Matsuzaki, S. et al.

Paper:

Evaluation of Seismic Vulnerability of Buildings Based on
Damage Survey Data from the 2007 Pisco, Peru Earthquake
Shizuko Matsuzaki∗ , Nelson Pulido∗∗ , Yoshihisa Maruyama∗ ,Miguel Estrada∗∗∗ , Carlos Zavala∗∗∗ , and Fumio Yamazaki∗∗ Graduate School of Engineering, Chiba University

1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan
E-mail: matsu.shizuko@gmail.com∗∗ National Research Institute for Earth Science and Disaster Prevention, Ibaraki, Japan∗∗∗
Japan-Peru Center for Earthquake Engineering Research and Disaster Mitigation,
National University of Engineering, Lima, Peru
[Received July 30, 2014; accepted September 9, 2014]

The seismic vulnerability of buildings located in Pisco,Peru, was studied using damage survey data and seismic ground motion simulation. Inventory and damage
information for more than 10,000 buildings was registered in survey data compiled by CISMID at Peru’s
National University of Engineering. The soil classes
in the Pisco district were classified into three zones
based on the predominant periods of microtremors at
85 sites, and damage ratios were calculated for eachzone. Surface ground motions in each zone were estimated on the basis of base-rock motion simulationand shallow soil-column response analysis. Finally,fragility curves for adobe and brick masonry buildings
were derived in terms of PGA and PGV. The results
were compared with fragility functions developed inother studies.
Keywords: seismic vulnerability, the 2007 Pisco earthquake, building damage, damage survey

1. Introduction
The Pacific coast of South America is a segment of thecircum-Pacific seismic belt along which a large numberof thrust earthquakes have occurred [1]. Peru is locatedin an area of very high seismic activity. Buildings in different countries vary considerably in their materials andconstruction methods and thus in their seismic behavior.
To assess earthquake-induced damage, it is necessary toconsider the regional characteristics of buildings. For example, most mid-rise and low-rise buildings in provincial
cities in Peru are constructed of bricks or adobe (air-dried
mud brick) [2]. The patterns of collapse of such buildings are different from those of framed buildings. Residential buildings are built by local workers or by the
inhabitants themselves, without sufficient knowledge ofengineering. Because of inadequate financial resources,
people buy construction materials little by little and add
on to the buildings in which they live over the course ofyears [3].
1050

The 2007 Pisco, Peru earthquake occurred off the coastof central Peru on August 15, 2007, at 18:40 local time
(23:40 UTC). According to the United States Geological Survey (USGS), the earthquake had a moment magnitude of 8.0. The earthquake caused extensive damage tocities in Ica Region, including Pisco, Chincha, and Ica.
Approximately 500 people were killed, and more than
90,000 buildings collapsed [4].
This study presents the results of an assessment of theseismic vulnerability of buildings located in Pisco, Peru,
conducted using damage survey data and simulated seismic ground motions. Fragility curves for adobe and brickmasonry buildings were constructed based on the results.
Fragility curves are widely used to predict building damage due to earthquakes. Fragility curves have been developed in other studies from statistical analyses of actual
damage data [5–7] and analyses of the seismic capacityof buildings [8–11]. To reflect regional seismic characteristics appropriately in damage assessment, it is necessary
to confirm the validity of the damage evaluation methodology used. Hence, the fragility curves developed in thisstudy were compared with curves developed in other studies.

2. Damage to Buildings in Pisco, Peru as a Result of the 2007 Earthquake
2.1. Breakdown of Building Types from Damage
Survey Results
The District of Pisco is the capital of Pisco Province,
which belongs to the Ica Region of Peru. The district isapproximately 250 km south of Lima, the capital of Peru.
The size of the main urban area of Pisco is about 2 km2 .
Pisco faces the Pacific Ocean and has a desert climate.
According to Peru’s National Institute of Statistics and Information (INEI), the urban population was estimated to
be 55,000 in 2007 [12]. The district is located 10 to 30 m
above sea level and has a few topographic undulations.
The Pisco River runs 2 km north of the town, and there
Journal of Disaster Research Vol.9 No.6, 2014

Evaluation of Seismic Vulnerability of Buildings Based on
Damage Survey Data from the 2007 Pisco, Peru Earthquake
Acceleration 003

