disaster risk preparedness & management: cavinato - ii
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ASSESSMENT ANALYSIS OF SEISMOLOGIC RISK
AND GEOHAZARD VULNERABILITY OF FIRST LEVEL
IN MAJOR CULTURAL HERITAGE SITES OF ALBANIA
Gian Paolo Cavinato (*), Llambro Duni (**), Massimiliano Moscatelli (*), Iris Pojani (**),
Maurizio Simionato (*), Giuseppe Cosentino (*), Alessandro Pagliaroli (*)
(*) CNR- Istituto di Geologia Ambientale e Geoingegneria, Rome, Italy
(**) University of Tirana, Albania
Berat, 8th May 2012Conference on Disaster Risk Preparedness and Management in Cultural Heritage Sites
Conference on Disaster Risk Preparedness and Management in Cultural Heritage Sites. Berat, 8th May 2012
ASSESSMENT ANALYSIS OF SEISMOLOGIC RISK
AND GEOHAZARD VULNERABILITY OF FIRST LEVEL IN
MAJOR CULTURAL HERITAGE SITES OF ALBANIA
Contributions
• Historical and archaeological assessment (Iris Pojani)
• Regional seismic hazard assessment (Llambro Duni)
• Local seismic hazard assessment (CNR-IGAG work group)
Conference on Disaster Risk Preparedness and Management in Cultural Heritage Sites. Berat, 8th May 2012
Risk = Hazard x Elements at risk x Vulnerability
from Managing Disaster Risks (UNESCO 2010)
Risk preparedness in CH sites
Conference on Disaster Risk Preparedness and Management in Cultural Heritage Sites. Berat, 8th May 2012
from Managing Disaster Risks (UNESCO 2010)
Risk preparedness in CH sites
Conference on Disaster Risk Preparedness and Management in Cultural Heritage Sites. Berat, 8th May 2012
from Managing Disaster Risks (UNESCO 2010)
Conference on Disaster Risk Preparedness and Management in Cultural Heritage Sites. Berat, 8th May 2012
Seismic hazard - Foreword• Surface effects due to an earthquake propagation are related to several physical
phenomena, that can be summarized in three groups as: 1) source mechanism; 2)
propagation of seismic waves; 3) site effects.
• When seismic waves propagate from a source, their amplitudes, frequencies, and
durations are modified due to local conditions. These “modifications” are globally
defined as site effects or local seismic response.
• Modifications of the seismic input for a specific site are defined in comparison to a
seismic bedrock, where the seismic signal is assumed to be unmodified. This
seismic bedrock is generally located below the ground surface and underlies the
covering geological formations inducing site effects.
• Seismic response can be defined for several sites and a map grouping zones whit
homogeneous site effects can be produced: this is the seismic microzonation.
• Seismic microzonation in urban areas is a tool suitable for planners and decision
makers. Moreover, the seismic action calculated for significant monuments is useful
for consolidation works.
Conference on Disaster Risk Preparedness and Management in Cultural Heritage Sites. Berat, 8th May 2012
REGIONAL
SEISIMC HAZARD
IN ALBANIA
Albania is characterized from an intensive seismic microactivity (1.0<M≤3.0), from many small earthquakes (3.0<M≤5.0), from rare medium-sized earthquakes (5.0<M≤ 7), and very seldom from strong earthquakes (M>7.0). CH sites
Conference on Disaster Risk Preparedness and Management in Cultural Heritage Sites. Berat, 8th May 2012
Seismic microzonation
The seismic microzonation studies are aimed at streamlining the knowledge of local seismic hazard, returning useful information for:• guiding the choice of areas for new settlements;• planning investigations and levels of detail;• establishing guidelines and criteria of interventions in urban areas and
CH sites.• defining priorities for interventions.In retrofitting of existing infrastructures or monuments, seismic
microzonation studies highlight the importance of phenomena such as possible amplification of shaking and permanent deformation.
Following the Italian "Addresses and Criteria for Seismic Microzonation" (ICMS, 2008), the levels of analysis for studies of seismic microzonation increase in complexity and effort going from level 1 to level 3:
• level 1 is an introductory level designed to divide the territory into seismic microzones qualitatively “homogeneous” in seismic perspective;
• levels 2 and 3 produces a quantitative map of seismic microzonation, by means of numerical simulations.
