deprem Geliyorum Demez

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Geothermal reconnaissance of the
Marmara Sea region (NW Turkey): surface
heat flow density in an area of active
continental extension
Article in Tectonophysics · June 1998
Impact Factor: 2.87 · DOI: 10.1016/S0040-1951(98)00032-8
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2. iiii
TECTONOPHYSICS
I II III I
ELSEVIER Tectonophysics 291 (1998) 77-89
Geothermal reconnaissance of the Marmara Sea region (NW Turkey):
surface heat flow density in an area of active continental extension
Martin Pfister a,,, Ladislaus Rybach b, Sakir Simsek c
a GSF - Research Centrefor Environment and Health, Ingolst?idter Landstr. 1, D-85764 Neuherberg, Germany
bInstitute of Geophysics, ETH Hi~nggerberg, CH-8093 Ziirich, Switzerland
c UKAM, Int. Research Centerfor Karst Water Resources, Hacettepe Univ., Beytepe, TR-06532 Ankara, Turkey
Received 17 January 1997; accepted 19 May 1997
Abstract
Northwestern Anatolia is an area of significant neotectonic activity. The Northern Anatolian Fault splits into different
branches and the tectonic regime changes from translation to a combination of extension and translation. High seismicity
as well as frequent and in places large hot springs are related to these tectonic features. The present study aims at
characterising the geothermal situation of this area by detailed heat flow density mapping and thermal spring studies.
High-resolution temperature logs and measurements of rock thermal conductivity were used to determine the terrestrial
heat flow density. Because of the shallowness of the available drillholes (maximum depth of 200 m), hydraulic influences
on the thermal profiles had to be taken into account. Conductive heat flow density was calculated considering possible
convective effects due to vertical water movements. In spite of these hydraulic influences, the temperature distribution
showed stability over a time period of at least one year. Stationary models could therefore be applied. Terrestrial surface
heat flow density varies regionally from 35 to 115 mW/m 2, with a mean value of 60 mW/m 2. The heat flow density
map shows that the extensional tectonics of the region south of the Marmara Sea is characterised by higher heat flow
density values. Regions with low tectonic activity such as parts of European Turkey or regions with compressional and
translational tectonics have average or slightly lower values. The spatial pattern of thermal springs in the Marmara Sea
region does not coincide with the terrestrial heat flow density distribution. Their appearance is bound to neotectonic faults
(= locally enhanced vertical permeabilities). © 1998 Elsevier Science B.V. All rights reserved.
Keywords: surface heat flow density; thermal springs; active tectonics; convection; temperature log; NW Turkey
1.1ntroducfion
The Marmara Sea region of northwestern Turkey
is a tectonically extremely active area. Large and
also frequent earthquakes are triggered by the in-
fluence of the westward-moving Anatolian platform
along the Northern Anatolian Fault zone (NAF) and
*Corresponding author. Fax: +49 89 3187 3361; E-mail:
martin.pfister@gsf.de
the extensional part of the Aegean plate which com-
bine to form a transtensional tectonic regime. Up
to 23 strong earthquakes with magnitudes greater
than 5.9 have occurred in the Marmara area since
1899 (Ambraseys and Finkel, 1991). The continen-
tal crustal stretching forces of the region south of
the Marmara Sea acting today were determined to
cause strain rates on the order of 0.03 ppm/yr by
Straub and Kahle (1994, 1995) using GPS measure-
ments. The Mannara Sea itself seems to undergo
0040-1951/98/$19.00 © 1998 Elsevier Science B.V. All rights reserved.
PII S0040- 195 1(98)00032-8

3. 78
25°30 '
0.1MW
1.0MW
M. Pfister et al./Tectonophysics 291 (1998) 77-89
Istanbul
• Ooo
• • •
• •
70
iii I °- O
J
• • •
0
-%
0.0"
-
Fig. 1. Naturalthermalspringsof the MarmaraSea regionand the neotectonicregime.Circlesare proportionalto the energyoutputof
thermalspringsaccordingto Eq. 1.Neotectonicfaultlinesaccordingto Schindler(1997).
much larger extension, in the range of up to 0.12
ppm/yr.
Furthermore, huge thermal springs occur all over
the described region. Fig. 1 displays the distribution
of hot springs, which are classified by their thermal
energy output. This energy output is calculated using
outflow rate and temperature, the latter reduced by
the mean surface temperature of 16°C (Eq. 1).
