EARTHQU A K E F I EL D I NV ES TI G ATI O N RE P O RT
L’ A Q U I L A
ITALY
EARTHQUAKE
April 6, 2009
2009 M6.3 L’Aquila, Italy, Earthquake Field Investigation Report
0A
| Acknowledgments
O
ur reconnaissance team consisted of Kit Miyamoto of Miyamoto International, Peter Yanev
of Global Risk Miyamoto, and Ilbe Salvaterra of Global Risk Consultants, who were at the
epicentral area within a week of the earthquake. The team worked with many individuals in
Italy and thanks them for their support and insights.
We would also like to thank the Miyamoto International and Global Risk Miyamoto staff, as well as our
clients, whose email messages of encouragement during the trip gave us a welcome respite from our days
of witnessing devastation. In particular, we would like to recognize Tom Chan for coordinating our base and
field teams and editing our daily reports, and also Rebecca Cully, Diana Ung, Shin Kao, and Chris Heaton
for their base support. Without them, this investigation and report would not have been possible.
This report is dedicated to all the people in the affected area. This earthquake was yet another somber
reminder to all of us in the structural engineering profession of the importance of our work and the responsibility that we all share in protecting lives and livelihoods.
(From Left) Kit Miyamoto,
Ilbe Salvaterra, and Peter Yanev
2009 M6.3 L’Aquila, Italy, Earthquake Field Investigation Report
00
| Contents
01
Overview ..................................................................................................................... 2
02
Earthquake Background and Seismicity ................................................................... 3
03
Historic Buildings ....................................................................................................... 7
04
Essential and Modern Facilities ............................................................................... 11
05
Commercial Buildings ............................................................................................. 14
06
Industrial Buildings................................................................................................... 16
07
Residential Buildings................................................................................................ 20
08
Multistory Apartment Complexes............................................................................. 22
09
Transportation Facilities .......................................................................................... 23
10
Lifelines and Utilities................................................................................................. 24
11
Emergency Response ............................................................................................. 26
12
Discussion ................................................................................................................ 27
13
References ............................................................................................................... 28
14
About Global Risk Miyamoto ................................................................................... 29
1
2009 M6.3 L’Aquila, Italy, Earthquake Field Investigation Report
01
| Overview
T
he magnitude 6.3 central Italy earthquake occurred on April 6, 2009, approximately
85 km (55 mi) northeast of Rome. The university town of L’Aquila (which means “the
eagle” in Italian) has one of the oldest educational institutions in Europe and a popula-
tion of close to 70,000. L’Aquila and nearby villages were especially hard-hit by the earthquake.
This earthquake resulted in 305 fatalities and thousands of injuries, displaced more than 25,000 people, and
caused significant damage to more than 10,000 buildings in the L’Aquila area. The event was felt throughout
central Italy, including Rome. Most of the deaths occurred when people were buried under collapsed buildings. After the earthquake, the Italian government set up shelters for people who were displaced.
The total cost of this earthquake, including financial losses and reconstruction efforts, is expected to
exceed US$16 billion. Earthquake damage was not limited to buildings, however; roadways and bridges
were also affected. In addition, industrial and commercial structures sustained damage, leading to business interruption and other financial losses.
Many of the types of damage from this event have also been observed in past earthquakes. For example,
damage to unreinforced masonry structures was widespread. However, buildings constructed in recent
years—and supposedly according to more advanced seismic codes—including hospitals, industrial plants,
and college campus buildings, also experienced damage.
A particular feature of this earthquake was the significant damage to historic and vintage buildings, including
churches. Many of these structures were built centuries ago, and therefore such damage is a great loss.
Within days after the earthquake, Miyamoto International and Global Risk Miyamoto engineers were on
the ground in the affected area, investigating and analyzing the damage; providing support to clients; and
documenting this earthquake, with the goal of supporting communities and preventing such catastrophic
losses in future events.
2009 M6.3 L’Aquila, Italy, Earthquake Field Investigation Report
02
2.1
| Earthquake Background and Seismicity
The Earthquake
On April 6, 2009, at 3:32 a.m. local time, a magnitude 6.3 earthquake occurred in central Italy. The epicenter was in Tornimparte, Abruzzo, which is at 42.334 degrees latitude and 13.334 degrees longitude, and 7
km northwest of the town of L’Aquila. This earthquake occurred on normal faulting on the Apennine mountain belt that runs from the Gulf of Taranto in the south to the southern edge of the Po Basin in northern
Italy. This faulting (Figure 1) is related to the collision of the Eurasian and African plates and the opening
of the Tyrrhenian Basin to the west. The tectonic activities in this area have resulted in major earthquakes
both in Italy and in the central Mediterranean (USGS 2009). Figure 2 presents the faulting sequence and
the location of the epicenter.
