OctreeBased Multiresolution FEM for Ground Motion Modeling in Basins

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Octree-Based Multiresolution FEM for Ground
Motion Modeling in Basins

• Jacobo Bielak
• work done in collaboration with
• Eui Joong Kim, Omar Ghattas, Jane Wang,
• Tiankai Tu, and David OHallaron

Carnegie Mellon University Presented at the
SCEC-ITR Project Meeting 9 June 2003
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Octree-Based Finite Element Method (OBFEM)
Standard element need only be scaled depending
on size and material properties
unstructured
OBM
?

M 24 K 2424

• Allows multiresolution mesh
• No global matrix storage
• Element by element calculations
• O(N) memory
• Better computational performance
• Enables increased frequency range

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Compatibility in OBM
Transition slave nodes and master nodes
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Framework
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SF10 Velocity Model (Plan View)
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SF10 Velocity Model (Cross Section)
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Performance Check
LA1 (100 m/s) 2048PEs 950 Gflops 450 Mflps/PE
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1994 Northridge Earthquake (JFP)
Jensen Filtration Plant (34.312, -118.496)
S-wave distribution along depth
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Northridge Earthquake (TAR)
Tarzana (34.160, -118.534)
S-wave distribution along depth
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CMU-WCC-UCSB (JFP)
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CMU-WCC-UCSB (TAR)
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JFP (S-wave) LA1-Vs100 Model
Scale LA1-Vs100 is 1000 size of LA2-Vs500 for a
structured grid 8 times in freq 125 times in
velocity
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FFT at JFP (s-wave)
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TAR (s-wave)
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FFT at TAR (s-wave)