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Earthquake Rate Models on “A” faults In Northern California for the

Earthquake Rate Models on “A” faults In Northern California for the National Seismic Hazard Maps and Working Group on California Earthquake Probabilities. Menlo Park, CA January 17, 2007. Types of earthquake recurrence models considered: Segmented models from WG 2002

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Earthquake Rate Models on “A” faults In Northern California for the

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  1. Earthquake Rate Models on “A” faults In Northern California for the National Seismic Hazard Maps and Working Group on California Earthquake Probabilities Menlo Park, CA January 17, 2007

  2. Types of earthquake recurrence models considered: • Segmented models from WG 2002 • B-fault type models as used by NSHMP

  3. A fault Major fault with high slip rates and sufficient data on slip rates, timing of past events, and slip per event that detailed models of fault zone behavior can be constructed B fault Faults that have significant slip rates but inadequate data on displacement or timing of past earthquakes to constrain detailed fault models C fault Zone of distributed shear with defined slip rate from geodetic and plate model where earthquakes may occur on recognized or unrecognized faults.

  4. Characteristic earthquakes on a segment of an A fault Parameters • Slip rate • Characteristic or maximum magnitude • Epistemic and aleatory uncertainty Log Ń(m) Wt=.6 Wt=.2 Wt=.2 0.2 0.12 magnitude mchar

  5. Parameters Slip rate Characteristic or maximum magnitude Epistemic and aleatory uncertainty Ratio of Characteristic to Floating Rupture moment rate Minimum magnitude b-value Floating ruptures Total Characteristic USGS Magnitude-frequency model for B-faults 2/3 Moment rate split into three magnitudes 1/3 Moment rate for floating ruptures (GR)

  6. Development of earthquake rate models • Earthquake rates depend on slip rates and are as consistent as possible with paleoseismic data. • All segments and combinations of segments have rates of earthquakes in three models • Minimum earthquake rate model • Maximum earthquake rate model • Geologic insight model • Southern San Andreas based on detailed numeric analysis by Weldon and Biasi • Other A-faults based on “hand-built” models due to sparse data

  7. Example, Calaveras fault, modifications WG2002 model to remove “floating”, sub-segment ruptures.

  8. Key question, and only significant modification to earthquake rate models: How to incorporate Recurrence Data from Arano Flat in the Santa Cruz Mountains. RI at Arano Flat is 105 yr, approximately half RI of full-segment and multi-segment ruptures predicted there by WG02. Is there a small segment here with frequent smaller earthquakes? Are these sub-segment earthquakes? Are all of these full segment or multi-segment earthquakes?

  9. Rates of full-segment and multi-segment earthquakes on the Northern San Andreas fault, if 5, 7, or 9 of the 9 earthquakes at Arano Flat are full- or multi-segment ruptures.

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