A 11 ID 2 715A71

NBS

PUBLICATIONS

NBSIR 87-3667

The Whittier Narrows Earthquake of

October 1, 1987

A Reconnaissance Report

By H. S. Lew

U.S. DEPARTMENT OF COMMERCE

National Bureau of Standards

National Engineering Laboratory

Center for Building Technology

Gaithersburg, MD 20899

November 1987

U.S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS

QC

100

U56

87-3667

1987

C.2

Kesearch Information Center

(National Bureau of Standards

Gaithersburg, Maryland 20899

THE WHITTIER NARROWS EARTHQUAKE OF

OCTOBER 1, 1987

A RECONNAISSANCE REPORT

NBSIR 87-3667

Oaoo

WO,

By H. S. Lew

U.S. DEPARTMENT OF COMMERCE

National Bureau of Standards

National Engineering Laboratory

Center for Building Technology

Gaithersburg, MD 20899

November 1987

U.S. DEPARTMENT OF COMMERCE, C. William Verity, Acting Secretary

NATIONAL BUREAU OF STANDARDS, Ernest Ambler, Director

ABSTRACT

Within hours following the Whittier Narrows earthquake of October 1, 1987,

a structural engineer from the Center for Building Technology, National Bureau

of Standards surveyed the damage to buildings and other structures. The area

investigated covers Los Angeles and other communities including Whittier,

Alhambra, and Pasadena. This report consists of photographs, all of which were

taken by the author. The photographs presented herein are intended to serve

as (1) documentation of the damage resulting from the earthquake and (2) as

a source document for further studies, research and recommendations.

Key words: Bridges; buildings; earthquake; highways; housing;

seismic; structural engineering.
.

s

mm •
INTRODUCTION

At 7:42 a.m. (Pacific Daylight Time), on October 1, 1987, an earthquake

with a magnitude of approximately 6.1 on the Richter scale occurred, with its

epicenter located about 20 km east of downtown Los Angeles, California, at

34° 05' N and 118° 07' W, The earthquake resulted from a fault rupture

along a northwest extension of the previously identified Whittier fault

(see fig.l). The initial shock originated approximately 11 km below the

earth's surface. Following the main shock, many aftershocks occurred

including the ones that occurred on October 4, 1987 with a magnitude of 5.5

and on October 5, 1987 with a magnitude of 4.3.

Ground shaking in the vicinity of the epicenter ranged from 0.2g (gravity)

to 0.45g in the horizontal direction and from 0.14g to 0.2g in the vertical

direction. Maximum ground accelerations recorded at some of the stations near

the epicenter are listed below. These stations are maintained by the California

State Division of Mines and Geology (CDMG) , which provided preliminary

readings of their instruments. The solid circles in Figure 2 show the locations

of these stations.

Location Dist. From

Epicenter

Vert . Acc

iz

Horz . Acc

izl

Fremont School

Alhambra

7 km 0.20 0.40

S W Academy

San Marino

8 km 0.14 0.20

Cal. State Univ.

Los Angeles

9 km 0.14 0.39

Obregon Park

Los Angeles

10 km 0.15 0.45

Sears Warehouse

Los Angeles

14 km 0.09 0.18

Downey 17 km 0.17 0.20

116th School

Los Angeles

22 km 0.11 0.40

Union Oil Co.

Inglwood

25 km 0.08 0.28

Calif. Fed. Savings 26 km 0.10 0.22

1
The ground accelerograms recorded by CDMG stations at Obregon Park and Fremont

School are shown in Figure 3. These traces show that the magnitude of

accelerations in the east-west direction and the north- south direction were

about the same, and that strong shaking lasted for about 5 seconds.

Compared to other major earthquakes, the Whittier Narrows earthquake was

moderate. Listed below, for comparison, are some earthquakes of substantial

magnitude

.

Location Magnitude Date

Anchorage , Alaska 8.4 March 27

,

1964

San Francisco, Calif. 8.2 April 18, 1906

Kern County, Calif. 7.7 July 21, 1952

Olympia, Washington 7.1 April 13, 1949

El Centro, Calif. 7.1 May 18, 1940

Coalinga, Calif. 6.7 May 2, 1983

San Fernando, Calif. 6 .

6

Feb 9, 1971

Imperial Valley, Calif. 6.5 Oct 15, 1979

Morgan Hill, Calif. 6.1 April 24, 1984

Whittier Narrows, Calif. 6.1 Oct 1, 1987

The most severe damage to building structures occurred in communities east

of Los Angeles and near the epicenter. These communities include Whittier,

Montebello, Monterey Park, Alhambra, Rosemead, San Gabriel, San Marino and

Pasadena. No severe structural damage to high-rise structures in downtown Los

Angeles was reported. However, some buildings sustained non- structural

damage. Severe damage to one interchange structure (I-605/I-5) resulted in

closing of 1-605 for about a day. While six persons lost their lives as a result of the main shock, only one person died due to failure of a structural

component

.

