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Regional Conference 2010Supercomputing Supercomputing -- New Challenge for Science New Challenge for Science

and Industryand IndustrySofia, 9 - 10 December 2010

Application of High Performance Computing in the modeling of seismic impact

I. Paskaleva, V. Pavlov, N. Koleva, S. Shanov, M.Kouteva, A. Boikova

Bulgarian Academy of Sciences NIGGG,GI

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CONTENT

Introduction to the seismic risk assessmentsDefinition of the problemUsed methodology and tools for calculationsInput dataMain results and disscutionConclutionACKNOWLEDGEMENT

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PROCESSES FOR BECOMING EARTHQUAKE RESILIENT

IMPROVING PUBLIC AWARENESSIMPROVING PROFESSIONAL EDUCATION AND TRAININGIMPROVING IMPROVING MONITORING AND MONITORING AND WARNING SYSTEMSWARNING SYSTEMS

IMPROVED BUILDING CODES FOR NEW BUILDINGSIMPROVED STANDARDS FOR NEW INFRASTRUCTURESTRENGTHENING AND RETROFIT OF EXISTING STRUCTURESEXPANDING INTERNATIONAL COOPERATION

P1

Slide 3

P1 PASKALEVA; 10/8/2010

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IMPLEMENT PUBLIC POLICY

IMPLEMENT IMPLEMENT PUBLIC PUBLIC POLICY POLICY

RISK ASSESSMENT

•• VULNERABILITY VULNERABILITY

•• EXPOSUREEXPOSURE

•• EVENTEVENT

POLICY ASSESSMENT

•• COSTCOST

•• BENEFITBENEFIT

••CONSEQUENCESCONSEQUENCES

REDUCE LOSSES FROM NATURAL AND REDUCE LOSSES FROM NATURAL AND TECHNOLOGICAL HAZARDSTECHNOLOGICAL HAZARDS

HAZARDHAZARDHAZARD EXPECTED LOSS

EXPECTED EXPECTED LOSSLOSS

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EARTHQUAKE HAZARDS MODEL EXPOSURE MODEL VULNERABILTY

MODEL

SEISMOTECTONIC SETTING

LOCATION OF STRUCTURE

QUALITY OF DESIGN AND

CONSTRUCTION

RESISTANCE TO LATERAL FORCES

IMPORTANCE AND VALUE OF

STRUCTURE

POLITICAL PROCESS

ACCEPTABLE RISK

MITIGATION COSTS

EXPERIENCE AND RESEARCH

DAMAGE ALDORITHM

INCORPORATE NEW KNOWLEDGE

INSPECTION AND REGULATION

IMPLEMENTATION OF SEISMIC SAFETY

POLICY

IMPLEMENTATION OF IMPLEMENTATION OF SEISMIC SAFETY SEISMIC SAFETY

POLICYPOLICY

ASSESSMENT OF RISK

ASSESSMENT ASSESSMENT OF RISKOF RISK

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Risk of losses Framing equation

Decision variable• risk of losses

DV

Damage measure• casualties• capital loss• downtime

D

Engineering demandparameter• displacement• drift• etc

EDP

Intensity measure• hazard curve• level of shaking

IM

( ) ∫∫∫= )(||| IMdIMEDPdGEDPDMdGDMDVGDVv λ

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Engineering demand parameters and forces

Eik -design seismic force I-th mode of vibration at point “k” of the structureKc - seismic coefficient DGA, determined in accordance with Seismic Zoning Map (1000 in BG code 475 year return period in EU8) βi - dynamic coefficient corresponding to the I-th mode of vibration and soil group: R - response coefficient of the structure under seismic excitations; C - importance coefficient, numerical valuesηik - coefficient of distributionXik , Xij - the modal displacement amplitude of the I-th mode of vibration at point “k” of the structure;Qk - the weight of the lumped mass at point “k”n - number of the degree of freedom;

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MODELLING

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SCHEMATICAL MODELSCHEMATICAL MODEL

Bedrock

Local site

Half space

Seismic Source

Receivers

Quake Quake abbrabbr

Lat.(oN)

Long.(oE)

Magnitude Magnitude MwMw

Focal Focal depth, kmdepth, km

Strike angle,o

Dip angle,o

Rake angle, o

Sce_1Sce_1 45.76 26.53 7.27.2 132.7132.7 240 72 97Sce_2Sce_2 45.80 26.7 7.87.8 150150 225 60 80

