 1/2 ; Δ is the distance between the observation point of maximum macroseismic intensity. POTSDAM, GERMANY, June 3-5, 2009

30 SAFER: Seismic eArly warning For EuRope Result 8 : By using the earthquake on Aug. 30,1986 as control earthquake it was obtained the banana shape of the attenuations curves family of the macroseismic intensity I (along the directions defined by azimuth Az), in the case of an Vrancea earthquake at a depth 80< x 160 km. The innovation part is the concept of control earthquake. POTSDAM, GERMANY, June 3-5, 2009 The isoseismal map of the maximum possible Vrancea earthquake(M GR =7.5)

31 SAFER: Seismic eArly warning For EuRope Rapid magnitude determination for Vrancea early warning system. NIEP early warning system consists of several different parts: (i)-A dedicated acquisition system, algorithms to rapidly detect seismic events, (ii)-Algorithms that eliminate false detections and alarms and methods to estimate the earthquake magnitude and to send the warning to the users. All of these parts have to work automatically, in real time, without interruption for a long period of time. As a fit between maximum 1Hz low-pass filtered vertical acceleration and Mw magnitude, the following relation was assumed ( Marmureanu A.,2009): y=A 1 e -x/t1 +y 0 where A 1= 3.97902e-7 ; t 1 =-0.4029, y 0 =-9.69317e-4. This can be used to approximate very well earthquake magnitude in the first seconds after detection. The average absolute error is 0.271 magnitude degrees using all existing recorded data. This error is satisfactory, taking into account that the magnitude is computed on 4-5 seconds after P wave is detected in the epicenter area. POTSDAM, GERMANY, June 3-5, 2009

32 SAFER: Seismic eArly warning For EuRope POTSDAM, GERMANY, June 3-5, 2009 Fit between maximum 1Hz LP filtered acceleration and Mw magnitude

33 SAFER: Seismic eArly warning For EuRope POTSDAM, GERMANY, June 3-5, 2009 Absolute error in magnitude estimation (|M computed – MROMPLUS|) for all recorded events at the three stations (MLR, VRI, PLOR) Result 9 / Novelty : The software developed by NIEP was tested at last Vrancea earthquake on April 25, 2009 when the magnitude (Mw =5.7) of the earthquake was computed in first 5 seconds and it was an accurate value.

34 SAFER: Seismic eArly warning For EuRope Integrated of early warning system, alert, shake and disaster in disaster reduction and risk management Early warning system is viewed as part of an real-time information system that provide rapid information, about an earthquake impeding hazard, to the public and disaster relief organizations before ( early warning ) and after a strong earthquake ( shake map ). The USGS shake map software has been installed and modified for the Bucharest area.Two main problems have been encountered: first, the USGS software uses for site characterization V S-30 and second, the attenuation relationships implemented in the software are not valid for Vrancea earthquakes. By using USGS shake map software, we can see shake map for strong Vrancea earthquake on Nov.10,1940 (Mw =7.7) and March 4,1977(Mw=7.4) which differ totally from observed distribution of macroseismic intensity. Then, NIEP made the decision to use real data in real time. POTSDAM, GERMANY, June 3-5, 2009

35 SAFER: Seismic eArly warning For EuRope POTSDAM, GERMANY, June 3-5, 2009 Observed distribution of macroseismic intensity (left) and shake map made by using USGS Shake Map software for strong Vrancea earthquake on Nov.10,1940(Mw = 7.7 )

36 SAFER: Seismic eArly warning For EuRope POTSDAM, GERMANY, June 3-5, 2009 Observed distribution of macroseismic intensity (left) and shake map made by using USGS Shake Map software for strong Vrancea earthquake on March 4,1977 (Mw = 7.4 )

37 SAFER: Seismic eArly warning For EuRope POTSDAM, GERMANY, June 3-5, 2009 The epicenter and the alert map The place of EWS, alert, shake and disaster maps in seismic risk management

38 SAFER: Seismic eArly warning For EuRope Result 10 / Innovation: The innovation with comparable or related systems worldwide is that NIEP will use the EWS to generate a virtual shake map (alert map for Bucharest-140 km away of epicentre) immediately after the magnitude is estimated (in 4-5 seconds after the detection in epicentre) and later make corrections to construct real shake map by using real time dataflow from each K2 accelerometers installed in Bucharest area (42 K2 units), inclusively nonlinear effects, to generate shake map, in real time. Thus, developing of a near real-time shake map for Bucharest urban area is of highest interest, providing valuable information to the civil defense, decision makers and general public on the area where the ground motion is most severe. POTSDAM, GERMANY, June 3-5, 2009

39 SAFER: Seismic eArly warning For EuRope POTSDAM, GERMANY, June 3-5, 2009 Thank you for your attention !

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