Environ Earth Sci (2016) 75:1354
DOI 10.1007/s12665-016-6151-y
ORIGINAL ARTICLE
Investigation of site properties in Adapazarı, Turkey, using
microtremors and surface waves
Ali Silahtar1 • Emrah Budakoğlu1 • Gündüz Horasan1 • Eray Yıldırım2
H. Serdar Küyük3,4 • Evrim Yavuz5 • Deniz Çaka5
•
Received: 23 January 2016 / Accepted: 30 September 2016 / Published online: 14 October 2016
Ó Springer-Verlag Berlin Heidelberg 2016
Abstract Determination of suitable areas for new residential buildings is crucial to increase the resilience of
buildings against earthquake hazards. After the 1999 Izmit
earthquake Mw 7.4, the city of Sakarya has been expanding
rapidly in terms of both the population and number of
superstructures. Despite the fact that Sakarya suffered
several large earthquakes in the last two decades, the
geophysical properties of the region have not been adequately investigated. In this study, the site properties of
Sakarya University, Esentepe Campus, and its surrounding
Serdivan district, which is one of the important parts of the
city, are determined using microtremor measurements and
surface wave analysis. Nakamura’s spectral ratio method
(spectral ratio between the horizontal and vertical components, H/V or HVSR) was used to determine the fundamental frequency and site amplification values. The shear
wave velocity profiles of the studied sites were determined
using the multichannel analysis of surface waves method.
Seismic measurements were performed at 34 locations to
record the surface waves in the area. The fundamental
frequency and site amplification values are determined as
1.02–11.68 and 1.33–5.96 Hz, respectively, from the
microtremor measurements. The fundamental frequency is
between 4.0 and 11.5 Hz in the campus area and between
1.3 and 2.0 Hz near the D-100 intercity highway. The site
amplification was determined to be 1–2.5 in the campus
area. The greatest site amplification (6) is obtained at thick
alluvium deposits in the valley between hills. The average
shear wave velocity values are within the range of 300 and
1120 m/s. Some parts located on the hill area have better
soil condition (B) categories, according to the National
Earthquake Hazard Reduction Program, and have comparatively high shear wave velocities in the range of
740–1080 m/s, whereas low velocity values are found at
the thick alluvium deposits (D). We found that the geological properties and topographies play very important
roles on the shear wave velocity and the amplification
factors in the investigated area.
& Gündüz Horasan
[email protected]
Keywords Microtremor Surface waves Vs30 Adapazarı
1
2
Department of Geophysical Engineering, Faculty of
Engineering, Sakarya University, 54187 Serdivan, Sakarya,
Turkey
Department of Civil Engineering, Faculty of Natural
Sciences, Architecture and Engineering, Bursa Technical
University, 16330 Bursa, Turkey
3
Department of Civil Engineering, Faculty of Engineering,
Sakarya University, 54187 Serdivan, Sakarya, Turkey
4
Kandilli Observatory and Earthquake Engineering Institute,
Bogazici University, 81220 Istanbul, Turkey
5
Department of Geophysical Engineering, Faculty of
Engineering, Kocaeli University, 41000 İzmit, Kocaeli,
Turkey
Introduction
The seismicity of the area in Sakarya Prefecture, Turkey, is
controlled by the North Anatolian Fault Zone (NAFZ). The
NAFZ is located in the south of the Adapazarı basin, and it
passes through approximately 19 km south of Adapazarı
(Fig. 1). This fault zone has created large earthquakes in
the region (Ms 6.6 1943 Hendek-Adapazarı; Ms 7.1 1957
Abant-Bolu; Ms 6.8 1967 Mudurnu-Bolu; Ms 7.8 1999
Izmit and Ms 7.5 1999 Düzce earthquakes). Thousands of
people have lost their lives, and hundreds of buildings have
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Environ Earth Sci (2016) 75:1354
Fig. 1 Regional topographic map showing the North Anatolian Fault Zone (NAFZ) and large earthquakes (1943 Hendek-Adapazarı; 1957
Abant-Bolu; 1967 Mudurnu-Bolu; 1999 Kocaeli and 1999 Düzce) pointed out with red stars. The study area is marked by a shaded rectangle
been damaged heavily because of these earthquakes. One
of the largest of these earthquakes, the August 17, 1999,
Izmit earthquake Mw 7.4, ruptured 140 km in the segment
of the North Anatolian Fault (NAF), which extends from
Izmit bay in the west to Akyazi in the east, and caused
approximately 20,000 losses of lives and 20,000 collapsed
buildings.
