1 The SCEC Broadband Ground Motion Simulation Platform Paul Somerville, Scott Callaghan, Philip Maechling, Robert Graves, Nancy Collins, Kim Olsen, Walter Imperatori, Megan Jones, Ralph Archuleta, Jan Schmedes, Thomas H. Jordan

Southern California Earthquake Center Collaboration of 600+ scientists at 60+ institutions SCEC conducts earthquake system science –Many physical phenomena involved –Community Modeling Environment (CME) improves computational models 2 Anticipation time monthdayyeardecadecenturyweek Fault rupture Origin time Response time  0 minutehourday yeardecade Aftershocks Surface faulting Seismic shaking Structural & nonstructural damage to built environment Human casualties Disease Fires Socioeconomic aftereffects Landslides Liquifaction Nucleation Tectonic loading Stress accumulation Seafloor deformation Tsunami Dynamic triggering Slow slip transients Stress transfer Foreshocks -----

Earthquake Simulations Scenario earthquake simulations increase understanding of ground motions Valuable in determining seismic hazard SCEC performs a variety of large-scale scenario simulations 3 N

Broadband Platform Collaborative software system –SCEC research groups –CME software development Computes seismograms from 0-10 Hz Can be run by scientists or engineers without detailed knowledge of the code details Open development and user access 4

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Features and Attributes Transparency / Reproducibility –Software is open and downloadable Software Control –Formal releases with documentation –Version control Flexibility –Modular architecture –Standardized data formats Expandability –Designed for easy addition / revision of computational modules 6

Current Capabilities Can run historical earthquakes –Validate simulations against observed results Scenario earthquakes –Ground motions due to potential earthquakes –User supplies earthquake description User provides list of sites at which to perform simulations User selects modules to run –Multiple implementations of same functional steps –Compare and contrast codebases 7

Source Description CFM, ERF M w, Dimension, Geometry Kinematic Rupture Generator Standard Rupture Format GF Libraries Site Lists Velocity Models High Frequency Simulation (> 1 Hz) Low Frequency Simulation (< 1 Hz) Combine into BB, add Site Response Broadband Time Series (0 – 10 Hz) Schematic Workflow

Current Modules 9 UCSBURSSDSU / ETH Kinematic Rupture Generator XX 1D Low Frequency Wave Modeling XX 1D High Frequency Wave Modeling XXX Site Response XXX URS:Graves, R. W. and A. Pitarka (2010). “Broadband Ground-Motion Simulation Using a Hybrid Approach.” BSSA., 100, , doi: / SDSU / ETH:Mai, P.M., W. Imperatori, and K.B. Olsen (2010). “Hybrid broadband ground motion simulations: combining long-period deterministic synthetics with high frequency multiple S-to-S back-scattering.” BSSA, 100, , doi: / UCSB:Schmedes, J., R. J. Archuleta, and D. Lavallée (2010). “Correlation of earthquake source parameters inferred from dynamic rupture simulations.” JGR, 115, B03304, doi: /2009JB

Rupture Generation Converts user-provided simple earthquake description into full kinematic rupture description (SRF file) Optional module (can supply SRF) 10 MAGNITUDE = 6.67 FAULT_LENGTH = DLEN = 0.2 FAULT_WIDTH = DWID = 0.2 DEPTH_TO_TOP = 5.0 STRIKE = 122 RAKE = 90 DIP = 40 LAT_TOP_CENTER = LON_TOP_CENTER = HYPO_ALONG_STK = 6.0 HYPO_DOWN_DIP = 19.4 DT = 0.01 SEED = CORNER_FREQ = 0.15 Source DescriptionRupture with slip

Seismogram Generation Low-frequency generation –Generates 0-1 Hz seismograms –Deterministic, calculated from 1-D Green’s functions –Two implementations 11 High-frequency generation –1-10 Hz seismograms –Stochastic attributes –Three implementations

Combine into Broadband 12 Matched filters at 1 Hz –Low-cut for HF –High-cut for LF –Sum to get BB (Seyhan et al., 2011)

Site Effects Adjusts seismograms based on site specific properties Current modules Vs30 based 13 Before site responseAfter site response

Optional comparisons Response spectra –Examine frequency behavior –Can compare against observed or simulated results Goodness-of-fit –Compares response spectra from ≥3 stations 14

Data Products 15 Rupture Plots Velocity and acceleration seismograms Station and fault trace maps

Comparison Data Products 16 Spectral response comparison Seismogram comparison Goodness-of-fit

Software Engineering Modular design Code integration Software testing Formal release 17

Modular Design Each module represented by Python class User chooses which implementation 18 User input: URS SDSU UCSB … Workflow description URS SDSU UCSB … Low freq High freq Site response Execute modules Construct description URS UCSB SDSU …

Example Invocation 19 #./run_bbp_2G.py Welcome to the SCEC Broadband Platform. Please select the modules you want to run. Do you want to perform a validation run (y/n)? n Do you want to run a rupture generator (y/n)? y Rupture generators: URS (1) UCSB (2) ?1 Using region: Southern California Choose a low frequency module: URS (1) UCSB (2) ?2 Found multiple BBP station list files in the start directory. Please select one: nr_one_stat.stl (1) valid_test_stat.stl (2) nr_five_stat.stl (3) ?3 Choose a high frequency module:... You can find results in /home/scec-00/scottcal/bband/...

Code Integration Goal to make platform easy to run without detailed code knowledge Modified codes to read and write common (i.e., standardized) formats Simplifies addition of future modules 20

Software Testing Need to verify platform is installed correctly Three levels of testing –Checksums to verify data files –Unit testing Each module checked for correct performance –Acceptance testing All combinations of modules run to check integration Very useful in locating problems Gives users confidence in results 21

Formal Release Platform targeted at wide variety of users Requires extra effort with science codes Detailed user’s guide Track system for bugs Version released on February 18, 2011 Official web site 22

Current Applications NGA-West 2 –Footwall / hanging wall simulations NGA-East –Simulations to help constrain ground motion prediction equations (GMPEs) Zeng et al. 11:45 am today 23

Future Plans Reduce software dependencies (e.g. OS, compilers) Additional modules New modules –1D GF calculator –3D GF calculator Parallel version Increase support for varied execution environments –Virtual machines –Cloud 24

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Verification and Validation Similar results verifies multiple complex codes 27 Finite element (CMU)Finite difference (AWP-ODC)Finite difference (URS)

Small-scale simulations Hundreds of thousands of potential M5+ events in Southern California Enable individual scientists to run simulations Compare results from multiple codebases 28

Schematic 29