Oral Presentation

Earthquake scenarios aim to provide an example of the damages a catastrophic earthquake can create for a community and highlight the preparedness planning and mitigation that could reduce those risks. The earthquakes used in such efforts, whether regional or local in scope, are designed to generate serious impacts and are scientifically grounded in local, specific knowledge of the fault behavior, expected ground motions, and secondary effects. This presentation reviews the basis of earthquake scenarios and illustrates how decades of work by the SCEC community position us to rapidly develop rupture models and compute ground motions based on rich scientific knowledge of the local terrain. I will then discuss ongoing work with the ShakeOut Scenario 2.0 Technical Activity Group (TAG) to generate updated earthquake scenarios for major events in southern California – a mainshock like the original 2008 ShakeOut Scenario rupture and a large aftershock in the Los Angeles area designed to test the built environment in higher-density population centers. To build the ShakeOut Scenario 2.0, we convened a series of presentations by experts in our community for an open discussion about the geologic basis for these ruptures. The foundational talks, focused on the geometry of the source faults, their geologic setting and history, revealed the wealth of data collected and modeled by this community in the last 20 years while underscoring remaining questions about California’s geologic structures. Follow-on discussion with experts in the stress field and rheologic behavior of the source faults provided insight into the stress orientation along the faults and the slip behavior with depth. Others examined aftershock statistics and static stress loading, offering scientific justification for locating the aftershock on the Raymond-Hollywood faults. Work is underway using these insights to develop dynamic rupture models and ground-motion parameters for these events. Future earth science efforts include fault zone displacements and new approaches to landslide and liquefaction effects. The work of the TAG could not have proceeded at this pace without the foundations of the SCEC community models and collaborative efforts; we look forward to building new partnerships to translate these results into societal impacts and identify key mechanisms for reducing earthquake losses.