Adapazarı has been developed on the young floodplain
deposits of Sakarya River. Therefore, soft soil deposits
123
were thought to have large effects on these past damages.
The elastic properties of near-surface materials and their
effects on seismic wave propagation are very important in
both earthquake/civil engineering and environmental/earth
science studies. The increase of amplitudes in soft sediments is one of the most important factors responsible for
the amplification of earthquake motions. To characterize
the local conditions in terms of the dynamic response of the
soil, the horizontal-to-vertical spectral ratio (HVSR or H/V)
Environ Earth Sci (2016) 75:1354
and the fundamental frequency have been used extensively
by many researchers (Nogoshi and Igarashi 1970; Nakamura 1989, 2000; Lermo and Chávez-Garcia 1993, 1994;
Theodulidis and Bard 1995; Suzuki et al. 1995; Lachet and
Bard 1994; Gallipoli and Mucciarelli 2009; Gosar 2010;
Ozalaybey et al. 2011; Akkaya 2015). Deriving the fundamental frequency of the soft sediments overlying bedrock using the HVSR method has become increasingly
popular because of its application simplicity and low cost.
Surface wave measurements also have great potential for
use in site characterization. The Kansas Geological Survey
has been conducting a three-phase research project since
1995 to estimate the near-surface S-wave velocities from
Rayleigh waves. Surface waves have been processed using
the 1D multichannel analysis of surface waves (MASW)
method to infer the shear wave velocity profile of soil. This
MASW technique has been effectively used to map bedrock
(Xia et al. 1998; Miller et al. 1999; Park et al. 1999). All
variations of the MASW methods are environment-friendly,
noninvasive, low cost, rapid and robust; moreover, they
consistently provide reliable shear wave velocity profiles
within the first 30 m below the surface (Xia et al. 2002;
Kanlı et al. 2006; Martı́nez-Pagán et al. 2014). Microzonation studies are frequently performed based on the use of the
average shear wave velocity in the uppermost 30 m (Vs30)
because of the limited exploration depth of invasive methods; this approach is adopted by the National Earthquake
Hazard Reduction Program (NEHRP) classification in the
USA. The original work of Borcherdt (1992) on Vs30 was
based on data from the western USA; the first papers discussing advantages and disadvantages of the Vs30 method
were Anderson et al. (1996) and Wald and Mori (2000). The
general principle in surface wave methods is the utilization
of the dispersive characteristic of surface waves recorded by
passive (environmental noise) or active (horizontal or vertical) sources. The MASW method, which is one of the most
effective active-source surface wave methods, is used to
determine soil characterization up to 30 m.
A limited number of researchers have studied the site
parameters of the Sakarya basin. Komazawa et al. (2002),
Kudo et al. (2002), Ozel and Sasatani (2004), Siyahi and
Selçuk (2005), Ozcep et al. (2013) and Firat et al. (2016)
determined the site effect parameters in a few regions of
the Adapazarı basin after the 1999 Izmit earthquake. Ozel
and Sasatani (2004) studied the site effects of the Adapazarı basin, Turkey, where heavy damage occurred during
the 1999 Izmit earthquake based on the strong- and weakmotion data obtained using a temporal array observation. In
their study, the S-wave amplifications in the basin were
evaluated by using the traditional spectral ratio method.