This report consists of photographs taken by the author illustrating the type

and intensity of damage. Most of these photographs were taken from the street,

as entry into the damaged buildings was not allowed immediately following the

main shock.

DAMAGE OBSERVATIONS

Unreinforced Masonry Buildings

There are many unreinforced masonry buildings in the communities shaken by

the earthquake. The extent of damage to these buildings varied considerably,

ranging from minor cracks in walls to partial collapse of a building. The most

severe damage to unreinforced masonry buildings appeared to have occurred in

the "Uptown Business District" in Whittier. Typical damage to unreinforced

masonry buildings included cracks in the exterior walls , collapse of

parapets and exterior walls, and collapse of roofs. Similar damage was also

observed in the old downtown section of Alhambra and in the "Old Town"

section of Pasadena. Several of the damaged buildings in Pasadena had been

2
posted by the building official as unsafe for occupancy prior to the

earthquake. In general, severe damage was concentrated in a localized area

of these communities. For example, in Whittier damage was concentrated in

the uptown business zone and in the adjoining residential area. Photos 1

through 6 illustrate the types of damage observed in unreinforced masonry

buildings

Residential Buildings

Most residential buildings which sustained damage can be divided into three

categories. The first category includes single -story houses which were built

of clay tile and other masonry units. Typically, these houses sustained either

severe cracking in walls or partial collapse of walls. The second category

includes houses which were not fully anchored to the foundation wall. As a result, these houses sustained horizontal cracks along the top of the

foundations, walls. In some extreme cases, houses were completely dislodged

from their foundations. The third category includes residential structures

described as "house-on-garage . " Typically, these structures have dwelling

units built on top of garages having large door openings. In general, most

of the damaged residential structures were relatively old and had been

constructed before the 1971 San Fernando earthquake. The San Fernando

earthquake revealed many weaknesses in residential construction that led to

revisions to building code requirements.

As in previous earthquakes, many chimneys collapsed. Damage to chimneys was

observed in many areas including Whittier, Alhambra and Pasadena. In some

cases, chimneys toppled and fell though roofs.

In general, wood frame houses did not sustain serious damage. In many cases,

the exterior stucco cracked, particularly at the corners of window openings.

When window openings existed at the corners of wood frame buildings, many

window panes were broken due to large distortions of the window frames.

Masonry walls are commonly erected at the boundaries of adjoining properties.

If these walls are not reinforced, they are highly susceptible to collapse

when subjected to a moderate shaking. Many such unreinforced concrete block

walls collapsed in Whittier.

Photos 7 through 17 depict types of damage sustained by residential structures

and walls

Reinforced Concrete Frame Structures

Most of the major buildings on the California State University, Los Angeles

campus are reinforced concrete frame structures. The buildings were constructed

during the mid- and late - sixties . For example, the 8-story administration

building was constructed in 1969. The campus was subjected to maximum ground

accelerations of 0.39g in the horizontal direction and 0.14g in the vertical

direction. Three multi-story buildings and a garage building which were

inspected showed signs of structural distress. These included cracks in

concrete shear walls and columns, cracking in the flat slabs around columns,

damage to concrete members due to pounding of two structurally separated

3
sections of a building, and connection failures of a precast concrete fascia

panel. A student died when she was crushed when this panel fell from a parking

structure. Photos 18 through 24 illustrate some of the structural damage seen

on the campus

.

Extensive damage occurred to a reinforced concrete structure in Whittier. A

garage in Whittier Quad experienced a partial collapse of the upper level

floor and severe cracking in the columns. The garage was constructed in 1964.

Deep beams, which supported the floor slab, were seated on circular interior

columns and rectangular perimeter columns. Because of the short length of the

interior columns, they attracted large shear forces and experienced brittle

shear failure. The exterior columns did not have adequate ties to resist large

shear forces and some of them failed. These exterior columns appeared to have

widely spaced #2 and #3 bar ties. Photos 25 to 32 show structural damage to

the garage

.

Glass Breakage

Many stores in the uptown Whittier shopping area occupy renovated one- or twostory unreinforced masonry structures. Typically, the front of these stores

have large windows. The glass in many windows fractured into large pieces and

fell on sidewalks. Fortunately, at 7:42 a.m. the shopping area was not crowded

with people and no one was injured seriously. Photos 33, 34 and 35 show store

fronts which lost glass panes.