EW, cm/s

2

200

162.4

0
−200
0

50

100

150

NS, cm/s

2

200

200

211

0
−200
0

50

100

150

UD, cm/s

2

200

200

88.3

0
−200
0

50

100

150

200

sec

Fig. 2. Simulated bedrock accelerations at city center of Pisco.
Fig. 1. Slip distribution of the 2007 Pisco, Peru earthquake
from source process by Sladen et al. [13].

are some marshes in the northern part of the town and near
the coast. The Pisco district was the district most severely
affected by the August 15, 2007 earthquake, which had a
Modified Mercalli Intensity (MMI) of IX (USGS).
Ground motion records were not obtained in Pisco andnearby Chincha during this earthquake. Ground motions
were recorded in Lima and Ica and at the Parcona station(PCN) in the Ica region. Fig. 1 shows a slip model ofthe seismic source, and Fig. 2 shows simulated bedrock
accelerations at the city center of Pisco [14]. The records
from Lima and Ica both consist of two distinct sub-events.
At PCN, a peak ground acceleration of 484 cm/s2 wasrecorded.
The present authors investigated the building damage
situation soon after the earthquake. A field survey was
conducted by the Japan–Peru Center for Earthquake Engineering Research and Disaster Mitigation (CISMID) in
the National University of Engineering (UNI). A total of
12,000 building lots in the Pisco district were surveyed.
The occupancy category, number of stories, structural
type, and damage level were recorded for 10,480 building lots. Building damage was analyzed statistically by
Zavala et al. [15] and Matsuzaki et al. [16]. More than
40 investigators were employed to conduct the field survey, which took almost three months to complete.
According to the survey, most of the structures were
low-rise buildings; 72% were one-story buildings, and
23% were two-story buildings. The tallest building, which
was six stories, was used as a hotel. Of the brick masonry buildings, 65% were one story, 29% were two stories, 5.3% were three stories, and 0.4% were four or morestories. Of the adobe buildings, in contrast, 99% were one
story. Overall, the central part of Pisco district was foundto be densely built-up with low-rise buildings. Roofs were
mostly flat; roof tile was not typically used because of thedesert climate of the region. In terms of building occuJournal of Disaster Research Vol.9 No.6, 2014

pancy, 75% were residential, 7% were commercial, andthe others were schools, hospitals, factories, and buildings
used for other purposes.
Most of the buildings in Pisco were masonry: 16%
were adobe masonry, and 71% were burned brick masonry. The other 13% were reinforced concrete (RC),
Quincha, or mixed structures. Adobe houses can be foundin almost every part of the world; however, their construction methods and seismic performance vary from region
to region. In the rural areas of Peru, adobe blocks are typically made by buildings’ inhabitants, and in urban areas,
ready-made adobe blocks are sold at do-it-yourself home
centers. Quincha (a Kechua word pronounced “kincha”)
is a type of construction that is traditional in South America and employs panels supported by wooden frames andcane-and-mud walls [17]. A few of the RC buildings
surveyed were commercial buildings, such as banks andsmall hotels.
In Peru, the national building seismic code covers bothbrick masonry (under E.070) and adobe structures (under E.080) [18]. Most Peruvian brick masonry structures
are known as confined masonry. These structures haverelatively high horizontal stiffness because concrete slabs
and RC columns and beams are often used. The crosssectional areas of the RC columns are usually greater than
25 cm2 , unlike RC columns used for similar purposes inother countries, such as Indonesia [3]. On the other hand,
adobe structures with mud-and-bamboo roofs are highly
vulnerable to earthquakes [2].

2.2. Extent of Building Damage
During the survey, building damage levels were classified into four grades, namely, No damage, Slight damage,Moderate damage, and Severe damage. The definitions of
the damage levels and their relationship to the European
Macroseismic Scale (EMS) 1998 [19] damage categories
are shown in Table 1. Slight damage is manifested as repairable small cracks on the finishing walls. Severe dam1051

Matsuzaki, S. et al.

Table 1. Description of damage classifications used in
the survey by CISMID and corresponding damage levels in
EMS 1998.