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Methods to solve the equations of particles' motion due to the seismic waves propagation

In general there are two main classes of methods to solve the equations of particles' motion due to the seismic waves propagation in anelastic laterally heterogeneous media: analytical and numerical methods.Analytical methods should be preferred when dealing with models whose dimensions are several orders of magnitude larger than the representative wavelengths of the computed signal, because of the limitations in the dimensions of the model that affect the numerical techniques. Among the methods that are suitable to solve the equations of motion in flat laterally heterogeneous inelastic media with numerical techniques applied to analytical solutions, two main complementary classes can be distinguished: methods based on ray theory and methods based on mode coupling. The arrivals associated with surface waves (fundamental and higher modes) usually represent the dominant part of the seismogram [Saragoni et al, 1995] and they supply the data with the most favorable signal/noise ratio for seismic hazard studies with engineering implications.

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Surface waves cannot be modeled easily with methods based on ray theory, because of computational problems: it is not a theoretical, but a practical limitation. On the other hand, the modal summation is a natural technique for modeling the dominant part of the seismic ground motion. The key point of the method applied is the description of the wavefield as a linear combination of given base functions: the normal modes characteristic of the medium. The technique used shares the idea that the unknown wavefield, generated by the lateral heterogeneity, can be written as a linear combination of base functions representing the normal modes (Love and Rayleigh) of the considered structure, therefore the problem reduces to the computation of the coefficients of their expansion.

Methods to solve the equations of particles' motion due to the seismic waves

propagation (Cont.)

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Scheme Methods for solving particles’ equation of motion

Numerical methods

Analytical methods

Hybrid methods

MFD (finite dif.)

MFE (finite el.)

MBE

Ray Theory

Mode Coupling

PSM (pseudo spectral method)

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METHODOLY USED AND TOOLS FOR CALCULATIONS

Synthetic seismograms are created with the software package SPECFEM3D, due to Komatitsch and Tromp [D. Komatitsch et al.], [2], [3]SPECFEM3D simulates seismic wave propagation using the spectral-element method (SEM) [4_A. T. Patera]SEM was introduced by Patera in 1984 and combines the flexibility and generality of the Finite Element Method (FEM) with the accuracy of the Spectral Method.In SPECFEM3D, SEM is used to solve the seismic wave propagation equation – a specialized version of the non-compressible Navier-Stocks equation.5th order Legendre polynomials on Gauss-Lobatto-Legendre collocation points are used for interpolation and integration, which allows for diagonal mass matrix.Full anisotropy is supported and attenuation model with 3 standard linear solids is used.

The package can simulate both point sources and finite sources of earthquakes.

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Mesh properties

Conformant hexahedral mesh with distortable elements;The shape of the elements is adapted to the major geological discontinuities (illustrations are due to [D. Komatitsch, S. Tsuboi, J. Tromp. The Spectral-element Method in

Seismology. Seismic Earth: Array Analysis of Broadband Seismograms]).

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Model propertiesThe most difficult task in seismic wave propagation simulation is to prepare an adequate Earth model.In the original SPECFEM3D package, effects due to lateral variations in compressional-wave speed, shear-wave speed, density, a 3D crustal model, topography and bathymetry are included for Southern California.We had to modify the package and adapt the model to our domain, including a new Mohorovich boundary map, a new Basement map and a new set of data for lateral variations in compressional-wave and shear-wave velocity for certain areas.Comparisons between synthetic and real seismograms show that the model is adequate but more data and effort is needed to make it even better.

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NESSESARY INPUTfor regional model

Mohorovičić surface / Moho/. Map of the surface of the crystalline basement for the regional model. The body wave veleocity Vp for the surface of the crystalline basement for the regional model[km/s].The body wave veleocity Vp for the sedimentarylayer above the crystalline basement for the regional model [km/s].Epicentral map of the earthquakes occurred within the region.Lithostratigraphical table for the area of the local model.

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The obtained Moho map is quite different as general configuration from the maps that have been published so far. The deepest Mohodiscontinuity is again beneath the Rila Mountain and the lowest depths are obtained in the eastern part of the investigated territory. An elongated structure in NW-SE direction, with maximum depths under Rila Mountain, illustrating the discovered data anisotropy (133°) is observed. Interesting structure is observed in the region of the East Rhodopes, where Moho discontinuity appears at about 30 - 32 km(confirmed also by comparison with Zdraveva et al., 1996). Lower Moho depths are observed also on the South on Thessaloniki (up to 30km) and in NE Bulgaria, as well as in the Black Sea aquatory.