Non- Structural Damage

During an earthquake, falling light fixtures, suspended ceilings and ceiling

tiles pose serious hazards to the occupants. Current codes require that light

fixtures and suspended ceilings be properly secured so that they will not fall

during an earthquake. During the main shock, light fixtures and suspended

ceilings fell in many buildings located within a 10-km radius of the epicenter,

particularly the Whittier area. Photos 36 through 39 show loss of ceiling

tiles and light fixtures.

Highway Bridges

Immediately after the main shock, highway bridges were inspected by the

California Department of Transportation (Cal Tran) . Very little damage was

sustained by most of the bridges near the epicenter except at the interchange

of 1-605 and 1-5, where the columns in the center bent were severly

damaged. The damaged bent supported 2 spans of precast concrete I-girders

for the 1-605 Freeway which crosses over the 1-5 Freeway. Restraining

cables installed by Cal Tran after the San Fernando earthquake, kept the

precast girders from being dislodged from the bentcap. The interchange was

closed to traffic for 22 hours after the main shock. Temporary shoring was

placed on both sides of the damaged bent to support the precast girders.

Photos 40 through 45 show the damaged overpass and columns and the temporary

support system.

4
OBSERVATIONS

1. Unreinforced masonry structures sustained major damage during the earthquake,

2. Walls with large window openings provided little in-plan stiffness; resulting

large distortions caused breakage of glass.

3. Residential structures which were not anchored slid off their foundation

walls and sustained severe damage.

4. Reinforced concrete columns which did not have adequate shear reinforcement

experienced extensive diagonal cracking and crushing of the concrete core.

5. Inadequately braced light fixtures and suspended ceilings fell during

the earthquake.

6. Wood frame single-family houses with stucco exteriors sustained little

damage

7. Restraining cables kept precast bridge girders from sliding off the

bentcap

5
6

Figure

1

Location

of

known

faults

in

the

Los

Angeles

area
Figure 2 Location of strong-motion seismographs in

the Los Angeles area (California State

Division of Mines and Geology)

7
Obregon Park, Los Angeles

North-South (L44g

Vertical 0.15 g

East-West 0.45g

Fremont School, Alhambra

North-South Q.40g

I ’ Vertical 0* 20g

East-West 0.30g

0 1

Figure 3 Seismograph records at Obregon Park and

Fremont School

8
Photo 1 Total collapse of brick masonry wall of 2-story

unreinforced masonry building in Uptown, Whittier.

Photo 2 Collapsed unreinforced brick parapet and wall of a building in Uptown, Whittier. Falling bricks crushed

cars parked adjacent to the building.

9
Photo 3 Typical collapse of unreinforced brick wall, Whittier.

Photo 4 Partially collapsed and severely cracked unreinforced

brick wall, Whittier.

10
Photo 5 Wood trusses fell from a damaged masonry wall resulting

in a partial collapse of the roof of a store, Whittier.

Photo 6 Masonry parapet of a three -story unreinforced masonry

building fell, causing the collapse of an adjacent

building, Pasadena.

11
Photo 7 Many houses with unreinforced hollow clay tile walls

sustained severe damage . This house at the corner of

Greenleaf Avenue and Beverly Blvd. in Whittier lost

the front wall.

Photo 8 Large pieces of clay tile fell on the front yard of

the house shown in Photo 7

.

12
Photo 9 This house on Greenleaf Avenue lost part of the

entrance and sustained severe cracks in the walls of

unreinforced hollow clay tile.

Photo 10 Close-up view of the partially-collapsed front

entrance to the house in Photo 9. Exterior walls were

unreinforced clay tile and stucco.

13
Photo 11 A wood- frame house on Beverly Blvd. , Whittier, was damaged

severely when it slid off its foundation wall.

Photo 12

The house in Photo 11 dropped

vertically about one ft. and moved

laterally about one and a half ft.

14
Photo 13 A wood- frame house adjacent to the house in Photo 11

on Beverly Blvd. , Whittier, also sustained severe

damage when the earthquake dislodged the house from

its foundation wail.

Photo 14 Close-up view of the house in Photo 13.

15
Photo 15 Damaged two- story wood frame apartment building in

Whittier . Large garage door openings reduced the

stiffness of the wall in the plane of the garage doors

and reduced the resistance to lateral loads.

Photo 16 Large cracks developed at the corners of window

openings. Note broken window panes at the corner of

the building, Whittier.

16
Photo 17

Collapsed unreinforced concrete

block wall in the residential

section of Whittier*

Photo 18 The library building complex on the campus of the

California State University in Los Angeles. The two

buildings are connected by a structurally- separated

walkway structure.

17
Photo 19

Glass panels at both ends of the

walkway structure were broken due

to an inadequate gap in the

connection joint.

Photo 20

Cracks developed in some of the

first- story columns of the walkway

structure

.

