Thread: CIG Seismic Cycles Webinar Series

Started: 2022-05-03 15:04:57
Last activity: 2022-05-03 15:04:57
Alice Gabriel
2022-05-03 15:04:57
Dear colleagues,

The Seismic Cycles Working Group of the Computational
Infrastructure for Geodynamics (CIG) presents this weekly seminar series in
preparation for a virtual symposium this Fall on seismic cycles modeling.
The weekly seminar series will stretch until July 2022. Each week, we
invite two speakers to give a 30-minute talk.

The seminar series kicks off on *May 6, 9A-10A PDT* on the topic of
physics-based foreshock and aftershock modeling - what can explain the
observed rate of aftershocks and the possible origins of the
Gutenberg-Richter frequency-size distribution:

*Speaker 1: So Ozawa, University of Tokyo*
*Title: Mainshock and aftershock sequence simulations in a nonplanar fault
Abstract: Aftershocks seem to be located along the trace of the mainshock
fault; however, due to the location error, we do not know their exact
location relative to the mainshock fault. Here, we hypothesize that most
aftershocks occur on small subsidiary faults instead of the mainshock
fault, and they are triggered by the local increase of stress due to the
rough geometry of the mainshock fault. To explore this scenario, we perform
2-D earthquake sequence simulations considering a rough main fault and
numerous subsidiary faults that obey the rate and state friction law. We
show that many aftershocks occur at the side of the main fault, delineating
the main fault trace. We also show that the roughness of the main fault
decreases the concentration of aftershocks around the tip of the mainshock
fault. Our numerical simulation reproduces the Omori-Utsu law for the
temporal decay of aftershocks and the log-time expansion of the aftershock
zone. This is one of the first earthquake sequence simulations based on the
continuum mechanics framework that reproduces realistic spatiotemporal
aftershock activities.

*Speaker 2: Shiying Nie, University of Southern California*
*Title: Rupture styles and recurrence patterns in seismic cycles linked to
physical properties of the fault zone*
Abstract: Rupture styles emerge in a broad range of rupture styles, from
slow-slip events collocated with or without tremors to pulse-like
earthquake sequences. Meanwhile, Earthquake catalogs exhibit various
recurrence patterns, from periodic and characteristic earthquakes to
chaotic sequences with super-cycles, aftershocks and dissimilar ruptures.
The underlying physical mechanisms of these phenomena are usually
documented separately and the potential connection between them is poorly
understood. Here, we explore a wide range of frictional properties using
quasi-dynamic models of seismic cycles in two dimension to assess the link
between rupture style and recurrence patterns. We obtain a broad spectrum
of rupture behaviors controlled by several non-dimensional parameters,
including the Dieterich-Ruina-Rice number Ru, which is the ratio of
asperity to a characteristic nucleation size, and Rb, which reflects the
relative amplitude of weakening and strengthening effects. Seismogenic
slow-slip events are the natural behavior of near-velocity neutral
condition (low Rb) with a small characteristic nucleation size (high Ru),
which is commonly found below the seismogenic zone. The deviation from
periodic and characteristic recurrence behaviors are responses of
homogeneous or compliant fault-zone models with high Ru numbers. The
presence of a compliant zone can be incorporated into the Ru number in
quasi-dynamic simulations. Observations of rupture characteristics and
recurrence patterns can bring useful constraints on the physical properties
of fault zones.

*More info: *


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