DETERMINING THE DEFORMATIONS IN WESTERN ANATOLIA WITH GPS AND GRAVITY MEASUREMENTS

Transcription

1 DOKUZ EYLÜL UNIVERSITY GRADUATE SCHOOL OF NATURAL AND APPLIED SCIENCES DETERMINING THE DEFORMATIONS IN WESTERN ANATOLIA WITH GPS AND GRAVITY MEASUREMENTS by Ayça ÇIRMIK November, 2014 İZMİR

2 DETERMINING THE DEFORMATIONS IN WESTERN ANATOLIA WITH GPS AND GRAVITY MEASUREMENTS A Thesis Submitted to the Graduate School of Natural and Applied Sciences of Dokuz Eylül University In Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy in Geophysical Engineering by Ayça ÇIRMIK November, 2014 İZMİR

3 Ph.D. THESIS EXAMINATION RESULT FORM We have read the thesis entitled DETERMINING THE DEFORMATIONS IN WESTERN ANATOLIA WITH GPS AND GRAVITY MEASUREMENTS completed by AYÇA ÇIRMIK under supervision of PROF. DR. ZAFER AKÇIĞ and we certify that in our opinion it is fully adequate, in scope and in quality, as a thesis for the degree of Doctor of Philosophy. Prof. Dr. Zafer AKÇIĞ Supervisor Prof. Dr. Mustafa AKGÜN Prof. Dr. Hasan SÖZBİLİR Thesis Committee Member Thesis Committee Member Prof. Dr. Ferruh YILDIZ Doç. Dr. Oya PAMUKÇU Examining Committee Member Examining Committee Member Prof.Dr. Ayşe OKUR Director Graduate School of Natural and Applied Sciences ii

4 ACKNOWLEDGMENTS The GPS data (stations of CORS-TR project and General Command of Mapping) were obtained by Dokuz Eylul University Scientific Research project, 2012.KB.FEN.126. First of all, I would like to thank my supervisor, Prof. Dr. Zafer AKÇIĞ for his helps and advices on Ph.D. thesis and Assoc. Prof. Dr. Oya PAMUKÇU for her suggestions, helps and encouraging and being near me whenever I need during my all graduate career. I would like to thank members of Ph.D. committee, Prof. Dr. Müjgan ŞALK and Prof. Dr. Hasan SÖZBİLİR and members of examining committee, Prof. Dr. Ferruh YILDIZ and Prof. Dr. Mustafa AKGÜN for their advices for improving the thesis. I am grateful and would like to thank Asst. Prof. Dr. Tolga GÖNENÇ for his advices and lots of helps. I would like to thank Assoc. Prof. Dr. Muzaffer KAHVECİ for introducing me with GPS measurements and for his advices on processing GPS data. I would like to thank Prof. Dr. Carla BRAITENBERG for her advices and helps on my research when I was at Trieste University as an Erasmus exchange student and Jean CHERY for helping me numerical modeling when I was at Montpellier University. I would like to thank Assoc. Dr. Uğur DOĞAN for improving my knowledge about geodesy by following his graduate lesson at Yıldız Technical University, Department of Geomatic Engineering. I would like to thank Prof. Dr. Bradford Hager for helping me on my research and improving myself by following his graduate lessons when I was at MIT as the Council of Higher Education scholar. I would like to thank Prof. Dr. Thomas HERRING and Dr. Bob KING for their precious advices and answering my questions about GAMIT/GLOBK software, patiently. I am grateful to Asst. Prof. Dr. Mickael BONNIN for his helps on processing on ADELI software. I would like to thank Assoc. Prof. Dr. Mehmet ERGIN and other members of The Scientific and Technological Research Council of Turkey (TUBITAK), Marmara Research Center, Earth and Marine Science Institute iii

5 for helping on providing the GPS data of TURDEP project. I would like to thank the project manager, Assoc. Prof. Dr. Oya PAMUKÇU and all researchers of TUBITAK project, No:108Y285 for allowing me to use the GPS results of the project. I would like to thank my professors and colleagues at Dokuz Eylül University, Departments of Geophysical and Geological Engineering. I wish to thank all members of Student Affairs Department of Dokuz Eylul University, Graduate School of Natural and Applied Science for answering to all my questions patiently during graduate career. Finally, but at the top of the list, I thank my dear parents, Sevil & Muammer YURDAKUL and my dear brother Tolga YURDAKUL for encouraging me at all my life and being near and helping me in my long academic career. I thank my dear mother-in-law Semra ÇIRMIK for creating a study environment during the writing of my thesis. I thank my dear husband Ömer for his unwavering support and encouragement, not just during the writing of this thesis, but throughout my undergraduate and graduate career. Finally, I wish to thank my dear son Yiğit ÇIRMIK for being the meaning of my life. I wish to dedicate my thesis to my dear family. Ayça ÇIRMIK iv

