Proposed components for ca for feb 2007 version of national maps
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Proposed Components for CA for Feb. 2007 Version of National Maps. Because of issues with inversion for A faults : Use WG02 for northern CA A-faults Use Biasi and Weldon for southern San Andreas (slip rates OK?); a key issue here

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Proposed components for ca for feb 2007 version of national maps
Proposed Components for CA for Feb. 2007 Version of National Maps

Because of issues with inversion for A faults:

Use WG02 for northern CA A-faults

Use Biasi and Weldon for southern San Andreas (slip rates OK?); a key issue here

Use WG06 a priori geologic insight model for multisegment ruptures on San Jacinto, Elsinore, and Garlock faults (adjusted to get observed slip rates)

Use B faults from WG06; link up some B faults as suggested

No new C zones (some of them seem to be problematic: some very narrow zones with a lot of slip; how many M6.5’s?)


Possible components for ca for feb 2007 version of national maps continued
Possible Components for CA for Feb. 2007 Version of National Maps, continued

Remove about 10% moment from A and B faults to account for afterslip, aftershocks, coupling, etc.

Use new Felzer catalog (aftershocks/foreshocks removed) to make background seismicity grid; use corrections for mag. uncert. and rounding; use b-value of 0.8

Adjust rate of M ≥ 6.5 events from background to fit rate of observed events not on A or B faults (or could determine new b-value above M≥5.0)

Remove Mendocino fault; treat with anisotropic smoothed seismicity


  • Keep transpressional/transtensional boundary used in 1996 and 2002 maps (e.g., GR-char weighting)

  • Keep treatment of Mchar uncertainty on faults used in 2002 maps

  • Adhere to non-overlapping magnitudes between background and faults, as in 2002

  • We estimate that this model will overpredict rate of M≥6.5 earthquakes by about a factor of 1.5, for the non-extensional portion of CA


Battle of the m 6 5 bulge
Battle of the M and 2002 maps (e.g., GR-char weighting) ≥6.5 bulge

  • All rates are for non-extensional part of CA:

  • Predicted rate of M≥6.5 from 2002 model: 0.414 (including 0.076 from gridded seismicity)

  • Make Parkfield less than M6.5, rate becomes: 0.373

  • Remove Mendocino fault (0.0284), rate becomes: 0.345

  • Remove 10% of fault rate (0.027) for aftershocks, etc.: 0.318

  • Adjust gridded rate by -0.05, assuming rate of M≥ 6.5 events not on a and b faults is 0.026

  • Now total rate is: 0.268

  • Observed rate without events west of -125: about 0.17-0.19 (Mueller’s rate for all CA is 0.21; take 10% off for more limited area; 0.17 if you adjust Felzer’s total rate of 0.19)

  • So overprediction is about factor of 1.4-1.6 (depending on which observed rate is used).

  • Predicted rate will be reduced further by using multi-segment rupture model for San Jacinto, Elsinore, and Garlock faults, and connecting some B faults

  • There’s also the issue of completeness of M6.5’s back to 1850.


Treatment of uncertainty in mchar in 2002 maps
Treatment of Uncertainty in Mchar in 2002 maps and 2002 maps (e.g., GR-char weighting)

  • Aleatory sigma of 0.12 m.u. (truncated at about 2.5 sigma)

  • Epistemic uncertainty: Ellsworth B and Hanks and Bakun; equal weight

  • Additional epistemic uncertainty: -0.2, 0., +0.2 m.u., with weights of 0.2, 0.6 ,0.2 (reduced to ± 0.1 for longest ruptures)

  • Gives additional epistemic sigma of 0.12 m.u., since 0.2, 0.6, .2 wt corresponds to 90% confidence limit, (1.65 sigma).

  • Wells and Coppersmith (1994): sigma of 0.25


Nshmp schedule for 2007
NSHMP Schedule for 2007 and 2002 maps (e.g., GR-char weighting)

  • Feb. 15: deliver draft maps to BSSC

  • March 15: finish written report on draft maps

  • April 15: Review meeting of external advisory panel; get comments to revise maps

  • June 1: Put first set of trial maps on Web for public review

  • Aug. 1: end of public comment period

  • Aug 15: Second meeting of external advisory panel

  • Sept. 30: Release final maps to BSSC


Proposed cascadia model
Proposed Cascadia model and 2002 maps (e.g., GR-char weighting)

  • Using advice from Alan Nelson and Brian Atwater; based on paleoseismic data summarized in Nelson et al. (2006)

  • M8.8-M9.2: rupture whole CSZ, average recurrence time of 500 yr

  • M8.0-8.6: floating ruptures, average recurrence time of 600 yr; uniform distribution in magnitude

  • Use same logic tree for rupture geometry as in 2002 maps

  • Produces similar hazard values as 2002 maps


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