Figure 1. Geodynamic model for the Mediterranean
region (Devoti et al. 2008)
Figure 2. Seismic sequence (INGV 2009)
The April 6 earthquake was a shallow event, with an epicentral depth of approximately 8 km. Because the
seismic waves associated with shallow quakes can reach the surface without losing much energy, they
produce stronger shaking and usually more damage. Figure 3 presents the shake map intensity for the
magnitude 6.3 event, as felt according to the Modified Mercalli Intensity (MMI) scale. This quake is classified as a VI to VII event on the MMI scale. Such an MMI corresponds to strong shaking and moderate
damage. The main shock was followed by many aftershocks (Figure 4).
Figure 5 presents the estimated peak ground accelerations (PGAs) for this event. It is notable that a maximum PGA of 0.2g in the epicentral area is indicated in this figure. Such accelerations should not cause
extensive damage. The ground displacement was estimated to be 150 mm (6 in.).
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02| the earthquake
2009 M6.3 L’Aquila, Italy, Earthquake Field Investigation Report
Figure 3. MMI ShakeMap (USGS 2009)
Figure 4. Aftershocks (EMSC 2009)
Figure 5. Peak ground acceleration (PGA)
(USGS 2009)
Figure 6. Historical seismicity from 1964 to present
(EMSC 2009)
2.2
Seismicity of Italy
Italy is one of the world’s most earthquake-prone countries, with tremors occurring frequently. Table 1 lists
some of the major earthquakes that have affected Italy. Figure 6 presents the locations of earthquakes from
1964 to the present.
2009 M6.3 L’Aquila, Italy, Earthquake Field Investigation Report
Table 1.
Major Italian Earthquakes (USGS 2009)
Date
Magnitude
Location
Fatalities
1349
6.5
L’Aquila
1693
7.5
Sicily
1703
6.7
L’Aquila
3,000
1783
?
Calabria
50,000
1857
6.9
Naples
11,000
1905
7.9
Calabria
560
1908
7.2
Messina
70,000
1915
7.0
Avezzano
33,000
1919
6.3
Mugello
100
1920
6.4
Toscana
170
1930
6.5
Irpinia
1968
6.5
Sicily
1976
6.5
Northeast Italy
1,000
1980
6.4
Southern Italy (Naples)
3,000
1997
6.4
Central Italy
11
2002
5.9/6.0/5.8
Southern Italy
31
2002
5.4
Central Italy (Molise)
30
800
60,000
1,400
230
As shown in Figure 7, many active faults are located in the area affected by the April 2009 earthquake.
These faults have caused a number of earthquakes and significant damage and loss of life. A 1997 earthquake caused serious damage to the Basilica of St. Francis in Assisi and destroyed priceless medieval
frescoes. That event occurred approximately 50 km to the north of the April 2009 earthquake.
The next significant earthquake to hit central Italy occurred on October 31, 2002. The magnitude 5.4 Molise
Earthquake damaged recently constructed buildings in nearby villages. A school building in the village
of San Giuliano di Puglia collapsed, resulting in the death of 26 (out of 51) students and one teacher. The
extent of damage was attributed to the near-surface geology for the site (Azzara et al. 2003). Following the
2002 earthquake, a new seismic code was adopted and local laws were enacted that included requirements for evaluation and repair of structures (Giovinazzi and Podestà 2008).
2.3
The 2006 Seismic Code
The 2006 earthquake code used in Italy divides the country into five seismic regions: Zones 1, 2, 3a, 3b,
and 4. Zone 1 has the highest intensity (Figure 8). This system is similar to that used by earlier editions of
the building codes in the United States.
A close-up of the seismic zonation for L’Aquila (Figure 9), as identified in the 2006 earthquake code, shows
the L’Aquila area to be in Zone 2, which indicates moderate seismicity. However, past earthquakes (Figure
6) and fault maps (Figure 7) indicate that the area really should be rated as Zone 1 or high seismic hazard.
The April 2009 earthquake was a moderate event that resulted in localized but spectacular damage. A
large earthquake in this area, which is probable, would result in thousands of casualties and much greater
and widespread damage.