6 DETERMINING THE DEFORMATIONS IN WESTERN ANATOLIA WITH GPS AND GRAVITY MEASUREMENTS ABSTRACT Western Anatolia is one of the most seismically active and rapidly extending regions in the world and is currently experiencing an approximately N S continental extension. Due to this important case of Western Anatolia, deformations of the region were examined by GPS and gravity measurement in this study. Firstly, the GPS stations of TURDEP poject, CORS-TR Project and General Command of Mapping were processed relative to Eurasia fixed frame and the velocities of the stations were found as approximately mm per year. Besides, the Anatolian Block and Aegean block solutions the velocity magnitudes were obtained between approximately 3-15 mm per year. As second step, the GPS and microgravity data, which were obtained simultaneously at 6 points; Akhisar (Manisa), Eşme (Uşak), Çal (Denizli), Bademli (İzmir), Borlu (Manisa), Karacasu (Aydın), were compared for discussing about vertical mass changes on the measurement points. As third step, obtained GPS velocities by using GAMIT- GLOBK software were compared with the modeled GPS velocities by Coulomb 3.3 software on the northern normal fault of Gediz graben and southern normal fault of the Büyük Menderes graben by using Coulomb 3.3 software and coulomb stress changes were obtained for these faults and compared with earthquakes. As the last step, the numerical models were created by using finite elements for determining the deformation of Western Anatolia during the geological time scales. As a result, all the results were compared with the previous geophysical and geological studies and earthquake focus depth distributions. Keywords: Western Anatolia, GPS, gravity, coulomb stress changes, numerical modeling, finite elements. v

7 BATI ANADOLU BÖLGESİNDEKİ DEFORMASYONLARIN GPS VE GRAVİTE ÖLÇÜMLERİ İLE BELİRLENMESİ ÖZ Batı Anadolu dünyadaki sismik olarak çok aktif ve ani açılma gösteren bölgelerden biridir ve halen yaklaşık K-G yönünde kıtasal açılma göstermektedir. Batı Anadolu bölgesinin bu önemli durumundan dolayı, bu çalışmada bölgedeki deformasyonları irdelemek için GPS ve mikrogravite ölçümleri kullanılmıştır. İlk olarak TURDEP, TUSAGA-AKTİF ve Harita Genel Komutanlığı ndan temin edilen GPS verileri Avrasya sabit çözümler ile proses edilmiş, yılda yaklaşık mm'lik hızla hareket ettiği saptanmıştır. Ayrıca, rejyonel deformasyonu gözlemlemek için Ege ve Anadolu blok çözümleri yapılmıştır ve istasyonların hız değişimleri yaklaşık yılda 3-15 mm olarak saptanmıştır. İkinci adımda, 6 noktada Akhisar (Manisa), Eşme (Uşak), Çal (Denizli), Bademli (İzmir), Borlu (Manisa), Karacasu (Aydın), eşzamanlı olarak alınmış GPS ve mikrogravite verileri, düşey yöndeki kütle değişimini irdelemek için birlikte değerlendirilmiştir. Üçüncü adımda, Gamit-Globk yazılımı ile elde edilen GPS hızları ile Coulomb 3.3 yazılımıyla modellenen GPS hız verileri Gediz grabeninin kuzeyindeki normal fay ve Büyük Menderes Grabeninin güneyindeki normal fay için birlikte değerlendirilmiş ve bu faylardaki Coulomb stres değişimi elde edilmiştir. Son olarak jeolojik dönemler boyunca Batı Anadolu bölgesindeki deformasyonu incelemek için sonlu elemanlar yöntemi ile bölgeye ait sayısal modelleme yapılmıştır. Sonuç olarak, bu çalışmada elde edilen tüm bulgular, çalışma alanında yapılmış jeofizik ve jeolojik çalışmaların sonuçlarıyla ve deprem odak derinlik dağılımları ile karşılaştırılmıştır. Anahtar Kelimeler: Batı Anadolu, GPS, gravite, coulomb stres değişimleri, sayısal modelleme, sonlu elemanlar. vi

8 CONTENTS Page THESIS EXAMINATION RESULT FORM... ii ACKNOWLEDGEMENTS... iii ABSTRACT....v ÖZ... vi LIST OF FIGURES... x LIST OF TABLES... xix CHAPTER ONE INTRODUCTION... 1 CHAPTER TWO GEOLOGY OF THE STUDY AREA... 4 CHAPTER THREE DEFORMATION ESTIMATIONS WITH GPS PROCESSING The Segments of GPS The Space Segment The Control Segment The User Segment Reference Coordinate System of GPS Earth-Centered Inertial (Space-fixed) (ECI) Coordinate System Earth-Centered Earth-Fixed (ECEF) Coordinate System World Geodetic System-1984 (WGS-84) Sources of Errors Ephemeris (Orbital Position) Errors Satellite and Receiver Clock Errors Atmospheric Effects Selective Availability Multipath Receiver Antenna Phase Center Error vii