Fig. 3. Damage distribution of 1,865 lots of adobe buildings.
Adobe buildings were found largely in the old urban area of
the Pisco district.

age includes collapse, which means that walls and roofs
have partially or completely fallen down. Moderate damage covers structural damage, which needs evaluation by
an expert to establish retrofitting needs. This classification system was originally developed by CISMID on thebasis of local structural characteristics. The system is wellknown in Peru and is widely accepted among decision
makers, researchers, professors, and people involved inbuilding construction. Fig. 3 shows the damage distribution for the adobe buildings surveyed, and Fig. 4 shows
the damage distribution for the brick masonry buildings.
Figure 5(a) and Table 2 show the number of damagedbuildings’ lots and the damage ratios by structural type.
The total number of buildings’ lots whose structural types
could be identified was 10,480. “Other” structure types in
the figure and table were Quincha, mixed, or other structure types. An example of a mixed structure is a mixture of adobe and Quincha. The proportion of all of thebuildings’ lots that collapsed or suffered fatal (classified
as severe) damage was 27%, and the combined proportion of moderate and severe damage was 40%. The degree of earthquake-induced damage observed depends onthe characteristics of masonry structures, specifically theirlack of rigidity, which makes them prone to collapse.
Adobe is quite vulnerable to earthquake damage. In
this study, 83% of the adobe structures surveyed had severe damage. Although adobe buildings make up no morethan 17% of all buildings in the district, 1,543 of the2,779 lots (56%) that suffered severe damage were adobe.
1052

Fig. 4. Damage distribution of 8,298 lots of masonry buildings.

The severe damage ratio for concrete buildings was alsohigh (22%). The severely damaged concrete structures
were assumed to be pre-code buildings and/or to havebeen constructed without the involvement of professional
engineers.
Figure 5(b) and Table 3 show the damage ratios formasonry buildings with respect to the number of stories.
In general, the greater the number of stories was, the heavier the damage was. However, for one-story buildings, theratio of severe damage was rather high (17.2%) and in fact
greater than that for two-story buildings (4.8%). For masonry buildings, the degree of damage observed was not
related to the building occupancy (use) or the natural period. With regard to the occupancy, there were no significant differences between one-story and two-story buildings. In the case of one-story buildings, 89% were residential, and 8% were commercial. In the case of two-story
buildings, 87% were residential, and 10% were commercial. Assuming that the natural period of a brick masonrybuilding with an RC frame is proportional to the numberof stories, with a coefficient of 0.08, the natural period of
Journal of Disaster Research Vol.9 No.6, 2014

Fig.2
Evaluation of Seismic Vulnerability of Buildings Based on
Damage Survey Data from the 2007 Pisco, Peru Earthquake
8298

1865
5.6% 2.2%
9.4%

27

290

25.9%

19.7%

39.9%

㻤㻜㻑

Damage Ratio

14.8%

10480 Lots

27.9%
26.5%

82.7%

31.2%

37.0%

12.1%
14.4%

15.5%

㻞㻜㻑

13.4%

80%

40.3%

2391

40.3%

41.5%

Concrete

Others

40%

30.7%

33.2%

11.7%
17.2%

All Type

33.3%

No DamageSlight

29.0%

0%

Brick
Masonry

62 Lots

60%

20%

㻜㻑

Adobe

435

22.6%

26.5%

22.2%

5370

19.4%

32.6%

㻢㻜㻑

㻠㻜㻑

100%

Damage Ratio㻝㻜㻜㻑

1-story

33.9%

Moderate

24.2%

Severe,Collapse

30.3%
20.5%
4.8%

7.4%

2-story

3-story

4 or more(a) Damage by structural type(b) Masonry damage by number of stories
Fig.5 (b)Fig. 5. (a) Building damage ratio by structure type and (b) damage ratio of masonry buildings by number of stories.
Table 2. Number of damaged building lots by structure type.
No damageSlightModerate
Severe, Collapse
Total (Lots)

Adobe
41
105
176
1,543
1,865

Brick masonry
3,315
2,586
1,284
1,113
8,298

Concrete
7
4
10
6
27

Others
57
81
35
117
290

Total
3,420
2,776
1,505
2,779
10,480

Table 3. Number of damaged building lots by number of stories for 8252 brick masonry buildings.
Fig.10 (b)1-story
2-story
3-story
4 or moreTotal
No damage
2,165
993
145
12
3,315
Slight
1,651
794
126
14
2,585
Moderate
631
490
132
21
1,274
Severe, Collapse
923
114
32
15
1,084
Total (Lots)
5,370
2,391
435
62
8,258