E = (Tmeasured- - To)Qcp (1)
where E is thermal energy output (W), To is
mean surface temperature (16°(2, from Pfister, 1995),
T,~u~ is spring temperature (°C), c is heat capacity
of water (J/kg°C), p is water density (kg/m3), and Q
is outflow rate (l/s).
The entire region is covered by thermal springs,
but large hot springs with an energy output of sev-
eral megawatt occur in distinct areas only. Esti-
mates of the total thermal energy output from drill-
holes are about 100 MW (Simsek and Okandan,
1990) and, from natural thermal springs, about 60 to
130 MW (based on Pfister, 1995). Added together,
the possible amount of thermal energy output (230
MW) distributed over the investigation area (85,000
km2) corresponds to a theoretical convective heat
flow component of ca. 2.5 mW/m 2. Therefore, the
geothermal areas of northwestern Anatolia form sig-
nificant anomalies only locally.
The basic question about the thermal boundary
conditions, within the Earth's crust, of this geother-
mal potential has not yet been answered. Preliminary
investigations on terrestrial heat flow density distri-
bution have been documented by Tezcan and Turgay
(1991), Ilkisik (1995) and Tezcan (1995). All stud-
ies rely on estimates of rock thermal conductivity
as well as partly on estimates of the temperature
distribution in the underground. Generally all studies
obtained rather high values in the region south of
the Marmara Sea compared to the global average
continental heat flow density.

4. M. Pfister et al./ Tectonophysics 291 (1998) 77-89 79
The present study aims at characterising the
geothermal situation of this area by detailed heat flow
density mapping and geothermal modelling studies.
For these purposes, temperature profiles in shallow
drillholes (up to 200 m depth range) were measured.
Rock thermal conductivity from local samples were
also obtained. These two parameters permitted the
calculation of terrestrial heat flow density. Advec-
tive/convective heat transfer had to be considered by
means of Peclet-number analysis because of the shal-
low range of depth data. Temperature profiles of oil
wells partly permitted a comparison of deep and shal-
low heat flow densities. Thermal water wells and their
temperature profiles were interpreted by simple phys-
ical models based on vertical water movement over a
certain depth range and basal heat flow density values.
The study described below leads to a consistent
picture of the geothermal map considering all ob-
tained information about terrestrial heat flow density,
which is an indispensable boundary condition for
modelling geothermal processes in the uppermost
part of the Earth's crust.
2. Data acquisition
The search for available and suitable drillholes
was mainly made possible with the help of the
following national organisations with offices in dif-
ferent cities: the DSI (State Hydraulic Works) and
K6y Hizmetleri (Rural Services). A first selection
of unused or abandoned wells (which are especially
suitable due to the absence of disturbing water flow
caused by pumping) had to be checked by personal
field trips. Three field measuring campaigns during
the summers of 1991, 1992 and 1993 led to valu-
able temperature data for 44 shallow water wells.
The temperatures were recorded using two measure-
ment equipments with different resolutions: -4-0.I°C
and +0.02°C, respectively, and with different depth
sample intervals of 4 m and 0.1 m, respectively.
High-resolution temperature logging is described in
detail in Pfister and Rybach (1995, 1996). Nine se-
lected records are shown in Fig. 2, the complete
measurements are presented in Pfister (1995). The
selected data records show representatively the char-
10 16 18 20 22 24
0 0
50
100
150
12 14
1 1
50
100
150
10 12 14 16 18 20 22 24
temperature [°CI
Fig. 2. Selected temperature profiles (1-9) measured in shallow wells (line: high-resolution temperature logs; dots: low-resolution
temperature logs). Water movement is interpreted as the main cause for non-linear temperature increase with depth. Changes of thermal
conductivity of the underground are considered as secondary effects over these small depth ranges.

5. 80 M. Pfister et al./Tectonophysics 291 (1998) 77-89
0
10
20
30
E 40
0
50
60
70
' ' ' ' I ' ' ' ' I ' ' ' '
(a)
reducing gradient = 2°C/lOOm
14 15
reduced temperature [°C]
0
;0
(b)
~0
i0
1991
o 1992
reducing gradient: 2°C/lOOm
80 , L , , I , J I ' I
13 16 16.4 16.6 16.8
reduced temperature [°C]
Fig. 3. Repeated measurements of the temperature profile at two different drill sites, Soguksu (a) and Kite (b), both near the city ot'
Bursa. Note the stable conditions over one year (reduced temperature scale).
acter of the temperature profiles for shallow depths.
