Soil characterization for seismic damage scenarios purposes: application to Angra do HeroÃsmo (Azores)

Bull Earthquake Eng (2013) 11:401–421DOI 10.1007/s10518-013-9424-9

ORIGINAL RESEARCH PAPER

Soil characterization for seismic damage scenariospurposes: application to Angra do Heroísmo (Azores)

Paula Teves-Costa · Idalina Veludo

Received: 6 June 2012 / Accepted: 10 January 2013 / Published online: 2 February 2013© Springer Science+Business Media Dordrecht 2013

Abstract Angra do Heroismo, the main town of Terceira Island in the Azores Archipelago,was hit in 1980 by a 7.2 magnitude earthquake that caused great destruction in the centralpart of the town. Taking into consideration the high seismic hazard of the region and thecultural and social importance of Angra do Heroísmo, the elaboration of damage scenariosis of particular importance to implement measures for preserve and protect the town againstfuture earthquakes. The first step is to perform microzonation studies in order to characterizethe soil seismic behaviour. Taking into consideration the available geologic, geotechnical andgeophysical information, a detailed soil characterization was performed based on the resultsfrom numerical modelling and the analysis of microtremor experimental measurements.Nine different soil profiles were identified, characterized and classified. Discussion on thedetailed soil classification and the Eurocode 8 soil classification is presented. This studyshows that even with an available code, microzonation studies must be developed in orderto identify differences on soil behaviour inside the interested area. It shows also that the useof experimental measurements presents a great help on soil characterization. The obtaineddetailed classification will be used on the estimation of damage scenarios for Angra doHeroísmo.

Keywords Soil classification · Microzonation · Azores soils · Seismic soil response

P. Teves-Costa (B) · I. VeludoInstituto D. Luiz, University of Lisbon, Campo Grande,Edifício C8, 1749-016 Lisbon, Portugale-mail: [email protected]

P. Teves-CostaFCUL-DEGGE, University of Lisbon, Campo Grande,Edifício C8, 1749-016 Lisbon, Portugal

I. VeludoInstituto Português do Mar e da Atmosfera, Rua C do Aeroporto,1749-017 Lisboa, Portugale-mail: [email protected]

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402 Bull Earthquake Eng (2013) 11:401–421

1 Introduction

Earthquakes are still a threat in several areas in the world, causing a lot of damage and killingthousands of people. Since the beginning of this millennium several destructive earthquakeshave occurred, which caused a large number of human and economic losses (Gujarat, India2003; Bam, Iran 2003; Boumerdes, Algeria 2003; Banda Aceh/ Sumatra, Indonesia 2004;Kashmir, Pakistan 2005; Sichuan, China 2008; L’Aquila, Italy 2009; Port-au-Prince, Haiti2010; Sendai, Japan 2011). Besides the active tectonics of each region, which can producemedium to large earthquakes, it is known that the effect of surface geology on seismic groundmotion characteristics can be very important inducing, very often, an increase on the observedlocal intensity (examples may be found in Bouckovalas and Kouretzis 2001; Guidobonni et al.2003; Giammarinaro et al. 2005; Fritsche et al. 2009; Picozzi et al. 2009; Gosar and Martinec2009; Navarro et al. 2009; Maugeri et al. 2011; Compagnoni et al. 2011). In order to evaluatethe importance of the seismic behaviour of the shallow geological formations, microzonationstudies must be conducted for the urban zones most exposed to strong earthquake occurrence.

We all know that it is not possible to reduce the seismic hazard of a certain region becauseit is controlled by nature. However, the reduction of seismic risk in areas of high populationconcentration should be a primary concern for the whole community and it is necessary tourgently implement policies to minimize this risk. One way to contribute towards this purposeis to estimate realistic damage seismic scenarios, which are composed by several components.One of the first components is the study of the seismic behaviour of the surface layers, whichcould be included in a microzonation study. In general, the main purpose of a microzonationstudy is to provide input for urban planning and for the estimation of damage scenarios.

Since the nineties, many microzonation studies were based on microtremor analysis, usingthe H/V spectral ratio following Nakamura’s methodology (Nakamura 1989, 1996, 2000;Lermo and Chávez-García 1993; Seth and Wohlenberg 1999; Ansal et al. 2001; D’Amicoet al. 2008; Gosar and Lenart 2010). Furthermore, other techniques using ambient vibrationrecordings have been implemented, in particular following the SESAME and NERIES (JRA4research activity) European projects, which are often used together with other techniques (Fähet al. 1997, 2003; Chávez-García et al. 2005, 2006; Di Giulio et al. 2008; Havenith et al. 2007;Picozzi et al. 2009; Boaga et al. 2010). The validation of the use of ambient vibrations hasbeen the subject of several papers (experimental, empirical and numerical) for several years(Lachet et al. 1996; Bard 1999; Mucciarelli et al. 2003; Bonnefoy-Claudet et al. 2006a,b;Haghshenas et al. 2008; Albarello and Lunedei 2010; Endrun et al. 2010). However, mostauthors call attention to the fact that microtremor measurements must be performed underproper conditions (Chatelain et al. 2008; Guillier et al. 2008) and its processing and inter-pretation must be adequately conducted. It was also recognized that for complex geologicalenvironments the H/V Nakamura technique does not give reliable results and can only be usedas complementary information (Chávez-García et al. 2007; Castellaro and Mulargia 2009).Recently, and taking into consideration the soil classification presented in Eurocode 8 (EC8)(CEN 2004), many authors presented microzonation studies based on VS30 estimation (Muc-ciarelli and Gallipoli 2006; Cadet et al. 2008). However, it has already been recognized bydifferent authors that, in many cases, VS30 can not be considered a representative parameterof soil seismic behaviour, especially when more complex geology is present (Mucciarelli andGallipoli 2006; Kanh et al. 2006; Chávez-García et al. 2007; Castellaro et al. 2008; Lee andTrifunac 2010; Maugeri et al. 2011). As result, several authors proposed soil classificationsthat are not only based on code recommendations (VS30 values), but also use complementaryinformation, usually F0, obtained from microtremor analysis (e.g., Cadet et al. 2008, 2012;Lermo et al. 2009; Luzi et al. 2011).

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Taking into consideration several methodologies used by different authors, and the dis-advantages and benefits of each method, Ansal et al. (2010) presented a set of indicationsto conduct an adequate microzonation study and, in particular, to estimate the soils seismicresponse. As evident, the options to be made should take into consideration not only thepurpose of the microzonation study, but also the available information and the possibility offinancial support to perform new studies.

The present study intends to present and discuss soil characterization and classificationin Angra do Heroismo (Azores) to be used for damage scenarios estimation. Taking intoconsideration the available information and results from previous studies, the methodologydeveloped in this study is composed by the following steps:

• Compilation of the available geophysical, geological and geotechnical data.• Definition of preliminary soil profiles based on the previous collected information.• Computing site response analysis for each soil profile using real and synthetic accelero-

grams, taking into consideration the distances and the seismogenic potential of the mostimportant sources, according to the historical and instrumental seismicity.

