S-WAVE RECEIVER FUNCTION IMAGE OF THE CENTRAL NORTH ANATOLIAN FAULT ZONE

by

Hande E. Adiyaman

A Prepublication Manuscript Submitted to the Faculty of the

DEPARTMENT OF GEOSCIENCES

In Partial Fulfillment of the Requirements

for the Degree of

MASTER OF SCIENCE

In the Graduate College

THE UNIVERSITY OF ARIZONA

2010

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S-wave Receiver Function Image of the Central North Anatolian Fault Zone

SUMMARY

The North Anatolian Fault (NAF), which accommodates the westward escape of the Anatolian

plate, is a young transform boundary forming an active deformation zone along the northern part

of Turkey. In this study the lithospheric scale deformation beneath the central portion of the

North Anatolian Fault Zone (NAFZ) and the northern part of central Anatolia is investigated by

applying S-wave receiver function analysis. The data used in this study is from the North

Anatolian Fault passive seismic experiment. The S-wave receiver function method is applied

using 56 teleseismic events recorded on 39 broad-band seismic stations.

We calculated individual receiver functions at each station and then applied CCP processing to

identify crustal and lithospheric scale discontinuities. The Moho depth is interpreted as 35-40 km

beneath the region. A negative arrival is prominent in most of the receiver functions indicating

the top of a low velocity region varying between 80 -100 km. A significant offset in crustal

thickness or lithospheric scale structure is not observed along or across the NAFZ. Our

interpretation is that there is very thin lithosphere beneath the region and the low velocity region

in the upper mantle is asthenosphere.

Key words: Continental lithosphere, Seismic discontinuities, S-wave receiver function analysis,

North Anatolian Fault Zone.

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1. INTRODUCTION

The North Anatolian Fault (NAF), located in northern Turkey, is one of the largest active

continental strike-slip faults on Earth and forms the northern margin of the Anatolian plate

(Barka 1996; Piper 1997; Sengor 2005; Stein 1997). The tectonics of the Anatolian region is

controlled by the motions of the northward moving African and Arabian plates with respect to

the relatively stable Eurasian plate as shown in Figure 1 (Ambraseys, 1998; Cavazza, 2003;

Jimenez-Munt, 2002; McClusky, 2000). The convergence of these plates led to the closure of the

Neo-Tethyan Bitlis ocean and plate tectonic re-organizations around 11 Ma, which led to the

formation of the NAF (Facenna, 2006; Sengor 1979; Sengor and Natal’in, 1996; Keskin, 2008).

The northern and southern blocks of the fault zone contain different geologic units, therefore

identifying the differences across and along the fault zone is important in understanding its

structure. The geology of the northern block consists of Triassic subduction accretionary

complexes and sedimentary sequences, and the southern block consists of Neogene and Tertiary

deposits and volcanics, accretionary complexes, granites and metamorphic rocks (Figure 2)

(Boztug, 2008; Dhont et al., 1998; Keskin et al., 2008; Okay and Tuysuz, 1999).

This study focuses on the central portion of the North Anatolian Fault Zone (NAFZ) which is

approximately a 1400 km long transform boundary with mostly continental basement structure to

its north and subduction-accretion material to its south (Kocyigit A. 1991; Sengor et al. 2005).

Many destructive earthquakes such as the 1999 Ms=7.4 Izmit earthquake occurred along the

right lateral NAF, which has an average slip rate of 20-24 mm/yr (Barka, 1996; Hearn, 2002;

Hubert-Ferrari, 2002; Kozaci et al., 2007; McClusky, 2000; Provost et al., 2003; Stein et al.,

1997; Yavasoglu, 2006) and an estimated total offset of 75-125 km (Armijo et al. 1999; Barka,

2000; Bektas, 2007; Hamiel, 2007; Sengor, 1979; Westaway, 1994).