LOCAL
SEISIMC HAZARD
EVALUATION
When seismic waves propagate from a source, their amplitudes, frequencies, and durations are modified due to local conditions. These “modifications” are globally defined as site effects or local seismic response.
Conference on Disaster Risk Preparedness and Management in Cultural Heritage Sites. Berat, 8th May 2012
Seismic microzonation of level 1
How is created?The input information can be summarized as follow:1) topographic (e.g., maps and Digital Terrain Models) and
geomorphological (e.g., escarpments and landslides) information ;2) geological maps with information on litho-type, i.e., “different kinds of
rocks or terrains”;3) already available geological, geotechnical, and geophysical
information from boreholes and other in situ tests;4) thickness of soft geological formations covering the seismic bedrock;5) evaluation of the seismic bedrock depth from noise measurements.
What is on the map?
• Stable zones, where significant local effects of any nature are unlikely. • Stable zones susceptible to local amplifications, where intensifications
of ground motion are likely.• Zones susceptible to geological instability, in which the predominant
and expected seismic effects are due to permanent deformations.
LOCAL
SEISIMC HAZARD
EVALUATION
When seismic waves propagate from a source, their amplitudes, frequencies, and durations are modified due to local conditions. These “modifications” are globally defined as site effects or local seismic response.
Conference on Disaster Risk Preparedness and Management in Cultural Heritage Sites. Berat, 8th May 2012
GEOLOGICAL
SURVEY FOR
LEVEL 1 SEISMIC
MICROZONATION
Different lithotypes behave in different ways when interested by a seismic wave: they have to be carefully mapped.Zones susceptible of permanent deformations in seismic conditions (i.e., landslide prone areas) have also to be mapped. Apollonia
Conference on Disaster Risk Preparedness and Management in Cultural Heritage Sites. Berat, 8th May 2012
NEW
GEOPHYSICAL
SURVEY FOR
LEVEL 1 SEISMIC
MICROZONATION
Microtremor measurementsperformed to define site the fundamental frequencies, i.e., soil resonance frequencies when affected by an earthquake event.
ApolloniaTHE MONASTERY
f0=Vs/4H
Conference on Disaster Risk Preparedness and Management in Cultural Heritage Sites. Berat, 8th May 2012
ApolloniaTHE MONASTERY
NEW
GEOPHYSICAL
SURVEY FOR
LEVEL 1 SEISMIC
MICROZONATION
MASW enable to characterize the velocity structure of the subsoil. The lower the shear velocity Vs, the poorer the «quality» of the soil in terms of site response. The higher the velocity contrast between superimposed layers of soils, the higher the susceptibility to local seismic amplification.
700 m/s
Conference on Disaster Risk Preparedness and Management in Cultural Heritage Sites. Berat, 8th May 2012
ApolloniaTHE THEATRE
SUSCEPTIBILITY
TO INSTABILITY
Define zones susceptible to geological instability, i.e., slope instability, differential settlement, liquefaction, in which the predominant and expected seismic effects are due to permanent deformations (amplification of ground motion is also possible).
earth flowaccumulation
crowns
Conference on Disaster Risk Preparedness and Management in Cultural Heritage Sites. Berat, 8th May 2012
SEISMIC
MICROZONATION
OF LEVEL 1 OF
APOLLONIA
Conference on Disaster Risk Preparedness and Management in Cultural Heritage Sites. Berat, 8th May 2012
What is critical?
The seismic microzonation level 1 enables to divide the territory of Apollonia in two main zones: 1) the hilly area, less susceptible to seismic amplification; 2) the coastal plain, more susceptible to seismic amplification, given the presence of Quaternary very soft sediments.
Where the weaknesses are?
The main uncertainties are related 1) to not well known distribution of lithotypes characterizing the geological bedrock, and 2) to not well known thickness of the Quaternary cover in the lateral valleys and coastal plain. For this motive is desirable that these uncertainties can be reduced through i) a detailed geological-geotechnical survey of the archaeological area, and ii) the use of geophysical methods which provide information on the thicknesses of the recent soft covers.