Water movement is interpreted as the main cause for
non-linear temperature increase with depth. Changes
in thermal conductivity of the underground are con-
sidered as secondary effects over these small depth
ranges. Most of the locations showed constant lithol-
ogy over the whole measurable depth range. Re-
peated measurements at the same drill sites were also
performed (Fig. 3). In spite of the hydraulic influ-
ences, the temperature distributions showed stability
over a time period of at least one year. Stationary
models could therefore be applied.
High-resolution digital temperature logging is
even able to resolve convection cells of the water
within the drillhole. Gretener (1967) as well as Di-
ment and Urban (1983) describe typical relationships
of such cells. Pfister and Rybach (1995) observed
and analysed convection cells in a well in north-
ern Switzerland. According to Diment and Urban
(1983), the cells show the following relation:
R = AG'a (2)
where R is maximal temperature difference within
the convection cell (°C), A is cell aspect ratio
(height/drillhole radius), G' is geothermal gradient
(°C/m), and a is drillhole radius (m).
Fig. 4 shows several temperature logs from the
study area with typical convection cell patterns de-
pending on drillhole diameter and temperature gra-
dient. The cell sizes show greater vertical dimen-
sions at larger well diameters, and larger temperature
ranges at higher geothermal gradients, as described
by Eq. 2.
Furthermore, temperature records from a total of
nine oil wells (data from the Turkish Petroleum
Agency, TPAO Ankara) reaching depths up to 2500
m were obtained. Fig. 5 shows temperature profiles
for five onshore wells digitised with a depth interval
of 25 m from analogue data on paper. These data, as
well as the BHT data of four other offshore wells,

6. M. Pfister et al./Tectonophysics 291 (1998) 77-89 81
Carik Koey,4.8°C/100m,6 '' Carik Koey,4.8°C/100m,8 '' Hacisungur,6.0°C/100m,8 '' Hacisungur,6.0°C/100m, 10''
76
78
8o
"O
82
84[,
14.40
:1oo? l
50 , i . . . .
52"
54
56
58
45 . .55
i . . . . i , • .66 1E68 A
14.00 14.05 14.10
40 . . . .
:[46[ 1
48
14.15 14.20
Mecidiye, l.0°C/100m,6'' Mecidiye, 1.0°C/100m,8 '' Selimiye,9.0°C/100m,6 '' Selimiye,9.0°C/100m,8 ''
621 ° -
4 A--l° -
t~.15 12.20 12.25
red. tcmpcraturc[°C]
461
481
501
52,
54
12.15
o A---4
o
A=I0
. . . . i .
12.20 12.25
red. temperature[°C]
,o 24 . . . . .
~5 95
red. temperature[°C]
• i . . . . i ,
52- ~ ~ AA-~
54
56
58
14.85 14.90
red. temperature[°C]
Fig. 4. Observations of convection cells in drillholes. The eight different graphs show convection cells which depend on the drillhole
radius a and the geothermal gradient G'. The temperature scale of each graph is reduced by the local geothermal gradient (indicated in
the top line). The drillhole site and name are indicated at the top of each figure (cf. Appendix B) and two examples of convection cell
sizes are plotted for each example (ellipses with axes corresponding to heights and temperature amplitudes). These convection cell sizes
are calculated by Eq. 2 for different values of A, 4 and 10. The measurements show a good agreement with the criterion of Diment and
Urban (1983) (see text).
were used to calculate mean geothermal gradients as
listed in Appendix A.
Temperature records from four thermal water
wells (data from the General Directorate of Min-
eral Research and Exploration, MTA Ankara) show
the strong influence of fast-rising water in hot spring
areas (compare Fig. 7). The accuracy of such records
lies in the range of +10°C, because measurements
were taken at the wellhead (mud data).
Rock samples from surface outcrops were col-
lected at the specific drill sites of the shallow wells.
Thermal conductivities of these samples were mea-
sured at ambient temperatures and water-saturated
conditions. Pribnow (1994) describes in detail dif-
ferent measuring methods. For our purposes, the
transient method of a heated line source (Carslaw
and Jaeger, 1959) was applied. This theory is easily
changed into a model of a heated line source over a
half space; the source temperature is compared to the
logarithm of heating time. Thermal conductivity ~. is
calculated according to Eq. 3 at large times t:
Q At
. . . . (3)
2zr AT
where L is thermal conductivity (W m -1 K-l), Q is
heat produced per unit line length and time (Wm -1
s-l), AT is measured temperature difference (K),
and At is time difference (s).