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Understanding the characteristics of the crustal and lithospheric structure beneath a continental

transform fault zone is essential in understanding its tectonic development. The aim of this study

is to look at the discontinuity structures beneath the region such as the crust-mantle boundary

(Moho) and the lithosphere-asthenosphere boundary (LAB). Despite the geological work at the

surface (Boztug, 2006; Okay, 2006; Tuysuz, 1999), the deeper structure of the NAFZ is

relatively unknown and it one of the first studies to investigate the scale and structure of seismic

discontinuities in the underlying central-north Anatolian lithosphere. The studies on the central

part of the North Anatolian Fault mainly focus on the surface geology and tectonic evolution of

the region. The deep structure of the fault zone is relatively unknown. Correlating the results for

the deep structure of the NAF with existing studies for the region and surrounding areas will

contribute to an understanding of the crustal and lithospheric structure of the fault zone and

surrounding region. The six major lithospheric fragments in Turkey are described as the

Strandja, Istanbul and the Sakarya Zones, the Anatolide-Tauride Block, Kırsehir Massif, and the

Arabian Platform by Okay and Tuysuz, 1999. The central part of the NAFZ includes parts of the

Istanbul zone, Central Pontides and the Kirsehir Massif (Figure 1). As the NAFZ cross-cuts the

ophiolitic suture between the Pontides and the Anatolides, it is thought to be active since the

closure of the northern branch of the Neo-Tethys in the late Cretaceous (Andrieux, 1995;

Stampfli, 2000).

According to Facenna et al (2006), the Tethyan slab broke off under the eastern Anatolia

collisional belt. The slab detachment propagated westward to the eastern end of the Hellenic arc

resulting in an increase of the slab pull force on the Hellenic trench (Facenna et al. 2006). The

indentation of the continent in eastern Anatolia led to the Miocene-Pliocene re-organizations in

the Anatolia-Aegean region permitting the lateral escape of material towards the west and the

formation of the NAF. The dextral faulting activity migrated during the late Neogene resulting in

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a simple and narrow fault zone today (Andrieux, 1995). The geology of the region shows the

juxtaposition of different fragments that came together during the latest subduction and collision

events in and around the area. The complex tectonic history and the active tectonics motivated us

to look at the deeper structure. Our goal is to image the fault zone beneath our seismic array to

look for any correlation between the deeper structure and the surface tectonics.

Receiver functions, which are time series computed from three-component seismic data that

isolate the receiver side response, are commonly used to detect the crustal or lithospheric seismic

discontinuities (Cakir 2000; Kumar 2005; Hansen 2007; Heit 2008; Li 2004; Rychert 2005;

Soudoudi 2009; Vinnik 2007; Wilson 2005; Yuan 2006; Zhu 2000). We used S-wave receiver

functions to study NAFZ. The S-to-P converted phases, which arrive before the S-wave is free of

reverberations, making it possible to isolate the seismic discontinuities. The depth converted S-

wave receiver functions from the NAF array provides some of the first images of the crustal

thicknesses and lithospheric scale structure beneath central North Anatolian Fault Zone and the

surrounding region.

2. DATA AND METHOD

The S-wave receiver function analysis is applied by using the data from the NAF Passive

Seismic Experiment (Biryol et al., 2010). We deployed 39 broad-band seismometers on multiple

transects across the fault and its major splays during the summers of 2005 and 2006 (Figure 3).

The seismic instruments were provided by the Incorporated Research Institutions for Seismology

(IRIS) Program of Array Seismic Studies of the Continental Lithosphere (PASSCAL)

Consortium. The array recorded regional and global earthquakes continuously at 40 samples per

second during a 2 years period.

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The S-wave receiver function (SRF) method isolates the S-to-P (Sp) conversions from seismic

discontinuities beneath a station. A converted Sp phase is generated when an incoming S phase

crosses a velocity discontinuity beneath a seismic station and is converted to a P wave. The SRFs

represent a response of the Earth’s medium in the vicinity of the station from the excitation of

teleseismic S waves. As the converted P leg of the ray travels with a higher velocity than the

direct S leg, S-to-P converted phases arrive at the receiver prior to the S wave onset, while the

multiple reverberations appear after the S onset (Figure 4).