Mohorovičić Surface in the Central part of the Balkan Peninsula

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Combined maps

• Map of the Moho surface in the Central part of the Balkan Peninsula, constructed considering all published data and making use of the innovative tool of geostatistics.

• Map of the surface of the crystalline basement for the regional model. The isolines are in km beneath the sea level.

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Combined maps (Vp)

Isolines of the body wave veleocity Vp for the surface of the crystalline basement for

the regional model [km/s].

Isolines of the body wave veleocity Vp for the sedimentary layer above the

crystalline basement for the regional model [km/s].

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Epicentral map of the earthquakes occurred within the territory of the investigated region in the time period 1973 – 2010 (NEIC) .

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VRANCEA SOURCE STATE OF THE ART

The Vrancea zone, located in Romania, at the sharp bend of the South-Eastern Carpathians is a well-defined seismic region in Europe, with unique properties. The seismicity is concentrated in an extremely narrow, high-velocity, focal volume in the depth range from 60 to 200 km. A relatively high seismic energy is persistently released (four shocks with magnitude greater than 7 occurred during the past century) by a seismogenic process still far from being fully understood. At more shallow levels (0-60 km) the seismicity here is sporadic and weak (magnitude below 5.5), and seems to be decoupled from the seismic activity in the subcrustal lithospheric slab. All the major shocks are characterized by a quite stable reverse faulting focal mechanism with the rupture plane oriented in a NE-SW direction, parallel to the Carpathians arc, and following the orientation of the epicenters distribution (Gusev et al., 2002). The maximum magnitude achieves about 7.4 on the Gutenberg-Richter scale, MGR, according to different estimations [Zaicencoand Alkaz, 2005]. The increase of magnitude appears to be positively correlated with the increase of depth [Georgescu and Sandi, 2000 and references therein]. The largest Vrancea earthquakes radiate mostly at frequencies below 1 Hz (Gusev et al., 2002). The analysis of local short-period data indicates that, for a given seismic moment, the source area of the intermediate-depth Vrancea events is significantly smaller than the size usually observed for shallow events, and implicitly the stress drop is higher (Oncescu, 1989; Radulian and Popa, 1996; Popa and Radulian, 2000).

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"No where else in the world is a center of population so exposed to earthquake originated repeatedly from the same (Vrancea) source”. (Charles Richter (1977)

Earthquakes coming from the Vrancea are of great interest due to the social and economical impact on the territory of the adjacent countries. The attenuation toward NW is shown to be a much stronger frequency-dependent effect than the attenuation toward SE for higher frequencies (> 1Hz).The maximal seismic intensity reached the level of VIII-IX degrees on MSK scale, while the territory covered by the VI-degree (region with severe ground motions and buildings' damage) includes Romania, Republic of Moldova, a large part of Bulgaria and South-WesternUkraine.

This problem is essential for Vrancea earthquakes, which exert influence on large area with linear size more 1500 km. The total area of the territory more influenced by Vrancea earthquakes comprises about 407000 km2, populated by more than 37 million people. In addition there are Russia (other European part), Hungary, Serbia, Croatia, Bosnia and Herzegovina, Macedonia, Belorus, Estonia, Lithuania, Latvia.

The unusually small attenuation at low frequency has important consequences on the seismic hazard assessment not only in Romania, but in the neighboring countries as well (e.g., Bulgaria, Rep. of Moldova, Ukraine and even Russia). This essential effect is not at all noticeable in the probabilistic maps (Musson, 2000), while it is well represented in the deterministic maps (Radulian et al., 2000).

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6974 quakes, 4 < M < 8372 eq. 70 < H < 150 km

VRANCEA DANGER, PECULIARITIES &VRANCEA DANGER, PECULIARITIES &SCENARIOUSSCENARIOUS

Regional Seismicity, USGS / NEIC (PDE) 1973 – Present,

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VRANCEA PECULIARITIESVRANCEA PECULIARITIES

26

[Radulian et al., 2007].

[Gusev et al., 2006].[Raykova et al., 2007].

