[ghsc-seminars] GHSC Seminar - Art Frankel, USGS, January 17, 2023

Thu Jan 12 20:43:31 UTC 2023

Dynamic Earthquake Rupture Simulations With Asperities and Subevents

Speaker: Art Frankel
         USGS Earthquake Science Center
                Seattle, WA
Location: online*
               *The speaker will be virtual, but we'll be projecting the talk in the Golden entry-level
                 conference room if you'd like to join us after the pre-seminar coffee and donuts!*
Date/Time: Tuesday, Jan 17, 2023 10-11am MST

Abstract: The terms “asperity” and “subevent” have been used, sometimes interchangeably, to describe areas on an earthquake rupture zone with high strength or stress. Observations of crustal and subduction-zone earthquakes indicate that portions of the rupture zone that radiate most of the high-frequency (> 0.5 Hz) strong ground motions are not the locations of peak co-seismic slip. I have done 3D dynamic rupture simulations that elucidate the differences between asperities and subevents.  Subevents are localized areas of heterogeneous initial stress or strength with patches of high stress drop that generate high-frequency seismic energy, but have relatively low slip. Asperities are areas with higher initial stress or strength that varies smoothly along the fault. The asperities produce the peak slip but generate relatively little high frequency ground motions. Many observations show that subevents are located on the deeper portion of the rupture, near the brittle-ductile transition. I speculate that spatial variations in physical conditions or material properties, such as temperature and activation energy of creep, can produce heterogeneous stress near the brittle-ductile transition. This heterogeneous stress near the brittle-ductile transition may lead to subevents in large earthquakes that generate high frequency ground motions. Thus, the study of high frequency ground motions can provide insights into the physical properties of faults and the spatial variability of these properties.

For questions, comments, or speaker suggestions, please contact the GHSC Seminar Committee: Andrea Llenos <allenos at usgs.gov>, Benjamin Murphy <bmurphy at usgs.gov>, Lauren Schaefer <lschaefer at usgs.gov>

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