9 3.4 Differential Observations Based on GPS Measurements Single Differences Double Differences Triple Differences The Principle of GPS Measurement The Principle of Phase Measurement Data Processing Steps Processing: The Three-Step Method Pre-Processing Steps Processing Steps Processing Steps of GAMIT Program Processing Steps of GLOBK Program The Applications Other Relatively Solutions Anatolian Block Solutions Aegean Block Solutions CHAPTER FOUR ANALYZING MASS CHANGES OF WESTERN ANATOLIA BY USING MICROGRAVITY AND GPS DATA Applications GPS data Processing Comparison of GPS and Microgravity Results CHAPTER FIVE - COULOMB STRESS CHANGES CALCULATIONS Applications Northern Normal Fault of Gediz Graben Southern Normal Fault of Büyük Menderes Graben The Relative Calculations on Study Area viii

10 CHAPTER SIX - NUMERICAL MODELING Physical Problem (continuum) and Equilibrium Equations Constitutive Laws Elastoplasticity Viscoelasticity General Algorithm of the Finite Element Modeling Software (ADELI) Applications CHAPTER SEVEN - CONCLUSIONS REFERENCES ix

11 LIST OF FIGURES Page Figure 2.1 Simplified tectonic map of Turkey showing major neotectonic structures and neotectonic provinces. Red square shows the study area... 4 Figure 3.1 GPS segments... 9 Figure 3.2 The space segment of GPS Figure 3.3 The control segment of GPS Figure 3.4 Sources of signal interference Figure 3.5 General classifications of GNSS Positioning methods Figure 3.6 Principle of GPS phase measurement Figure 3.7 The GPS stations are located Western Anatolia Figure 3.8 The GPS stations which used in the study are shown in general tectonic structures map of Western Anatolia Figure 3.9 The IGS stations which used in processing are shown by red circle Figure 3.10 The processing solutions of AYD1 for the days between 180th-195th of the years between Figure 3.11 The processing solutions of BALK for the days between 180th-195th of the years between Figure 3.12 The processing solutions of CESM for the days between 180th-195th of the years between Figure 3.13 The processing solutions of DEIR for the days between 180th-195th of the years between Figure 3.14 The processing solutions of DENI for the days between 180th-195th of the years between Figure 3.15 The processing solutions of HARC for the days between 180th-195th of the years between Figure 3.16 The processing solutions of IZMI for the days between 180th-195th of the years between Figure 3.17 The processing solutions of KIKA for the days between 180th-195th of the years between x

12 Figure 3.18 The processing solutions of MUGL for the days between 180th-195th of the years between Figure 3.19 The processing solutions of SALH for the days between 180th-195th of the years between Figure 3.20 The processing solutions of USAK for the days between 180th-195th of the years between Figure 3.21 The processing solutions of AKHT for the days between 180th-195th of the years between Figure 3.22 The processing solutions of BDMT for the days between 180th-195th of the years between Figure 3.23 The processing solutions of BORT for the days between 180th-195th of the years between Figure 3.24 The processing solutions of CALT for the days between 180th-195th of the years between Figure 3.25 The processing solutions of ESMT for the days between 180th-195th of the years between Figure 3.26 The processing solutions of IZMT for the days between 180th-195th of the years between Figure 3.27 The processing solutions of KRCT for the days between 180th-195th of the years between Figure 3.28 The processing solutions of KRPT for the days between 180th-195th of the years between Figure 3.29 The processing solutions of TRBT for the days between 180th-195th of the years between Figure 3.30 WRMS values for North-East-Up directions from combination of TURDEP and CORS-TR projects stations for 2009, 2010 and Figure 3.31 WRMS values for North (N)-East(E)-Up(U) directions from combination of IGS for the days between 180th-195th of 2009, 2010 and Figure 3.32 The processing solutions of BAYO for 261st and 262nd days of 2000, 211st and 212nd days of 2001, 123rd and 124th days of xi

