effects of deep intraplate earthquakes in subduction...

Effects of deep intraplate

earthquakes in subduction

zones

Dr. Freddy E. Pina, P.Eng.PBRV Consulting Ltd.

The University of British Columbia

August 2013, Vancouver, BC

Subduction Zones

GEIYO 2001 – Mw 6.7

• Deep quake - 50km

• 3700 Buildings damaged

• 2 casualties

NISQUALLY 2001 – Mw 6.8

• Deep quake - 52km

• $1 billion losses

• 1 casualty + 400 injured

El Salvador 2001 – Mw 7.7

• Deep quake – 60 km

• $1.2 billion losses

• 800 casualty (landslide)

Punitaqui 1997 – Mw 7.1

• Deep quake – 100 km

• 8 deaths

• 60000 homeless

Estimating impact of deep quakes

• Part I: Santiago, Chile

– Preliminary risk estimates vs Subduction

quakes

– Study per municipalities

• Part II: Vancouver, BC

– Risk estimates

– Impact in the BC public school seismic

assessment/retrofit program

Chile Subduction

Location of selected earthquakes

SantiagoCoast Mountain

Epicenter Date MagnitudeNo.

Stations

Distance

Range

(km)

Elastic Spectra - Santiago - Site Class C

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

0.01 0.10 1.00 10.00

Period (s)

Sa

(g

)

Subduction - Median

Subduction - 84th %ile

Subduccion - Max

Deep - Median

Deep - 84th %ile

Deep - Max

Code


0.0

0.2

0.4

0.6

0.8

1.0

1.2

0.01 0.10 1.00 10.00

Period (s)

Sa

(g

)

Subduction - Median


Deep - Median

Deep - 84th %ile

Code

Comparison

• In terms of earthquake shaking:

– Subduction dominates hazard values for most

periods

– Large deep quake spectral accelerations at

periods shorter than 0.5sec

• However, we need to see responses in

terms of structural parameters…

Santiago, Chile

• 34 districts (municipalities)

• 5.4 million people

• 1.45 million houses (urban areas)

1- to 2-

storey

houses

4- to 15-

storey

buildings

Main material/systems

Confined Masonry

Wood housesRC buildings

Structural system classification

Group Structural No of % in Estimated Estimated R factor

Name System storeys Santiago Period - sec Ductility factor (Miranda 1993)

G1 - MASONRY 2S Confined Masonry 2 49 0.2 2 1.8

G2 - MASONRY 4S Confined Masonry 4 8 0.4 2 2.0

G3 - CONCRETE 2S Reinforced Concrete Walls 2 8 0.2 2 1.8






G9 - CONCRETE 10S Wood Shear Walls 2 10 0.2 5 2.9

Ductility = 2.0

Ductility = 6.0

Risk = Probability of Code values

being exceeded

G1 -

MA

SO

NR

Y 2

S

G2 -

MA

SO

NR

Y 4

S

G3 -

CO

NC

RE

TE

2S

G4 -

CO

NC

RE

TE

5S

G5 -

CO

NC

RE

TE

10S

G6 -

CO

NC

RE

TE

15S

G7 -

CO

NC

RE

TE

20S

G8 -

CO

NC

RE

TE

30S

G9 -

WO

OD

2S

0%

5%

10%

15%

20%

25%

30%

DEEP

SUBDUCTION

Main comments

• Current code does not address the effect of deep earthquakes, specially for short period structures, e.g. confined masonry houses

• Although deep quake hazard values are lower than that for subduction quakes, the effect of deep quake motions to a wide range of structures is likely to be similar

What’s next…

• Define design spectral values or recommendations to address deep quakes in Chile

• Next Part using SRG methodology

– Vancouver

– Victoria

– Interior BC

– Santiago

• Define ground motion records for risk calculations

Cascadia Subduction

& Vancouver – H Model ?

& Vancouver – H Model ?


0.0

0.2

0.4

0.6

0.8

1.0

1.2

0.01 0.10 1.00 10.00

Period (s)

Sa

(g

)

Subduction - Median


Deep - Median

Deep - 84th %ile

Code

Deep - H Model - Vancouver

Lower values for short periods


0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

0.01 0.10 1.00 10.00

Period (s)

Sa

(g

)

Deep - Median

Deep - 84th %ile

Deep - Max

Code

Deep - Model H - Vancouver

Lager values for long periods


0.0

0.2

0.4

0.6

0.8

1.0

0.10 1.00 10.00

Period (s)

Sa

(g

)

Deep - Median

Deep - 84th %ile

Deep - Max

Code

Deep - Model H - Vancouver

Recommended New Suites of Seed

Time Histories for SRG Database

• 11 Pairs from Crustal Earthquakes for Most Prototypes– Expected period longer than 1 sec

– Expected period between 0.5 and 1 sec with ductility larger than or equal to 2

– Scaling based on PSV* average

• 11 Pairs from Subcrustal Earthquakes for Other Prototypes– Expected period shorter than 0.5 sec

– Expected period between 0.5 and 1 sec with ductility smaller than 2

– Scaling based on Max Spectral Acceleration

Recommended New Suites of Seed

Time Histories for SRG Database

• 3 x 11 Pairs from Subduction Earthquakes for

All Prototypes

– Divide Province in 3 Zones

• Zone 1: Estimated Rupture Area + 25km

• Zone 2: 25km from Rupture Area + 100km

• Zone 3: 100km from Rupture Area

Thanks

effects of deep intraplate earthquakes in subduction...

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