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

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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


Proposed components for ca for feb 2007 version of national maps

  • 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≥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

  • 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

  • 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

  • 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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