3d physics-based numerical simulations: advantages...
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3D PHYSICS-BASED NUMERICAL SIMULATIONS: ADVANTAGES AND LIMITATIONS OF A NEW FRONTIER
TO EARTHQUAKE GROUND MOTION PREDICTION
Roberto Paolucci
Department of Civil and Environmental Engineering, Politecnico di Milano
6th National Conference on Earthquake Engineering&
2nd National Conference on Earthquake Engineering and Seismology
June 14-16, 2017
Roberto Paolucci
2Contents
Motivation for 3D physics-based earthquake ground motion simulations
the spectral element code SPEED
3D physics-based earthquake ground motion simulations in Istanbul
producing broadband ground motions
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3Approaches to earthquake ground motion prediction
Physics-based
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NGA West2 database (Ancheta et al., 2013)
range of potential
damage to structures
Limitations in the use of GMPEs
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5Limitations in the use of GMPEs
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6Limitations in the use of GMPEs
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7Limitations in the use of GMPEs
NGA2 recordsM>6 R<20km
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8Limitations in the use of GMPEs
INGV wordlwide near source dataset6 < M < 7 & PGA > 100 cm/s2
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9Physics-based 3D earthquake ground motion simulations
To create a numerical laboratory to simulate “earthquakeground shaking scenarios” as realistic as possible in terms of:
the complexity of the seismic source
the complexity of the geological and morphologicalenvironment
the frequency range of the seismic excitation and ofresulting ground motion
Objective
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… but you need
3D numerical models
high frequency
verifications on real earthquakes
GMPEs3D physics based GM simulations
Physics-based 3D earthquake ground motion simulations
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11Contents
Motivation for 3D physics-based earthquake ground motion simulations
the spectral element code SPEED
3D physics-based earthquake ground motion simulations in Istanbul
producing broadband ground motions
Roberto Paolucci
12SPEED (speed.mox.polimi.it)
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Faccioli E, Maggio F, Paolucci R, Quarteroni A. 2D and 3D elastic wave propagation by a pseudo-spectral domain decompositionmethodJournal of Seismology, 1997
Stupazzini M., Paolucci R., Igel H. Near-fault earthquake ground motion simulation in the Grenoble Valley by a high-performance spectral element code Bulletin of the Seismological Society of America, 2009
Mazzieri I., Stupazzini M., Guidotti R., Smerzini C. SPEED-Spectral Elements in Elastodynamics with Discontinous Galerkin. A non-conforming approach for 3D multi-scale problems. International Journal for Numerical Methods in Engineering, 2013
SPEED: some references
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Features 3D unstructured conforming and non-conforming hexahedral meshes ( e.g., between sub-domains Ω1,2, Ω3 and Ω4) Non uniform polynomial approximation orders(e.g., between sub-domains Ω1 and Ω2) leap-frog FD time advancing scheme visco-elastic and non-linear elastic soil behaviour
Kernel
hybrid parallel programming based on MPI and Open-MP METIS software library to handle partitioning and load balancing designed for multi-core machines or large clusters -optimized for HPC clusters (e.g., FERMI Blugene/Q)
SPEED: main features
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15SPEED: spatial discretization
Legendre-Gauss-Lobatto points
Lagrange polynomials
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ikjj
kik
kk
ij nnV
tMtm
),x(),x( 0
);(),x(0kR
kkkkk ttsAutM
shear modulus
Slip source function
co-seismic slip
volume of the kth subfaultslip and normal fault
vectors f(f,f,f)area How to introduce
high-frequencycomponents ?
How to introduce spatial
incoherency?
SPEED: Treatment of seismic input
Kinematic modeling of an extended seismic source
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SPEED: soil modelling17
clay
sand
Viscoelastic models
Q = cost
Q = Q0f
Rayleigh damping
Non-linear elasticity
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18Previous applications of SPEED (1)
Stupazzini M, Paolucci R, Igel H (2009) Near-fault earthquake ground-motion simulation in the Grenoble valley by a high-performance Spectral Element code. BSSA , 99: 286–301.
