Conveners: Ruth Harris and Ralph Archuleta
Dates: March 15, 2013
Location: USGS Menlo Park campus (Building 3, Room 3-237)
SCEC Award and Report: 12177

SUMMARY: The purpose of the March 15, 2013 SCEC Rupture Dynamics Code Comparison Workshop was to discuss the results for our group’s most recent benchmarks, TPV22-23, and 24-25, which are fault stepovers and fault branches, respectively, and to plan our next science steps for 2013-2014. We also observed a laboratory earthquake on the USGS’s ‘big block’, learned about how our work fits into the big picture of earthquake engineering application, and learned about spontaneous rupture models of the 2011 Tohoku earthquake. For more information about our code comparison group and the benchmarks, please see the SCEC/USGS Spontaneous Rupture Code Verification Project website.

PARTICIPANTS (37 Total, 8 Remote): Brad Aagaard (USGS), Ryosuke Ando (GSJ, AIST), Norm Abrahamson (PG&E), Pablo Ampuero (Caltech), Ralph Archuleta (UCSB), Michael Barall (Invisible Software), Sam Bydlon (Stanford), Luis Dalguer (ETHZ), Steve Day (SDSU), Kenneth Duru (Stanford), Ben Duan (Texas A&M), Eric Dunham (Stanford), Percy Galvez (ETHZ), Tom Hanks (USGS), Ruth Harris (USGS), Evan Hirakawa (UCSD), Yihe Huang (Caltech), Tran Huynh (USC), Junle Jiang (Caltech), Yoshi Kaneko (GNS), Yuko Kase (GSJ), Brian Kilgore (USGS), Jeremy Kozdon (NPS), Qiming Liu (UCSB), Julian Lozos (UCR), Shuo Ma (SDSU), Greg McLaskey (USGS), Morgan Moschetti (USGS), Ossian O'Reilly (Stanford), David Oglesby (UCR), Ryan Payne (Texas A&M), Arben Pitarka (LLNL), Daniel Roten (ETHZ), Surendra Somala (Caltech), Seok Goo Song (ETHZ), Lucas Wilcox (NPS), and Shiqing Xu (USC).

Presentation slides may be downloaded by clicking the links following the title. PLEASE NOTE: Files are the author’s property. They may contain unpublished or preliminary information and should only be used while viewing the talk.

FRIDAY, MARCH 15, 2013

REPORT: The 2012 SCEC Dynamic Rupture Code Comparison Workshop was held March 15, 2013, at the U.S. Geological Survey in Menlo Park, California. 37 people participated, including 8 remotely, and 29 in the meeting room. This year’s workshop included at least 9 new people, among them 3 new students and 4 new postdocs. Our attendees this year included scientists from 4 countries (Japan, New Zealand, Switzerland, U.S.A.), with outside-U.S. attendees primarily participating remotely. At least 15 of our 37 participants were either students or postdocs. Many thanks to Tran Huynh for all of her dedicated work that helped make this workshop happen.

This report specifically describes the March 15, 2013 (2012-funded) workshop. Please note that there is also another, companion annual report that has been written and delivered to SCEC for the 2012 SCEC group project 12156, ‘A Collaborative Project: Rupture Dynamics, Validation of the Numerical Simulation Method’.

Ruth Harris (USGS) introduced the workshop to the participants, who learned for the first time (or remembered, if they were code workshop veterans) about the previous science that has been done to test our computer codes that simulate earthquakes as spontaneous ruptures. A quick summary of all of the computer code benchmarks performed to date was presented. There was mention of the successes and challenges from last year’s benchmarks, in particular that the heterogeneous initial stresses planar-fault benchmark worked very well, and that the fault branch benchmark worked less well, and therefore had been reintroduced for this year’s modeling exercises.

The participants then learned about the SCEC Community Stress Model, in a talk by Brad Aagaard (USGS), who presented information about the progress and plans of the CSM Technical Activity Group.

Michael Barall (Invisible Software) then presented a comprehensive talk explaining the details of the newest completed SCEC Dynamic Rupture group’s benchmarks, the case of the fault stepover (TPV22-23), and the case of the fault branch (TPV24-25). The fault stepover benchmarks were successfully achieved by the codes that did the simulations with appropriate resolution. The fault branch in previous years had provided the modelers with challenges, and this year was the third try by our group with this fault geometry. Fortunately, this time around the codes that simulated the benchmarks and that also implemented the requested element-sizes, did successfully match each other well.

Ossian O’Reilly (Stanford) then gave a brief presentation about theoretical modeling approaches to friction-free fault branches.

The workshop attendees next joined workshop co-convener Harris in a discussion about how our group should frame our 2013 benchmarks, cases of the fault bend/curve. Proposed ideas included sinusoidal faults, circular faults of varying radii, planar faults with single bumps, and fault bends. Upcoming email conversations among the group’s members will pinpoint the exact desired parameters for this 2013 study of non-planar fault geometry that will likely first be implemented in 2D. Workshop time ran out before the group was able to discuss another activity that is planned for 2013, development of comparison metrics, but this theme is likely to be continued and enhanced in email dialogues among our group members. It was also suggested by workshop co-convener and Dynamic Rupture Code Comparison group project-lead Harris that this theme of comparison metrics could serve as a topic for our next big group paper.

Following lunch, USGS scientists Brian Kilore and Greg McLaskey presented the workshop in-person attendees with a tour of the big-block and one of the smaller rock friction machine setups in the USGS rock mechanics labs. Attendees were able to experience a laboratory earthquake, and view where rate-state history and empirically-based hypotheses about rate-state friction in both rock and plastic occurred over the past 30 years.

The workshop attendees then returned to the conference room where Norm Abrahamson (PG&E) gave a talk about upcoming deadlines for big projects that are related to engineering implementation. He discussed how computationally-based dynamic rupture simulations might be able to contribute to these implementation efforts. Among the topics that Abrahamson presented as needing better solutions are methodologies for simulating hanging wall vs. footwall ground motion effects, and representation of large earthquake sources on creeping faults and their resulting ground motions. Actual implementation in a robust framework would however require validation of the ground motions predicted by spontaneous rupture simulations. This validation could be accomplished by comparing the computational simulation results with ground motion recordings from actual events. The desired frequency range is up to 5 hz.

After a short break, the workshop attendees next heard four talks about spontaneous rupture models of the 2011 Tohoku earthquake. Benchun Duan (Texas A&M University) and Yihe Huang (Caltech) presented talks about their models that primarily implemented slip-weakening-type friction, Junle Jiang (Caltech) presented Hiroyuki Noda’s (JAMSTEC) and Nadia Lapusta’s (Caltech) work that implemented thermal pressurization, and Shuo Ma (San Diego State University) presented his models that implemented slip-weakening but set the fault in an elastoplastic setting.

For more information about our group, to download our group’s papers, for descriptions of our group’s benchmarks that we use to compare our codes’ results, and to view many of our workshop presentations, please see our SCEC/USGS Spontaneous Rupture Code Verification Project website.

Thank you to SCEC for funding this workshop.