3-D Modeling of Rupture Sequences of Shallow Subduction Earthquakes

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3-D Modeling of Rupture Sequences of Shallow
Subduction Earthquakes

• Yajing Liu1, James R. Rice1,2
• 1 Department of Earth and Planetary Sciences,
  Harvard University
• 2 Division of Engineering and Applied Sciences,
  Harvard University
• AGU Fall 2003, T42C-07

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We look at

• Complexities of modeled large shallow subduction
  earthquake populations
• Detailed slip behaviors during modeled great
  earthquakes
• Aseismic transients observed from simulations.

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Geometry and modeling setup
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Rate- and state-dependent friction law(including
a single state variable, Dieterich, 1978, 1981
Ruina, 1983)
Dieterich-Ruina friction (slowness law)

• Stability determining parameters
• velocity dependence of steady state friction
• nucleation size

(actual size 3 4 h)
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Depth distribution of friction parameters a and
(a ? b)
Introduce along-strike non-uniformities
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Overburden total normal stress and pore pressure

• Total normal stress
• Pore pressure
• Effective normal stress(at greater
  depth)

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Depth-averaged (over seismogenic zone) slip
versus x (along strike)
Lines plotted every 5 years
Event A
Starting time to compare results with two grid
resolutions
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Comparison of results from two grid resolutions
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Slip and slip velocity evolution of Event A
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Aseismic transients
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Another example

• Slip rate 10103 Vpl
• Initiate from the gap zones
• Migrate along strike near the downdip end of the
  seismogenic zone at an average speed 10-5 to
  10-6 of the rupture propagation speed during
  great events
• Not always rupture to the surface.

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Conclusions

1. Small along-strike variations in material
   frictional properties (or initial conditions)
   could perturb the system into a non-uniform slip
   mode, with large events occurring at various
   locations, different recurrence intervals, and
   multiple magnitudes.
2. With current h, and grid resolution, we observe
   events with aseismic slip rates (10103 Vpl),
   migrating along strike near the downdip end of
   the seismogenic zone.