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02| the earthquake
2009 M6.3 L’Aquila, Italy, Earthquake Field Investigation Report
Figure 7. Active faults in central Italy and L’Aquila area (INGV 2006)
Figure 8. Seismic zonation for Italy
(Italian Seismic Code 2006)
Figure 9. Close-up of the central Italy seismic zonation,
2006 code (Italian Seismic Code 2006)
2009 M6.3 L’Aquila, Italy, Earthquake Field Investigation Report
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3.1
| Historic Buildings
Overview
L’Aquila, a city of close to 70,000 residents, is situated on the left bank of the Aterno River. The city is at
an elevation of 655 meters (2,150 ft), in a valley surrounded by the highest mountains of the Apennines.
L’Aquila is the main historic and artistic center of the Abruzzo region. The town is renowned for its university, musical conservatory, arts academy, library, and theater. It is primarily an administrative center (Figure
10) for the large province. The economy of the town depends mainly on the chemical, mechanical, and
farming industries. Its major commodities include wine, grains, dairy products, and craftwork. L’Aquila also
serves as the hub for winter sports in the nearby mountains.
The heritage of the L’Aquila region’s medieval past and treasured architecture is represented by churches
and monuments. These include the symbol of the city, which is the Fountain of the Ninety-Nine Spouts; a
16th-century Spanish castle; the Basilica of St. Bernardino; and the Church of St. Mary in Collemaggio. The
Church of St. Mary was used to crown the Pope in 1294. The city itself dates back to the 1240s.
Figure 10. Collapsed government building
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03| historic buildings
2009 M6.3 L’Aquila, Italy, Earthquake Field Investigation Report
L’Aquila and the surrounding area experienced sporadic but significant damage to historic buildings, some
of which date back to Roman times, the Middle Ages, or the Renaissance. Given the heritage of this area, it
is important to protect these unique and invaluable structures.
These buildings are typically of unreinforced masonry (URM) or stone construction. Fortunately, this was
a moderate earthquake. The damage would have been much more substantial if this had been a larger
seismic event.
3.2
Cathedral of St. Massimo
The Piazza Duomo was constructed in the 13th century and holds the Cathedral of St. Massimo and St.
Mary of Holy Souls. The cathedral was destroyed in the 1700 earthquake and was reconstructed in the
19th century. This historic building sustained major damage in the April 2009 earthquake (Figure 11). In
particular, the magnificent dome of this structure collapsed (Figure 12).
Figure 11. Cathedral of St. Massimo
Figure 12. (Right) Collapsed dome of St.
Massimo
2009 M6.3 L’Aquila, Italy, Earthquake Field Investigation Report
3.3
Other Churches
Many historic churches, cathedrals, and other religious buildings are located in the earthquake zone.
These historic buildings were not designed to withstand earthquakes and, as such, many were damaged.
Figure 13 shows one of the churches with a damaged tower (on the left side).
Figure 14 depicts another church in the town of Fossa that dates back to the 13th century. In this structure,
the bell tower and the main building sustained damage.
Figure 13. Damaged church building
Figure 14. Damaged church and bell tower
The Basilica of St. Bernardino is one of the finest examples of Renaissance architecture in Abruzzo. This
three-story masonry and stone structure (Figure 15) had large diagonal cracks on the right-hand wall. The
main structure and the adjacent unit were of different construction, which likely contributed to the damage.
The earthquake also damaged many masonry or ornamental structures such as the historic gates in Figure 16.
9
Figure 15. Basilica of St. Bernardino
Figure 16. Compromised stone gates
03| historic buildings
2009 M6.3 L’Aquila, Italy, Earthquake Field Investigation Report
3.4
Other Historic Structures
The historic government building in L’Aquila was severely damaged (Figure 17). The upper story of this
stone and masonry building completely collapsed during the earthquake (Figure 18). The two-story historic
building shown in Figure 19 experienced significant cracking and spalling of the columns, walls, and roof
(Figure 20).
Figure 17. Collapsed government building
Figure 18. Collapsed government building
Figure 19. View of historic buildings
Figure 20. Structural damage to same historic building
The earthquake collapsed large sections of the ancient unreinforced masonry wall of L’Aquila (Figure 21).
In the town of San Panfilo d’Ocre, the 10th-century Castello d’Ocre was reduced to rubble (Figure 22).
The severe damage was likely caused by “focusing” effects of the earthquake energy at the top of the hill.
Damage to nearby historic structures in the village below was limited.
Figure 21. Collapsed section of L’Aquila city wall
Figure 22. Collapsed Castello d’Ocre
2009 M6.3 L’Aquila, Italy, Earthquake Field Investigation Report
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4.1
| Essential and Modern Facilities
Overview
Essential structures such as schools, hospitals, and emergency response facilities should be designed to
protect life safety and remain functional during and after earthquakes. Therefore, a more stringent seismic design is needed for these structures. Following the collapse of a school in the 2002 magnitude 5.4
central Italy earthquake, attention was focused on better seismic design for these important structures.