13 Figure 3.33 The processing solutions of CEIL for 271st and 272nd days of 2000, 211st and 212nd days of Figure 3.34 The processing solutions of CKOY for 208th and 209th days of 2001, 212nd and 213rd days of Figure 3.35 The processing solutions of EMET for 271st and 272nd days of 2000, 123rd and 124th days of Figure 3.36 The processing solutions of LTFY for 89th day of 2000, 97th and 297th days of 2001 and 157th and 158th days of Figure 3.37 The processing solutions of YENF for 258th and 259th days of 2000, 214th and 215th days of Figure 3.38 The processing solutions of ZEYT for 211st and 212nd days of 2001, 212nd and 213rddays of Figure 3.39 WRMS values for North-East-Up directions from combination of General Command Mapping stations for 2000, 2001, 2004 and Figure 3.40 WRMS values for North-East-Up directions from combination of IGS stations for 2000, 2001, 2004 and Figure 3.41 GPS horizontal velocities and their 95% confidence ellipses in a Eurasia fixed reference frame for the period of for TURDEP and CORS-TR stations which are shown by red vectors and for the period of and 2005 for General Command Mapping stations which are shown by green vectors Figure 3.42 a) GPS horizontal velocities of the study McClusky et al. (2000) for the period and GPS horizontal velocities of the TUBITAK project No:108Y285 for the period with 95% confidence ellipses in a Eurasia fixed frame are added to the study area stations given in Figure Figure 3.42 b) The stations which were given at Figure 3.42.a were separated to4 regions Figure 3.43 a) The velocity field with 95% confidence ellipses of the stations computed in Anatolian block frame from 3-year (2009, 2010 and 2011) GPS data xii

14 Figure 3.43 b) The stations are grouped to 3 regions and shown by red shapes. Line A shows the boundary of North Anatolian Region (NAR). Line B shows the separation of the group 1 and Figure 3.44 Geological map of Western Anatolia and its surrounding Figure 3.45 The velocity field with 95% confidence ellipses of the stations computed in Aegean fixed reference frame from 3-year (2009, 2010 and 2011) GPS data Figure 4.1 a) General tectonic of the Turkey NAFZ: North Anatolian Fault Zone, WAEP: Western Anatolian Extensional Zone EAFZ:Eastern Anatolian Fault Zone. b) The locations of GPS and microgravity stations Figure 4.2 WRMS repeatabilities of North-East-Up values from combination of 2007, 2008 and 2009 GPS data Figure 4.3 The daily processing results (between the days 139th and 142nd) of AKHT stations between the years 2007 and Figure 4.4 The daily processing results (between the days 139th and 142nd) of BORT stations between the years 2007 and Figure 4.5 The daily processing results (between the days 139th and 142nd) of ESMT stations between the years 2007 and Figure 4.6 The daily processing results (between the days 139th and 142nd) of CALT stations between the years 2007 and Figure 4.7 The daily processing results (between the days 139th and 142nd) of BDMT stations between the years 2007 and Figure 4.8 The daily processing results (between the days 139th and 142nd) of KRCT stations between the years 2007 and Figure 4.9 GPS horizontal velocities and their 95% confidence ellipses in a Eurasiafixed reference frame for the period of Figure 4.10 a) Gravity changes of AKHT stations between the years b) Displacement changes on vertical direction of AKHT stations between the years Figure 4.11 a) Gravity changes of BDMT stations between the years b) Displacement changes on vertical direction of BDMT stations between the years xiii

15 Figure 4.12 a) Gravity changes of KRCT stations between the years b) Displacement changes on vertical direction of KRCT stations between the years Figure 4.13 a) Gravity changes of BORT stations between the years b) Displacement changes on vertical direction of BORT stations between the years Figure 4.14 a) Gravity changes of CALT stations between the years b) Displacement changes on vertical direction of CALT stations between the years Figure 4.15 a) Gravity changes of ESMT stations between the years b) Displacement changes on vertical direction of ESMT stations between the years Figure 4.16 The Earthquakes distributions which occurred between the years Figure 4.17 a) Topographic map of study area b) The blue lines show the crosssections Figure 4.18 a) The topographic changes along to cross-section A-A' b) Earthquake distributions along to S-N direction near to AKHT station. Small Red square shows the location of the station Figure 4.19 a) The topographic changes along to cross-section B-B' b) Earthquake distributions along to S-N direction near to BDMT station. Small Red square shows the location of the station Figure 4.20 a) The topographic changes along to cross-section C-C' b) Earthquake distributions along to S-N direction near to KRCT station. Small Red square shows the location of the station Figure 4.21 a) The topographic changes along to cross-section D-D' b) Earthquake distributions along to S-N direction near to BORT station. Small Red square shows the location of the station Figure 4.22 a) The topographic changes along to cross-section E-E' b) Earthquake distributions along to S-N direction near to CALT station. Small Red square shows the location of the station xiv