two-story buildings is around 0.16 s, and that of a onestory building is less than 0.10 s. Because the predominant periods of the acceleration response spectra of thesimulated bedrock motion were between 0.2 s and 1.0 s,
resonance was not the cause of the damage observed in
the one-story buildings.
Other factors in the amount of damage seen may be
the structural specifications of masonry buildings. In general, two-story masonry buildings in Peru have reinforcement members, such as RC beams and columns, and concrete slabs, and thus they have a certain amount of seismic resistance. On the other hand, some one-story masonry buildings are not reinforced with RC members. In
the construction of confined masonry buildings, walls areoften constructed prior to columns, and hence the bondstrength between brick walls and columns is great. Thus,
RC column members can transmit their seismic resistanceto foundations [20].
Besides, RC slabs do increase floor rigidity, and hence
all the walls of a given story bear the shear force on thatstory. Consequently, the seismic capacity of the building as a whole is increased. Fig. 6(a) shows the exteriorof a reinforced masonry building in Peru for which somecolumns and an RC slab can be seen. Fig. 6(b) shows an
Journal of Disaster Research Vol.9 No.6, 2014

indoor view of an unreinforced masonry building without
RC elements. The walls are made of bricks, but the roof
is made of bamboo covered by mud.
Figure 7 shows the spatial distribution of damage ratios
for masonry buildings with moderate or severe damage orcollapse, with respect to the city block. The Pisco district
was divided into 183 blocks, each of which had at least
30 masonry buildings. Regional differences are evident in
the damage ratios: significant damage occurred in the area
along the coast and in the old urban area near the mainsquare, as also shown in [21]. The ages of the buildings
are unknown; however, masonry buildings do not sufferfrom degradation over time due to decay or ants, unlike
wooden Japanese houses [22]. Differences in ground motion intensity due to soil differences are believed to beamong the reasons for the differences observed in thedamage distribution.

3. Microzoning and Seismic Ground Motions
3.1. Seismic Microzoning Using Microtremors
According to the results of several standard penetration
tests (SPTs) conducted by CISMID, hard soil with gravel1053

Matsuzaki, S. et al.

(a) Reinforced brick masonry (RM)(b) Unreinforced brick masonry (URM)

Fig. 6. (a) Exterior view of reinforced masonry building
with RC frame in Peru and (b) indoor damage state of onestory unreinforced masonry (URM) building without RC elements. The URM building has a roof of bamboo coveredby mud.

Fig. 7. Spatial distribution of moderate or greater damage
ratio for masonry buildings by city block. Each block was
divided to include at least 30 masonry buildings.

can be found around the Pisco district below the shallow
surface soil layer. Near the coast, the groundwater table
is high, and liquefaction due to the earthquake was observed. From 2007 to 2011, CISMID and Johansson et al.
conducted microtremor measurements at 73 sites in the
Pisco area [23]. In 2012, 12 new sites, including three atwhich array measurements were conducted, were added
to the set of microtremor measurement sites.
Nakamura proposed that the H/V (horizontal-to- vertical) spectral ratio of microtremors could be considered
the spectral amplification ratio of subsurface soil layers
at a given site [24, 25]. Fig. 8 shows the locations of
the 85 sites at which microtremor measurements were
made, along with peak periods of the H/V spectra andthe spatially interpolated H/V peak periods. Using the inverse distance-weighted method [26], interpolation of thepeak periods was performed by averaging the data from
12 nearby points. The target area was divided into threezones, 1 to 3. Darker colors indicate longer peak periodsof the sites.
1054

Fig. 8. Location of three MASW/array measurements andresults of spatial interpolation of H/V ratio of single-point
microtremor for 85 peak periods, using the inverse distanceweighted method.

The ground was estimated to be firm if the peak period of the H/V ratio was less than 0.1 s. The peak periodof Zone 1 was between 0.04 and 0.07 s, that of Zone 2
was between 0.07 and 0.10 s, and that of Zone 3 was between 0.10 and 0.14 s. The northwestern part of the area
is classified as relatively soft ground (Zone 3), and thesoutheastern part is firm ground (Zone 1).
Following the microzoning based on microtremors, thedamage ratios shown in Fig. 9 for adobe and brick masonry buildings were obtained. For 8,298 lots of masonrybuildings, the damage ratios for both severe damage andmoderate or greater damage were higher for softer soils(from Zone 1 to Zone 3). Similarly, for 1,865 lots ofadobe buildings, firmer soils had lower damage ratios for
all damage levels. The building damage ratio appears to
be related to the soil classification through the peak period of the H/V ratio of microtremors, for both adobe andmasonry structures in Pisco.