Boundaries such as the lithosphere- asthenosphere transition, which are often obscured in the P

receiver functions by crustal multiple reverberations arriving in the same time interval, can thus

be better observed in the S receiver functions (Hansen et al., 2007; Heit et al., 2008; Kumar et

al., 2005; Li et al., 2004, 2007; Vinnik et al., 2004). Converted Sp phases from shallow

discontinuities (like crust-mantle and lithosphere- asthenosphere boundaries) are best observed at

epicentral distances between 60-85 degrees (Hansen et al., 2007; Wilson et al., 2005). The

method to compute S-wave receiver functions involves coordinate rotation and deconvolution.

The aim in applying S-wave receiver functions is to be able to map the deeper structure of the

region and to detect any changes across or along the fault that correlates with the different

tectonic units in the vicinity. We use the method of Hansen et al., (2007) for SRF processing.

The events were chosen between epicentral distances of 60-75 degrees. We processed 300

earthquakes from 2 years of data and found 56 events with magnitudes larger than 5.5 that could

be used for receiver function analysis (Table 1; Figure 3). As a first step each seismogram is

investigated carefully and S-waves with high signal-to-noise ratios are chosen among

earthquakes with magnitudes larger than 5.5 and epicentral distances between 60-75 degrees.

The direct S-arrival is picked after applying coordinate rotation (from the N-E-Z to the R-T-Z

coordinate system) to the waveforms. In order to clearly identify the converted phases the data is

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cut 100 s before and 20 s after the S-wave arrival. Then the data is rotated into the SH-SV-P

coordinate system. In the next step, deconvolution is applied using Hansen’s (2007) algorithm

which uses Ligorria and Ammon’s (1999) iterative deconvolution. The SV component is

deconvolved from the P component and S-wave receiver functions are calculated. The Gaussian

width factor a, which controls the frequency content of the receiver functions (Hansen 2007;

Ligorria and Ammon, 1999), is taken as 1. A Gaussian width factor of 1 is suitable for the SRFs

as they have lower frequency content than PRFs (Hansen 2009; Ligorria and Ammon 1999).

After the deconvolution the S-wave energy on the P-component is minimized in order to obtain

the converted P phase more clearly. The receiver functions are calculated at each individual

station and normal move-out correction with a reference P-wave slowness of 6.4 s/deg is applied

to the SRFs. In order to be able to directly compare to the P-wave receiver functions, the SRFs

are time flipped and multiplied by -1. The timing and amplitude of the arrivals in the S-wave

receiver function are related to the velocity structure. Positive amplitude arrivals indicate

velocity contrasts with velocity increasing downwards, while negative amplitude arrivals

indicate that the velocity decreases with depth.

The S-wave receiver functions are time-stacked at each station and then migrated to depth using

a P-wave velocity of 6.2 km/s above 40 km and 8.1 km/s below 40 km, and a constant Vp/Vs

ratio of 1.78 (Figure 5). To see the whole structure beneath the study area, cross-section plots are

created using the depth migrated SRFs. We also used the Common Conversion Point (CCP)

stacking method of Gilbert (2006) to make cross-sections (Figure 6). The receiver functions are

sampled using 20 km bin spacing and again a Vp/Vs ratio of 1.78, and Vp of 6.2 km/s and 8.1

km/s for above and below 40 km respectively. The cross sections are used to identify the Moho

and the character of the upper mantle down to 200 km depth (Fig. 6). Figure 7 shows a map of

the depth to Moho for our study region. SRF technique has been commonly used in previous

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studies for identifying the lithospheric thickness (Hansen 2007; Farra and Vinnik 2000; Kumar

2005; Li 2004; Mohsen 2006; Oreshin et al., 2002; Rychert et al., 2005; Wilson et al., 2005) and

also crustal thickness (Yuan 2006). In this study the crust-mantle boundary is clearly observed as

a positive arrival beneath the entire region followed by a broad negative arrival that is prominent

in most of the receiver function indicating the presence of a low velocity zone beneath the study

area.