16 Figure 4.23 a) The topographic changes along to cross-section F-F' b) Earthquake distributions along to S-N direction near to ESMT station. Small Red square shows the location of the station Figure 5.1 The axis system used for Coulomb stresses calculations of on optimum failure planes Figure 5.2 The parameters of fault geometry Figure 5.3 GPS velocities of North stations (AKHT, BORT, ESMT and CALT) and South stations (TRGT and SALH ) relative to each other Figure 5.4 Blue vectors represent the obtained GPS velocities by Gamit/Globk and red vectors represent modeled GPS velocities by Coluomb Figure 5.5 The view of stress control panel of Coulomb 3.3 software for calculating Coulomb Stress Changes for the northern normal fault of Gediz Graben at 6 km depth Figure 5.6 a) Coulomb stress changes between the depth of 0-4 km b) Earthquake focus distributions on the study area. USGS earthquake archive was used between the years Figure 5.7 a) Coulomb stress changes at depth 4 km b) Earthquake focus distributions on the study area. USGS earthquake archive was used between the years Figure 5.8 a) Coulomb stress changes between the depth of 0-6 km b) Earthquake focus distributions on the study area. USGS earthquake archive was used between the years Figure 5.9 a) Coulomb stress changes at depth 6 km b) Earthquake focus distributions on the study area. USGS earthquake archive was used between the years Figure 5.10 GPS velocities of North stations (AYD1, BDMT and CALT) and South stations (KRPT, KRCT and DENI ) relative to each other Figure 5.11 Blue vectors represent the obtained GPS velocities by Gamit/Globk and red vectors represent modeled GPS velocities by Coluomb Figure 5.12 The view of stress control panel of Coulomb 3.3 for calculating Coulomb stress Changes for the Southern normal fault of Büyük Menderes Graben at 3 km depth xv

17 Figure 5.13 a) Coulomb stress changes between the depth of 0-3 km b) Earthquake focus distributions on the study area. USGS earthquake archive was used between the years Figure 5.14 a) Coulomb stress changes at 3 km depth b) Earthquake focus distributions on the study area. USGS earthquake archive was used between the years Figure 5.15 a) Coulomb stress changes between the depth of 0-5 km b) Earthquake focus distributions on the study area. USGS earthquake archive was used between the years Figure 5.16 a) Coulomb stress changes at 5 km depth b) Earthquake focus distributions on the study area. USGS earthquake archive was used between the years Figure 5.17 GPS velocities of left side stations (KIKA, AKHT and TRGT shown by black vectors) and right side stations (DEIR, BORT, USAK and ESMT shown by red vectors) relative to each other Figure 5.18 GPS velocities of left side stations (KIKA, AKHT and TRGT shown by black vectors) and right side stations (USAK and ESMT shown by red vectors) relative to each other Figure 5.19 GPS velocities of left side stations (KIKA, AKHT, TRGT, DEIR and BORT shown by black vectors) and right side stations (USAK and ESMT shown by red vectors) relative to each other Figure 5.20 GPS velocities of left side stations (BDMT, AYD1 and KRPT shown by black vectors) and right side stations (CALT, KRCT and DENI shown by red vectors) relative to each other Figure 6.1 a) The model of elastoplastic material b) The deformation of elastoplastic material due to stress Figure 6.2 a) The model of viscoelastic material b) The behavior of the viscoelastic solid Figure 6.3 The simple model created with 'gmsh' Figure 6.4 The view of 3D meshing with 'gmsh' Figure 6.5 The view of initial model. Green arrows represent the extensional forces were given the borders xvi

18 Figure 6.6 The view of finite strain (deviatoric epsilon) of model after 0.7 Myr Figure 6.7 The view of finite strain (deviatoric epsilon) after 1.1 Myr Figure 6.8 The view of the profile length of the numerical model Figure 6.9 The initial view of the model Figure 6.10 The topographic cross-section of the study area Figure 6.11 Crust-mantle interface values Figure 6.12 The temperature distributions on model after 5 Myr for 200K-500K Figure 6.13 The finite strain field on model after 5 My for 200ºK-500ºK Figure 6.14 a) The velocity fields on model after 5 Myr for 200ºK-500ºK Figure 6.14 b) The velocity field with vectors on model after 5 Myr Figure 6.15 The temperature distributions on model after 10 Myr for 200K-500K 144 Figure 6.16 The finite strain field on model after 10 My for 200ºK-500ºK Figure 6.17 a) The velocity fields on model after 10 Myr for 200ºK-500ºK Figure 6.17b) The velocity fields with vectors on model after 10 Myr for 200ºK- 500ºK Figure 6.18 The temperature distributions on model after 15 Myr for 200ºK-500ºK Figure 6.19 The finite strain fields on model after 15 Myr for 200ºK-500ºK Figure 6.20 a) The velocity fields on model after 15 Myr for 200ºK-500ºK Figure 6.20b) The velocity fields with vectors on model after 15 Myr for 200ºK- 500ºK Figure 6.21 The temperature distributions on model after 5 Myr for 273K-773K Figure 6.22 The finite strain fields on model after 5 Myr for 273ºK-773ºK Figure 6.23 a) The velocity fields on model after 5 Myr for 273ºK-773ºK Figure 6.23b) The velocity fields with vectors on model after 5 Myr for 273ºK- 773ºK Figure 6.24 The temperature distributions on model after 5 Myr for 273ºK-900ºK 150 Figure 6.25 The finite strain fields on model after 5 Myr for 273ºK-900ºK Figure 6.26 a) The velocity fields on model after 5 Myr for 273ºK-900ºK Figure 6.26b) The velocity fields with vectors on model after 5 Myr for 273ºK- 900ºK Figure 6.27 Temperature distributions on model after 5 Myr for 273ºK-1400ºK xvii