3.2. One-Dimensional Soil Response Analysis Using
Simulated Bedrock Motion
Using synthetic aperture radar (SAR) interferometry
data and teleseismic waveforms, the source model for the
Pisco earthquake was constructed to reproduce the nearsource strong ground motion recordings measured at the
Nana (NNA) and PCN stations and shown in Fig. 1. The
earthquake motions at the depth of the seismic bedrock(Vs = 3, 260 m/s) were obtained by numerical simulation [14].
To estimate the seismic ground motions during the
Pisco earthquake, the soil profiles at points P1, P2, andP3 in the three zones, shown in Fig. 8, were used. Multichannel analysis of surface waves (MASW) of the P1 sitedata, measured in relatively firm soil, was carried out in2007. Array microtremor measurements were also carriedout in 2012 at the P2 and P3 sites, in moderately soft andsoft soils. The shear-wave velocity profiles at the threesites, up to GL-1,200 m, were estimated from an inversion between the phase velocity and the period, as shown
Journal of Disaster Research Vol.9 No.6, 2014

Evaluation of Seismic Vulnerability of Buildings Based on
Damage Survey Data from the 2007 Pisco, Peru Earthquake

Damage Ratio

㻤㻜㻑

425
㻞㻟
㻡㻝

852
㻟㻢 㻝㻡
㻢㻤

588 Lots
㻝㻤
㻟㻥

(a)

㻢㻥
㻿㼘㼕㼓㼔㼠

㻢㻜㻑

㻣㻟㻟

㻠㻜㻑

㻡㻞㻤

㻞㻤㻞

㻹㼛㼐㼑㼞㼍㼠㼑
㻿㼑㼢㼑㼞㼑㻘㻌
㻯㼛㼘㼘㼍㼜㼟㼑

㻞㻜㻑

㻜

㻝㻡

㻝㻜㻜㻑

Damage Ratio

㻤㻜㻑

4025

㻣㻝㻞

㻝㻤㻜㻟

Zone 3

㻤㻠㻤
㻠㻜㻑

㻢㻜㻝

㻝㻝㻟㻣
㻟㻥㻞

㻞㻜㻑

㻜㻑

㻺㼛㻌㼐㼍㼙㼍㼓㼑㻿㼘㼕㼓㼔㼠

㻢㻜㻑

㻞㻣㻟

㻢㻝㻥

㻝㻠㻟

㻠㻢㻢

Zone 1

Zone 2

㻜

㻞㻜㻜

㻠㻜㻜

㻢㻜㻜

㻤㻜㻜 㻝㻜㻜㻜 㻝㻞㻜㻜 㻝㻠㻜㻜(b)2544 Lots㻤㻜㻜

Zone 3㻞㻜㻌㼂㼟㻌㻔㼙㻛㼟㻕(a) Adobe
1729

Zone 2

㻝㻜㻟㻜

Zone 2

㻌㻼㻝
㻌㻼㻞
㻌㻼㻟

㻞㻡

㻜㻑

Zone 1

Zone 1㻡㻺㼛㻌㼐㼍㼙㼍㼓㼑㻰㼑㼜㼠㼔㻌㻔㼙㻕㻝㻜㻜㻑㻹㼛㼐㼑㼞㼍㼠㼑
㻿㼑㼢㼑㼞㼑㻘㻌
㻯㼛㼘㼘㼍㼜㼟㼑

㻡㻜㻠

Zone 3(b) Brick masonry

Fig. 9.
Damage ratios by soil zone classification for(a) adobe buildings and (b) brick masonry buildings.

