epistemic uncertainty in california-wide simulations of synthetic seismicity
DESCRIPTION
Epistemic uncertainty in California-wide simulations of synthetic seismicity. Fred Pollitz, USGS Menlo Park. Acknowledgments: David Schwartz, Steve Ward. Ward (2000). Rundle et al. (2008). Capabilities of this simulator. Inherently discrete fault zone (Ben-Zion and Rice model) - PowerPoint PPT PresentationTRANSCRIPT
Epistemic uncertainty in California-wide simulations of synthetic seismicity
Fred Pollitz, USGS Menlo Park
Acknowledgments: David Schwartz, Steve WardAcknowledgments: David Schwartz, Steve Ward
Ward (2000)Ward (2000)
Rundle et al. (2008)Rundle et al. (2008)
Capabilities ofCapabilities ofthis simulatorthis simulator
• Inherently discrete fault zoneInherently discrete fault zone
(Ben-Zion and Rice model)(Ben-Zion and Rice model)
• Homogeneous, planar faultsHomogeneous, planar faults
• Viscoelasticity of lower crust/upper mantleViscoelasticity of lower crust/upper mantle
--> loading through backslip in the--> loading through backslip in the
fully relaxed limitfully relaxed limit
• Fault network and slip rates courtesy of Steve Ward (June, 2009)
• Original set of ~4 x 3 km2
patches are re-grouped and subdivided into set of smoothly-connected, non-overlapping ~1 x 1 km2 patches
• 101208 fault patches
Stress history on a single fault patch
Static frictional stress
Dynamic frictional stress
Arrest stress
Dynamic overshoot parameter:
Stress reduction parameter: = s - a
D = s - a)/(s - d)
Simulator parameters
Dynamic overshoot parameter:
Stress reduction parameter: = s - a
D = s - a)/(s - d)
Shape of slip-weakening curve
Mantle viscosity m
Twenty consecutive M>6.7 ruptures
M6.9M6.9
M7.2M7.2
M7.0M7.0
M7.6M7.6
M6.7M6.7
M7.5M7.5
M7.6M7.6
M7.2M7.2
M6.7M6.7
M6.7M6.7
M7.7M7.7
M7.3M7.3
M7.5M7.5
M7.3M7.3
M7.3M7.3
M7.2M7.2
M6.7M6.7
M7.2M7.2
M7.3M7.3
M7.5M7.5
• mean recurrence interval (for given magnitude threshold)
• magnitude-frequency statistics, e.g. b-value
• coefficient of variation
• conditional rupture probability
Simulator results
Hanks and Bakun (2007Hanks and Bakun (2007))
Magnitude-frequency statistics
magnitude
log10
[earthquakeproduction rate (yr-1)]
With slip weakeningD=1.25m= 1.2 x 1019 Pa s
With slip weakeningD=1.25m= 1.2 x 1019 Pa s
Low Mantle Viscosity
High Mantle Viscosity
magnitude
log10
[earthquakeproduction rate (yr-1)]
• Fault system behavior is sensitive to simple parameters
• Simulations capture Gutenberg-Richter and characteristic-earthquake behavior
• Comparison of slip maps for the southern SAF suggests that the ‘slip barrier’ nature of a segment boundary depends substantially on mantle viscosity
• Characteristic magnitude and mean recurrence interval may exhibit a systematic dependence on mantle viscosity
Conclusions