The L’Aquila Earthquake caused significant damage to essential facilities. Also troubling is the damage
to recent-vintage buildings that should have been constructed to comply with more modern codes. More
severe damage or collapse would have occurred if this had been a larger earthquake.
4.2
San Salvatore Hospital
The three-story San Salvatore Hospital is located in western L’Aquila. This large, modern facility was constructed in 2000 and should have withstood a magnitude 6.3 earthquake with minimal damage.
The unreinforced masonry (URM) infill walls at the third level of the hospital collapsed onto the emergency
entrance area (Figure 23), knocking down the large “Emergency” sign. When the exterior walls tore away,
the concrete beams and columns were exposed. The ground motion here was not strong enough to collapse the structure, but the URM walls were not anchored properly and, as such, collapsed. Other nearby
buildings did not have much damage because of the low level of ground motion at the site.
At the time of our visit, the hospital was dark and nearly deserted. Patients were evacuated and attended to
outdoors in the parking area (Figure 24). Had this facility been fully functional, it could have been used to
treat many of the thousands of people injured in the area.
Figure 23. San Salvatore Hospital
Figure 24. Treatment facilities set up outdoors
11
essential damage
facilities
04| 04|
geotechnical
2009 M6.3 L’Aquila, Italy, Earthquake Field Investigation Report
4.3
University of L’Aquila
The University of L’Aquila campus is located on a hilltop in the southern part of L’Aquila. There was widespread damage at the university, including the collapse of many interior and exterior masonry walls (Figure
25). For example, a modern, 10-year old university building (Figure 26) did not have much structural damage, but nonstructural damage was so significant that the structure could not be occupied.
On the outside of this modern building, the masonry veneer collapsed. Many architectural concrete masonry walls and suspended ceilings had also collapsed (Figure 27). Simply put, there were no connections
or braces to stabilize these walls and ceilings. Many of the concrete masonry walls collapsed onto student
and faculty desks (Figure 28). Fortunately, this was a smaller earthquake and it occurred early in the morning, when the classrooms were unoccupied. Had this been a larger earthquake that occurred when classes
were in session, it could have resulted in many fatalities.
The engineering faculty building is a five-story structure (Figure 29) built in the 1930s. It has a concretemoment-frame structural system with URM infill walls. These walls dampened the earthquake forces and
limited the damage to architectural components. Hollow clay infill partition walls were damaged (Figure 30)
throughout the building, including exit hallways. Figure 31 shows the third-floor office of one of the faculty
members where a heavily damaged infill wall collapsed onto the professor’s desk.
The University of L’Aquila dormitory, in the Old Town, is
a modern structure that sustained significant damage (Figure 32). This damage killed several college
students.
Figure 25. Damaged masonry wall
2009 M6.3 L’Aquila, Italy, Earthquake Field Investigation Report
Figure 26. (Left) Damaged modern structure on University
of L’Aquila campus
Figure 27. (Middle left) Fallen nonstructural components
Figure 28. (Middle right) Fallen walls in a classroom
Figure 29. Engineering faculty building
Figure 30. Architectural damage, including hollow clay
walls at corridor
Figure 31. (Bottom left) Collapsed infill wall into faculty
office
Figure 32. (Bottom right) Damaged dormitory building
13
2009 M6.3 L’Aquila, Italy, Earthquake Field Investigation Report
05
| Commercial Buildings
Commercial building damage consisted mainly of cracking and/or collapse of unreinforced masonry infill
walls, veneers and interior partitions, ceilings, and other finishes (Figures 37 and 38). In L’Aquila, a fourstory, mixed-use, reinforced-concrete-frame building with URM exterior and interior infill walls sustained
minor structural damage (Figure 33), but significant URM infill wall and partition damage (Figure 34). The
glass panels on the ground floor remained intact, and inventory and displays inside the building had only
light damage—another testament to the low ground motions of this moderate earthquake (Figure 35).
A one-story coffee shop (Figure 36) that was situated among heavily damaged, new industrial buildings
in L’Aquila did not sustain any structural damage. Inside the building, there was no broken glass and only
very minor nonstructural damage.