in Fig. 10. The soil profiles at the three sites were assumed to have a common soil structure at depths greaterthan GL-400 m.
The transfer functions and ground motions at the surface were derived from the results of a one-dimensional
layered soil response analysis conducted using EERA,
which is a version of the SHAKE program for Microsoft
Excel developed by Bardet et al. [27]. Using as input
the ground motion simulated by Pulido et al. (2013) atthe outcrop base rock, one-dimensional (1D) equivalentlinear seismic response analyses were performed. Straindependent nonlinearity of the soil was considered only forthe uppermost layer. The clay model in EERA was usedas the material type for the stress–strain and damping–strain curves. The default value for clay [28] was used forthe modulus of the top layer. The ratio of the effective tothe maximum shear strain was assumed to be 0.65.
The predominant periods of the transfer functions wereapproximately 0.07 s for P1 (Zone 1), 0.21 s for P2(Zone 2), and 0.23 s for P3 (Zone 3). The simulated
bedrock motions were available for these three points.
The maximum ground surface acceleration and velocity(PGA and PGV) for each zone are summarized in Table 4.
The resultant of the two horizontal components was also
obtained for the three locations.

Journal of Disaster Research Vol.9 No.6, 2014

P1 (Zone 1)
P2 (Zone 2)
P3 (Zone 3)
Depth
Vs
Depth
Vs
Depth
Vs
(m)
(m/s)
(m)
(m/s)
(m)
(m/s)
0-2
230
0-4
95
0-7
164
2-7
520
4 - 12370
7 - 13840
7-8
336 12 - 200
585
13 - 400
1020
8 - 400
981 200 - 400
700
400 - 700 1500 400 - 700 1500 400 - 700 1500
700 - 1200 2600 700 - 1200 2600 700 - 1200 2600
1200 - ∞3260 1200 - ∞3260 1200 - ∞3260
Fig. 10. (a) Comparison of shear-wave velocity profiles
among three measurement sites, P1 (Zone 1), P2 (Zone 2),
and P3 (Zone 3), up to GL-30 m, and (b) up to GL-3,000 m.

Table 4. Maximum ground surface acceleration and velocity from one-dimensional response analysis for three zones.

PGA(cm/s2 )PGV(cm/s)

Site

EW

NS

Zone 1 (Hard)
Zone 2
Zone 3 (Soft)
Zone 1 (Hard)
Zone 2
Zone 3 (Soft)

331.9
523.0
576.9
60.4
64.1
84.7

441.6
365.8
461.2
75.9
81.0
94.3

Resultantvector
552.4
554.4
611.1
94.4
99.5
113.8

4. Development of Fragility Curves and Comparison with Curves from Previous Studies
4.1. Development of Fragility Curves
Fragility curves for adobe and masonry structures wereconstructed from the relationship between the damage ratio and the peak ground motion values (PGA and PGV).
Assuming a log-normal distribution for the probability ofdamage occurrence greater than or equal to rank R, the cumulative probability PR (x) for a peak ground motion value
x is expressed by the following equation:
PR (x) = Φ ((ln x − λ )/ζ ) . . . . . . . . . (1)where Φ is the standard normal distribution and λ and ζ
are the logarithmic mean and logarithmic standard deviation of ln x, respectively. The values of these terms wereobtained by regression analysis using log-normal probability paper.
1055

Matsuzaki, S. et al.

Table 5. Coefficients of fragility curves for adobe and masonry buildings in Pisco.

Adobe
Masonry

Moderate or greater
Severe, Collapse
Moderate or greater
Severe, Collapse

λ-0.785-0.710-0.413-0.285

The results of the regression analysis are shown in Table 5. According to Fig. 9(b), the damage ratios associated with slight or greater damage in Zone 1 were higher
than those in Zone 2, while the PGA and PGV in Zone 1
were smaller than those in Zone 2. Therefore, a reasonable fragility function for slight or greater damage was
not obtained in this study. As the regression for moderate or greater damage for masonry buildings had significant variation in the data around the regression line, the ζvalue obtained for the severe damage state was assumed
for this damage state as well.