Smerzini C, Villani M (2012)Broadband numerical simulations in complex near field geological configurations: the case of the MW 6.3 2009 L'Aquila earthquake, BSSA, 102: 2436–2451
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19Previous applications of SPEED (2)
Gubbio (Central Italy)
Sulmona (Central Italy)
Santiago de Chile
Christchurch earthquake February 22, 2011 (New Zealand)
Wellington (New Zealand)
Po Plain earthquake May 29, 2012 (Northern Italy)
Marsica earthquake 1915 (Central Italy)
Thessaloniki (Greece)
Istanbul (Turkey)
Beijing (China)
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20Contents
Motivation for 3D physics-based earthquake ground motion simulations
the spectral element code SPEED
3D physics-based earthquake ground motion simulations in Istanbul
producing broadband ground motions
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21Past century earthquakes along the North Anatolian Fault
after Bohnhoff et al., 2013
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22Princes Islands segment of the NAF
Yellow stars mark estimated epicentres of major earthquakes along the Princes Islandssegment during the last 2,000 years. After Bohnhoff et al., 2013
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23Setup of the 3D physics-based numerical simulations
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24Construction of the numerical model (1)
Combined digital elevation/bathimetry model
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25Construction of the numerical model (2)
Vs model
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26Construction of the numerical model (3)
Fault geometry model
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27Construction of the numerical model (4)
Spectral element numerical model (resolution: fmax= 1.5 Hz)
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28Slip distribution along the fault
HB94: Herrero and Bernard (1994)CA15: Crempien and Archuleta (2015)
Kinematic slip distribution models
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29Construction of scenario earthquakes
45 scenario earthquakes of M ranging from 7 to 7.4 where constructed by considering randomly generated hypocenter and slip distribution models, with both HB94 and CA15 approaches
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30Post-processing 45 shaking scenarios (7.0 Mw 7.4)
Forward directivity PGV (cm/s) Scen Antidirective PGV (cm/s)Neutral directivity PGV (cm/s) Backward directivity PGV (cm/s)
Comparison of Mw7 scenarios: effect of directivity
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31Post-processing 45 shaking scenarios (7.0 Mw 7.4)
Ground motions for a selected scenario
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32Post-processing 45 shaking scenarios (7.0 Mw 7.4)
Ground motions for a selected site
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33Post-processing 45 shaking scenarios (7.0 Mw 7.4)
Neutral Forward Backward
Animation of ground motion: effect of directivity
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when 3 segments are ruptured, the FW directivity scenario wrtIstanbul is the most likely to occur
Dependendance of results on ruptured segments
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35Comparison with GMPEs
Bray & Rodriguez-Marek (2004)only FW directivity
Chiou and Youngs (2008)
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Bray & Rodriguez-Marek (2004)only FW directivity
Chiou and Youngs (2008)
Comparison with GMPEs
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37Components of single-station standard deviation
between-event s.d.within-event s.d.
total s.d.
records of Christchurch earthquakes(Chen and Faccioli, 2013)
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38Contents
Motivation for 3D physics-based earthquake ground motion simulations
the spectral element code SPEED
3D physics-based earthquake ground motion simulations in Istanbul
producing broadband ground motions
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(1) A hybrid broadband is first produced by combining the low-frequencysimulation with the high-frequency ground motion generated from stochastic approaches
Producing broadbands from SPEED
lack of correlation of the LF and HF parts100
10-1
100
101
102
f (Hz)
FA
S (
cm/s
)
LF(SPEED)HF(SP96)BB
0 1 2 3 40
0.5
1.0
f (Hz)
fl f
h
LF filter HF filter
0 5 10 15 20 25 30
-200
0
200
LF
(cm
/s2 )
0 5 10 15 20 25 30
-200
0
200
HF
(cm
/s2 )
0 5 10 15 20 25 30
-200
0
200
BB
(cm
/s2 )
t (s)
LF: SPEED (f < 1.5 Hz)
HF: SP96 (f > 1.5 Hz)
BB ( 0 < f < 25 Hz)
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40Producing broadbands from SPEED
(2) An ANN is trained (una tantum) based on a strong motion dataset(SIMBAD, Smerzini et al., 2014)
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(3) The "hybrid" broadband is scaled in order to match the ANN trained response spectrum
T
Sa
T*
region of validity of numerical simulations
hybrid response spectrum
ANN responsespectrum
3D physics-basedsimulated response
spectrum
hybrid
ANN-matched
Producing broadbands from SPEED
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(4) Verification on real case studies: simulation of Po Plain eqk, May 29 2012
Producing broadbands from SPEED
response spectra Fourier spectra
rec velocity
rec acceleration sim acceleration
sim velocity
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(4) Verification on real case studies: simulation of Po Plain eqk, May 29 2012
Spatial correlation of PGAs
Producing broadbands from SPEED
reco
rded
sim
ulat
ed
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(4) Verification on real case studies: simulation of Po Plain eqk, May 29 2012
Spatial correlation of Sa=1s
Producing broadbands from SPEED
reco
rded
sim
ulat
ed
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453D numerical simulations of the May 29 2012 Po Plain earthquake
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463D numerical simulations of the May 29 2012 Po Plain earthquake
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47Producing ground motion movies: 2012 Po Plain eqk
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Pros
accounting for specific geologic and tectonic conditions
capturing physics of earthquake ground motion, especially near-source
proper spatial correlation of motion between adjacent sites
Cons
large number of scenarios needed: how to cluster them?
limited reliability in the high-frequency range, although in progress
need of vast amount of input data: suitable for large urban areas
Conclusions
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