Figure 33. Four-story, concrete-frame, mixed-use building
2009 M6.3 L’Aquila, Italy, Earthquake Field Investigation Report
Figure 34. (Left) Fallen URM outside same commercial building
Figure 35. (Middle left) Fallen inventory inside mixed-use building
Figure 36. (Middle right) Fallen display inside coffee shop
Figure 37. (Bottom left) Damaged walls at exterior of store
Figure 38. (Bottom right) Collapsed suspended ceiling inside store
15
2009 M6.3 L’Aquila, Italy, Earthquake Field Investigation Report
06
| Industrial Buildings
6.1
Overview
Damage to industrial buildings in the affected region directly correlated to the construction type and the
distance to the earthquake epicenter. For example, industrial buildings in the L’Aquila area were significantly affected. Many of these buildings are of newer vintage, and given the low amplitude of the earthquake, the level of damage was a surprise. Most of the damaged structures had precast-concrete framing
systems.
We also surveyed several industrial facilities in the area near Pescara, a town on the scenic Adriatic coastline approximately 50 to 70 km from the epicenter. Such a distance is generally too great to cause damage to modern buildings. However, for precast-concrete-frame structures, minor cracking was observed,
highlighting the low seismic resistance of this building type.
The equipment at industrial plants in both the
L’Aquila area and Pescara was generally unanchored or inadequately braced (Figure 39) for earthquakes. As seen during the recent earthquakes in
Niigata, Japan, and Sichuan, China, unanchored
equipment will move and/or collapse, causing major business interruption. It is very cost-effective to
retrofit this equipment using simple anchors.
The area east of Rome houses much of the hightech industry in Italy, and some of these facilities are
in the L’Aquila area. Two weeks after the earthFigure 39. Unanchored equipment outside an industrial
facility
Figure 40. Dislodged precast walls
2009 M6.3 L’Aquila, Italy, Earthquake Field Investigation Report
quake, several of the plants were still not operational. Business interruption and revenue loss are likely to
be significant.
6.2
Surveyed Buildings
Among the surveyed buildings near L’Aquila was a new reinforced-concrete structure with precast exterior
wall panels. The structural frame was undamaged, but the precast-concrete walls had partially collapsed
(Figure 40).
One new industrial building that was under construction and close to completion, located approximately 10
km from the epicenter, was subjected to moderate ground motion, which should not have caused significant damage. However, the roof and exterior wall panels of this building collapsed (Figure 41). The collapsed walls of this building were a direct result of inadequate anchorage between the wall panels and roof
and floor framing members (Figure 42). Figure 43 shows a tie between the exterior walls and the concrete
framing. Such a tie is clearly inadequate for the anticipated lateral loads. Figure 44 shows another exterior
wall panel connection failure.
Figure 41. Collapsed roof of industrial building
Figure 42. Collapsed wall panels
Figure 43. Tie for exterior walls
Figure 44. Exterior wall connection pullout
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06| industrial
2009 M6.3 L’Aquila, Italy, Earthquake Field Investigation Report
A recently completed office building appeared undamaged from the outside. However, interior damage was evident when we looked in. This turned out
to be another precast-concrete-frame building with
extensive URM infill cracking and collapse. Noticeable movement of the beam and column corbel
support is evident (Figure 45).
A three-story industrial building was under construction and used concrete framing and masonry
infill walls. As shown in Figure 46, the masonry
walls were not properly anchored to the concrete
framing, and they collapsed. Additionally, the first
Figure 45. Interior damage
floor of this building is much taller than the upper
floors are, creating a soft-story condition that can
lead to building collapse in a strong earthquake.
Near the Aterno River, a two-story factory is located
at the east end of town. This factory manufactures
a variety of building construction materials, ranging
from wood beams to steel reinforcing bars. The corners of the factory’s precast walls tore away from
the building and fell to the ground (Figure 47).
Figure 46. Collapsed masonry walls
Figure 47. Two-story factory
2009 M6.3 L’Aquila, Italy, Earthquake Field Investigation Report
Figure 48. Precast-concrete framing
Figure 48 shows a typical industrial building constructed of heavy precast-concrete frames with precast
wall and roof panels. This type of construction is very common in Italy and other countries in the Mediterranean region. If not properly detailed for earthquakes, this construction type often suffers extensive damage
and collapse in strong earthquakes. Typical problems include: (1) the precast cantilever columns are tall
and work like flagpoles, so they will sway excessively and damage critical frame connections that hold the
building together; (2) precast-concrete roof members are heavy and add large seismic mass to the tops of
the buildings, aggravating the “flagpole” column problem; (3) precast-concrete wall panels are inadequately tied to the building, so strong ground motions will tear connectors and collapse wall panels; and
(4) many of the precast member connections are improperly designed to accommodate prestress shrinkage behavior common to this construction type. When precast-concrete elements are restrained from
shrinkage movements, connection cracking and other damage will occur before an earthquake strikes,
weakening the building’s capacity to resist future earthquakes.