4.2. Comparison of Fragility Curves for Adobe
Buildings
The fragility curves obtained as described above werecompared with fragility curves obtained in previous studies in terms of PGA using the capacity spectrum method.
The curves developed in previous studies applied to typical building types in a particular country or region. In
addition, the demand spectrum for each case was the one
for an assumed earthquake scenario. In the previous development of fragility curves, the spectral displacement(Sd ) or the spectral acceleration (Sa ) was often used as anintensity measure, rather than the MMI seismic intensity
or the PGA.
Tarque et al. derived fragility curves for one-story
adobe dwellings in Cusco, Peru [9] as a function of PGA,
based on an acceleration response spectrum for a seismic
motion scenario. The fragility curves for conditions denoted by LS4 (near collapse or collapse) and LS3 (lifesafety) were considered to correspond to the severe damage and moderate or greater damage levels, respectively,in the present study.
Figure 11 shows a comparison between the curves
for Cusco and Pisco. The comparison suggests that thefragility curves for adobe in Pisco are similar to those foradobe in Cuzco, especially for the severe damage level.
The damage ratio for Pisco is slightly lower than that of
Cuzco, but the slope of the curve is steep. For both curves,the damage ratios for moderate or greater damage exceed
90% for PGA values of 0.6 g. The seismic performanceof adobe buildings in Cuzco, as evaluated by Tarque etal. [9], is similar to that observed in this study.
4.3. Comparison of Fragility Curves for Masonry
Buildings
The fragility curves for brick masonry structures in
Pisco were compared with those for RM2L lifeline build1056

PGA
ζ
0.171
0.184
0.223
0.223

R2
0.559
0.490
0.614
0.898

λ
4.280
4.393
4.828
5.033

PGV
ζ
0.242
0.253
0.355
0.355

R2
0.787
0.727
0.608
0.994

Adobe

㻝㻜㻜㻑

Probability of Damage (%)

Damage Grade㻤㻜㻑

Adobe, Pisco
Moderateor greater㻢㻜㻑Serious,Collapse
Tarque et al.
(2012)
Life-safety㻠㻜㻑

Near or collapse

㻞㻜㻑

㻜㻑
㻜㻚㻜㻌

㻜㻚㻞㻌

㻜㻚㻠㻌

㻜㻚㻢㻌

㻜㻚㻤㻌

㻝㻚㻜㻌

㻝㻚㻞㻌

PGA (g)Fig. 11. Comparisonoffragilitycurvesobtainedinthisstudyfor buildings in Pisco with those obtained by Tarque et al. [9]for buildings in Cusco.

ings in HAZUS and URM (unreinforced masonry) in
Istanbul (developed by Erberik [10, 11]), as shown in
Fig. 12. It is reasonable to assume that pre-code buildings in HAZUS correspond to non-conforming buildings
under the present Peruvian building code regulations.
HAZUS-MH MR3 [8] is a standard multi-hazard tool
for loss estimation due to seismic motion and ground failure for buildings, transportation systems, and lifeline facilities. The fragility curves of lifeline buildings are expressed as a function of an equivalent PGA. From among
the lifeline building types, the low-rise RM2L (one- tothree-story reinforced masonry bearing walls with precast
concrete diaphragms) was selected for comparison, basedon its similarity to the types of building structures found in
Pisco. However, it is not as clear whether masonry bearing walls in HAZUS are similar to certain types of structures found in Peru, such as confined masonry buildings.
“Masonry” refers broadly to a construction method basedon layers using stone, brick, concrete block (CB), etc. The
category of masonry includes various types of structures,such as brick masonry reinforced with a light-gauge steel
frame [29]. The results of the comparison suggest thatthe brick masonry buildings in Pisco are much more vulnerable than RM2L buildings in HAZUS. This may be
because HAZUS deals with other structural specifications
than those considered in this study. As described previously, masonry buildings in HAZUS might include not
only brick masonry but also CB.
Journal of Disaster Research Vol.9 No.6, 2014

Evaluation of Seismic Vulnerability of Buildings Based on
Damage Survey Data from the 2007 Pisco, Peru Earthquake

adobe, the difference between the ground motion that produces moderate or greater damage and the ground motionthat produces severe damage is small. This observationis consistent with the fact that adobe buildings are likely
to exhibit significant damage suddenly and suffer brittle
failure.

Masonry (Reinforced/Unreinforced)

Probability of Damage (%)

100%

80%

60%

5. Conclusions

40%

20%

0%
㻜
RM, Pisco
Moderateor greater
Serious,Collapse

㻜㻚㻞

㻜㻚㻠

㻜㻚㻢

PGA (g)㻜㻚㻤

URM, Erberik(2010)
Moderate
Severe, Collapse㻝㻝㻚㻞

RM, HAZUS
Pre-Code
Extensive
Pre-CodeComplete

Fig. 12. Comparison of fragility curves (RM) for one- totwo-story reinforced brick masonry buildings in Pisco withthose (RM2L) for one- to three-story reinforced masonry
bearing walls with precast concrete diaphragms in lifelinebuildings in HAZUS [8] and those (URM) for one-story unreinforced regular buildings with solid brick walls in Istanbul
obtained by Erberik [10, 11].

