next-level shakezoning for earthquake hazard definition in the intermountain west john n. louie,...
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Next-Level ShakeZoning for Earthquake Hazard Definition
in the Intermountain West
John N. Louie, with
Will Savran, Brady Flinchum, Gabriel Plank,
Graham Kent, Kenneth D. Smith
Nevada Seismological Laboratory
Satish K. Pullammanappallil, Aasha Pancha
Optim Seismic Data Solutions
Werner K. Hellmer
Clark County Dept. of Development Services
J. Louie, CTBTO S&T, 8 June 2011
Seismic-Hazard Mapping in Nevada
Goal is to predict earthquake shaking For hazard mapping, planning Building-code development and enforcement Provide time histories of shaking to designers Shaking characteristics of Nevada geology
affect NTS data sets and arrays USGS ShakeMap
Based on statistical averages; sparse data Most data came from California, Japan,
Taiwan– Geology not similar to Nevada
J. Louie, CTBTO S&T, 8 June 2011
New, Dense Data Sets Enable“Next-Level ShakeZoning”
Next-Level ShakeZoning for Nevada and Intermountain Western US Based on: Wave Physics Geological & Geotechnical data
• Parcel Map unsurpassed in detail Validating against Nevada earthquake records Complete gridding software and data sets
available from crack.seismo.unr.edu/ma
J. Louie, CTBTO S&T, 8 June 2011
Clark County & Henderson Parcel Map10,721 Measurements Parcel Class for IBC
J. Louie, CTBTO S&T, 8 June 2011
Build Parcel Map into
ShakeZoning
Does it Make a Difference?
ShakeZoning Geotech Vs30 Map
Warmer colors: lower Vs30 (meter)
Parcel Map on top of IBC default Vs30
J. Louie, CTBTO S&T, 8 June 2011
Adding Fault and Basin Geology
Black Hills Fault in Google Earth with USGS Qfaults trace
USGS Basin Map
J. Louie, CTBTO S&T, 8 June 2011
Adding Physics
Black Hills M6.5 event Short trace but 4-m scarps
noted LLNL’s E3D (Larsen) and
WPP (Petersson) viscoelastic F-D solutions
0.5-Hz frequency 0.20-km grid spacing A few hours on our small
cluster Mode conversion, rupture
directivity, reverberation, trapping within and tunneling between basins
J. Louie, CTBTO S&T, 8 June 2011
Black Hills M6.5 Scenario Results
Max Peak Ground Velocity (PGV) >140 cm/sec
PGV over 60 cm/sec (yellow) bleeds into Las Vegas basin from an adjacent basin
Large event for a short fault
Unlikely, but add to hazard probabilistically
J. Louie, CTBTO S&T, 8 June 2011
J. Louie, CTBTO S&T, 8 June 2011
Surprising Effect of Parcel Map Over IBC Defaults1-D Amplification Used in IBC, ShakeMap
3-D Amplification from ShakeZoning
J. Louie, CTBTO S&T, 8 June 2011
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
Wells, NV M6.0
2/21/2008
NW-steep-dip fault from initial Dreger CMT
Eastward rupture directivity
Many basins channel shaking
J. Louie, CTBTO S&T, 8 June 2011
J. Louie, CTBTO S&T, 8 June 2011
Wells, NV M6.0
2/21/2008
PGV map
Eastward rupture directivity
Many basins channel shaking
With Many Scenarios, Define Probabilistic Hazard
J. Louie, EGGE 3/25/2011
Japan and New Zealand Lesson: Don’t Ignore Worst Case!
dePolo, 2008, NBMG Map 167
Parcel Mapping
Surface-Wave Arrays
Every One Hand-Modeled
J. Louie, CTBTO S&T, 8 June 2011
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
J. Louie, CTBTO S&T, 8 June 2011
Frenchman Mountain Fault M6.7 ScenarioPossible Scarp in Neighborhood
Event Inside the LVV Basin
J. Louie, CTBTO S&T, 8 June 2011
J. Louie, CTBTO S&T, 8 June 2011
2-Segment Frenchman Mtn. Fault M6.7
Effect of Parcel Map Over IBC Defaults
J. Louie, CTBTO S&T, 8 June 2011
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.
J. Louie, CTBTO S&T, 8 June 2011