• Fine adjusting of unknown thickness and seismic velocities of the shallower layers,by comparing the H/V peak obtained from microtremor analysis with the fundamentalfrequency of the theoretical transfer functions.

• Identification of the main soil profiles with their characteristics.• Mapping the distribution of the fundamental frequencies and amplification factors, as

well as PGA and spectral acceleration amplification factors.

Angra do Heroismo, the main town of Terceira Island (in the Azores Archipelago, locatedclose to the Middle Atlantic Ridge) (Fig. 1), was hit in 1980 by a 7.2 magnitude earthquake,whose epicenter was located about 45 km west of the city. It caused great destruction in

Fig. 1 Seismicity for Terceira Island and the surrounding Atlantic region, from 1997 to 2007 (data source:SIVISA). The stars indicate the approximate location of the seismic sources selected by Veludo et al. (2012)to elaborate damage seismic scenarios. Background bathymetry from Lourenço et al. (1998). Inset: locationof Angra do Heroísmo town, in Terceira Island

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the town (EMS intensity VIII), in particular at its central part (Oliveira et al. 1992). Afterthis earthquake the central part of the town was completely rebuilt, following the samearchitectural pattern of the XV century and, in 1983, Angra do Heroísmo was classified byUnesco as World Heritage. Due to its cultural and social importance, Angra do Heroísmoshould be preserved and, in particular, should be protected against future earthquake effects,taking into consideration the high seismic hazard of the region.

In this paper we will present the methodology developed for soil classification applied tothe central part and surrounding quarters of the town, which correspond to the “Angra doHeroismo Classified Zone” (AHCZ). The obtained results were applied on seismic damagescenarios estimation, presented in the following paper by Veludo et al. (2012).

2 Available information and previous studies

The first microzonation study performed in Angra do Heroísmo was made by Teves-Costaand Senos (2004) and consisted on the analysis of ambient vibrations recorded in 230 sitesdistributed along the streets with a more dense coverage in the central part of the town. Dataprocessing was performed according to the Nakamura methodology (Nakamura 1989, 2000)and H/V curves were obtained. The results were presented in Teves-Costa et al. (2007) interms of the amplitude and the frequency of the H/V peaks. Figure 2 illustrates the distributionof the H/V peak frequencies obtained.

This important information can be used, for instance, to check building resonance (Gal-lipoli et al. 2004; Veludo 2008). However, it is not straightforward to directly introduce thisinformation on the characterization of the soil seismic behavior in general. It is necessary tocomplement this information with geologic, geotechnical and/or other geophysical data.

One adequate way to perform the soil zonation for damage scenarios estimation purposesis to define representative soil profiles for each work unit. Taking into consideration thisobjective, the Census tract defined by the Portuguese Statistics (INE 2001) was selected as awork unit. Accordingly, one or two soil profiles were defined inside each Census tract.

Fig. 2 Distribution of the H/V peak frequencies (in Hz) in Angra do Heroísmo, obtained from the analysisof ambient vibration records (from Teves-Costa and Senos 2004). Background: Census tracts of the AHCZ

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Table 1 EC8 soil classification (CEN 2004)

Soil typesa Description VS30(m/s) NSPT(bl/30 cm)

A Rock or other rock-like geological formation, includingat most 5 m of weaker material at the surface

>800 –

B Deposits of very dense sand, gravel, or very stiff clay, atleast several tens of meters in thickness, characterized bya gradual increase of mechanical properties with depth

360–800 >50

C Deep deposits of dense or medium-dense sand, gravelor stiff clay with thickness from several tens to manyhundreds of meters

180–360 15–50

D Deposits of loose-to-medium cohesionless soil (with orwithout some soft cohesive layers), or of predominantlysoft-to-firm cohesive soil

<180 < 50

E A soil profile consisting of a surface alluvium layer withVS values of class C or D and thickness varying betweenabout 5 and 20 m, underlain by stiffer material with VS >

800 m/s

aThere are still two special soil types (S1 and S2), mainly composed by clay and/or with liquefaction potential,with no importance in this paper

Table 2 Example of soil profileproposed for Angra doHeroísmo—Sé site (fromMalheiro and Nunes 2007)

Average thickness (m) Geological formations

0.4–0.6 Top soil

1.0–5.0 Surtseyan tuffs (massive, cohesiveand compact formations)

10.0–15.0 “Plinian sequence”: pumice falldeposits (ash, lapilli and blockssize), non welded ignimbrites andmud flows /lahars deposits

>5.0 Basalts s.l.

All the islands of the Azores Archipelago have a volcanic origin and the land is composedby rocks and deposits of volcanic nature. This kind of geological formations are not verycommon in Europe and, up to 2010, the soil classification presented in the EC8 (CEN 2004)did not take into account volcanic formations (see Table 1). The recent published EC8 Por-tuguese National Annex (IPQ 2010) presents, for the first time, a classification for the Azoreansoils: 5 geologic profiles, corresponding to situations that can be found in the Azores, withcorrespondent mean shear wave velocities similar to VS30. Besides, shear wave velocities forthe volcanic materials and soil type classifications (A–C) associated to each geologic profileare also presented. This resulted from the work developed by several authors and compiledand presented in Malheiro and Nunes (2007). However, these authors emphasized that theamount of geophysical and geotechnical data used to quantitatively characterize the volcanicformations (as Standard Penetration Test, NSPT, shear-wave velocities, VS, or unit weight,ρ) was very small. Table 2 presents an example of a soil profile proposed by those authorsfor the central part of Angra do Heroísmo. This soil profile corresponds to the soil profile 2,present in the EC8 Portuguese National Annex, and is classified as soil type B with a meanshear wave velocity of 850 m/s. It is easy to understand that due to the variability of the layersthickness, different situations can arise.

Table 3 presents some geotechnical properties for these volcanic formations, accord-ing to the work performed by different authors (Forjaz et al. 2001; Malheiro and Nunes

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123


Fig. 3 Surface geology of Angra do Heroísmo (on the left) and three geologic profiles (on the right). Legend:(a) landfill; (p) beach sands; (dv) cliff deposits; (aa/phβ1) basaltic lava flow; (t) Surtseyan tuffs; (sp) pumiceand pyroclastic deposits and non-welded ignimbrite; (τ ) trachitic lava flow (from Nunes et al. 2001)

2007). However, we have to enhance that in these islands all geological formations are veryheterogeneous, and it is usual to find a set of harder formations with intercalations of softerlayers, corresponding to different eruptions episodes. The NSPT values presented in Table 3evidence this fact: even in the soft formations high values of NSPT can be observed due tothe occurrence of intermediate thin lava flows or the existence of large pyroclastic blocks.It is also common to find some voids or small caves in the lava flows or in other geologicalformations (NSPT = 0 appears often in the geotechnical measurements). So, the NSPT val-ues must be carefully used for the classification of the geological formations and/or for theestimation of VS values.

Aware of the need of detailed geological information, Nunes et al. (2001) performed a1:10,000 scale geologic map of Angra do Heroísmo, as well as some geological profiles whichwere based on seismic studies and borehole data information (Fig. 3). The surface geologicalformations identified were: landfill, beach sands, cliff deposits, basaltic lava flow, Surtseyantuffs, pumice and pyroclastic deposits, non-welded ignimbrite and trachitic lava flow.