19 Figure 6.28 The finite strain fields on model after 5 Myr for 273ºK-1400ºK Figure 6.29 a) The velocity fields on model after 5 Myr for 273ºK-1400ºK Figure 6.29 b) The velocity fields with vectors on model after 5 Myr for 273ºK- 1400ºK Figure 6.30 The finite strain fields on model after 5 Myr for 273ºK-900ºK with Pa Figure 6.31The velocity fields on model after 5 Myr for 273ºK-900ºK with 0.e125 Pa xviii

20 LIST OF TABLES Page Table 3.1 The coordinates and observation days of the stations Table 3.2 The coordinates and observation days of the General Command of Mapping Stations Table 3.3 The Coordinates of IGS stations which used in the processing Table 3.4 Horizontal GPS velocities of TURDEP and CORS-TR projects stations in a Eurasian fixed frame and 1-σ uncertainties Table 3.5 Horizontal GPS velocities of General command Mapping stations in a Eurasian fixed frame and 1-σ uncertainties Table 3.6 Euler Vectors Relative to Eurasia Table 4.1 Horizontal GPS velocities of study area sites in a Eurasian fixed frame and 1-σ uncertainties Table 4.2 Correlation coefficients of GPS and gravity observation results Table 6.1 Physical parameters used in the numerical modeling xix

21 CHAPTER ONE INTRODUCTION Western Anatolia is one of the most seismically active and rapidly extending regions in the world and is currently experiencing an approximately N S continental extension since at least Miocene time (Şengör et al., 1985; Yılmaz et al., 2000). Due to this important case of Western Anatolia, deformations of the region were examined by GPS and gravity measurement in this study. Firstly, in the second chapter, the geological settings of the study area were given briefly. In the application sections, in chapter three, the basic information of Global Positioning System and data processing steps of GAMIT/GLOBK software were explained. The GPS stations of TURDEP project, CORS-TR project and General Command of Military were processed by using GAMIT/GLOBK software relative to Eurasia fixed frame. The velocities of the stations were found as approximately mm/year to SW direction and the solution was compared with the previous study of McClusky et al. (2000) and the results of TUBITAK project No:108Y285. Due to the differences on the velocity directions, the study was separated to four regions. Additionally, for determining the regional deformation, by using Euler vectors, the Aegean and Anatolian block fixed solutions were presented. In Anatolian block solutions, the area was separated into 3 groups according to the velocities of the stations and the magnitude of the velocities was found as approximately 3-15 mm/yr. Finally, the GPS solutions; Eurasia fixed frame, Anatolian and Aegean block fixed solutions were compared with each other. In chapter four, the GPS and microgravity data, which were obtained simultaneously at 6 points; Akhisar (Manisa), Eşme (Uşak), Çal (Denizli), Bademli (İzmir), Borlu (Manisa), Karacasu (Aydın), were compared for discussing about vertical mass changes on the measurement points. For this purpose, the correlation coefficients between these data set were calculated. The earthquakes distributions which occurred between the years and topographic changes were 1