A manufacturing plant located approximately 50 km east of the epicenter experienced minor damage Figure 49). At this distance, there should have been no damage. However, evidence of URM infill wall cracking
can be seen in Figure 50 where the infill is starting to pull away from the precast column.
19
Figure 49. Heavy manufacturing plant
Figure 50. Cracking of walls
2009 M6.3 L’Aquila, Italy, Earthquake Field Investigation Report
07
| Residential Buildings
Many residential buildings in the area use unreinforced masonry (URM) or stone construction with poor or
degraded materials. URMs are extremely vulnerable to earthquake damage and are often the first building
type to experience damage when an earthquake strikes. Collapse has been seen in many past earthquakes, and the L’Aquila Earthquake was no exception. Proper reinforcement with ductile detailing and
connections can prevent such failures.
In the old part of L’Aquila, many residential buildings were damaged. The damage ranged from cracking
(Figure 51 and Figure 52) to collapsed exterior masonry walls (Figure 53). For many brick houses, the wall
corners cracked and collapsed (Figure 54). Corners are dangerous areas for brick construction because of
stress concentration.
The town of Sant’Eusanio Forconese was deserted at the time of our survey. The town center had been
Figure 51. Cracking of masonry walls
Figure 52. Diagonal cracking of exterior masonry walls
Figure 53. Collapsed masonry wall
Figure 54. Damage concentrated at building corner
2009 M6.3 L’Aquila, Italy, Earthquake Field Investigation Report
constructed on a hilltop and was heavily damaged
because of focused earthquake shaking (Figure 55).
Onna is a small village in a valley near a river about
6 km east of L’Aquila. Many buildings either collapsed or were near collapse. Soft soils in this river
meadow area may have contributed to the higher
ground acceleration and destruction. Earthquake
motions tend to increase in soft-soil areas. Residential buildings in Onna were made of unreinforced
brick and concrete floors (Figure 56), one of the
most dangerous building types. More than 40 peo-
Figure 55. Devastation in Sant'Eusanio Forconese
ple were killed in this village of 300. One residential
three-story building was leveled (Figure 57). Such
a collapse is typically sudden (brittle) and does not
provide any warning to the occupants to escape.
Figure 57. Collapsed three-story building
Figure 56. Damaged masonry building in Onna
21
2009 M6.3 L’Aquila, Italy, Earthquake Field Investigation Report
08
| Multistory Apartment Complexes
Multistory residential buildings in the affected region are typically constructed of reinforced-concrete
moment frames with exterior and interior unreinforced masonry (URM) infill walls. These buildings are
generally not designed to withstand strong earthquakes.
URM exterior and interior infill panels are hazardous and prone to significant cracking and collapse (Figure
58). Infill panels are significantly stiffer than the surrounding concrete frames, so when an earthquake
strikes, the increase in stiffness causes the building period to shift to a region of higher spectral acceleration. This higher acceleration often damages the concrete frame columns (a phenomenon called “short
column effect”), leading to partial collapses in stronger events.
Several multistory apartment buildings in the L’Aquila region collapsed. Figure 59 shows a collapsed threestory building. The building was constructed of unreinforced brick walls supporting concrete floors—one
of the most dangerous building types throughout the world. This structure was constructed without any
visible moment frame or wall system.
Figure 60 shows a collapsed multistory building in the foreground and a damaged six-story structure in
the background. In the background building, the photograph shows cracking and spalling of the exterior
facade and exposure of the URM infills. Additionally, the adjacent buildings did not have proper separation,
and so pounding of the buildings resulted in structural damage near the roofs.
Figure 58. (Right) Collapsed infill panels
Figure 59. Collapsed multistory building
Figure 60. (Far right) Collapsed multistory
building
2009 M6.3 L’Aquila, Italy, Earthquake Field Investigation Report
09
| Transportation Facilities
Infrastructure damage in the earthquake-affected area was minimal. Serious damage to major structures
would be expected for a larger earthquake or one with a longer duration of strong shaking. Figure 61
shows the detail for a typical bent cap for a bridge. In this structure, there is no transverse shear key, and
the bridge girders are supported on the bearings. Figure 62 shows an in-span hinge for another bridge
structure that appears to be too short. The supported span can unseat and fall if the lateral displacements
are large from a more severe earthquake.
Figure 61. Bent cap and superstructure details
Figure 62. In-span hinge
A short, three-span concrete bridge over a small river, near Poggio Picenze and not far from the epicenter,
collapsed, dropping the bridge deck onto the riverbed (Figure 63). The bridge’s column had punched
through the deck. Bridges designed adequately for seismic forces should not collapse from an earthquake
with a magnitude of the April 2009 event. This type of damage used to be common in California earthquakes before strict seismic design guidelines were adopted and bridges retrofitted.