They performed a quantitative interpretation of the
empirical amplifications based on the S-wave velocity
structures at the stiff-soil reference site as well as the basin
Page 3 of 15
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sites, which were estimated by microtremor array measurements. Ozcep et al. (2013) determined the soil-type
information based on the Vs30 values. They found that the
Genç, Seker, Babalı and Hastane stations were located on
soft soil, whereas the Imar and Toyota areas were located
on stiff soil or soft rock. Firat et al. (2016) performed onedimensional ground response analyses at Adapazarı region
(Teverler, Yeni cami, Sakarya high school, Atatürk stadium) using the August 17, 1999, Izmit earthquake strong
ground motion records. However, many areas in the city
that are susceptible to the next expected Marmara Earthquake have not been studied adequately.
Recently, many new buildings are being constructed in
new residential areas, such as around the Sakarya University, Esentepe Campus, and the Serdivan and Beşköprü
provinces. The areas of high risk around these regions
should be determined. The aim of this study is to assess the
fundamental frequency, site amplification and Vs30 velocity values at the Esentepe Campus and its environment. We
also classified the study areas based on the Vs30 values in
the seismic design code (NEHRP).
Geological setting
The simplified geological map of Adapazarı and its surroundings is shown in Fig. 2. The city of Adapazarı lies
essentially on the active floodplain of the Sakarya River,
and the river has deposited the near-surface soft sediments
underlying the majority of the city. The Adapazarı basin
contains quaternary alluvial sediments covering the tectonic units within the boundaries of the basin. The quaternary aged alluvium mainly consists of silt and fine sand
deposited by the Sakarya River; silt-sand layers are found
in the downtown Adapazarı by Sancio et al. (2002). Sarıaslan et al. (1998) summarized the characteristics of the
surroundings of the work area as follows:
Sultaniye metamorphics (PTRs): This metamorphic unit
primarily outcrops on higher hills south and southwest of
Sapanca. Sultaniye metamorphics consist of schist-marble,
limestone and ophiolite schist, and it is covered discordantly by the upper cretaceous-tertiary older formation.
The unit is of Permian–Triassic age.
Akçay metamorphics (Ka): Outcrops at the south of the
Adapazarı, Akçay valley and near Memnuniyet village.
The outcrops consist of limestone, mudstone, quartzite,
quartz schist, gravel, tuff, basalt, recrystallized limestone
and marble.
Akveren formation (KTa): Our study area is situated in
the Akveren formation. This formation yields an outcrop at
the south and southwest hills of Adapazarı and the Serdivan district. The Akveren formation is mainly composed of
argillaceous limestone, marl, claystone, siltstone, gravel,
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Fig. 2 Simplified surface
geology map of Adapazarı
region (modified after Sarıaslan
et al. 1998)
Environ Earth Sci (2016) 75:1354
N
SAKARYA
Tç
Tçy
Qa
Kta
Sapanca Lake
NAF
Qa
Qa
Rs
Tör
Tör
PT
Ka
Tç
Study Area
Çaycuma Fm
5 km
0
Eocene
Quaternary
Qa
Pliocene
Tör
Örencik Fm
Upper Cretaceous
Lower Eocene
reef limestone and volcanic rocks. The age of this formation is upper Cretaceous to Eocene.
Çaycuma formation (Tc): This formation consists of
limestone, mudstone, volcanic rocks and gravel. It outcrops
at the hills west of Adapazarı. It is from middle Eosen.
Yıgılca formation (Tçy): This formation outcrops at the
hill at the west side of Serdivan district. It consists of andesite,
basalt, gray and brownish thick-layered agglomerate, tuff,
local sandstone with volcanic material and nummulitic
limestone layer. The age of this formation is lower Eosen.
Örencik formation (Tor): This formation consists of
gravel, limestone, mudstone and claystone. It outcrops
mostly at the towns of Sapanca and Karapürçek. This formation settled in river and floodplains and is of Pliocene age.
Alluvion (Qa): Most of Sakarya and its districts remain
on the hardened quaternary aged alluvium base. The quaternary aged sediment base is primarily coarse-grained near
the edges and fine-grained in the inner parts.