3. RESULTS AND DISCUSSION

3.1 The Moho

The SRF results indicate a strong Moho beneath central NAF. A prominent Moho arrival can be

observed at most of the stations at 4-5 sec corresponding to an average crustal thickness of 35-

40 km assuming a crustal velocity of 6.2 km/s and a Vp/Vs ratio of 1.78 (Table 2; Figure 5a-b).

The results do not indicate a distinctive offset in the Moho structure across or along the NAF

zone, assuming a constant Vp/Vs ratio and crustal velocity. The depth to Moho obtained from

depth migrated stacks are listed in Table 2. In most of the S-wave receiver functions obtained

from the listed stations (Table 2) there is a positive arrival around 5 sec corresponding to a

crustal depth of ~35 km. Previous studies using P-wave receiver functions (PRF) also report

similar crustal thicknesses in or around our study area. Park and Levin (2001) present PRF

results from the Global Seismographic Network (GSN) station ANTO which is also in our study

area. The Moho depth from their study is approxiamtely 35-40 km. Cakir et al. (2000) used a

Turkey broad-band seismic station TBZ, which is located north-east of NAF array, to process

PRFs. They modeled the crustal structure and found the crustal thickness beneath TBZ to be 32-

40 km. Ozacar et al. (2009) presented their preliminary PRF results using the same data from the

NAF array and found a crustal thickness of 35-40 km similar to our results.

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Figure 6 shows the CCP stacks of four E-W and N-S profiles. The arrivals from Moho can be

clearly identified from these cross-sections. Figure 7 shows a map of the depth to Moho

determined from the SRF stacks. The Moho depth is fairly consistent throughout the entire

region as shown in the crustal thickness map (Figure 7). A significant change in crustal thickness

across the profiles is not observed, suggesting that NAF is not offsetting the Moho beneath this

region.

3.2 The Upper Mantle

By applying the S-wave receiver function method, we are also looking for deeper discontinuities

beneath the Moho in the central NAF and surrounding region. Phases with negative amplitudes

are detected in most of the stacks. There are two sets of negative arrivals which are at

approximately 80 km and at 100 km (Figure 5a and 6b). Although these negative arrivals are

observed at most of the stations, the sharpness of the phases varies for different stacks and there

is no continuous structure that can be interpreted as a simple lithosphere-asthenosphere boundary

beneath the region (Figure 6). The discontinuous image of the negative arrivals and the broad

character of the negative arrival suggest a gradient with a thin or no lithospheric lid. Below the

broad double low velocity zone is a positive arrival indicating an increase in velocity at ~160-

180 km depth. Four E-W and N-S profiles are shown in Figure 6. Other CCP stacking profiles

are shown in Appendix A.

The deep signature of the fault zone is not evident in the SRF results. In Table 2 the negative

arrivals between 10-15 sec are listed for each station used in the study. The negative phases on

the receiver functions are the lithospheric arrivals from approximately 80 and 100 kms. Previous

studies by Biryol et al (2010) and Gans et al (2009), which also use the NAF project data, also

suggests that NAFZ lacks a deep-seated signature. However recent tomography results show a

vertical structure down to 200 km at the northwestern part of our array (Biryol et al., 2010b).

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Gans etal (2009) has used Pn tomography to look at the Pn velocity structure of the region and

concluded that either the fault doesn’t offset the Moho or it does not penetrate deep into the

mantle. Biryol etal (2010) suggests from SKS splitting results, which are uniform across the fault

zone, that NAFZ doesn’t have a deep signature extending into the mantle (Biryol et al., 2010b).