Figure 64 shows a roadway failure, likely resulting from ground movement. Minor landslides throughout
the mountainous region also blocked some roads.
23
Figure 63. Collapsed concrete bridge
Figure 64. Minor roadway damage
2009 M6.3 L’Aquila, Italy, Earthquake Field Investigation Report
10
| Lifelines and Utilities
The 180-megawatt power plant with three sets of boilers (Figure 65, full-page photo at right) in the town of
Celano, about 30 km from the epicenter, was completed in 1999. The plant buildings and structures are
well-engineered steel structures that appeared undamaged. These were the only steel-frame buildings
observed in our reconnaissance.
Some of the equipment, particularly the generation-related equipment, was well anchored. Much of the
other equipment, however, was not anchored for earthquakes. The emergency battery racks were not
braced, and the batteries were not strapped to the racks (Figure 66). Batteries may seem trivial, but they
are crucial for turbine operations after an earthquake-triggered stoppage.
The ground motion at the plant was weak and did not cause any damage. Absolutely nothing fell in the
earthquake, not even books from shelves. Conventional buildings around the power plant were also
undamaged.
The power plant’s high-voltage substation is owned by the national transmission company. The substation
equipment was not designed to resist earthquakes. Most of the substation components were interconnected with rigid busses instead of flexible connections (Figure 67). When subjected to ground shaking,
these rigid busses impart additional loading at the top of the insulators (because the busses do not deform) and can lead to toppling and fracture of the brittle porcelain components. Such a failure would result
in the loss of power transmission and delay post-earthquake response. In addition, the transformers in the
station were also unanchored (Figure 68). Damage to the substation equipment could result in the loss
of operations. Fortunately, reliable, simple, and cost-effective retrofit solutions are readily available. Such
methods could improve the reliability of this plant for future large earthquakes.
Overall, there was little damage to utilities from the April 2009 earthquake, with the only exception being
some local electrical outages when collapsed buildings damaged power lines and equipment.
Figure 66. Unanchored battery rack
Figure 67. Rigid bus connectors between the
insulators
Figure 65. Power plant stack
25
Figure 68. Unanchored transformer
2009 M6.3 L’Aquila, Italy, Earthquake Field Investigation Report
11
| Emergency Response
At the time of our reconnaissance, many mountain villages were deserted, and businesses were closed
even though many of the buildings had no apparent damage. One contributing factor to people’s response
was the exaggerated report of collapses by the media. In one village, a cluster of government-issued blue
tents was set up at the edge of town (Figure 69). Residents left their homes and took shelter in the tents
because they were afraid that their houses would collapse in aftershocks.
Another factor contributing to the general public’s response was the lack of a formal post-earthquake
engineering inspection program. Such inspections would have evaluated the condition of the buildings,
tagged them for safety (green, yellow, or red), and informed people whether they could safely reoccupy
their homes and businesses. Not performing these inspections increases the number of displaced people,
delays recovery, and increases the post-earthquake response and recovery costs. In Japan and California,
post-earthquake building inspection programs are well established and include thousands of pretrained
volunteer engineers who will inspect buildings after major earthquakes.
Given the concentration of damage to a small area, the civil emergency response presented little challenge
to Italian authorities. International support was not necessary. Response operation centers were quickly set
up, and relief efforts were well mobilized immediately after the earthquake.
Local police and firefighter response units were at the scene shortly after the earthquake. Besides performing search and rescue operations, they quickly secured heavily damaged areas. We found the crews to be
very organized and helpful (Figure 70).
Figure 69. Tents set up outside a village
Figure 70. (Right) Local emergency response crew
2009 M6.3 L’Aquila, Italy, Earthquake Field Investigation Report
12
| Discussion
The April 2009 L’Aquila Earthquake provides lessons that, unfortunately, have been taught repeatedly in
past earthquakes. This was a moderate earthquake that would likely have had many fewer casualties if the
buildings were properly retrofitted or designed. This earthquake highlighted the following issues:
•
The April 2009 L’Aquila Earthquake is an important reminder of the high seismicity in Italy. This region is
likely to experience future large earthquakes, with greater amplitude and devastation. The 2006 Italian
Building Code assigns a Zone 2 to the L’Aquila area for seismic design. This designation appears to
be inadequate based on the L’Aquila area’s long history of large earthquakes, including the 1706 event
that destroyed the town and killed more than 5,000 people. A Zone 1 designation is recommended.