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RESULTS AND DISCUTION

Influence of the duration on the amplificationInfluence of the distance to the sourceInfluence of the geologyInfluence of the local geological conditionsComparison with real records

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Influence of the duration on the amplification

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Distance to the source influence on the amplification (Lom and Russe stations)

The spectral content is not to sensitive the change of distance. The amplification is bigger for the Russewhich is closer to the source

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Influence of the local geological conditions

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Influence of the regional geology

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Amplification –dynamic effects

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MAIN CONCLUSIONS MAIN CONCLUSIONS

Here we would like to emphasize that the software package SPECFEM3D used to model the ground motion is capable to provide realistic acceleration, velocity, and displacement time histories and related quantities of earthquake engineering interest.

Bulgaria is under high seismic hazard and can suffer serious damages because of soil conditions, with deep soil deposits and severe local site amplification.

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The used approach computed “data base” of synthetic signals, considering simultaneously data from many disciplines, supplies an important set of parameters for practical interest, which proper use can lead to an effective reduction of seismic vulnerability and improvement of earthquake preparedness.There is no need to wait many years to collect real records and create “data base” for practical uses.

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The program package SPECFEM3D is used only for scenarios for earthquakes from Vrancea (Romania) source. The reason was that the seismic hazard for mine site is controlled from that source.In this regard, we believe that validation, the results of the software package for SPECFEM3D sources in Bulgaria, should be done too.The output of the program package SPECFEM3D can be used for assessing the vulnerability of particular elements of infrastructure with the expected losses(case study for Sofia) that allow to make recommendations and suggest possible measures to reduce seismic risk. Comparisons between synthetic and real seismogram (accelerogram) show that the model is adequate, but more data and effort needed to be improved. We have data allowing to recognize the impact of topography and bathymetry along the Black Sea. Should be expected to significantly affect the parameters (amplitude, frequency composition) of the generated signals.

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Bibliography[1] D. Komatitsch, Q. Liu, J. Tromp, P. Süss, C. Stidham, and J. H. Shaw. Simulations of strong ground motion in the Los Angeles Basin based upon the spectral-element method. Bull. Seismol. Soc. Am., 94(1):187–206, 2004.[2] D. Komatitsch and J. Tromp. Introduction to the spectral-element method for 3-D seismic wave propagation. Geophys. J. Int., 139(3):806–822, 1999. doi: 10.1046/j.1365-246x.1999.00967.x.[3] D. Komatitsch and J. P. Vilotte. The spectral-element method: an efficient tool to simulate the seismic response of 2D and 3D geological structures. Bull. Seismol. Soc. Am., 88(2):368–392, 1998.[4] A spectral element method for fluid dynamics - Laminar flow in a channel expansion. Journal of Computational Physics, 54:468--488, 1984.[5] D. Komatitsch, S. Tsuboi, J. Tromp. The Spectral-element Method in Seismology. Seismic Earth: Array Analysis of Broadband Seismograms. Geophysical Monograph Series 157. Copyright 2005 by the American Geophysical Union 10.1029/156GM13.[6] G.F. Panza, M. Radulian, T. Kronrod, I. Paskaleva, Sl. Radovanovic, M. Popa, A.

Drumea, K. Gribovszki, D. Dojchinovski, M. Kouteva, P. Varga & L. Pekevski (2010) Integrated Unified Mapping of the Vrancea Macroseismic Data for the CEI Region, 14 ECEE, Ohrid 30.08-03.09, CD, Ref. 301.[7] Nenov D, Georgiev G, Paskaleva I, Lee V W, Trifunac M. (1990). Strong Ground motion data in EQINFOS: accelerograms recorded in Bulgaria between 1981-1987, Bulg. Acad. of Sci., Centr. Lab. for Seism. Mech. And Eq. Eng., & Dept. of Civ. Eng. Dpt.No 90-02, Univ. of S. California, L. A., California.

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ACKNOWLEDGEMENT

The work presented is the result of research sponsored by the National Center for Supercomputing Applications (NCSA)in the frame work of the project “Creating and testing a dynamic model of seismic resistance of the open pit and adjacent settlements for the needs of the Energy Project Lom lignite “.The authors remind, with profound gratitude to The authors remind, with profound gratitude to the Professor St. Markovthe Professor St. Markov and Prof. Marginov for the encouragement to develop this assessment.

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THANK YOU VERY MUCH

FOR YOUR KIND ATTENTION