SEISMIC
MICROZONATION
OF LEVEL 1 OF
APOLLONIA
Conference on Disaster Risk Preparedness and Management in Cultural Heritage Sites. Berat, 8th May 2012
GEOLOGICAL
SURVEY FOR
LEVEL 1 SEISMIC
MICROZONATION
Different lithotypes behave in different ways when interested by a seismic wave: they have to be carefully mapped.Zones susceptible of permanent deformations in seismic conditions (i.e., landslide prone areas) have also to be mapped.
Berat
Conference on Disaster Risk Preparedness and Management in Cultural Heritage Sites. Berat, 8th May 2012
BeratTHE CASTLE
NEW
GEOPHYSICAL
SURVEY FOR
LEVEL 1 SEISMIC
MICROZONATION
Microtremor measurementsperformed to define site the fundamental frequencies, i.e., soil resonance frequencies when affected by an earthquake event.
f0=Vs/4H
Conference on Disaster Risk Preparedness and Management in Cultural Heritage Sites. Berat, 8th May 2012
BeratTHE OSUM RIVER
NEW
GEOPHYSICAL
SURVEY FOR
LEVEL 1 SEISMIC
MICROZONATION
Microtremor measurementsperformed to define site the fundamental frequencies, i.e., soil resonance frequencies when affected by an earthquake event.
f0=Vs/4H
Conference on Disaster Risk Preparedness and Management in Cultural Heritage Sites. Berat, 8th May 2012
NEW
GEOPHYSICAL
SURVEY FOR
LEVEL 1 SEISMIC
MICROZONATION
MASW enable to characterize the velocity structure of the subsoil. The lower the shear velocity Vs, the poorer the «quality» of the soil in terms of site response. The higher the velocity contrast between superimposed layers of soils, the higher the susceptibility to local seismic amplification.
BeratTHE CASTLE
1200 m/s
Conference on Disaster Risk Preparedness and Management in Cultural Heritage Sites. Berat, 8th May 2012
NEW
GEOPHYSICAL
SURVEY FOR
LEVEL 1 SEISMIC
MICROZONATION
MASW enable to characterize the velocity structure of the subsoil. The lower the shear velocity Vs, the poorer the «quality» of the soil in terms of site response. The higher the velocity contrast between superimposed layers of soils, the higher the susceptibility to local seismic amplification.
BeratTHE OSUM RIVER
1300 m/s
< 200 m/s
Conference on Disaster Risk Preparedness and Management in Cultural Heritage Sites. Berat, 8th May 2012
SUSCEPTIBILITY
TO INSTABILITY
Define zones susceptible to geological instability, i.e., slope instability, differential settlement, liquefaction, in which the predominant and expected seismic effects are due to permanent deformations (amplification of ground motion is also possible).
BeratTHE HISTORIC CENTER
Conference on Disaster Risk Preparedness and Management in Cultural Heritage Sites. Berat, 8th May 2012
SEISMIC
MICROZONATION
OF LEVEL 1 OF
BERAT
Conference on Disaster Risk Preparedness and Management in Cultural Heritage Sites. Berat, 8th May 2012
What is critical?
No relevant Vs contrasts were recorded in Berat, except for the Osum River valley, even if steep slopes can induce local seismic amplification and trigger gravitational instabilities.By the way, the main geohazard affecting the city of Berat is represented by the instability of rock escarpments overlooking the historic city center. The risk related to this criticality is high in static conditions and could be even higher if a seismic event should occur.
Where the weaknesses are?
We suggest to carry out a detailed study of structural and geomechanical setting of the limestone cropping out along the escarpments, if not already available.
SEISMIC
MICROZONATION
OF LEVEL 1 OF
BERAT
Conference on Disaster Risk Preparedness and Management in Cultural Heritage Sites. Berat, 8th May 2012
GEOLOGICAL
SURVEY FOR
LEVEL 1 SEISMIC
MICROZONATION
Different lithotypes behave in different ways when interested by a seismic wave: they have to be carefully mapped.Zones susceptible of permanent deformations in seismic conditions (i.e., landslide prone areas) have also to be mapped.