This constituted the available information on the surface geology and soil properties ofAngra do Heroísmo.

3 Seismic scenarios and strong ground motion estimation

The Azores archipelago, located in the North Atlantic Ocean near the triple junction betweenthe North-American, the Eurasian and the African plates, presents high seismicity charac-terized by several long seismic swarms, usually associated with volcanic activity, and somemoderate to strong shocks that often produce little to great damage. Since the discovery ofthe Azores Archipelago, in the XV century, historical reports described the occurrence ofseveral destructive earthquakes and volcanic eruptions in the Central and Oriental Groups(Costa-Nunes 1998). Earthquakes such as those of October 22, 1522 (S. Miguel Island), July9, 1757 (S. Jorge Island), January 1, 1980 (Terceira Island) and July 9, 1998 (Faial Island)resulted in a dramatic number of causalities. Other destructive earthquakes occurred in his-torical and instrumental times in the Central Group. Some of these events hit Terceira Islandand, in particular, the town of Angra do Heroísmo (Costa-Nunes 1998; Silva 2005).

The comprehensive estimation of soil effects, in the aim of microzonation studies fordamage scenarios purposes, requires input acceleration time histories compatible with

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Table 4 Characteristics of theselected seismic scenarios (afterVeludo et al. 2012)

Seismic scenario/source Mw D (km)

Offshore Angra 5.5 6

Lajes Graben 6.5 15

1980’s source 7.0 45

Table 5 Magnitude and distance ranges for the real data, synthetic accelerograms and seismic scenarios

Real data Japanese model Italian model Seismic scenarios

Magnitude (MW) 6.6–7.6 (MW) 4.1–7.3 (MS if ≥ 5.5; ML if < 5.5) 4.6–6.8 (MW) 5.5–7.0

Distance (km) 6–60 3.5–100 1.5–110 6–45

Nb of records 5 9,390 190 –

earthquakes associated to the main seismic sources. Taking into consideration the histor-ical and instrumental seismicity, as well as the macroseismic effects occurred in Angra doHeroísmo, three main seismic sources were identified and were used to elaborate damagescenarios (Veludo 2008; Veludo et al. 2012): two seismic sources corresponding to local,short distance earthquakes (Lajes Graben and Offshore Angra), and one distant source cor-responding to the structure responsible for the 1980 earthquake. The characteristics of theselected seismic scenarios are summarized in Table 4 and the approximate locations of theseismic sources are displayed in Fig. 1.

To simulate ground motion associated with the main identified seismic sources, realaccelerograms recorded at the Azores or similar regions should be used. After a searchon strong motion databases (PEER Strong Motion Database; European Strong Motion Data-base; K-net Japanese Database) it was found that the selected data, chosen according tothe target magnitude and distance ranges, was very few, showing the need to use syntheticgenerated signals for ground motion estimation. With this purpose, two different empiricalmodels, developed after analysis of seismic and geologic environments in Italy (Sabetta andPugliese 1996) and in Japan (Pousse et al. 2006), were tested. As main requirement, the datato which synthetic models are empirically related should represent the range of distances andmagnitudes of the identified main seismic sources (Table 5).

To test the more adequate model, the variability of the output was checked, taking intoconsideration the incertitude on ground motion estimation and the inexistence of reliableattenuation laws for the Azores region (Carvalho et al. 2001). Figure 4 presents the envelopsof 50 response spectra, generated with both models, for a 7.0 magnitude event at 45 kmof epicentral distance. It is possible to observe that the Japanese model presents highervariability, which seems to be more appropriate. The only accelerogram recorded in theAzores, with suitable magnitude and distance, was obtained during the July 9, 1998 Faialearthquake (MW = 6.1; epicentral distance of 15 km). Comparisons between the syntheticand the real record, as well as the corresponding response spectra, are presented in Fig. 5 (thesoil type was taken in consideration for the synthetic records). By visual inspection it seemsthat the record obtained with the Japanese model is more close to the real record. However,the fit to the response spectra is not so simple: the Japanese model fits the short period rangebetter, while the Italian model seems to get a shape close to the real record, but with smalleramplitude.

Taking all these aspects into consideration, the Japanese model was preferred to simulatethe ground motion at the bedrock for the three seismic scenarios. The objective was to submit

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Fig. 4 Spectral envelops of 50 response spectra corresponding to 7.0 magnitude events recorded at 45 km ofepicentral distance, generated with the Japanese (red) and the Italian (blue) models

Fig. 5 Record of the 1998.07.09 Faial event (in blue) and the synthetic accelerograms (in red) obtained with:a Japanese model; b Italian model. c Correspondent response spectra

the soil profiles to different input motions, with variable acceleration levels and differentfrequency content. Real and simulated acceleration records were used as input motion toinduce signal variability. Special attention was devoted to medium to large magnitude events,at short and long distances. Considering that almost all the real available records correspondto strong earthquakes located at close distances, the synthetic acceleration time histories werecomputed for a medium size earthquake located at a large distance. At the end, 10 recordswere selected as input motion (Table 6): 5 real accelerograms recorded in bedrock (obtainedduring the ChiChi, Kocaeli, Cape Mendocino, Nahanni and Northridge earthquakes) and 5synthetic records (four obtained with the Japanese model and one obtained with the Italianmodel).

4 Soil characterization

Starting from the geological profiles presented in Fig. 3, a set of 17 soil profiles were defined inthe AHCZ, taking into consideration the lithology and the thickness of the different geologicalformations. The physical parameters used are presented in Table 7. The range of valuesselected for the different parameters in each geological formation was based on the workof Malheiro and Nunes (2007) and Motta and Nunes (2002), as well as on other studies

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Table 6 Selected input motion for soil characterization

No Name Date M MS MW Distance(km)a

PGA (g) PGV(cm/s)

1 ChiChi–Taiwan 1999 7.3 (ML) 7.5 6.95 (1) 0.902 102.4

2 Kocaeli–Turkey 1999 7.4 7.8 369.3 (2) 0.011 2.3

3 Cape Mendocino–Mexico

1992 7.1 7.1 8.5 (1) 1.497 127.4

4 Nahanni–Canada 1985 6.8 6.9 6.0 (1) 0.978 46.0

5 Northridge–United States

1994 6.6 (ML) 6.7 8.0 (1) 1.585 55.7

6 Synt_J1 6.8 60 (3) 0.257

7 Synt_J2 6.8 60 (3) 0.226

8 Synt_J3 6.8 60 (3) 0.362

9 Synt_J4 6.8 60 (3) 0.293

10 Synt_I1 6.8 45 (3) 0.121

a (1) closest distance to rupture; (2) hypocentral distance; (3) epicentral distance

Table 7 Physical parameters of the soil layers (initial values)

Geological formation Unit weight (kN/m3) Maximum thickness (m) VS(m/s)

Cliff deposits 15–17 10 80–200

Surtseyan volcanic tuff 11–17 12 130–800

Pumice and pyroclastic deposits andnon-welded ignimbrite

7–23 30 250–700

Trachytic lavas 20–24 60 600–1,000

Basaltic lavas 22–29 ∞ 800–2,500

performed for similar regions (Lopes 2005; Vallejo et al. 2007; Rodríguez-Losada et al.2007) and expert opinions. These values (in particular the shear wave velocity, VS) presentlarge dispersion and may seem smaller than the ones present in the code. However, oneshould be aware for the fact that these materials are often strongly weathered and, as alreadymentioned, can contain voids that will reduce the predicted shear wave velocity.

