Earthquake Reconnaissance Data Collection

Training

Conducting

Damage

Assessments in

Structural

EngineeringDAVID COCKE, S.E., F.SEI, F.ASCE

STRUCTURAL FOCUS

My Structural Engineering

Experience

Practicing since 1981

Focused mainly on Existing Buildings – evaluations, repairs, rehab

Historic buildings – Ferry Building, Hotel del Coronado, Wilshire Boulevard Temple

University buildings – Stanford, UC Berkeley, Univ. of Redlands, Pitzer College, Scripps College, Woodbury College

Adaptive reuse – Red Bull, W. Annenberg Center for Performing Arts, 3Labs, The Reserve, Hercules, Google

New Design – IMAX, Warner Bros., DWA, Sony, Specialty Labs, Culver Studios, Agensys

Experience in EQ reconnaissance

Coalinga 1983

Loma Prieta 1989

Costa Rica 1991

Cape Mendocino 1992

Northridge 1994

Coalinga

Date May 2, 1983

Origin time 23:42 UTC

Magnitude 6.2 Mw[1]

Depth 10 kilometers (6 mi)[1]

Epicenter 36.23°N 120.31°W[1]

Areas affected Central California

United States

Total damage $10 million USD[2]

Max. intensity VIII (Severe)[1]

Landslides Yes

Aftershocks 5.9 MW July 22 at 02:39[3]

Casualties 94 injured[2]

Young engineers loaded up

a van and drove from S. F.

for a day long

reconnaissance trip

Loma Prieta Date October 17, 1989

Origin time 5:04:15 PDT[1]

Duration 8 – 15 seconds[2]

Magnitude 6.9 Mw[2]

Depth 19 km (12 mi)[1]

Epicenter 37.04°N 121.88°WCoordinates: 37.04°N

121.88°W[1]

Type Oblique-slip

Areas affected Central Coast (California)

San Francisco Bay Area

United States

Total damage $5.6 – 6 billion[1][3]

Max. intensity IX (Violent)[1]

Peak acceleration .65g (at epicenter)[2]

Tsunami Yes[4][5]

Landslides 1,000 – 4,000[1][2]

Foreshocks 5.3 ML June 27, 1988[6]

5.4 ML August 8, 1989[6]

Casualties 63 killed, 3,757 injured[1][7]

Occurred during my

commute home from S. F.

office. 70 hour works weeks

for months.

Costa Rica, Puerto Limon

Date April 22, 1991

Magnitude 7.7 Mw

Depth 10 km (6.2 mi)

Epicenter 9.685°N

83.073°WCoordinate

s: 9.685°N 83.073°W

Areas affected Costa Rica

Panama

Casualties 48 dead, 1712

injured

Firm sent two engineers for

reconnaissance and fact finding.

Arrived 2 days after event, stayed 5

days.

Cape Mendocino Date April 25, 1992

Origin time 11:06 PDT

Duration 9 seconds[1]

Magnitude 7.2 MW[2]

Depth 10.5 km (7 mi)[3]

Epicenter 40.33°N

124.23°WCoordinates:

40.33°N 124.23°W[2]

Areas affected Northern CaliforniaUnited States

Total damage $48.3 – 66 million[2][4]

Max. intensity IX (Violent)[3]

Peak acceleration 2.2g (est)[5]

Tsunami Yes

Aftershocks 6.5 MW April 26 at 0:41

6.6 MW April 26 at 4:18

Casualties 356 injuries[2][3]

Occurred while attending a

conference in Eureka with

my family.

Northridge Date January 17, 1994

Origin time 4:30:55 PST[1]

Duration 10 – 20 seconds

Magnitude 6.7 Mw

Depth 11.4 mi (18.3 km)

Epicenter 34.213°N

118.537°WCoordinate

s: 34.213°N 118.537°W

Type Blind thrust

Areas affected Southern California

United States

Total damage $20 billion

Max. intensity IX (Violent)[2]

Peak acceleration 1.82g horizontal[3]

Casualties 57 killed

> 8,700 injured

Took packed bags to office in

S.F., left on airplane in early

afternoon for reconnaissance,

but intercepted by US&R.

Why reconnaissance?

Confirm that structures perform as we

intended – both original AND retrofitted

Confirm that known deficiencies really

don’t work

Look for any surprises

“Some of us used to argue that you shouldn’t really get your

structural license until you’ve chased an earthquake… No

matter how much you read the reports, the impact doesn’t

really strike you until you’ve seen the damage.” Henry Degenkolb in Connections: EERI Oral History Series, Volume 1, 1994

What do we do with reconnaissance data?

1. Gather info at the site

2. Compare the observations to what is expected based on current practice

coupled with site specific seismic data

3. Note consistencies and surprises

4. Write reports and publish

5. Compare with others’ reconnaissance data

6. Form conclusions and suggest changes

7. Test by research at Universities and others

8. Confirm effectiveness of proposed changes thru research

9. Incorporate changes into code writing process & eventually into practice

10. Confirm improved performance after next earthquake

Confirm known

deficiencies

Soft-Story at “tuck–under

parking” (Northridge)

Short column effect &

irregularities (Costa Rica)

Look for Surprises

Non-Ductile concrete

reinforcing (San Fernando EQ

1971)

Steel Moment Frame

damage (Northridge, 1994)

Photo by Exponent

Photo from

NISEE.Berkeley.edu

Prepare for your site visit

Use EERI’s Post-Earthquake Investigation Field

Guide

Gather latest seismic information about the

event – ground motion data, location of

epicenter, local soil conditions, etc.

Research the known building stock at the site –

age and types of structures

Research communications capabilities at site –

cellular services, power?

While on site

Stay safe, hardhats

don’t make you

invulnerable! (remember Chuck Thiel)

Beware of aftershocks

that could occur at

any time!

Key things to look for

Vulnerable building types:

URM

Unretrofitted URM in

Coalinga, 1983

Retrofitted URM

in Napa, 2014

Vulnerable Building types:

Pre-1980 Non-Ductile

ConcreteCSUN Parking

Structure, 1994

Kaiser MOB,

1994

Cypress Viaduct, 1989

Vulnerable Building types: Soft Story Buildings

Northridge Apt. Buildings, 1994San Francisco, 1989

Data CollectionGo to

http://bayquakealliance.org/fieldnotes/#building for

EERI Data Collection Form

Data to collect:

Structure type

Occupancy

Damage levels – reference ATC-20

Number of stories

Notes

Judge Structure typeVisual:

Size of wall piers and spandrel beams

Exterior material

Obvious shear walls or braces

Age of construction

Regional construction practices

From ATC-20

Judge damage

level

From ATC-20

Other notes - Ask yourself:

Did the soil conditions affect damage?

Is there evidence of a predominant direction of

shaking?

Was there a strong vertical component?

Would longer duration have caused more

damage?

Do you think the level of damage is consistent with

the reported level of shaking and duration?

Is the damage level consistent with nearby

buildings? What are the key damage points?

More questions:

What was sequence of damage?

What saved the building?

If the building has been retrofit, did it work?

If not retrofitted, what retrofit would have worked?

What did the EQ find that we might have missed in a

pre-EQ seismic evaluation?

If you were going to design temporary shoring, what

would you do?

Examples…

Questions?

http://bayquakealliance.org/fieldnotes/#building

dcocke@structuralfocus.com