Difference between revisions of "CyberShake Background Seismicity"

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Latest revision as of 19:34, 20 April 2020

Goal: determine the importance of background seismicity in different parts of CA to either validate it's exclusion in CyberShake or motivate an inclusion strategy.

UCERF2

To illustrate what events UCERF2 includes in background seismicity, below are plots of the magnitude-frequency distribution for the UCERF2 ERF in both linear and log scale. Blue is the full UCERF2 distribution, and black is the on-fault ERF used in CyberShake. All UCERF2 finite-fault ruptures are included in CyberShake, regardless of magnitude, though the GR distribution applied to type B faults is only for M>=6.5, and floating rupture sources start at M6.5, which is why there are fewer CyberShake events for M<6.5.

Ucerf2 mfd linear.png Ucerf2 mfd log.png


Calculation parameters:

  • GMPE: NGA-West2 GMPE (average of 4 models)
  • ERF: UCERF2, with and without background seismicity
  • Site Effects: Vs30 is from Wills (2015), no basin depth terms included
  • IMT: 2 second SA.
Model 10% in 50yr 2% in 50yr 1% in 50yr
Excluding Background
Ngaw2 exclude 2sec 10p in 50.png
Ngaw2 exclude 2sec 2p in 50.png
Ngaw2 exclude 2sec 1p in 50.png
Including Background
Ngaw2 include 2sec 10p in 50.png
Ngaw2 include 2sec 2p in 50.png
Ngaw2 include 2sec 1p in 50.png
Ratio Exclude/Include
Ratio ngaw2 exclude ngaw2 include 10p in 50.png
Ratio ngaw2 exclude ngaw2 include 2p in 50.png
Ratio ngaw2 exclude ngaw2 include 1p in 50.png

UCERF3

Calculation parameters:

  • GMPE: NGA-West2 GMPE (average of 4 models)
  • ERF: UCERF3, with the following configurations
    • Supra-seismogenic ruptures only (only supra-seismogenic ruptures have finite fault surfaces in UCERF3, all others treated as gridded)
    • Supra and Sub-seismogenic ruptures only (this adds gridded ruptures that correspond to sub-seimogenic ruptures on known faults)
    • Supra, Sub-seismogenic, and off fault ruptures (complete model)
  • Site Effects: Vs30 is from Wills (2015), no basin depth terms included
  • IMT: 2 second SA.
Model 10% in 50yr 2% in 50yr 1% in 50yr
Supra-Seismogenic On-Fault Only
Ucerf3 supra only 10p in 50.png
Ucerf3 supra only 2p in 50.png
Ucerf3 supra only 1p in 50.png
Sub+Supra-Seismogenic On-Fault Only
Ucerf3 sub+supra 10p in 50.png
Ucerf3 sub+supra 2p in 50.png
Ucerf3 sub+supra 1p in 50.png
Complete Model (Supra+Sub+Off)
Ucerf3 sub+supra+off 10p in 50.png
Ucerf3 sub+supra+off 2p in 50.png
Ucerf3 sub+supra+off 1p in 50.png
Ratio Supra-Only/Complete
Ratio ucerf3 supra only vs sub+supra+off 10p in 50.png
Ratio ucerf3 supra only vs sub+supra+off 2p in 50.png
Ratio ucerf3 supra only vs sub+supra+off 1p in 50.png
Ratio Supra+Sub/Complete
Ratio ucerf3 sub+supra vs sub+supra+off 10p in 50.png
Ratio ucerf3 sub+supra vs sub+supra+off 2p in 50.png
Ratio ucerf3 sub+supra vs sub+supra+off 1p in 50.png
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