To compute the seismic response of the soil profiles ProShake software (Idriss and Sun1992) was used. Each soil profile was submitted to the input motions presented in Table 6.Their responses can be observed through the analysis of the theoretical transfer functions,and by comparing the input and the output signals.

ProShake computes the 1D seismic ground response for a particular soil profile submittedto an input motion. It makes use of the equivalent linear method (Schnabel et al. 1972) tosimulate the nonlinear, inelastic behavior of soils. Each soil profile is defined by a set ofhorizontal layers over the bedrock. For each layer, it is necessary to introduce the followingparameters:

1 thickness;2 unit weight;3 plasticity index (PI);4 modulus reduction and damping curves;5 shear wave velocity.

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From the geological profiles, only the thickness and the lithology of each layer were knownand it was necessary to estimate the other physical properties according to the followingassumptions:

• the unit weight was estimated taking into account the lithology type, and consideringmean values (see Table 7);

• the geological formations present in Angra do Heroísmo have low plasticity and thereforethe PI should be less than 10 (this was observed on collected field samples);

• soil model behavior, expressed by modulus reduction and damping curves, were chosenfrom the available curves present in ProShake (Seed and Idriss 1970; Ishibashi andZhang 1993; Sun et al. 1998) taking into consideration the compaction and texture of thegeological formations;

• the values for shear waves velocities were estimated taking into account the a prioriinformation, allowing variations along a reasonable range according to other physical/geotechnical parameters and previous knowledge (see Table 7);

• shear wave velocity for the bedrock, composed by basaltic lavas flow, was considered800 m/s, following EC8 specifications for rock formations and taking into account thefact that this geological formation is, very often, much weathered.

To define the final shear wave velocity for each layer, the results from the ambient vibrationanalysis, performed by Teves-Costa and Senos (2004), were used. The transfer functioncomputed for each soil profile is compared with the H/V curve obtained from the ambientvibration analysis performed for a site located over (or as close as possible to) the soil profile(according to Nakamura 1989, the H/V curve approaches the transfer function and can berecognized as a pseudo-transfer function). Tests were performed to see the sensitivity ofthe transfer function changing the different parameters. Only shear wave velocity and layerthickness variations produce significant changes on the transfer function shape. These twoparameters were then adjusted in order to match the frequency peak of the H/V curve withthe fundamental frequency of the transfer function. Two examples are illustrated in Fig. 6.

The estimated physical properties of the different geologic formations underlying Angrado Heroísmo are summarized in Table 8. Taking into account that some soil profiles werevery similar and other soil profiles occupy only a very small area, it was considered suitableto reduce the number of soil profiles to 9. These 9 soil profiles, which are representative of thesoil conditions in the AHCZ, are schematically presented in Fig. 7. The depth of the bedrockwas taken directly from the geological profile, whenever possible; if not, it was estimated byincreasing the thickness of the last identified layer, taking always in consideration the shearwave velocity values already estimated and the peak frequency of the transfer function.

Fig. 6 Example of the fitness between transfer functions and H/V curves for two soil profiles. Black bold:H/V curves obtained from ambient vibration analysis, for two different sites located over (or very close to)the correspondent soil profile. Thin colored: soil profile transfer functions for the input motions presented inTable 6

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Table 8 Physical characteristicsof the soil and rock surface layers(final values)

Soil Unit weight (kN/m3) VS(m/s)

Cliff deposits 15 90–120

Volcanic tuff 16 135–160

Pumice 17 290–330

Trachytic lavas 22 600–650

Basaltic lavas 24 800

Fig. 7 Schematic soil profiles identified in AHCZ

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Table 9 Peak frequency (F0)

and correspondent amplitude(A0) of the transfer functionscomputed for the identified soilprofiles with the input motionspresented in Table 6

Soil profile F0 (Hz) A0

1 1.54 ± 0.74 4.19 ± 0.48

2 1.85 ± 0.57 4.00 ± 0.55

3 2.66 ± 1.04 2.88 ± 0.46

4 0.75 ± 0.23 3.26 ± 0.21

5 1.15 ± 0.35 3.30 ± 0.19

6 3.17 ± 0.16 3.16 ± 0.69

7 3.02 ± 1.17 2.43 ± 1.17

8 5.36 ± 0.22 1.59 ± 0.01

9 1.00 ± 0.32 3.04 ± 0.42

Fig. 8 Distribution of soil profiles in AHCZ

Table 9 summarizes the transfer function parameters (the fundamental frequency, F0, andthe correspondent amplitude level, A0) obtained for each soil profile. Mean values as wellas the corresponding standard deviation are presented. The large dispersion is due to the soilnon-linearity: it should be noticed that these transfer functions were determined for differentmagnitude events at several epicentral distances (see Table 6).

In order to make the soil characterization useful for damage scenario estimation, it willbe suitable to define the soil profiles associated to each census tract. Figure 8 presents thesoil profiles distribution in the AHCZ. It was realized that it was no need to associate morethan one soil profile to each census tract because in the census tracts where two soil profileswere firstly identified (it was only in 3 census tracts) we checked that one of the soil profilesoccupied a very small area percentage and it was discarded.

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Table 10 Synthesis of the soil profiles seismic response

Soil profile

Amplif PGA

(near-far)

VS30

(m/s)F0

(Hz)A0 F0

(H/V)(Hz)

Spec acc ratio

(0.15-0.5 s)(0.5-1.5 s)

EC8 Detailed classification

8 1.2 – 1.2 600 5.36 1.6 6.61 1.3 – 1.0 B A13 1.0 – 1.5 384 2.66 2.9 3.10 1.7 – 1.5 B B12 1.4 – 1.6 363 1.85 4.0 1.60 1.8 – 2.0 B B21 1.4 – 1.6 345 1.54 4.2 2.41 1.6 – 1.9 C B27 1.1 – 1.6 317 3.02 2.4 3.73 1.4 – 1.8 C C16 1.2 – 1.5 280 3.17 3.2 2.52 2.2 – 1.8 C C25 0.9 – 1.3 238 1.15 3.3 1.86 1.4 – 2.0 C C34 0.6 – 1.1 226 0.75 3.3 1.19 1.1 – 1.9 C C39 0.7 – 1.1 210 1.00 3.0 1.16 1.2 – 1.9 C C3

5 Results and discussion

In order to analyze the seismic behavior of the different soil profiles, in particular in whatconcerns the ground motion amplification and soil classification, it was decided to subjectthe soil profiles to more 30 input motions, corresponding to the three seismic scenarios (10synthetic time stories corresponding to each seismic scenario presented in Table 4).