7. 82 M. Pfister et al./Tectonophysics 291 (1998) 77-89
0 i , i I i
1000
e~
-8
1500
I ' ' ' ' 1 ' ' '
o Kandamis-1
• Vakiflar-1
2000 v Maltepe-1 ~,
• Corlu-1
Karapuercek-1 •
2500 , , I , ~ ~ ~ I .... I ....
40 60 80 100
temperature[°C]
Fig. 5. Temperaturelogs of fiveoil wellsin Thrace.The logsare
digitisedwitha samplingintervalof 25 m fromanaloguedataon
paper.
An approximation of the heating curve according
to Erbas (1985), based on Blackwell (1954), is used
to calculate the final values of thermal conductivity.
Two equipments were used: a QTM and a TK04. The
sample size was typically ca. 9 cm in diameter with
a minimum thickness of 3 cm. Erbas (1985) gives
penetrating depths of 2 to 3 cm of the heat wave into
the sample size using a TK04.
The different lithologies show a wide range of val-
ues but group reasonably well (Fig. 6). Each dot in
the plot represents a different sample from one spe-
cific outcrop. Usually, up to ten measurements were
performed on each sample. The standard deviations
of the measurements range from +0.02 to +0.4 W
m -I K-j . Thermal conductivities of sandstones vary
strongly due to different salt and clay contents. Lime-
stones appear generally with higher values, granitic
rocks show intermediate values, whereas volcanic
rocks (andesites, ignimhrites and tuffites) yield lower
values.
The data set described above requires careful
analysis and special treatment of the temperature
data. The shallow underground, up to 200 m in
depth, is often dominated by groundwater flow. The
following section summarises the necessary calcula-
tion procedures to extract reliable information about
terrestrial heat flow density, even from severely dis-
turbed temperature logs.
3. Convective/advective heat transport by water
movement
Vertical terrestrial heat flow density is defined
according to Eq. 4, which is based on the physical
model of purely conductive heat transfer:
OT
q~ = -)~-- (4)
0z
where qz is terrestrial heat flow density (mW/m2),)~
is thermal conductivity (W K-1 m-l), and OT/Oz is
temperature gradient (°C/km).
In shallow depth ranges, this model is often vi-
olated: horizontally and vertically moving ground-
water can also easily transport heat. This effect can
be detected by the non-linearity of the measured
temperature profile. Three different cases of moving
groundwater and its influence on the temperature
profile are presented in Pfister and Rybach (1995,
1996): vertical groundwater flow in the environs of
the borehole, vertical water flow in a limited depth
range and vertical water flow within the borehole.
The three conceptual models were described accord-
ing to their mathematical solution. The main goal
of such a treatment is to obtain information about
conductive heat flow density at the deepest point of
the observed depth range.
Convective and/or advective vertical heat trans-
fer is considered here, regardless of whether this
fluid movement is caused by hydraulic gradients
(forced convection, 'advection') or by temperature-
dependent fluid densities leading to buoyancy (free
convection, 'convection').
Generally, the measured temperature profile is
simulated by the analytical solution of the specific
physical model. Then, terrestrial (conductive) heat
flow is determined by different approaches: either
by a linear regression of ln(qz) versus depth (z) in
case of vertical groundwater flow in the environs

8. M. Pfister et al. /Tectonophysics 291 (1998) 77-89 83
.,5
C)
5
4 •
3 • •
mm
2 m m
I
m m •
Sandstones
with silt and/or clay
5
43
2
1
Limestones
~5
0
E
5
Volcanic rocks
4
3
2 • •
¥
1
f,,
0
Granitic rocks ~"
Q
Metamorphic rocks
4
3 •
(3 (3
2
1
• Granite,Granodiorite • Quarzite, Schist
<) Monzonite, Amphibolite, © Greenschist,Serpentinite
Fig. 6. Thermalconductivitiesfor differentlithologiesof rocksamplesfromsurfaceoutcrops.
of the borehole; by varying the parameter 'heat
flow' until the simulated temperature profile fits the
measurement well in case of vertical water flow in
a limited depth range; or by varying the parameter
'geothermal gradient' until the model fit is satisfying
in case of water flow within the borehole (for details
see Pfister and Rybach, 1996). Appendix B lists
all the investigated drillholes, also indicating the
treatment method used to determine the undisturbed
heat flow density.
