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