There are two possibilities for the broad low velocity zone in the upper mantle (Figure 8 a and

b): 1) There is almost no mantle lid and the asthenosphere is near the base of the crust. 2) There

is a thicker lithosphere and the low velocity region is a complex structure within the lithosphere.

Based on recent tomography studies (Biryol etal., 2010b) in the region and the geologic history

we suggest that case 1 is the most likely.

4. CONCLUSION

We use S-wave receiver functions to image the Moho and discontinuities in the upper mantle

beneath the central portion of the North Anatolian Fault and surrounding regions. The SRFs

indicate a sharp and continuous crust-mantle boundary (Moho) extending beneath the fault zone

with no observed offset of the NAF at the Moho. Prominent negative arrivals are observed at 80-

100 km in most receiver functions. The negative arrivals at 80 and 100 km depths beneath the

region suggest a broad LVZ below the Moho. We propose two possibilities for the broad low

velocity zone in the upper mantle: 1) There is almost no mantle lid and the asthenosphere is near

the base of the crust. 2) There is a thicker lithosphere and the low velocity region is a complex

structure within the lithosphere. In conclusion, NAF is a newly forming active continental fault

zone and it doesn’t have a deep signature in the SRFs beneath its convex central portion. Our

preferred interpretation is that there is very thin or no lid beneath our study region and the

asthenosphere is near the base of the crust.

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Figure 1. Tectonic map of the study area (Anatolian Plate) and surrounding regions (African,

Arabian and Eurasian plates). Tectonic structures and faults are shown with white lines. Tethyan

sutures are shown with gray lines (modified from Okay and Tuysuz 1999). Plate velocities with

respect to the stable Eurasian plate are shown with filled arrows (Barka and Reilinger 1997;

McClusky 2000; Reilinger et al. 1997). The seismic stations of the NAF array are shown as blue

triangles. EAFZ: East Anatolian Fault Zone; NAFZ: North Anatolian Fault Zone.

Figure 2. Map of broadband seismic station locations (yellow stars) and geologic units within

the study area (modified from Okay and Tuysuz, 1999). NAFZ: North Anatolian Fault Zone.

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Figure 3. Map of the NAF seismic array of 39 broad-band stations. Tectonic structures and

faults are shown with white lines. Tethyan sutures are shown with red lines (modified from Okay

and Tuysuz 1999). The teleseismic earthquakes used in this study are shown at the top right

corner. Blue filled circles show the good events and red filled circles show the bad events. The

seismic stations of the NAF array are shown as blue triangles. EFZ: Ezinepazari Fault Zone;

NAFZ: North Anatolian Fault Zone.

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A

B

C

Figure 4. A. Raypaths of direct S, P, P to S and S to P converted phases from the crust-mantle

boundary with assumed velocities of Vp= 6.5 km/s and Vs=3.75 km/s for crust; and Vp=8.0

km/s and Vs=4.47 km.s for the mantle. B. Simplified synthetic S-wave receiver function

showing the Sp converted phases from the crust-mantle (Moho) and lithosphere-asthenosphere

boundaries (LAB) and the later arrivals (multiples). Direct S-wave is marked on the record as

black dashed line C. Synthetic S-wave receiver function reversed in time and multiplied by -1 in

order to be directly comparable to PRFs. (Modified from Sodoudi, 2005)

S-wave

S-wave

Multiples removed

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Figure 5a. Stacked S-wave receiver functions for each station on the NAF array. Cross sections

of North-South profiles of receiver function stacks are shown at the top. Cross sections of East-

West profiles of receiver function stacks are shown at the bottom. A P-wave velocity of 6.2 km/s

above 40 km and 8.1 km/s below 40 km, and a constant Vp/Vs ratio of 1.78 are used for

stacking. Red (positive) arrivals are from the Moho discontinuity and the blue (negative) arrivals

are possible structures in the lithosphere.

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Figure 5b. Profiles of the individual stacked receiver functions. EFZ: Ezinepazari Fault

Zone, NAFZ: North Anatolian Fault Zone, IAESZ: Izmir-Ankara-Erzincan Suture Zone.