4. Interpretation of thermal drillholes
The thermal spring area of Armutlu on the Yalova
Peninsula was investigated and the hydrogeology and
geology of the region was documented by Eisenlohr
(1995). A thermal drillhole was deepened within the
spring area. Fig. 7 shows the measured temperatures
(dots), the lithology profile, outflow temperatures of
several springs and the analytical simulation of the
measured temperature profile.
The simulation was carried out using the model
of vertical water flow in a limited depth range as
mentioned above. A zone with a top at a depth of
150 m and a thickness of 50 m enables the water
to rise vertically and advective/convective as well
as conductive heat transport is possible over this
depth range. Above and below this zone, conductive
heat transport only takes place. Further model input
parameters are listed in Table 1.
The thermal water of the springs shows temper-
atures similar to those of the moving groundwater
at a depth of 150 to 200 m and apparently has its
origin outside of this depth range. Heat flow density

9. 84 M. Pfister et aL / Tectonophysics 291 (1998) 77-89
. . . . . . . . . . . . . .
200
400~ [~
5 0 0 . . . . I . . . . , . . . . , , , , , , , , Mieasehilas
0 20 40 60 80 100
Temperature (°C)
Fig. 7. Measured (symbols) and modelled (line) temperatures
of the Armutlu thermal water well. The depth of the zone
with vertical water movement is indicated by two parallel lines;
q0: surface heat flow (600 mW/m2); q~: basal heat flow (65
mW/m2).
• Travertine (4m)
Oriel (2m)
Diabase
Micaschists
Calcarcous
selaim
Table 1
Model input parameters for the Armutlu well simulation
Parameter Value
Darcy velocity 0.5 m/yr
Surface heat flow ca. 600 mW/m 2
Heat flow at 500 m depth 65 mW/m 2
Peclet-number - 2.2
Layer thickness with water flow 50 m
Thermal conductivity 2.0 W K-j m-l
Surface temperature 16°C
Depth of layer 150 m
is not elevated (65 mW/m2) below this upflow zone.
Above this zone, very high temperature gradients
of up to 30°C/100 m and therefore high conductive
heat flow density of up to 600 mW/m2 occur. As
a main conclusion it follows that the relatively fast
movement of groundwater in certain depth ranges is
able to transport heat near to the surface and enables
the building up locally of thermal springs where flow
paths to the surface are available.
5. Heat flow density map
A total of 44 shallow wells and their temperature
records were processed for heat flow density calcu-
lation (Appendix B). Constant gradients served for
heat flow density calculation according to Eq. 4 (def-
inition of heat flow density). Convective/advective
effects of the groundwater movement were consid-
ered according to the previously summarised 1D
physical models. Measured temperatures were sim-
ulated using these models over a depth range for
each log individually selected. At the base of such
observed/modelled depth intervals, heat flow density
was determined (listed in Appendix B, q~).
It must be emphasised here that the heat flow
density so determined characterises only near surface
conditions. In the heat flow signal, however, the
influence of integrated geological processes of the
deeper crust, and even the upper mantle of the Earth,
is present.
The data set of shallow heat flow built the base
for mapping by geostatistical methods. The kriging
method described below was used for isoline inter-
polation.
Semivariance analysis (Davis, 1986) describes the
spatial dependence of the heat flow density data
(q~). Values of two points with a distance larger
than a have no statistical relation to each other
(Fig. 8, semivariogram). This value a and the value
are used for kriging interpolation. A spherical model
according to Eq. 5 simulates the semivariogram (line
in Fig. 8).
(3hA (hA) 3)
Yha = cry. 2a 2a3 (5)
where a is span or range (0 geograph, length), or02
is variance (mW2/m4), A is 0.5° geograph, length
(42.5 kin), and h is 1, 2, 3 ...
The 44 heat flow density values (q~) were in-
terpolated using the kriging method with the pa-
rameters a = 150 kin, A = 0.5° (42.5 km) and
a2 = 3557 mW2/m4. The map of Fig. 9 contains
the 44 well locations with the specific heat flow
density values. The isolines delimit four intervals:
35-55 mW/m2, 55-75 mW/m2, 75-95 mW/m2
and 95-115 mW/m2. Analysis of oil wells in the
Thrace region (Appendix A and Fig. 5) reveals sim-
ilar ranges of values for this region. Temperature
gradients based on singular BHT data (Appendix A)
are very uncertain and cannot be used for heat flow
density calculations. The interpretation of thermal
well data (one example in Fig. 7) yields heat flow
density values (q~) which fit well into the regional
field. The histogram of the data from the 44 shal-

10. M. Pfister et al. / Tectonophysics 291 (1998) 77-89 85
40001 42.5 85 [km] 127.5 170 212.5
' ' ' i . . . . i . . . . i . . . . i . . . .