22 compared together for interpreting the vertical changes on these points with the relations between the GPS and microgravity. In chapter five, obtained GPS velocities by using Gamit/ Globk software were compared with the modeled GPS velocities by Coulomb 3.3 software on the northern normal fault of Gediz graben and southern normal fault of the Büyük Menderes graben by using Coulomb 3.3 software. In Gediz Graben application, the modeled and observed GPS velocities are fitted at AKHT (Akhisar), BORT (Borlu) and TRGT (Turgutlu). But there is not compliance between the velocities for SALH (Salihli). Additionally, Coulomb software can not model velocities for ESMT and CALT stations due to their far away locations from the fault. Then, the coulomb stress changes were calculated and plotted for the depths of 4 km and 6 km and additionally for the depth range between 0-4 km and 0-6 km. In Büyük Menderes graben application, the modeled and observed GPS velocities are fitted for KRPT and KRCT. The coherence between the modeled and observed velocities for CALT is not well. Additionally, the modeled and observed velocities of BDMT have same directions and they are fitted but the magnitude of the modeled velocity is higher than the observed one. By these parameters the coulomb stress changes were calculated and plotted for the depths of 3 km and 5 km and additionally for the depth range between 0-3 km and 0-5 km. Additionally, the coulomb stress changes were compared with the earthquakes occurred at the region between the years Complex structures systems are often too complicated to simply derive relationships between applied loads and internal stresses. Hence, large structures are divided up into many individual finite elements; that have a much simpler structural form. The relationship between load, displacement, stresses and strains in a finite element can be determined. Thus, it is computationally possible for a complex structure to be modelled by assembling many individual finite elements. The assembling process must satisfy equilibrium and continuity (Chandrupatla & Belegundu, 2002). By this idea, in the last chapter (chapter six), the finite element software ADELI was used for modeling deformation of Western Anatolia. The south border of Menderes Extensional Metamorphic Complex (MEMC) at south side and the North Anatolian Fault zone at north side were chosen as the boundary conditions 2

23 of the model. To the initial model, 3 mm/yr velocity magnitude was given to the borders for giving extension to the model. The strain and velocity fields after 5Myr, 10Myr and 15 Myr of deformation were obtained. Finally, the findings were compared with the topography and bottom topographic map for investigating the crustal extension. 3

24 CHAPTER TWO GEOLOGY OF THE STUDY AREA Western Anatolia is one of the most seismically active and rapidly extending regions in the world (Dewey & Şengör, 1979; Şengör & Yılmaz, 1981; Jackson & McKenzie, 1984; Şengör et al., 1985; Eyidoğan & Jackson, 1985; Şengör, 1987; Seyitoğlu & Scott, 1992; Bozkurt, 2001). It has continental extension approximately N S direction with the rate of mm/year (Oral et al., 1995; Le Pichon et al., 1995, McClusky et al., 2000). Western Anatolia is the part of the Aegean Extensional Province which is the region of distributed extension (Bozkurt, 2001) (Figure 2.1). Figure 2.1 Simplified tectonic map of Turkey showing major neotectonic structures and neotectonic provinces. Red square shows the study area (modified from Bozkurt 2001). The Aegean Extensional Province has experienced several compressional and extensional deformational phases which have been summarized in many papers (Şengör & Yılmaz, 1981; Okay & Tüysüz, 1999; Ring et al., 2010; Rimmelé et al., 2003; van Hinsbergen et al., 2005, 2010; Çemen et al., 2006 and Jolivet et al., 2013). All researchers agree that the province has experienced a Cenozoic extensional tectonics and it is still effective. On the other hand, the initial time of the Cenozoic 4

25 extension has been controversial. Many researchers recommended that the Cenozoic extensional tectonics in the western Anatolian began in the Middle Miocene (Yılmaz et al., 2000) or earliest Miocene (Seyitoğlu et al., 1992). Several recent studies, however, suggested that the extension began in Late Oligocene in Western Anatolia (Lips et al., 2001; Catlos & Çemen; 2005; Çemen et al., 2006), or in Early Eocene in the Rhodope region (Jolivet & Brun, 2010) (Ersoy et al.,2014). The cause and origin of the Cenozoic extension has also been controversial. The proposals fall into five different models: (1) Tectonic escape model: the westward extrusion of the Anatolian block along its boundary structures since the late Serravalian (12 Ma) (Dewey & Şengör, 1979; Şengör, 1979, 1980, 1987; Şengör & Yılmaz, 1981; Şengör et al., 1985; Görür et al., 1995; Çemen et al., 1999). (2) Back-arc spreading model: back-arc extension caused by the south southwestward migration of the Aegean Trench system. However, there is no consensus on the inception date for the subduction roll-back process and proposals range between 60 Ma and 5 Ma (McKenzie, 1978; Le Pichon & Angelier, 1981; Jackson & McKenzie, 1988; Spakman et al., 1988; Meulenkamp et al., 1994; Jolivet & Brun, 2010; Jolivet et al., 2013). (3) Orogenic collapse model: the extension is induced by the spreading and thinning of over-thickened crust following the latest Paleocene collision across Neotethys during the latest Oligocene Early Miocene (Seyitoğlu & Scott,1992; Seyitoğlu et al., 1992). (4) A three-stage continuous simple shear extensional model as a result of the 'tectonic escape', 'back-arc spreading' and 'orogenic collapse' mechanisms (Çemen et al., 2006; Gessner et al., 2013). (5) Episodic : a two-stage graben model: that involves a Miocene Early Pliocene first stage (orogenic collapse), and a Plio-Quaternary second phase (westward escape of the Anatolian block) of N S extension (Sözbilir & Emre, 1996; 5