The study by Erberik [10, 11] addressed one-story unreinforced brick buildings with well-formed plans in Istanbul, Turkey. The brick masonry buildings consideredin the present study were mainly one- to three-story buildings, and the two structural types are different. With respect to materials, brick masonry buildings in Istanbul are
made of solid brick, whereas in Pisco, the walls on thesecond floor of a brick masonry building are made of perforated brick, and those on the ground floor are made ofsolid brick. Compared to the fragility curves for brickmasonry in Istanbul, the fragility curves developed in thisstudy indicate that the damage that occurs in confined masonry in Pisco (in one- and two-story buildings) starts tooccur at a larger PGA value than in one-story unreinforced
masonry in Istanbul but exhibits higher damage ratios atlarger PGA values. The slopes of the fragility curves developed in this study were steeper than those developedin previous studies. The damage ratios for masonry buildings after the Pisco earthquake were smaller than thoseestimated using the fragility functions developed by Erberik [10, 11].
The results of the comparison of the damage ratios
for structural types in Pisco indicate that more than 80%
of adobe buildings suffered severe damage at a PGA of
0.6 g. The damage ratio for masonry buildings, for thesame seismic excitation level, was 15%. The two fragility
curves exhibit a clear difference in performance by structural type. The slopes of the adobe fragility curves aresteeper than those of the masonry fragility curves, whichsuggests that just a small increase in the ground motion
will result in serious damage in adobe. In other words, for
Journal of Disaster Research Vol.9 No.6, 2014

In this study, relationships between peak ground motion indices and building damage caused by the 2007
Pisco, Peru earthquake were investigated using damage
survey data collected in the Pisco district and simulated
ground motion records. Approximately 80% of the adobebuildings in the survey area suffered from serious damage,such as collapse, as a result of the earthquake. In contrast,
the ratio of serious damage for brick masonry buildings
was only approximately 13%. The extent of the damage
observed varied widely, depending on the structural properties of the buildings surveyed, such as the presence orabsence of concrete reinforcing members.
The subsurface soils in the area of Pisco were divided
into three zones based on the predominant periods of microtremors measured at 85 sites. The relationship between a site’s ground conditions and the damage ratio foreach zone was confirmed. Compared to fragility functions derived by analytical methods in previous studies,
the means and standard deviations for adobe structures in
Pisco were quite similar to those for structures in Cusco.
For brick masonry, the means in Istanbul and Pisco weresimilar, but within the range of ground motion of the Pisco
earthquake (0.56 to 0.65 g), the damage ratio in Istanbul
was 20% larger than in Pisco.
The damage survey conducted in Pisco covered a small
area of only 2 km2 . The estimated ground motions exhibited no significant differences. It would be preferable toverify the reliability of the damage ratios determined using data from lower-damage-ratio areas for adobe structures and data from higher-damage-ratio areas for masonry buildings. In this study, one-story brick masonrybuildings in Pisco were found to be a mixture of goodand poor structures in terms of their seismic performance.
Through a detail survey of floor specifications and withinformation on the proportion of unreinforced buildings,
it might be possible to further validate the relationship between the structure type and degree of damage.
Acknowledgements
The authors are grateful to Prof. Hiroaki Yamanaka and Dr. Kosuke Chimoto of the Tokyo Institute of Technology and Mr. Fernando Lazares of UNI for their support during the array measurements in Pisco.

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Name:
Shizuko Matsuzaki

Affiliation:
Project Researcher, Department of Urban Environment System, Graduate School of Engineering, Chiba University

Address:
1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan

Brief Career:2013 Dr. Eng., Chiba University
2013 Project Researcher, Chiba University

Selected Publications:• “Visual damage interpretation of buildings using QuickBird images
following the 2007 Peru earthquake,” Proc. of the third Asia Conf. on
Earthquake Engineering, ACEE-P-067, 2010.

Academic Societies & Scientific Organizations:• Architectural Institute of Japan (AIJ)• Institute of Social Safety Science (ISSS)• Japan Association for Earthquake Engineering (JAEE)

Journal of Disaster Research Vol.9 No.6, 2014