Microtremor data analysis
Microtremor data are used frequently to determine the local
soil conditions in earthquake engineering. The horizontalto-vertical spectral ratio has been used by many researchers
123
Tçy
Yığılca Fm
Upper Jura
Lower Cretaceous
Kta
Akveren Fm
Permian-Triassic
Ka
PTRs
Akçay Metamorphic
Sultaniye Metamorphic
to characterize the local conditions in terms of the dynamic
response of the soil. In this study, we used the well-known
Nakamura (1989, 2000) methods to analyze the microtremor data. This method is based on three components to
perform single-station measurements and is called the
horizontal-to-vertical spectral ratio method. We used a
Guralp CMG-6TD broadband seismometer with three
components (UD, NS and EW) to obtain the microtremor
data at the Sakarya University, Esentepe Campus, and its
environment. Microtremor measurements were conducted
at 34 sites in the study area (Fig. 3). The sampling rate of
the recorded data was 100 samples per second, and the
recording time was approximately 15 min at each site. The
acquisition system was equipped with a 24-bit digitizer.
Microtremor data analysis was performed using Geophysical Signal Database for Noise Array Processing
(GEOPSY 1997) software developed during the Site EffectS assessment with the AMbient Excitations (SESAME
2004) European Project (Bard 2000). The window length
selected for computing the H/V spectral ratio was 25 s.
Next, a cosine taper of 10 % was applied on the signal to
remove the oscillations. All signals were bandpass-filtered
between 0.1 and 20 Hz, and then the Fourier spectra were
calculated for the three components. The spectra were
smoothed using the Konno and Ohmachi algorithm (1998)
Fig. 3 Location of microtremor and surface wave measuring sites (red circles both HVSR and MASW, white circle only MASW, yellow circle only HVSR)
Environ Earth Sci (2016) 75:1354
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Environ Earth Sci (2016) 75:1354
Fig. 4 Examples of spectral ratio (H/V) curves at six sites (esv, cmp-11, klm, e5-3, bsk-1 and bsk-2) in Fig. 3 labelled with white-colored letters
indicating the locations. Thick lines are the average HVSR values
with a smoothing constant value of 40. Subsequently, the
logarithmic average and the standard deviation were
obtained at each site for all spectral ratios in the frequency
range between 0.1 and 20 Hz.
The spectral ratios of six different sites at the study area
are shown in Fig. 4. The fundamental frequency (f0) and
the corresponding H/V amplitude at every site were estimated; the contour maps of f0 and H/V amplitude variations
are shown in Figs. 5 and 6. The fundamental frequencies
were determined to range from 1 to 11.5 Hz, and the
maximum H/V amplitude was six.
Surface wave analysis
The measurements of the surface waves were conducted at
34 sites (Fig. 3). The data were collected using the
12-channel geometrics Smartseis S-3000 seismograph and
the channel streamer (which consists of 4.5-Hz vertical
geophones). The spacing between each geophone was 5 m,
and the total length of the spread was 75 m. A 7-kg sledge
hammer source was used. The offset interval from the first
123
geophone was equal to 20 m. SeisImager/SW seismic
software was used for preprocessing, editing, visualization
and 1D/2D spectral analysis. The processing includes two
main steps: The first step is to calculate the dispersion,
namely the change in phase velocity with frequency, using
the Pickwin module [note: surface wave dispersion can be
significant in the presence of velocity layering, which is
common in the near-surface environment (SeisImager/SW
2005)]; the second step is to calculate the shear wave
velocity (Vs) profile by mathematical inversion (based on
the least square method) of the dispersive phase velocity of
the surface waves using the WaveEq module. The steps
involved in these calculations are presented for one site in
Fig. 7.