Butrint
fault scarp
Conference on Disaster Risk Preparedness and Management in Cultural Heritage Sites. Berat, 8th May 2012
ButrintTRICONCH PALACE
NEW
GEOPHYSICAL
SURVEY FOR
LEVEL 1 SEISMIC
MICROZONATION
Microtremor measurementsperformed to define site the fundamental frequencies, i.e., soil resonance frequencies when affected by an earthquake event.
f0=Vs/4H
Conference on Disaster Risk Preparedness and Management in Cultural Heritage Sites. Berat, 8th May 2012
ButrintACROPOLIS
NEW
GEOPHYSICAL
SURVEY FOR
LEVEL 1 SEISMIC
MICROZONATION
Microtremor measurementsperformed to define site the fundamental frequencies, i.e., soil resonance frequencies when affected by an earthquake event.
topographic effect
Conference on Disaster Risk Preparedness and Management in Cultural Heritage Sites. Berat, 8th May 2012
SUSCEPTIBILITY
TO INSTABILITY
ButrintTHEATRE AND DWELLING WITH ATRIUM
differential settlements
coastal plain
faul
t sca
rp
rock falls
Conference on Disaster Risk Preparedness and Management in Cultural Heritage Sites. Berat, 8th May 2012
SEISMIC
MICROZONATION
OF LEVEL 1 OF
BUTRINT
Conference on Disaster Risk Preparedness and Management in Cultural Heritage Sites. Berat, 8th May 2012
What is critical?
The territory of Butrint is heterogeneous in terms of susceptibility to seismic amplification, due to extreme geological variability. The most critical zone in terms of possible site amplifications is the coastal plain. High susceptibility to geological instability, both for differential settlements and rock falls, is related to the presence of the fault scarp bounding the Acropolis.
Where the weaknesses are?
The seismic microzonation of level 1 of Butrint is affected by high level of uncertainty because of the lack of information about lithology, thickness, and shear wave velocity of the lithotypes. Lithostratigraphic and geometric uncertainty could be pulled down by means of one deep borehole located close to the Vivari channel, associated with Electrical Resistivity Tomographies (ERTs) oriented perpendicular to the fault scarp. Shear wave velocity could be detected by means of MASW measurements.
SEISMIC
MICROZONATION
OF LEVEL 1 OF
BUTRINT
Conference on Disaster Risk Preparedness and Management in Cultural Heritage Sites. Berat, 8th May 2012
GEOLOGICAL
SURVEY FOR
LEVEL 1 SEISMIC
MICROZONATION
Different lithotypes behave in different ways when interested by a seismic wave: they have to be carefully mapped.Zones susceptible of permanent deformations in seismic conditions (i.e., landslide prone areas) have also to be mapped.
Gjirokastra
Conference on Disaster Risk Preparedness and Management in Cultural Heritage Sites. Berat, 8th May 2012
GjirokastraTHE CASTLE
NEW
GEOPHYSICAL
SURVEY FOR
LEVEL 1 SEISMIC
MICROZONATION
Microtremor measurementsperformed to define site the fundamental frequencies.These frequencies are related to the thickness of soft soils covering the basal rigid bedrock through the shear velocity, Vs.
f0=Vs/4H
topographic effect
Conference on Disaster Risk Preparedness and Management in Cultural Heritage Sites. Berat, 8th May 2012
GjirokastraTHE STADIUM
NEW
GEOPHYSICAL
SURVEY FOR
LEVEL 1 SEISMIC
MICROZONATION
Microtremor measurementsperformed to define site the fundamental frequencies.These frequencies are related to the thickness of soft soils covering the basal rigid bedrock through the shear velocity, Vs.
Conference on Disaster Risk Preparedness and Management in Cultural Heritage Sites. Berat, 8th May 2012
SUSCEPTIBILITY
TO INSTABILITY
GjirokastraTOPPLED BLOCKSAND ALLUVIAL FAN
historic wallsfracturedconglomerates
rafting blocks
rafting blocks
debries flows fromalluvial fan
castle
Conference on Disaster Risk Preparedness and Management in Cultural Heritage Sites. Berat, 8th May 2012
SEISMIC
MICROZONATION
OF LEVEL 1 OF
GJIROKASTRA
Z1 Z2 Z3 Z4 Z5-Z6
Conference on Disaster Risk Preparedness and Management in Cultural Heritage Sites. Berat, 8th May 2012
What is critical?
