3D waveforms simulationfor earthquakes and scenario events
Shiann‐Jong Lee
Institute of Earth Sciences, Academia Sinica

TEM Workshop, NCU, 2012/06/04‐2012/06/05
Seismic Hazard Assessment Issues in the island arc of Taiwan and Japan

Introduction•Taiwan is formed by a collision
between the Philippine Sea plate
and the Eurasian continental
margin.

•In the last 20 years, numerous
large hazardous earthquakes had
caused remarkable damages withconsiderable casualties.

•It is therefore an importantscientific mission to simulate andto understand the hazardous
earthquakes by using highresolution, advanced numericalsimulation techniques.

Block diagram showing arc‐continent collision and tectonic
setting of Taiwan (by CHANG,2001)

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Earthquake simulation ‐ Source, Path and SiteSource‐ M<6: Point source parameters‐ M>6: Finite‐fault source model‐ Fault and seismogenic zone
‐ Kinetic and dynamic analyses

Path and site
‐ Large‐scale velocity model‐ Local velocity model‐ Surface topography‐ Moho, plate boundary‐ Basin, sedimentary plain, … etc.

Earthquake simulation‐ ShakeMovie: 3D wave propagation‐ ShakeMap: PGA, PGV, Intensity map‐ Synthetic waveforms‐ Visualization
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Path: Numerical velocity and structure model
Spectral‐element method mesh model‐ Large scale velocity model‐ Local structure model‐ Surface topography‐ Basin model4

Path: Realistic topography effects
Shamao Mountain area

LiDAR DTM data (1m)Aerialtopographicmap

40‐m DEM

LiDAR DSM (1m)

LiDAR DTM (1m)Path: Realistic topography effects
Spectral‐element meshes

Relative change in PGA(LiDAR DTM, 2m SEM mesh at surface)(Determined from 10 Hz simulation)

Lee et al. 2009a, BSSA
Lee et al. 2009b, BSSA

PGA amplification factor: subtract the PGA value for the model
without topography from the value for the model withtopography, dividing the result by the PGA value for the model
without topography, and multiplying it by 100 to obtain apercentage
6Site: Taipei Basin
Map view of the Taipei

Taipei basin SEM mesh

Lee et al. 2008a; 2008b, BSSA
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I-Lan Doublet Event
2005/03/06 ML = 5.9, 5.9

Taipei Basin

Doublet eventTopography
BasinMoho
3D Velocity

100km(in 2005)

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Source: Numerical source modelM < 6.0: Point source
Broadband array in Taiwan for seismology:
http://bats.earth.sinica.edu.tw

M > 6.0: Finite‐fault source model
1999 Chi‐Chi earthquake (M7.6) finite‐fault source model

Lee et al. 2006 (Updated 2009)10

Source: Numerical source model
Rupture snapshots
March 3, 2010 Jiashian earthquake (ML6.4)

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Lee et al., 2012

Numerical earthquake simulation and visualization
ShakeMovie: Example of 2010 Jiashian earthquake

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Numerical earthquake simulation
ShakeMap : Example of Jiashian earthquakeCWB intensity observation

ShakeMap(Simulation)

ShakeMap(CWB report)

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Ground motion simulation and prediction
Stations used in the inversion

Velocity
0.05‐0.5 HzAll CWB RTD stations in Taiwan

Velocity
0.05‐0.2 Hz

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Realistic ground motion simulation and prediction
HybridHigh frequency

Frequency Ratio

Numerical +Stochastic

Numerical simulation

Numerical vs.
Observation

1Hz synthetic

5Hz synthetic

Observation

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Hengchun earthquake scenario
Hengchun fault

Summaryz Realistic surface topographyz Large scale velocity modelz Local velocity modelz

Moho, plate boundariesz Basin, sedimentary plain, … etc
z Travel‐time, Finite‐frequency,Adjoint tomography‐ Accomplish‐ routine‐ Update‐ refining‐ Ongoing‐ In plan

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Summaryz Point source parameters forearthquake M < 6z

Finite‐fault source rupture model forearthquake M > 6z

Kinetic source rupture analysisz

Dynamic source rupture analysisz

Fault and seismogenic zone model‐ Accomplish‐ routine‐ Update‐ refining‐ Ongoing‐ In plan

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Summaryz

ShakeMoviez

ShakeMapz

Synthetic waveformsz

Computational visualizationz Realistic ground motion simulationz Realistic ground motion prediction for

scenario earthquake‐ Accomplish‐ routine‐ Update‐ refining‐ Ongoing‐ In plan

19Thank you for your attention

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