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Figure 6. A. Map showing cross-section locations. B. CCP stacked cross sections of the S-wave

receiver functions. 4 N-S profiles (pink lines) and 4 E-W profiles (dark blue) are shown on the

regional map of stations (top left).

19

Figure 7. Moho thickness map of the Central North Anatolia region calculated from the S-wave

receiver functions. Contours show the depth in km. Dashed blue lines are suture zones (Okay and

Tuysuz, 1999). EFZ: Ezinepazari Fault Zone, NAFZ: North Anatolian Fault Zone, IAESZ:

Izmir-Ankara-Erzincan Suture Zone, IPS: Intra-Pontide Suture, ITS: Inner-Tauride Suture.

20

Figure 8. Different interpretations of the results are shown in two different velocity models. Model A

shows the negative arrival at 80 km, which indicates 80 km thick lithosphere and a complex LAB

structure. Model B shows a complex lithospheric structure with the LAB deeper than 180 km.

21

Table 1. List and properties of earthquakes used in this study.

Event Date Origin Time Latitude Longitude Depth (km) Magnitude

1 7/5/2005 1:46:30 1.9 97.1 21 6.7

2 7/11/2005 14:30:37 1.32 97.2 23.1 5.5

3 7/24/2005 15:35:41 7.93 92.15 10 7

4 8/16/2005 2:41:40 38.27 141.99 52.8 7.2

5 9/6/2005 10:55:22 0.08 97.62 30 5.7

6 10/15/2005 10:01:29 46.9 154.16 39.2 6.1

7 1/31/2006 19:10:11 2.74 96.06 10 5.9

8 2/3/2006 20:27:32 11.9 92.37 10 6

9 2/22/2006 22:12:51 -21.22 33.32 10 6.9

10 4/1/2006 9:57:16 22.91 121.2 10 6.1

11 4/20/2006 23:19:41 61.09 167.1 43 7.7

12 4/21/2006 11:08:54 61.39 167.53 39.5 6.1

13 4/25/2006 18:20:43 2.05 97 37.6 6.1

14 4/29/2006 16:52:49 60.66 167.43 10 6.3

15 5/16/2006 15:22:59 0.07 97.01 1.9 6.8

16 5/22/2006 11:06:38 60.75 165.88 11.1 6.6

17 7/27/2006 11:11:09 1.76 97.17 30 6

18 7/28/2006 7:35:04 24.14 122.55 21.2 6.1

19 8/11/2006 20:48:36 2.37 96.32 10 6

20 8/17/2006 15:15:17 46.58 141.86 32.3 5.6

21 8/24/2006 21:45:33 51.16 157.49 57.8 6.5

22 9/30/2006 17:45:33 46.42 153 22.6 6.3

23 10/9/2006 9:56:33 20.66 120.04 10 6

24 10/10/2006 23:53:26 37.24 142.71 30.1 6

25 10/13/2006 13:42:57 46.34 153.22 10 6

26 11/15/2006 21:17:39 47.34 154.1 22.9 6.2

27 11/16/2006 6:15:43 46.36 154.5 18.2 6.1

28 12/1/2006 3:52:30 3.49 99.09 215.5 6.3

29 12/7/2006 19:05:44 46.27 154.35 10.4 6.3

30 12/22/2006 19:44:07 10.68 92.39 45 6.1

31 12/26/2006 12:21:08 21.81 120.53 10 7.1

32 3/6/2007 5:44:10 -0.53 100.53 30 6.1

33 3/7/2007 10:47:57 1.95 97.89 30 5.9

34 3/11/2007 7:04:26 44.12 147.84 10 6.1

35 3/22/2007 6:04:30 -3.39 86.78 21 5.9

36 3/25/2007 0:36:52 -20.6 169.41 35 7.2