@
3000 spherical model
a = 1.75°, 0~o= 3557 mW2/m4
1000 •
O0 , , , , I , , , , I , , , , I , , , • l
1 2 3 4 5
hA [o east. length]
Fig. 8. Semivariogram for heat flow values from shallow depths. The line shows a spherical model, calculated with the values A = 0.5°
(42.5 km), a = 1.75" (150 km) and variance cr2 = 3557 mW2/m4 (dashed line).
I
47+1..8 57+1~). 33÷1-4 ::~ ~%
33+/-6 Q ......., Q
60+/~ 37.-6
, 56+/-4
30"
0
66+#16
70
Q
45+#12
45+/-10
Q
06 '/ %
"75 ~'
I0 30+1-5
%/(
,%
0
20+/-3
0
72+1-14
• 011wMll id~ wldll
(H~tmW~w) O (HWFk~
Oil wells thermalwells
{BXT- @ (Xwt Fk~
Grad~nt)
~lls
Fig. 9. Compilation of geothermal data of the Marrnara Sea region.

11. 86 M. Pfister et al. / Tectonophysics 291 (1998) 77-89
low wells shows a mean value of 60 mW/m 2 and a
variation range of 4-50 mW/m 2 (Fig. 7). The heat
flow density distribution of the Marmara Sea region
cannot be regarded as generally high. Only selected
areas show elevated surface heat flow densities of up
to 100 mW/m 2, such as regions south of the Mar-
mara Sea. The Thrace area (north of the Marmara
Sea), as well as the Istanbul and Bursa regions, are
characterised by normal values of up to 55 mW/m 2.
The near surface conditions provoke a further
thermal signal which has to be considered before
the interpretation of deeper processes. Recently new
thermal data from deep drillholes have become avail-
able, e.g. super deep drillholes in Russia (Kola, Ural)
or in Germany (KTB). Substantial differences be-
tween shallow and deep terrestrial heat flow data led
to reconsidering palaeoclimatic effects on the heat
flow data (IHFC, 1996). Considering these new find-
ings, a palaeoclimatic influence of up to 30% or even
60% in the shallow depth levels of the earth's crust
may be possible.
6. Conclusions
The compilation of geothermal data of the Mar-
mara region leads to the following conclusive reflec-
tions.
The described temperature measurements in shal-
low drillholes do not yield an ideal base for heat flow
calculations. The strong influence of water move-
ment on the temperature profile due to advective
and/or convective heat transport needs to be care-
fully considered in order to extract the undisturbed
heat flow density signal from the data. The determi-
nation of terrestrial heat flow density by data from
shallow depth ranges requires therefore detailed con-
siderations of the physical thermal transport model.
In following this procedure, no contradiction was
found between the shallow and deep heat flow data.
In the northern part of the investigation area, these
shallow values were confirmed by data from oil wells
within depths of up to 2500 m (Fig. 9).
The surface heat flow distribution of the Marmara
Sea region shows values ranging from 35 to !!5
mW/m 2, with a mean value of 60 mW/m 2. Two
different areas can be distinguished in Fig. 9: the part
south of the Marmara Sea with 75 to 95 mW/m 2 and
the other areas in the eastern and northern part of the
investigation area with up to 55 mW/m 2. Two differ-
ent heat flow regimes can be attributed to these areas
with different tectonic characteristics: increased val-
ues in the area south of the Marmara Sea correspond
to the general extensional tectonic regime of this
region (Straub and Kahle, 1994, 1995). Normal heat
flow values occur in the northern and eastern part of
the investigation area (Bursa, Iznik, Izmit and Thrace
regions), where stable or compressional components
appear in the tectonic regime (Crampin and Evans,
1986; Straub and Kahle, 1994, 1995).
On the other hand, the distribution of thermal
springs according to their energy output can not be
related to the terrestrial heat flow density field in the
area of investigation (Figs. 1 and 9). The occurrence
of the springs is much more bound to active tectonic
fault lines. Large thermal springs occur more fre-
quently where translational and extensional tectonics
appear together, within a so-called transtensional
tectonical regime.