•
This was a moderate event that nonetheless caused significant damage. Reconstruction costs are
estimated at more than US$16 billion, and 305 fatalities occurred. Had this earthquake been more
severe, the number of casualties and collapsed buildings would have been much greater.
•
Damage was spread over a wide geographic area but was sporadic. Damage was extensive at hilltops
and on soft-soil valleys. From a structural engineering perspective, no new failure modes were observed. Damage was heavily concentrated in unreinforced masonry (URM) buildings. However, there
was also substantial damage to buildings with nonductile concrete, soft-story irregularities, and new precast construction. The extensive damage to new precast-concrete structures for such a moderate event
was surprising for a modern country. These failures were primarily caused by a lack of seismic design.
•
Damage to nonstructural elements, for example, collapsed suspended ceilings and infill brick walls,
was widespread. Many of these components were not braced or anchored. Similarly, much of the
equipment in industrial facilities was unanchored. Nonstructural and equipment damage also shut
down operations at a large modern hospital—a facility needed the most during and after an earthquake. Anchorage and bracing of hazardous equipment, contents, and finishes is recommended.
•
Churches were the most affected historic structures and showed typical URM damage. This outcome
can be attributed to the tall, unbraced masonry walls; large interior spaces; poorly anchored bell
towers; and church domes that were not properly connected to the vertical structural elements. These
and other historic buildings should be strengthened to protect a country’s rich heritage and culture.
Seismic retrofit is simpler and more cost-effective than post-earthquake reconstruction.
•
Unfortunately, the structural deficiencies identified in this report for both new and historic structures
are found worldwide. Similar failures will be experienced in future earthquakes in many countries,
including the United States and Japan, which are considered to be the world leaders in the field of
earthquake engineering. Worldwide, there are many pre-1980 nonductile concrete structures, older
URM buildings, facilities with unbraced nonstructural elements, and structures with inadequate earthquake engineering.
27
2009 M6.3 L’Aquila, Italy, Earthquake Field Investigation Report
13
| References
Azzara, R. M.; Braun, T.; Cara, F.; Cultrera, G.; di Giulio, G.; Marra, F.; Rovelli, A. (2003) The ML 5.4 Molise
earthquake (central Italy) of October 31, 2002: why so destructive effects in San Giuliano di Puglia.
Boschi, (2008), ANSA, (Italian news service).
Devoti, R., et al. August 30, 2008. “New GPS constraints on the kinematics of the Apennines subduction.”
Earth and Planetary Science Letters, no. 273. DOI: 10.1016/j.epsl.2008.06.031.
European-Mediterranean Seismological Centre (EMSC). 2009. Website, http://www.emsc-csem.org.
Ganse, R.A., and J.B. Nelson. June 1982. “Catalog of significant earthquakes 2000 B.C. to 1979, including
quantitative casualties and damage.” Bulletin of the Seismological Society of America (BSSA) 72,
no. 3: 873–877.
Giovinazzi and Podestà, (2008), Analysis of an effective reconstruction process after the 2002 Molise
earthquake in Italy.
Istituto Nazionale di Geofisica e Vulcanologia (INGV). 2009. Website, http://portale.ingv.it/portale_ingv.
Italian seismic code, 2006.
United States Geological Survey (USGS). 2009. Website, http://www.usgs.gov.
Figure 71. Visited
locations in Italy
by the Global
Risk Miyamoto
reconnaissance team
2009 M6.3 L’Aquila, Italy, Earthquake Field Investigation Report
14
| About Global Risk Miyamoto
Global Risk Miyamoto (GRM) is a joint venture formed by Global Risk Consultants, the worldwide leader
in unbundled property loss control, and Miyamoto International, one of the largest structural engineering
firms in California. The company was formed specifically to provide the risk management community with
accurately quantified, site-specific risk identification and loss expectancies resulting from natural hazard
perils such as earthquakes, windstorms, hurricanes, typhoons, and floods.
Miyamoto and GRM staff has investigated most major and many moderate earthquakes that have
occurred in the United States and abroad since 1971, as well as numerous hurricane, windstorm, and blast
disasters. Our field investigations have produced firsthand knowledge of the problems caused by these
hazards and the strengthening and construction methods that are effective in preventing damage.
Miyamoto and GRM staff has identified and quantified the risks of many major corporations. Our
engineering analyses and recommendations address factors essential to sound business decisions,
including possible business interruption, risk reduction objectives, and safety. We have the technical
knowledge, planning skills, and experience to assist corporate management in establishing, prioritizing,
and implementing a realistic natural hazard risk control program.
Figure 72. Kit Miyamoto and Peter Yanev with Italian reporting crew
29
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