37 4/7/2007 9:46:00 2.93 95.74 30 5.7

38 4/27/2007 7:56:45 5.33 94.61 30 6.3

39 5/16/2007 8:49:43 20.47 100.7 38.1 6.1

40 6/2/2007 21:28:06 23.03 101.02 10 6

41 7/3/2007 8:20:40 0.71 -30.24 10 5.9

42 7/16/2007 6:32:46 37.49 138.41 59.6 5.8

43 8/20/2007 22:37:12 8.51 -40.16 10 6.5

44 12/22/2007 12:20:30 2.09 96.86 35 5.8

45 1/22/2008 17:09:18 0.93 97.46 12.8 6.2

46 2/8/2008 9:33:08 10.7 -41.88 10 6.8

47 2/20/2008 8:02:36 2.75 95.97 34.3 7.5

48 2/24/2008 14:41:07 -2.31 100.02 35 6.6

49 2/25/2008 8:31:19 -2.37 100.02 35 7.3

50 2/25/2008 18:00:49 -2.36 99.92 35 6.7

51 2/25/2008 20:57:03 -2.21 99.86 35 6.9

52 2/26/2008 18:13:24 -3.79 101.05 53.5 5.8

53 3/3/2008 2:32:11 -2.16 99.83 35 6.5

54 3/3/2008 9:26:17 46.57 153.04 35 6.4

55 3/3/2008 13:44:41 19.94 121.39 22 5.8

56 3/29/2008 17:25:05 2.94 95.3 10 6.3

22

Table 2. Station list with depths of converted arrivals at each station derived from S-wave

receiver function processing.

# Station All

Traces

Best

Traces

Moho

Sec

Moho

km

Lithosphere

Arrival sec

Lithosphere

Arrival km

1 ALIC 25 7 5 35 13 100

2 ALIN 38 5 5 35 - -

3 ALOR 14 4 - - - -

4 ARSL 17 5 5 35 12.5 96

5 BAGB 19 4 5 35 11.5 88

6 BEDI 29 19 5 35 15 broad

7 BEKI 29 20 5.7 40 - -

8 CAKM 10 7 - - - -

9 CALT 17 4 5.1 36 14.3 110

10 CAYA 7 5 5.7 40 broad

11 CRLU 7 6 - - 10.4 80

12 CUKU 11 4 5.7 40 broad -

13 DERE 5 3 3.7 26 - -

14 DOGL 9 4 - - - -

15 DUMA 8 4 5 35 broad 75-90

16 EKIN 15 3 5 35 broad 85

17 GOCE 7 5 - - - -

18 HASA 15 5 5 35 10.4 80

19 INCE 16 6 5 35 11.7 90

20 ISKE 8 4 4.2 30 - -

21 KARA 6 4 5.7 40 12.35 95

22 KGAC 10 6 4.4 31 broad 85-100

23 KIZIK 8 5 5 35 broad 100

24 KUZO 23 10 5.1 36 broad 100

25 OGUR 6 4 5 35 broad 90-110

26 PELI 13 6 5.2 37 15.6 120

27 SEYH 18 8 5 35 broad 120

28 SYUN 10 6 4.8 34 12.5 96

29 TEPE 18 9 5.2 37 broad 85-120

30 YIKI 9 6 7.5 52.5 11 85

1

APPENDIX A: CCP Stack Cross Sections

The east-west (E-W) and north-south (N-S) profiles are prepared by using Common Conversion

Point (CCP) stacked receiver functions, which are sampled using 20 km bin spacing and a Vp/Vs

ratio of 1.78, and Vp of 6.2 km/s and 8.1 km/s for above and below 40 km respectively. The

cross sections are used to identify the Moho and the character of the upper mantle down to 200

km depth. In the cross-sections red areas indicate positive amplitude arrivals and blue areas

indicate negative amplitude arrivals. The related profiles are shown in the region map below.

2

E-W Profiles

Profile 5

Profile 6

3

4

5

6

7

N-S Profiles

8

9

10

11

12

13