These observations were confirmed by simple 1D
model calculations to simulate temperature depth
profiles of selected thermal wells (Fig. 7) in shallow
depth ranges. The lower boundary values (conductive
heat flow density qoo) of the 1D model approaches
fit well with the overall distribution of values de-
termined by the other nearby shallow measurements
(Fig. 9).
Northwestern Anatolia is characterised by normal
to locally elevated terrestrial heat flow density com-
pared to a normal value defined by the world-wide
continental mean value of 65 mW/m 2 (Pollack et
al., 1993). The abundance and distribution of hot
springs, especially the very large ones, and geother-
mal fields in this region can only be explained by
local zones of strongly elevated vertical hydraulic
permeability due to active transtensional faulting
of the crust. The importance, within this context,
of the combination of strike-slip and normal faults
(transtensional regime) will be further clarified and
confirmed by the ongoing interdisciplinary approach
of the Poly-Project Marmara (Schindler and Pfister,
1997).
Acknowledgements
We would like to thank the General Directorate,
as well as the local offices, of the state organisations

12. M. Pfister et al. / Tectonophysics 291 (1998) 77-89 87
DSI (State Hydraulic Works) and of K6y Hizmetleri
(Rural Services) in different cities of northwestern
Anatolia for their kind collaboration. For three years
they allowed us free access to drillholes convenient
for our purposes. We also thank the General Direc-
torate of MTA (Mineral Research and Exploration).
Thanks are also due to all our partners working with
us on the Marmaraproject. We are especially grateful
to Prof. R. HOtter,ETH Vice-President for Research,
for his continuing help and support in many aspects
of this Poly-project. Fruitful discussions with Ch.
Clauser (Hannover, Germany) and Th. Kohl (Ziirich,
Switzerland) were helpful for various scientific as-
pects of our work.
Appendix A
Temperature gradients (°C/100 m, with standard deviations), stratigraphy, respective thermal conductivities (W m-I K-l , with standard
deviations) and calculated heat flow values (mW/m2, with standard deviations) of oil wells in the Thrace region, in the Marmara and
Aegean Sea
East. long. North. lat. Name Gradient Stratigraphy Thermal conductivity Heat flow
(°) (o)
26.9806 41.2252 Karaptircek 1 2.05 + 0.06 Oligocene 2.3 4- 0.3 47 4- 8
27.8759 41.1005 Corlu 1 2.71 4- 0.13 Oligocene 2.3 4- 0.3 62 4- 12
26.7108 41.0214 Maltepe 1 2.01 4- 0.17 Eocene 3.1 4- 0.2 62 4- 10
27.2328 41.1197 Kandamis 1 1.42 4- 0.02 Oligocene 2.3 4- 0.3 33 4- 5
27.6633 41.265 Vakiflar 1 2.46 4- 0.04 Oligocene 2.3 4- 0.3 57 4- 8
28.2859 40.6835 Marmara 1 2.6 4- 0.9 (BHT) ? ? ?
28.1851 41.0524 Kmarmara 1 3.2 4- 1.0 (BHT) ? ? ?
26.8099 39.5107 Edremit 1 3.2 4- 1.1 (BHT) ? ? ?
26.1919 40.5266 Saros 1 8.24-? (BHT) ? ? ?