A thorough assessment of the shallow shear wave
velocity is crucial for earthquake hazard assessment studies
(Wald and Mori 2000). The average shear wave velocity of
the upper 30 m (Vs30) was calculated using the following
expression:
Vs 30 ¼ PN
30
i¼1
hi =vi
ð1Þ
Fig. 5 Fundamental resonance frequency map of the study area
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Fig. 6 Contour map of H/V amplitude ratio
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Phase Velocity, [m/s]
0
Distance, [m]
500
0
75
1500
1000
2000
b
a
Frequency, [Hz]
10
0.2
20
30
40
Frequency, [Hz]
0
10
15
20
25
30
35
45
40
Phase Velocity, [m/s]
50
c
1800
0.4
Time, [s]
5
S/N ratio
1400
1000
600
0.6
obtained
estimated
200
0.0
Vs Velocity, [m/s]
0
200
400
600
800
1000
1200
d
6
Depth, [m]
0.8
12
18
24
1.0
30
Fig. 7 Main steps of the MASW processing technique (data acquired from esv site)
where hi and vi denote the thickness (in meters) and shear
wave velocity, respectively, of the ith formation or layer,
with a total of N layers existing in the top 30 m.
Results and discussion
Because of the high rate of urbanization of Adapazarı,
many new buildings are being constructed in new residential areas, such as around the Sakarya University,
Esentepe Campus, and Serdivan and Beşköprü provinces.
In this study, we obtained the site effect parameters for
these new developing areas. A limited number of
researchers have studied the site parameters of the Sakarya
basin after the 1999 Izmit earthquake (Komazawa et al.
2002; Kudo et al. 2002; Ozel and Sasatani 2004; Siyahi and
Selçuk 2005; Ozcep et al. 2013; Firat et al. 2016). Our
study area is different than the study areas of these previous
researchers. We determined the fundamental frequency and
the site amplification using the H/V spectral ratio method
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and the shear wave velocities for the top 30 m using the
multichannel surface wave analysis method for the Sakarya
University, Esentepe Campus, and its environment. Next,
the average shear wave velocities for the top 30 m were
classified and mapped in accordance with the NEHRP site
classification code (Fig. 9).
The estimated values of the fundamental frequencies
range from 1.0 Hz up to 11.5 Hz at the study area. The
estimated value of the amplification factor ranges from
1.33 to 5.96 at the study area. The distribution of the
fundamental frequencies and the site amplifications at the
Sakarya University, Esentepe Campus, and its surroundings are shown in Figs. 5 and 6. The resonance frequency f0
varies from 4.5 to 11.5 Hz at the top of the hill of the
campus. The hillside has lower f0 values of less than 4 Hz.
The lower frequency values (1.0–2.0 Hz) were also
obtained at the D-100 highway and the south-southeastern
parts of the study area. We obtained the maximum
amplification (Amax * 6.0) at the Beşköprü district.
Although HVSR is usually considered to be a lower bound
for amplification estimations compared with other techniques, we obtained meaningful amplification values in this
study. This high amplification and low frequency region is
located in the valley between two hills at the southeastern
part of the study area. The valley has been filled with thick
sediment over time (personal communication, Ramazanoğlu 2013). On the other hand, the estimated value of the
amplification factor ranges from 1.4 to 3.6 in the other part
of the study area. The minimum amplification was obtained
at the top of the campus area (Fig. 6). The site amplification and fundamental frequency values we obtained are
very similar to the values obtained by Siyahi and Selçuk
(2005). They obtained amplification values of 4.7 and 5.7
at the Istiklal and Karaosman districts, respectively, where
heavy damage occurred because of the 1999 Izmit earthquake. They also obtained fundamental frequencies
between 0.7 and 9 Hz at the alluvial site using microtremor
data. This wide range of change indicates the rapid increase
of sediment thickness. Komazawa et al. (2002) found a
sedimentary cover thickness in the range of 1000–1500 m
for the Adapazarı basin using gravity anomaly data.