The most critical zones in terms of possible site amplifications: 1) buried narrow valleys located at the mouth of mountain streams (zone 4), carrying high volumes of coarse clastic materials to the valley Drino River; 2) narrow ridges bonding the buried valleys, where topographic effects highlighted by microtremors measurements could induce site amplification.A rigid fractured layer of conglomerates generally occupies the top of the narrow ridges (e.g., where the castle is located) and is highly susceptible to rock falls and toppling of isolated blocks.
Where the weaknesses are?
Neither direct observation of subsoil nor Vs information are generally available for the site. No geotechnical parameters are available for a proper evaluation of the dynamic behavior of soils and rocks. An additional investigation survey and the passage to a level 3 of seismic microzonation is suggested.
SEISMIC
MICROZONATION
OF LEVEL 1 OF
GJIROKASTRA
Conference on Disaster Risk Preparedness and Management in Cultural Heritage Sites. Berat, 8th May 2012
What is useful for?
The seismic microzonation of level 3 is an advanced map that allows quantitatively to define homogeneous zones - in terms of site response - for a specific seismic input, i.e., for a specific earthquake scenario.
How is created?
The input information can be summarized as follow:
1) topographic (e.g., maps and Digital Terrain Models) and geomorphological (e.g., escarpments and landslides) information;
2) geological maps with information on lithotype, i.e., “different kinds of rocks or terrains”;
3) already available and new geological, geotechnical, and geophysical information from boreholes and other in situ and laboratory tests;
4) evaluation of the seismic bedrock depth from noise measurements.
5) seismic input from one or more earthquake scenarios.
Numerical modeling allows quantitatively to define site effects.
SEISMIC
MICROZONATION
OF LEVEL 3
Conference on Disaster Risk Preparedness and Management in Cultural Heritage Sites. Berat, 8th May 2012
Seismic microzonation of level 3 - Dynamic parameters
Vertical velocity gradient of the anthropic layer
Conference on Disaster Risk Preparedness and Management in Cultural Heritage Sites. Berat, 8th May 2012
Seismic microzonation of level 3 - Seismic input
Characteristics of the seismicity affecting Berat (left) andreference spectra selected for the microzonation (right)
Conference on Disaster Risk Preparedness and Management in Cultural Heritage Sites. Berat, 8th May 2012
Seismic microzonation of level 3 - Modeling of local
seismic response
Cross-section 2
Cross-section 7
Coliseum
Conference on Disaster Risk Preparedness and Management in Cultural Heritage Sites. Berat, 8th May 2012
Seismic microzonation maps of level 3 and response spectra
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ARCH OF TITUS
SAN TEODORO’SCHURCH
ARCH OF TITUS
SAN TEODORO’SCHURCH
lower orno mplification
higheramplification
Conference on Disaster Risk Preparedness and Management in Cultural Heritage Sites. Berat, 8th May 2012
Concluding remarks and future works
• Cooperation among the involved Institutions has been crucial for the project.
• The application presented in this work clearly demonstrates the potential for
full integration of geological, geophysical, and archaeological methodologies.
• Seismic microzonation in historical centers and archaeological areas is
strongly conditioned by the availability of data. For the sites of this project,
scarcity of data is the main factor affecting the reliability of seismic
microzonations of level 1.
• An integration of existing surveying is recommended for all the investigated
Albanian Cultural Heritage sites. Seismic microzonation of level 3 is
recommended for evaluating local seismic amplification, aimed at seismic risk
prevention and mitigation.
• Regarding seismic microzonation, addenda to available guidelines (i.e., for
seismic microzonation) is specifically required for archaeological areas or for
historical center of ancient and permanent urbanization.
Conference on Disaster Risk Preparedness and Management in Cultural Heritage Sites. Berat, 8th May 2012
Coming soon
Special issue of the Bulletin of Earthquake Engineering on:
Seismic Microzonation of the Central Archaeological
Area of Rome Editors: Massimiliano Moscatelli, Alessandro Pagliaroli, Gian Paolo Cavinato
(National Research Council), Sergio Castenetto, Giuseppe Naso (Italian Civil
Protection Department)
Contribution focused on:
Cultural heritage - proposal of guidelines for
evaluating local seismic hazard