Appendix B
Characteristics of 44 wells: number (No.) and coordinates of well location (East. long. and North. lat.); location name (Name); model of
heat flow calculation (Method): F = vertical groundwater flow in the environs of the borehole, B = vertical water flow in a limited depth
range, R = water flow within the borehole, G = linear gradient model (Eq. 4); observation interval length in depth scale (Int.), depth of
heat flow determination (Depth), thermal conductivity value (~.) and heat flow value (q) (both with standard error)
No. East. long. North. long. (o) Name Method Int. Depth ~ 4- tr q 4- tr
(°) (°) (m) (m) (W/K m) (mW/m2)
2 28.8765 40.1982 Kite R 80 140 2.0 4- 0.5 52 4- 15
3 29.4382 40.1059 Ineg61 F 120 130 2.0 4- 0.5 89 4- 22
5 28.9618 40.2522 Linyitleri F 76 96 3.5 + 0.6 88 4- 15
7 29.1588 40.2579 Kazikli G 46 96 2.0 4- 0.5 60 4- 19
11 29.0632 40.2703 Demirtas F 70 80 2.0 4- 0.5 26 4- 7
12 29.0800 41.0300 Ist. Cam. G 80 100 3.0 4- 0.2 37 4- 6
13 27.9060 39.6239 ~aiyrhisar F 120 140 2.0 4- 0.5 80 4- 20
15 27.9700 39.6700 K6seler G 110 130 2.0 4- 0.5 64 4- 18
18 27.6559 40.1802 G/Snen G 72 112 2.0 4- 0.5 130 4- 33
21 27.5926 40.0541 G6n. Bal~i F 30 40 2.0 4- 0.5 48 4- 12
22 27.9441 40.3029 Bandirma F 40 50 2.0 4- 0.5 51 4- 13
25 27.1588 40.2455 Biga G 30 40 2.0 4- 0.5 54 4- 17
101 28.4706 40.0495 Mustafak. B 28 84 3.5 4- 0.6 113 + 19
104 29.1118 40.3986 Ask. Vet. G 21 85 2.0 4- 0.5 17 -t- 10
t06 29.9294 40.2860 ~umali G 15 25 2.9 4- 0.2 65 4- 8
107 29.6941 40.3604 Mecidiye G 30 70 3.0 4- 0.2 30 4- 5
108 29.2020 39.7030 Ok~ular B 30 70 1.6 4- 0.2 20 4- 3

13. 88
Appendix B (continued)
M. Pfister et al./Tectonophysics 291 (1998) 77-89
No. East. long. North. long. (°) Name Method Int. Depth )~4- cr q 4- cr
(°) (°) (m) (m) (W/K m) (mW/m2)
109 29.3353 40.4234 Akharim G 20 76 2.0 4- 0.5 26 4- 7
110 29.4471 40.2027 Soguksu B 22 72 2.6 4- 0.3 56 4- 6
118 27.4448 39.4910 Iv. Kayapa B 62 102 3.2 4- 0.2 96 4- 6
119 27.8309 40.2613 (~arik F 80 90 2.3 4- 0.2 102 5:9
120 28.2971 39.4820 Turfullar G 110 120 1.7 + 0.2 75 4- 9
131 28.8460 41.2160 Kisirm. B 56 96 1.8 + 0.2 47 4- 15
136 27.9383 41.2590 Velikty B 12 68 1.9 4- 0.2 33 + 4
140 27.9324 39.6802 Anad. Lis. B 74 84 2.0 4- 0.5 70 4- 18
142 27.9015 39.4730 Selimiye G 86 96 1.7 4- 0.2 166 4- 20
150 26.3350 40.3190 Yolagzi F 90 100 2.0 4- 0.5 73 4- 23
201 27.4844 39.1977 Saricalar G 50 150 1.9 4- 0.2 55 4- 10
203 28.8235 40.5205 Armutlu B 70 80 2.5 4- 0.5 67 4- 14
206 30.2664 40.9099 Kaymaz B 10 45 3.1 -4-0.2 55 4- 4
207 28.0698 39.7703 Kiirse G 58 68 1.5 4- 0.2 45 4- 10
208 28.5000 39.6081 ~amkty F 45 75 3.3 4- 0.2 39 4- 3
209 27.9441 39.5135 Inkaya G 48 78 1.9 4- 0.2 95 4- 15
210 27.4882 40.5495 Ekinlik Ada G 30 50 2.7 4- 0.2 84 + 15
211 27.2063 39.0946 Bergama B 30 100 2.0 + 0.5 45 4- 12
212 30.0500 40,4750 Pamukova G 20 60 2.0 4- 0.5 20 4- 16
213 30.4375 40.9369 Findikli G 60 100 3.1 4- 0.2 66 4- 16
214 29.4048 40.9414 Akfirat B 63 78 3.1 4- 0.2 56 4- 4
215 28.6988 41.2000 Tasoluk F 130 150 2.3 4- 0.2 60 4- 6
216 28.5151 41.0360 Tiirkobasi B 110 145 1.9 -4-0.2 50 4- 5
217 27.0521 41.0428 Ytrgiiq G 45 75 2.0 4- 0.5 48 4- 15
218 27.5452 41.1104 Kepeneldi B 35 165 1.9 4- 0.2 43 4- 5
219 26.8692 39.2500 Besiktepe G 15 115 1.8 4- 0.3 75 4- 15
220 30.7460 40.589 Samanpaz. G 20 40 1.6 4- 0.2 72 ± 14
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