Ozel and Sasatani (2004) evaluated the S-wave amplification in the Adapazarı basin by using the traditional
spectral ratio method. These spectral ratios showed that the
S-waves are considerably amplified in the frequency range
of 0.5 to approximately 5 Hz at the basin sites but are
apparently damped at frequencies higher than approximately 10 Hz. They confirmed that the amplifications at
low frequencies are attributed to the thick sedimentary
layers in the Adapazarı basin and that apparent damping at
high frequencies is partly caused by the reference site
response. Parolai et al. (2001) stated that the resonance
frequency becomes lower in areas where the basement
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Environ Earth Sci (2016) 75:1354
depth is greater and higher where it is shallower. Accordingly, the presence of higher and lower values reflects the
variation in the thicknesses of sediments throughout the
area. We obtained similar results to the results of Ozel and
Sasatani (2004). We also obtained larger amplifications at
low frequencies for thick sediments and small amplification at high frequencies at the top of Esentepe Campus.
Ozel and Sasatani (2004) suggested that heavy damage in
downtown Adapazarı during the 1999 Izmit earthquake
was caused not only by strongly amplified S-waves but also
by the long-period basin surface waves of long duration.
Firat et al. (2016) obtained soil characteristics and depth
to engineering bedrock at the selected sites are different.
The observed level of structural damage at these sites
during the Izmit earthquake was also different. They found
the largest amplification for soil profiles is between 0.63
and 2.5 Hz. The highest peak ground acceleration is
obtained at the Yeni cami site.
Vs30 was accepted for site classification in the USA
(NEHRP) by the UBC (Uniform Building Code) in 1997
(Dobry et al. 2000; Kanlı et al. 2006) and also in the
Eurocode 8 (Sabetta and Bommer 2002; Sêco and Pinto
2002; Doğangün and Livaoğlu 2006; Sandikkaya et al.
2010). In order to reduce the earthquake hazard, it is very
important to select the correct areas for the new buildings.
In this study, we classified the average Vs30 values in the
upper 30 m of soil according to the NEHRP classification
code presented in Table 1. The results of the Vs profiles at
six sites (esv, cmp-11, kml, e5-3, bsk-1 and bsk-2) are
shown in Fig. 8. The hill zone at the top of the campus
(cmp-11) region has the highest velocity value compared to
that of the other regions. The average shear wave velocity
values range from 300 to 1120 m/s in the region (Fig. 9).
These velocity values show that the Esentepe Campus area
has a very thin sedimentary cover with high shear velocities, underlined by hard bedrock, except behind the Faculty
of Arts and Sciences area. Ramazanoğlu (2005) determined
a decomposed and blocked rock at depths in the range of
1.3–1.9 m and bedrock under this depth around the top of
the Esentepe Campus. In addition, the lower shear wave
velocities were observed along the D-100 highway and the
Table 1 NEHRP site classification
NEHRP
site class
Average shear wave
velocity to 30 m (m/s)
General
description
A
[1500
Hard rock
B
760–1500
Rock
C
360–760
Very dense soil
and soft rock
D
180–360
Stiff soil
E
\180
Soft soil
Environ Earth Sci (2016) 75:1354
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Fig. 8 Shear wave velocity profiles at six sites (esv, cmp-11, klm, e5-3, bsk-1 and bsk-2)
Beşköprü district. We determined three types of soil at the
Esentepe Campus and its surroundings: Type B soil
(1020–760 m/s), Type C soil (760–360 m/s) and Type D
soil (360–300 m/s). Type B soil (beneath the campus area)
was considered to be equivalent to engineering bedrock
(i.e., reference bedrock). A large fraction of the study
region corresponds to Type C soil. The alluvial basin
belongs to the D category, according to the NEHRP
standards.