Table 10 summarizes the most important results obtained for each soil profile withall input motions (40 time histories). Mean values were computed for the followingparameters:

• Amplif PGA (near-far)—ratio between the PGA observed at surface and at the bedrock,for near and distant events;

• VS30—mean value of the shear wave velocity for the upper 30 m;• F0, A0—fundamental frequency and the correspondent amplitude directly derived from

the transfer functions;• Spec acc ratio (0.15–0.5 s); (0.5–1.5 s) – ratio between the mean amplitude of the accel-

eration response spectra at the surface and at bedrock, for the period ranges 0.15 to 0.5 s,and 0.5 to 1.5 s;

Moreover, the peak frequency of the experimental H/V curve, F0 (H/V), and soil classificationare also presented in Table 10:

• EC8—Soil type classification according to EC8, taking into account the VS30 value (seeTable 1);

• Detailed classification—presented only in this study to discuss the differences amongthe soil profiles seismic behaviours

Table 10 presents the soil profiles in descending order of VS30. The following comments canbe made:

• Looking at the PGA amplification factors, it is possible to identify 3 different soil profilegroups: (i) soil profile 8 that amplifies in the same way, and with a negligible value, the farand near input motions; (ii) soil profiles that amplify almost equally, with small factorsthat do not exceed 1.6, the far and near input motions (soil profiles 1, 2, 3, 6 and 7); (iii)soil profiles that attenuate the near input motions and practically do not amplify the farinput motions (soil profiles 4, 5 and 9).

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• Then looking at the (F0, A0) transfer function values (i) it is clear that soil profile 8has a different behaviour, with the highest F0 and the smallest A0; (ii) it is possible todistinguish three different subgroups inside the second soil profile group: two soil profileswith F0 between 1 and 2 Hz and the largest A0 (soil profiles 1 and 2), one with F0 between2 and 3 Hz (soil profile 3), and two with F0 lager than 3 Hz (soil profiles 6 and 7). Theselast 3 soil profiles have A0 between 2.4 and 3.2. (iii) The last group (soil profiles 4, 5 and9) has the lowest F0, around 1Hz, and A0 around 3.

• Finally looking at the spectral acceleration ratios it is possible to see that all soil profilesexhibit very similar behaviour. However taking into consideration the previous groupedsoil profiles, the second group is the more heterogeneous.

The soil profiles classification according to EC8, taking in consideration the VS30 values,is also presented in Table 10. But, due to the differences present on the other parameters(amplification factors of the PGA and of the spectral acceleration for 2 period ranges; peakfrequency of the transfer function, F0, and its amplitude, A0) a detailed classification isalso presented. In this detailed classification we tried to define subclasses inside each EC8class; however we did not strictly respect the VS30 code limit for the transition between theclasses A, B and C because we took into consideration the similarities and differences ofall parameters. Soil profile 8 behaves like rock (subclass A1) and, for instance, it seemedmore reasonable to associate soil profile 1 to soil profile 2 (subclass B2) and distinguish themfrom soil profile 7 (subclass C1). This detailed classification is only to enhance the smalldifferences between the responses of the soil profiles but this is not intended to be a definitiveclassification. For instance, there are many similarities between soil profiles 6 and 7 and alsobetween these two and the soil profiles classified as B1 and B2 (see Table 10). All these soilprofiles could probably be grouped in the same class.

Figure 9 presents the distribution of all these parameters along the AHCZ. It should benoticed that, in these maps, there is only one value for each soil profile (assumed at the centralpoint of its area). The results were mapped using a linear interpolation in order to allow softtransition boundaries instead of the maintenance of the strict limits of each soil profile area.This must be taken into account on the analysis of this figure.

Ordering the soil profiles according to the peak frequency of the experimental H/V curve,F0 (H/V), it is possible to observe other similarities (Table 11). Now, it is easy to identify3 different classes (1A, 2B and 3C) corresponding to high values (∼6 Hz), medium val-ues (∼2–4 Hz) and low values (∼1 Hz) of F0. Comparing this (H/V) classification with thedetailed one, we can see that classes B1, B2, C1 and C2 could probably be integrated ina single one. This is in agreement with the similarities already noticed in the analysis ofTable 10.

The only noticeable discrepancy is the classification of soil type 2. In Table 10 (theoreticalresponse) it could be grouped to soil profiles 1, 3, 6 and 7 while in Table 11 (experimentalmeasurements) it is grouped to soil profiles 4, 5 and 9. This could be due to the geologicalheterogeneity of the AHCZ that can mislead the definition of the geological soil profile 2. Themost probably reason is that the definition of the geological soil profile 2 does not correspondto the H/V curve used to calibrate it. This may be happen because the selected H/V curveswere as close as possible to the geological profile (from which the soil profiles were defined)but not always over it.

According to several authors the classification of the soil characteristics should not bebased only on VS30 values (Mucciarelli and Gallipoli 2006; Castellaro et al. 2008; Lee andTrifunac 2010). The consideration of the fundamental frequency obtained by microtremormeasurements (F0), which produces independent information about the bedrock depth and

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Fig. 9 Distribution of all parameters influencing the soil classification along Angra do Heroismo ClassifiedZone (AHCZ) considering the 9 main soil profiles

Table 11 Classification of soilprofiles according to F0 (H/V)

Soil profile

F0 (H/V) (Hz)

Class (H/V)

Detailed classif.

8 6.61 1A A17 3.73 2B C13 3.10 2B B16 2.52 2B C21 2.41 2B B25 1.86 3C C32 1.60 3C B24 1.19 3C C39 1.16 3C C3

the stiffness of the surface materials, is also fundamental. Recently several authors proposeda classification based on the couple (F0, VS30) (e.g., Lermo et al. 2009; Luzi et al. 2011;Cadet et al. 2012). Luzi et al. (2011) and stated that in absence of VS30 information, soilclassification must be performed according to the fundamental frequency, F0, instead ofinferring a soil category from poor quality information. Consequently, the classification ofthe AHCZ soils in 3 groups / classes, according to Table 10 (where the soils B1, B2, C1 andC2 belong to the same group) or to Table 11, seems very reasonable.

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Furthermore, in the EC8 Portuguese National Annex (IPQ 2010) there are 5 soil profilesdefined for the Azores: one belonging to soil type A (profile 1), three classified as soil typeB (profiles 2–4) and one classified as soil class C (profile 5). The mean shear wave velocitieswhich decrease from profile 1 to profile 5, are 530 m/s and 330 m/s for profiles 4 and 5,respectively; there is nothing defined in between (namely, between classes B and C). So, wecan say that the proposed detailed classification does not seem to be unreasonable.

According to Malheiro and Nunes (2007) code profiles 1 and 2 exist in the AHCZ. Codeprofile 1 corresponds to soil profile 8 that, according to our analysis, is the hardest soil whichis in agreement with what is stated in the code. Code profile 2 corresponds to soil profile 4that, according to our analysis, should not induce significant amplification on ground motion.However, soil profile 4 seems less hard than the code profile 2 but this can be explained bythe geological heterogeneity. It is difficult to associate the remaining soil profiles to oneor more code profiles, due to the alternating of different volcanic formations with variablethickness. According to our analysis, soil profiles 5 and 9 must behave like soil profile 4,and the remaining soil profiles must present a behaviour between soil profile 8 and this lastgroup (soil profiles 4, 5 and 9)—see Tables 10 and 11.

