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Earthquake Hazard Class Mapping by Parcel in Las Vegas Valley

Earthquake Hazard Class Mapping by Parcel in Las Vegas Valley. John N. Louie Nevada Seismological Laboratory Satish K. Pullammanappallil Aasha Pancha , Travis West Optim Seismic Data Solutions Werner K. Hellmer Clark County Dept. of Development Services.

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Earthquake Hazard Class Mapping by Parcel in Las Vegas Valley

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  1. Earthquake Hazard Class Mapping by Parcel in Las Vegas Valley John N. Louie Nevada Seismological Laboratory Satish K. Pullammanappallil AashaPancha, Travis West Optim Seismic Data Solutions Werner K. Hellmer Clark County Dept. of Development Services

  2. Parcel Map Enables“Next-Level ShakeZoning” • Goal is to predict earthquake shaking • For hazard mapping, planning • Building-code development and enforcement • Provide time histories of shaking to designers • USGS ShakeMap • Based on statistical averages; sparse data • Most data came from California, Japan, Taiwan • Next-Level ShakeZoning for Nevada • Based on: Wave Physics • Geological & Geotech data: Parcel Map unsurpassed • Validating against Nevada earthquake records

  3. Clark County & Henderson Parcel Map 10,721 Measurements Urban Areas of County

  4. Parcel Mapping Surface-Wave Arrays Every One Hand-Modeled

  5. Blind Tests of Parcel Map • Different: • Equipment • Field crew • Dispersion interpreter • Vs(z) modeler • Match to Map Values: • 6 of 93 blind tests >10% off • 13.55% max diff. • 0.26% bias of average • 4.92% RMS difference

  6. Clark County & Henderson Parcel Map Parcel Classification for IBC NEHRP C & D classes “C+” class for NEHRP B velocities with soft surface

  7. Build Parcel Map into ShakeZoning Does it Make a Difference? ShakeZoning Geotech Map Warmer colors: lower Vs30 (meter) Parcel Map on top of IBC default Vs30

  8. Adding Fault and Basin Geology Black Hills Fault in Google Earth with USGS Qfaults trace USGS Basin Map

  9. Adding Physics • Black Hills M6.5 event • Short trace but 4-m scarps noted • Viscoelastic finite-difference solution • 0.5-Hz frequency • 0.20-km grid spacing • A few hours on our small cluster • Mode conversion, rupture directivity, reverberation, trapping in basins

  10. Black Hills M6.5 Scenario Results • Max Peak Ground Velocity (PGV) >140 cm/sec • PGV over 60 cm/sec (yellow) bleeds into LVV through Railroad Pass • Large event for a short fault • Unlikely, but add to hazard probabilistically • Need to know how unlikely

  11. Surprising Effect of Parcel Map Over IBC Defaults 1-D Amplification Used in IBC, ShakeMap 3-D Amplification from ShakeZoning

  12. ShakeMap versus ShakeZoning Yellow is 60 cm/sec on both Geotech estimated from topography ShakeZoning shows trapping in basins Hazard map is difficult to predict

  13. Frenchman Mountain Fault M6.7 Scenario Possible Scarp in Neighborhood Event Inside the LVV Basin

  14. 2-Segment Frenchman Mtn. Fault M6.7

  15. Effect of Parcel Map Over IBC Defaults

  16. With Many Scenarios, Define Probabilistic Hazard • Recurrence Intervals: • Black Hills- 15 ka • Frenchman Mtn.- 45 ka • e.g., PGV at UNLV: • ~20 cm/s from BHF • ~15 cm/s from FMF • Combine rates per annum: • >15 cm/s at 0.0001 p.a. • >20 cm/s at 0.00007 p.a.

  17. With Many Scenarios, Define Probabilistic Hazard dePolo, 2008, NBMG Map 167 • Japan and New Zealand Lesson: Don’t Ignore Worst Case!

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