18
Photo 21

A class room building on the

California State University

campus. The exterior concrete

frame for the precast concrete sun

screen was damaged due to pounding

of two structurally separated

sections of the building.

19
Photo 23 A. precast concrete fascia unit fell when anchors held

it to the concrete frame failed.

Photo 24 A precast concrete fascia unit fell two stories and fatally

injured a passer by. This was the only fatality of the

earthquake due to a structural failure.

20
Photo 25 A damaged reinforced concrete parking garage at the

Whittier Quad shopping center. Deep beams at the

columns slant toward the inside of the structure due

to the loss of support at the other side.

Photo 26 Extensive damage to relatively short columns and the

ends of deep beams.

21
Photo 27

Typical shear failure of columns.

Note #2 bars with large vertical

spacing were used for ties.

Photo 28

Damage to a beam- column connection.

Note that cardboard used to protect

vertical column reinforcement during

the construction stage was not

removed when concrete was placed.

This resulted in no bond between

reinforcing bars and concrete.

22
Photo 29 A collapsed upper level portion of the parking garage.

Photo 30

Damage to a concrete column

between the ground level and

the lower level. Note that no

ties are around the vertical bar.

23
Photo 31 Non-ductile failure of a concrete column in the garage

structure

.

Photo 32 Non-ductile failure of a short column. Note fractured

#2 tie and buckled vertical bars.

24
Photo 33 Distortion of the building caused damage to windows at

the corner of the building in the Uptown Whittier

shopping section.

Photo 34 Damage glass in a store in the Uptown Whittier

shopping section.

25
Photo 35 This remodeled masonry building experienced considerable

damage to windows. Because large pieces of brocken

glass were strewn on the sidewalk, the building was

cordoned off.

Photo 36 Fallen ceiling tiles in a classroom at the California

State University at Los Angeles.

26
Photo 37 Fallen large light fixtures in the gymnasium at the

California State University at Los Angeles.

Photo 38 This school building experienced minor structural

damage. Note no glass was broken at the corner of the

building.

27
Photo 39

Acoustic ceiling tile fell in

corridors and stair wells at

Rosemead High School.

Photo 40 Interstate I -605/1 -5 interchange. Temporary shores

have been installed at the center bent which supports

the 1-605 overcrossing. The bent has five concrete

columns

.

28
Photo 41

Close-up view of damaged column in

the center bent

Photo 42

Close-up view of damaged column in

the center bent

29
Photo 43

Close-up view of damaged column

in the center bent. Note the

cracked concrete core is confined

by the ties.

Photo 44 Shoring scheme used to temporaryly support precast

concrete girders.

30
Photo 46 Support detail for individual

shores

Photo 45

Method used to support individual

precast concrete girders.

31
NBS-114A (REV. 2-80

U.S. DEPT. OF COMM.

BIBLIOGRAPHIC DATA

SHEET (See instructions)

1. PUBLICATION OR

REPORT NO.

2. Performing Organ. Report No. 3. Publication Date

NBSIR 87-3667 NOVEMBER 1987

4. TITLE AND SUBTITLE

The Whittier Narrows Earthquake of October 1, 1987

A Reconnaissance Report

5. AUTHOR(S)

H. S. Lew

6. PERFORMING ORGANIZATION (If joint or other than NBS, see in struction s)

NATIONAL BUREAU OF STANDARDS

U.S. DEPARTMENT OF COMMERCE

GAITHERSBURG, MD 20899

7. Contract/Grant No.

8 . Type of Report & Period Covered

9.

SPONSORING ORGANIZATION NAME AND COMPLETE ADDRESS (Street. City. State. ZIP)

Center for Building Technology

National Engineering Laboratory

National Bureau of Standards

Gai thersburg , MD 20899

10.

SUPPLEMENTARY NOTES

J Document describes a computer program; SF»I85, FIPS Software Summary, is attached.

11.

ABSTRACT (A 200-word or less factual summary of most significant information . If document includes a significant

bi bl iography or literature survey, mention it here)

Within hours following the Whittier Narrows earthquake of October 1, 1987, a structural engineer from the Center for Building Technology, National Bureau of

Standards surveyed the damage to buildings and other structures. The area

investigated covers Los Angeles and other communities including Whittier, Alhambra,

and Pasadena. This report consists of photographs, all of which were taken by the

NBS team. The photographs presented herein are intended to serve as (1) documentation

of the damage resulting from the earthquake and (2) as a source document for further

studies, research and recommendations. 12.

KEY WORDS (Six to twelve entries ; alph abeti cal order; capitalize only proper names; and separate key words by semicolon s) bridges; buildings; earthquake; highways; housing; seismic; structural engineering

14. NO. OF

PRINTED PAGES

35

15. Price

$11.95

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