Obviously, this classification and the subjacent assumptions may be put into question. Forinstance, the values of the shear wave velocities for the different volcanic layers (Table 8)are not in agreement with the EC8 Portuguese National Annex (IPQ 2010). However, thiscan be due to the high fracturing level and weathered conditions of the surface formations.Our detailed classification was performed for a small area, and the code must be morecomprehensive and applicable to all situations in general.

The validity of this classification should be tested as experimental data is acquired. But,up to date, very few measures of VS were performed in the Azorean soils. In 2008, two arraysmeasurements were performed in Angra do Heroísmo: one inside the AHCZ and another atthe bottom of Monte Brasil, a volcanic cone in the southern part of the town (it can be seen inFig. 1). By inversion of the Rayleigh wave dispersion curve, VS profiles were estimated forthe two sites and VS30 values were computed (Teves-Costa et al. 2010). The site inside theAHCZ was located over soil type 5 and the computed VS30 was (244 ± 12)m/s. It is easy tosee that the theoretically estimated VS30 for soil type 5 (238 m/s, Table 10) agrees with thisexperimental study.

Finally, Fig. 10 presents the computed F0, from the theoretical transfer functions, andthe determined F0, estimated from the analysis of microtremor measurements (from Teves-Costa and Senos 2004). It should be noticed that the experimental F0 map was performed withvalues assigned to 230 points while the theoretical F0 map was performed with only 9 values

4278200

4278400

4278600

4278800

4279000

4279200

4279400

F0 (measured)

479800 480000 480200 480400 480600 480800 481000 481200 481400 481600 479800 480000 480200 480400 480600 480800 481000 481200 481400 481600

4278200

4278400

4278600

4278800

4279000

4279200

4279400

0

1

2

3

4

5

6

7

8

9

10

11

12

F0 (calculated)

Fig. 10 Left: map of the computed F0 obtained from the H/V curves (by analysis of ambient vibrationmeasurements); Right: map of fundamental frequencies obtained from theoretical transfer functions of theidentified soil profiles

123


assumed at the central point of each soil polygon area. The analysis of this figure should becarefully performed but it is possible to observe that both maps exhibit higher frequenciesin the northern part of the town which, according to the geological map, correspond to thehardest surface geologic formations (see Fig. 3); also, in the western part of the town, bothmaps present high frequencies. Besides, the map obtained with the microtremor analysisseems to correlate better with the surface geology. In particular, in the central part of thetown a narrow zone of higher frequencies between two areas of low frequencies seems to“identify” the fault trace presented in the geological map (see Fig. 3). However, this couldbe contested because, as noticed by Chávez-García et al. (2007), in regions where the localgeology is complex, as in volcanic environment, the H/V curves obtained with Nakamura’smethodology may not be representative of local site effects.

6 Conclusions

This study presents a detailed classification for the AHCZ, developed with the spe-cific purpose of being applied to damage seismic scenarios estimation in the town ofAngra do Heroísmo, and was based on the analysis of microtremor experimental mea-surements and on theoretical modeling using geological, geotechnical and geophysicalinformation.

The proposed classification, as obvious, does not intend to substitute the code classifica-tion. But for scenarios purposes, even with an available code, microzonation studies must beundertaken in order to perform a detailed study to identify the differences inside the inter-ested area. This is particularly true in the Azores due to the heterogeneity of the geologicalvolcanic formations. In this study, we identify 9 distinct soil profiles in the AHCZ that couldbe grouped (if suitable) in three more general classes. The use of experimental measurementspresents a great help for soil characterization.

The validity of this classification should be tested as experimental data is acquired, andits use on damage seismic scenarios estimation should be checked by comparison with past(and future?) real earthquake effects.

The presented methodology can be applied in other towns where microtremor measure-ments were (or can be) performed and where exist some geological, geophysical and/orgeotechnical information. The code classification should only be used when there are noadditional geophysical and geotechnical investigations.

Acknowledgements The authors would like to thanks Pierre-Yves Bard for his valuable help and con-tinuous support. Figure 1 was performed using Google Inc. (2009), Google Earth (Version 5.1.3533.1731).This work was partially supported by the COMICO Project (POCTI/CTE-GIN/57759/2004 & PPCDT/CTE-GIN/577579/2004), funded by the Portuguese Foundation for Science and Technology.

References

Albarello D, Lunedei E (2010) Alternative interpretations of horizontal to vertical spectral ratio of ambientvibrations: new insights from theoretical modeling. Bull Earthquake Eng 8(3):519–534

Ansal A, Iyisan R, Güllü H (2001) Microtermor measurements for the microzonation of Dinar. Pure ApplGeophys 158:2525–2541

Ansal A, Tönük G, Kurtulus A (2010) Microzonation for earthquake scenarios. In: Garevski M, Ansal A (eds)Earthquake engineering in Europe. Springer, Berlin, pp 45–65

Bard P-Y (1999) Microtremor measurements: a tool for site effect estimation? In: Irikura K, Kudo K, OkadaH, Satasani T (eds) The effects of surface geology on seismic motion. Balkema, Rotterdam, pp 1251–1279

123


Boaga J, Vaccari F, Panza GF (2010) Shear wave structural models of Venice Plain, Italy, from time crosscorrelation of seismic noise. Eng Geol 116:189–195

Bonnefoy-Claudet S, Cornou C, Bard PY, Cotton F, Moczo P, Kristek J, Fäh D (2006a) H/V ratios: a tool forsite effects evaluation. Results from 1-D noise simulations. Geophys J Int 167:827–837

Bonnefoy-Claudet S, Cornou C, Bard PY, Cotton F, Moczo P, Kristek J, Fäh D (2006b) H/V ratios: a tool forsite effects evaluation. Results from 1-D noise simulations. Geophys J Int 167:827–837

Bouckovalas GD, Kouretzis GP (2001) Stiff soil amplification effects in the 7 September 1999 Athens (Greece)earthquake. Soil Dyn Earthq Eng 21:671–687

Cadet H, Bard PY, Duval AM (2008) A new proposal for site classification based on ambient vibrationmeasurements and the KiKnet strong motion data set. In: Proceedings of 14WCEE, Beijing (China), 8p

Cadet H, Bard PY, Duval AM, Bertrand E (2012) Site effect assessment using KiK-net data: part 2—siteamplification prediction equation based on f0 and VSZ. Bull Earthquake Eng. Published on line: 06 July2011

Carvalho A, Sousa ML, Oliveira CS, Campos-Costa A, Nunes JC, Forjaz VH (2001) Seismic hazard for thecentral group of the Azores Islands. Boll Geofisica Teorica e Appl 42(1–2):89–105

Castellaro S, Mulargia F, Rossi PL (2008) Vs30: proxy for seismic amplification? Seismol Res Lett 79(4):540–543