Kudo et al. (2002) determined the S-wave velocity
structures at the Adapazarı basin using the spatial autocorrelation method (SPAC). They estimated the S-wave
velocity to be approximately 1000 m/s or higher on the
very hard soil at the SKR (40.737°N, 30.381°E) station,
whereas they estimated small S-wave velocities in the soft
layer (Vs of *230 m/s) and the intermediate hard layer (Vs
of *440 m/s) in the heavily damaged area of downtown
following the 1999 earthquake. The S-wave velocity values
obtained in this study are very similar to the values of Kudo
et al. (2002). We obtained a high S-wave velocity value
(1120 m/s) at the bedrock and a low S-wave velocity value
(300 m/s) at the soft soil in the study area. The Vs30 values
were used in the classification map of the Esentepe Campus
and the Serdivan and Beşköprü districts. The low S-wave
velocity region is considered to be at very high risk for
near-future earthquakes. Ozcep et al. (2013) investigated
the shear wave velocity distribution at the Adapazarı basin
using the MASW method. They also obtained amplifications using the reference station method and the fundamental periods using the single-station method at the
station sites (Imar, Toyata, Şeker, Hastane, Babalı and
Genç). They calculated the amplification and the fundamental periods at the Adapazarı basin range to be 1–8.4
and 0.1–1.1 s, respectively. They classified and mapped the
average shear wave velocities for the top 30 m in accordance with the Eurocode 8 standard. They found that
Hastane, Genç, Şeker and Babalı stations are located on
Type D sites, Toyota station is located on a Type C site,
and Imar is located on a Type B site. By comparing their
results to our results, we found lower amplifications values.
Although our study region is slightly different from those
of previous studies, high velocities are obtained at the rock
basin and low velocities are obtained at the alluvial and
soft basin in Adapazarı and its surroundings. Ozcep et al.
(2013) found that the amplifications obtained by Vs30 did
not agree well with the data from the observed earthquakes
in their study area. They highlighted the complex basin
structure of the region as the reason for their result. As
Ozel and Sasatani (2004) indicated, the Adapazarı basin is
characterized not only by considerable amplification of the
S-waves but also by long-period basin surface waves of
long duration. They noted that, in basin structures of this
type, Vs30 does not adequately represent amplifications
that occur under actual earthquake conditions. For this
reason, these types of complexity must be considered as
specific conditions in the seismic design codes.
The estimated fundamental frequencies together with
the site amplifications and the average shear wave velocities are shown in Fig. 10. We found that the parameters are
in agreement with each other. There is also a good correlation between cross sections AA0 and BB0 in Fig. 11. A
lower velocity area, i.e., a small part of the campus region
that is located behind the Faculty of Arts and Sciences area,
is examined in the cross section AA’. This small area
belongs to the D category according to the NEHRP standard. Beyond this area, the velocity values are higher
123
Fig. 9 Map showing average Vs30 variation in the study area obtained from the shear wave velocity profiles of sites shown in Fig. 3. Soil classification is given according to NEHRP site
classification
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Fig. 10 Fundamental frequencies together with spectral ratios (H/V) and the average shear wave velocities (Vs30)
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1000
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A'
A
800
800
Vs30
700
600
500
400
300
200
500
400
300
200
fo
9
11
Fundamental Frequency, [Hz]
Fundamental Frequency, [Hz]
A'
A
10
8
7
6
5
4
3
2
1
0
A'
A
3.0
1.8
1.4
1.0
0.6
0.2
B'
fo
9
8
7
6
5
4
3
2
1
0
B
B'
H/V
4.4
4.0
3.6
H/V ratio
2.2
B
10
4.8
H/V
2.6
H/V ratio
Vs30
600
0
0
3.4
B'
100
100
11
B
700
Vs 30 Velocity, [m/s]
Vs 30 Velocity, [m/s]
900
3.2
2.8
2.4
2.0
1.6
1.2
0.8
0.4
Fig. 11 Cross sections AA0 and BB0 for fundamental frequencies, spectral ratios (H/V) and average shear wave velocities (Vs30)
compared to those of soft soil. As a result, this study will
help in the selection of new residential areas during the
high rate of urbanization of Sakarya, Serdivan district.
Acknowledgments This study was partly supported by the Sakarya
University Research Fund (Project Number: 2010-01-14-004). We
thank the Geophysical Engineering students at Sakarya University for
their valuable support. We also thank the anonymous reviewers for
their constructive reviews and suggestions.
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