V/H Ratios from Megathrust Earthquakes

Nick Gregorg

Bechtel

November 4 2011November 4, 2011

COSMOS 2011 Technical MeetingCOSMOS 2011 Technical Meeting

Approaches for Vertical Ground Approaches for Vertical Ground Motions

Independent Vertical PSHA Requires Vertical GMPE (no subduction

models) Different controlling events from PSHA results

Scale Horizontal ground motions by V/H spectral ratio Consistency between Horizontal and Vertical

motions for given Scenario

Crustal Vertical GMPEs

Abrahamson and Silva (1997) Campbell (1997)p ( ) Sadigh et al. (1997) Campbell and Bozorgnia (2003)Campbell and Bozorgnia (2003) Ambraseys et al. (2005) NGA West 2 (in development) NGA West 2 (in development)

Crustal V/H Models

Bozorgnia and Campbell (2004) Ambraseys and Douglas (2003)y g ( ) Gulerce and Abrahamson (2011)

GA11 V/H ModelGA11 V/H Model(Earthquake Spectra, Nov. 2011)

Crustal NGA Dataset (M

Application for Megathrust Events

Magnitudes > 8+ Comparison with two recent earthquakesp q

2010 Chile (M8.8) 2011 Tohoku (M9.0)( )

2010 Chile Earthquake2010 Chile Earthquake

M8.8M8.8 Depth 35 km 26 stations Dist. 34-200km Vs30m 236-1,421m/s

from Hayes, NEIC

2010 Chile Earthquake PGA DiPGA vs. Distance

2010 Chile Earthquake PGA vs Vs30m

2010 Chile Earthquake T 1 0 DiT=1.0sec vs. Distance

2010 Chile Earthquake T=1.0sec vs Vs30m

2010 Chile Earthquake2010 Chile Earthquake

2011 Tohoku Earthquake2011 Tohoku Earthquake

M9.0 Depth 30 km 369 stations (K-Net,

Kik-Net)Di 44 989 k Dist. 44-989 km

Vs30m 107-1,433 m/s

from Hayes, NEIC

2011 Tohoku Earthquake PGA DiPGA vs. Distance

2011 Tohoku Earthquake PGA vs Vs30m

2011 Tohoku Earthquake PGA vs FA/BA

2011 Tohoku Earthquake T 1 0 DiT=1.0sec vs. Distance

2011 Tohoku Earthquake T=1.0sec vs Vs30m

2011 Tohoku Earthquake T=1.0sec vs FA/BA

2011 Tohoku Earthquake2011 Tohoku Earthquake

Summary

Preference of V/H ratios

Comparisons for 2010 Chile and 2011 Comparisons for 2010 Chile and 2011 Tohoku events

GA11 V/H Model applicable for large GA11 V/H Model applicable for large Megathrust events