Castellaro S, Mulargia F (2009) Vs30 estimates using constrained H/V measurements. BSSA 99(2A):761–773Chatelain JL, Guillier B, Cara F, Duval AM, Atakan K, Bard PY, WP02 SESAME Team, (2008) Evaluation

of the influence of experimental conditions on H/V results from ambient noise recordings. Bull Earthq Eng6(1):33–74

Chávez-García FJ, Rodríguez M, Stephenson WR (2005) An alternative approach to the SPAC analysis ofmicrotermors: exploiting stationarity of noise. Bull Seismol Soc Am 95(1):277–293

Chávez-García FJ, Rodríguez M, Stephenson WR (2006) Subsoil structure using SPAC measurements alonga line. Bull Seismol Soc Am 96(2):729–736

Chávez-García FJ, Domínguez T, Rodríguez M, Pérez F (2007) Site effects in a volcanic environment: acomparison between HVSR and array techniques at Colima, Mexico. Bull Seismol Soc Am 97(2):591–604

Costa-Nunes J (1998) Historical seismicity of the Azores. In: Proceedings of 1st symposium on meteorologyand geophysics of the APMG, Lagos (Portugal), pp 115–122 ( in Portuguese)

Compagnoni M, Pergalani F, Boncio P (2011) Microzonation study in the Paganica-San Gregorio area affectedby the April 6, 2009 L’Aquila earthquake (central Italy) and implications for the reconstruction. Bull EarthqEng 9:181–198

CEN (2004) EN 1998–1 Eurocode 8: design of structures for earthquake resistance -Part 1: General rules,seismic actions and rules for buildings. Brussels, Belgium

D’Amico V, Picozzi M, Baliva F, Albarello D (2008) Ambient noise measurements for preliminary character-ization in the urban area of Florence, Italy. Bull Seismol Soc Am 98(3):1373–1388

Di Giulio G, Improta L, Calderoni G, Rovelli A (2008) A study of the seismic response of the city of Benavento(Southern Italy) through a combined analysis of seismological and geological data. Eng Geol 97:146–170

IPQ (2010) NP-EN 1998–1 Eurocode 8—Design of structures for earthquake resistance. Part 1: general rules,seismic actions and rules for buildings. Instituto Português da Qualidade ( in Portuguese)

Endrun B, Ohrnberger M, Savvaidis A (2010) On the repeatability and consistency of the three-componentambient vibration array measurements. Bull Earthquake Eng 8:535–570

European Strong Motion Database (2004). http://www.isesd.hi.is/ESD_Local/frameset.htmFäh D, Rüttener E, Noack T, Kruspan P (1997) Microzonation of the city of Basel. J Seismol 1:87–102Fäh D, Kind F, Giardini D (2003) Inversion of local S-wave velocity structures from average H/V ratios, and

their use for the estimation of site-effects. J Seismol 7:449–467Forjaz VH, Nunes JC, Guedes JHC, Oliveira CS (2001) Geotechnical classification of the Azores Islands

soils: a proposal. In: Proceedings of 2nd symposium on meteorology and geophysics of the APMG, Évora(Portugal), pp 76–81 ( in Portuguese)

Fritsche S, Fah D, Steiner B, Giardini D (2009) Damage field and site effects: multidisciplinary studies of the1964 earthquake series in Central Switzerland. Nat Hazard 48:203–227

Gallipoli MR, Mucciarelli M, Castro RR, Monachesi G, Contri P (2004) Structure, soil-structure response andeffects of damage based on observations of horizontal-to-vertical spectral ratios of microtremors. Soil DynEarthq Eng 24:487–495

Giammarinaro S, Tertulliani A, Galli G, Leta M (2005) Investigation of surface geology and intensity variabilityin the Palermo, Italy, urban area after the 6 September 2002 earthquake. Bull Seismol Soc Am 95(6):2318–2327

Gosar A, Lenart A (2010) Mapping the thickness of the Ljubljana Moor basin (Slovenia) using microtremors.Bull Earthq Eng 8(3):501–518

123

http://www.isesd.hi.is/ESD_Local/frameset.htm


Gosar A, Martinec M (2009) Microtermor HVSR study of site effects in the Ilirska Bistrica town area(S. Slovenia). J Earthq Eng 13(1):50–67

Guidobonni E, Mariotti D, Giammarinaro MS, Rovelli A (2003) Identification of amplified damage zonesin Palermo, Sicily (Italy), during the earthquakes of the last three centuries. Bull Seismol Soc Am 93(4):1649–1669

Guillier B, Atakan K, Chatelain JL, Havskov J, Ohrnberger M, Cara F, Duval AM, Zacharopoulos S, Teves-Costa P, Team SESAME (2008) Influence of instruments on the H/V spectral ratios of ambient vibrations.Bull Earthq Eng 6(1):3–31

Haghshenas E, Bard PY, Theodulidis N, SESAME WP04 Team (2008) Empirical evaluation of microtremorH/V spectral ratio. Bull Earthq Eng 6(1):75–108

Havenith HB, Fäh D, Polom U, Roullé A (2007) S-wave velocity measurements applied to the seismic micro-zonation of Basel, Upper Rhine Graben. Geophys J Int 170:346–358

Idriss IM, Sun JI (1992) SHAKE91: a computer program for conducting equivalent linear seismic responseanalysis of horizontally layered soil deposits. University of California, User’s Manual 75p

INE (2001) CENSUS 2001: census of population and housing. Statistics Portugal, Instituto Nacional deEstatística, Portugal

Ishibashi I, Zhang X (1993) Unified dynamic shear moduli and damping ratios of sand and clay. Soils Found33(1):182–191

Kanh AI, Tildy P, Pronay Z, Pinar A, Hermann L (2006) Vs30 mapping and soil classification for seismic siteeffect evaluation in Dinar region, SW Turkey. Geophys J Int 165:223–235

KiK-net digital strong motion seismograph network (2005). http://www.kik.bosai.go.jp/Lachet C, Hatzfeld D, Bard PY, Theodulidis N, Papaioannou N, Savvaidis A (1996) Site effects and micro-

zonation in the city of Thessaloniki (Greece) comparison of different approaches. Bull Seismol Soc Am86(6):1692–1703

Lee VW, Trifunac MD (2010) Should average shear-wave velocity in the top 30m of soil be used to describeseismic amplification? Soil Dyn Earthq Eng 30(11):1540–1549

Lermo J, Chávez-García FJ (1993) Site effect evaluation using spectral ratios with only one station. BullSeismol Soc Am 83:1574–1594

Lermo J, Limaymanta F, Linera FW, Trujillo GR, Leyva R (2009) Land characterizing for seismic design inthe urban zone of Veracruz-Boca del Río, México (ZCV). In: Proceedings of 8th international workshopon seismic microzoning and risk reduction, Almeria, Spain, 11p

Lopes I (2005) Small strain characterization of soils. Application of the surface wave method. PhD Thesis,Lisbon University, ( in Portuguese)

Lourenço N, Miranda JM, Luis JF, Ribeiro A, Madeira J, Needham HD (1998) Morpho-tectonic analysis of theAzores Volcanic Plateau from a new bathymetric compilation of the area. Marine Geophys Res 20:141–156

Luzi L, Puglia R, Pacor F, Gallipolo MR, Bindi D, Mucciarelli M (2011) proposal for a soil classificationbased on parameters alternative or complementary to VS,30. Bull Earthq Eng 9:1877–1898

Malheiro AM, Nunes JC (2007) Volcanostratigraphic profiles for the Azores region. A contribution for theEC8 regulations and the characterization of volcanic rocks geomechanical behaviour. In: Proceedings ofinternational workshop on volcanic rocks, 11th congress ISRM, Ponta Delgada (Azores–Portugal), Taylor& Francis, London, pp 59–64

Maugeri M, Simonelli AL, Ferraro A, Grasso S (2011) Recorded ground motion and site effects evaluationfor the April 6, 2009 L’Aquila earthquake. Bull Earthq Eng 9:157–179

Motta J., Nunes J.C. (2002) Gravimetric studies in S. Jorge Island (Azores): first results. Proc. 3rd Spanish-Portuguese Assembly on Geodesy and Geophysics, Univ. Polit. Valencia (Spain), Tomo I: 266–268(in Portuguese).

Mucciarelli M, Gallipoli MR, Arcieri M (2003) The stability of the horizontal-to-vertical spectral ratio oftriggered noise and earthquake recordings. Bull Seismol Soc Am 93(3):1407–1412

Mucciarelli M, Gallipoli MR (2006) Comparison between vs30 and other estimates of site amplification in Italy.First European Conference on Earthquake Engineering and Seismology (1ECEES), Geneva (Switzerland),Paper No 270, 7p

Nakamura Y (1989) A method for dynamic characteristics estimations of subsurface using microtremors onthe ground surface. Q Rep RTRI 30(1):25–33

Nakamura Y (1996) Real-time information systems for hazards mitigation. In: Proceedings of 11WCEE,Acapulco, Mexico. CD-Rom

Nakamura Y (2000) Clear identification of fundamental idea of Nakamura’s technique and its applications. In:Proceedings of 12th world conference on earthquake engineering (12WCEE), New Zealand, Paper 2656,6p

123

http://www.kik.bosai.go.jp/


Navarro M, Vidal F, Enomoto T, Alcala F, García-Jerez A, Abeki N, Luzón F (2009) Correlation between siteeffects and damage distribution observed during moderate earthquakes in SE Spain. In: Proceedings of 8thinternational workshop on seismic microzoning and risk reduction, Almeria, Spain, 8p

Nunes JC, Forjaz VH, Oliveira CS (2001) Geological mapping of Terceira Island (Azores) urban centres asa way to better understand the seismic response of buildings. In: Proceedings of 2nd symposium of thePortuguese association for meteorology and geophysics. Évora, Portugal, pp 82–87 ( in Portuguese)

Oliveira CS, Lucas ARA, Guedes JHC (eds.) (1992) Monograph: 10 years after the January 1, 1980, AzoresEarthquake, SRHOP, LNEC, 2 volumes ( in Portuguese)

Picozzi M, Strollo A, Parolai S, Durukal E, Özel O, Karabulut S, Zschau J, Erdik M (2009) Site characterizationby seismic noise in Istanbul, Turkey. Soil Dyn Earthq Eng 29:469–482

Pousse G, Bonilla L, Cotton F, Margerin L (2006) Nonstationary stochastic simulation of strong ground motiontime histories including natural variability: application to the K-Net Japanese database. Bull Seismol SocAm 96(6):2103–2121

ProShake (2001) Ground response analysis program, Version 1.1, User’s Manual. EduPro Civil Systems, Inc.Redmond, Washington

PEER Strong Motion Database (2005). Pacific Earthquake Engineering Research Center. http://peer.berkeley.edu/products/strong_ground_motion_db.html

Rodríguez-Losada JA, Hernández-Gutiérrez LE, Olalla C, Perucho A, Serrano A, del Potro R (2007) Thevolcanic rocks of the Canary Islands. Geotechnical properties. In: Proceedings of international workshopon volcanic rocks, 11th congress ISRM, Ponta Delgada (Azores–Portugal), Taylor & Francis, London, pp53–57

Sabetta F, Pugliese A (1996) Estimation of response spectra and simulation of nonstationary earthquake groundmotions. Bull Seismol Soc Am 86(2):337–352

Schnabel PB, Lysmer J, Seed HB (1972) SHAKE—a computer program for earthquake response analysis ofhorizontally layered sites. Report EERC 72–12, University of California, Berkeley, 114p

Seed HB, Idriss IM (1970) Soil moduli and damping factors for dynamic response analyses. Report EERC70–10. University of California, Berkley, EERC

Seth MI, Wohlenberg J (1999) Microtremor measurements used to map thickness of soft sediments. BSSA89(1):250–259

SIVISA Preliminary bulletin of the seismological surveillance system of the Azores. Instituto de Meteorologiaand Azores University, Portugal ( in Portuguese)

Silva M (2005) Characterization of the historical seismicity of the Azores based on the reinterpretation ofmacroseismic data: contribution to the assessment of seismic risk in the islands of the central group. MScThesis on Volcanology and Geological Hazards, Geosciences Dept, Azores University ( in Portuguese)

Sun JI, Golesorkhi R, Seed HB (1998) Dynamic moduli and damping ratios for cohesive soils. Report NoUCB/EERC-88/15, Berkeley, 43p

Teves-Costa P, Veludo I, Rodrigues I, Almeida J (2010) Site characterization using ambient vibrations “array”measurements. In: Proceedings of Sísmica 2010–8th congress on seismology and seism Engineering, Aveiro(Portugal), Paper 110, 12p ( in Portuguese)

Teves-Costa P, Oliveira CS, Senos ML (2007) Effects of local site and building parameters on damage distri-bution in Angra do Heroísmo—Azores. Soil Dyn Earthq Eng 27:986–999

Teves-Costa P, Senos ML (2004) Seismic zonation of Angra do Heroísmo using ambient vibrations. In:Proceedings of 4th Spanish-Portuguese assembly on geodesy and geophysics, Figueira da Foz (Portugal),pp 75–76 (in Portuguese)

Vallejo LIG, Hijazo T, Ferrer M, Seisdedos J (2007) Geomechanical characterization of volcanic materials inTenerife. In: Proceedings of internationl workshop on volcanic rocks, 11th congress ISRM, Ponta Delgada(Azores–Portugal), Taylor & Francis, London, pp 21–28

Veludo I (2008) Cenários sísmicos para a cidade de Angra do Heroísmo. MSc thesis, DEGGE-FCUL, Uni-versity of Lisbon, 132p (in Portuguese)

Veludo I, Teves-Costa P, Bard PY (2012) Damage seismic scenarios for Angra do Heroísmo, Azores (Portugal).Bull Earthq Eng. doi:10.1007/s10518-012-9399-y

123

http://peer.berkeley.edu/products/strong_ground_motion_db.html

http://peer.berkeley.edu/products/strong_ground_motion_db.html

http://dx.doi.org/10.1007/s10518-012-9399-y

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Soil characterization for seismic damage scenarios purposes: application to Angra do HeroÃsmo (Azores)