26 Koçyiğit et al., 1999; Bozkurt, 2000, 2001, 2003; Işık & Tekeli, 2001; Lips et al., 2001; Sözbilir, 2001, 2002; Bozkurt &Sözbilir, 2004; Koçyiğit, 2005). Western Anatolia is the most important part of the Aegean Extensional Province which includes Menderes Extensional Metamorphic Complex (MEMC) (Bozkurt & Park, 1994; Emre, 1996; Lips et al., 2001; Işık & Tekeli, 2001; Çemen et al., 2006). MEMC is one largest metamorphic core complexes in the world and began to develop during the Late Oligocene-Early Miocene extensional deformation (Bozkurt & Park, 1994; Hetzel et al., 1995; Işık & Tekeli, 2001; Işık et al., 2004; Çemen et al., 2006; Glodny & Hetzel, 2007) and occurred in poly-phase deformation (Ersoy et al., 2014). The MEMC is bounded by NE-SW trending Miocene strike-slip faults along its eastern and western margins edges (Çemen et al., 2006; Sözbilir et al., 2011; Ersoy et al., 2011). The NE-SW trending strike-slip faulting along the western side of the MEMC is known as İzmir-Balıkesir Transfer Zone (İBTZ; Sözbilir et al., 2003; Erkül et al., 2005; Kaya et al., 2007; Uzel & Sözbilir, 2008; Ersoy et al., 2011; Gessner et al., 2013). Several Miocene to Recent transtensional areas and basins were developed along this zone. The eastern side of MEMC is bounded by the NE- SW trending Southwestern Anatolian Shear Zone (Çemen et al., 2006; Karaoğlu & Helvacı, 2012) which includes lots of oblique-slip faults and associated extensional basins (Ersoy et al., 2014). It has been proposed that the Cenozoic extensional tectonics in the Aegean was begun as early as in Eocene (~45 Ma) by slab-roll back processes (Dinter & Royden, 1993; Brun & Faccenna, 2008; Brun & Sokoutis, 2012). The Cenozoic extensional tectonics and related core complex formation migrated to the south with time, and during the Late Oligocene to Middle Miocene times, Kazdağ, Cycladic and Menderes Extensional Core Complexes formed (Ersoy et al., 2014). The northern side of the MEMC was formed in three main stages: (1) latest Oligocene-Early Miocene detachment faulting along the Simav Detachment Fault (Işık & Tekeli, 2001; Isik, et al., 2003), (2) Middle Miocene detachment faulting along Gediz (Alaşehir) Detachment Fault (Emre, 1996; Seyitoğlu et al., 2002) and 6

27 Büyük Menderes Detachment Fault (Bozkurt, 2000; Çemen et al., 2006; Gürer et al., 2009), (3) Pliocene-Quaternary high-angle normal faulting, cutting the older structures throughout the western Anatolia (Yılmaz et al., 2000). Each of these stages is responsible for deformation, basin formation, sedimentation and extensive volcanic activity in the upper plate (Ersoy et al., 2014). By the radiometric age determination studies, it was supported that the first stage Cenozoic extensional deformation in the northern MECM, along the Simav Detachment Fault, has begun during the Late Oligocene. Several supra-detachment basins in the upper plate, such as Demirci, Selendi and Uşak-Güre basins are located in the northern MECM (Purvis et al., 2005; Çemen et al., 2006; Ersoy et al., 2011). On the other hand, there is no supradetachment basin in the southern MEMC. It means that the first-stage exhumation of the MEMC was occurred asymmetrically. The second stage of the Cenozoic extension in the MEMC occurred in its central parts, along the north-dipping Gediz (Alaşehir) Detachment Fault and south-dipping Büyük Menderes Detachment Fault. These faults have also controlled the basins in the upper plate (Sözbilir, 2002; Çemen et al., 2006; Çiftçi & Bozkurt, 2009; Şen & Seyitoğlu, 2009; Öner & Dilek, 2013). The episodic forming of the MEMC was accompanied also by Miocene to Recent NE-SW-trending strike-slip faulting along its western margin (Ersoy et al., 2011) known as the IBTZ (Sözbilir et al., 2003; Erkül et al., 2005; Uzel and Sözbilir, 2008; Ersoy et al., 2011; Uzel et al., 2013). Complex deformation along the IBTZ is also resulted in basin formation and volcanic activity (Ersoy et al., 2014). 7

28 CHAPTER THREE DEFORMATION ESTIMATIONS WITH GPS PROCESSING The Global Positioning System (GPS) is a satellite-based radio-navigation system which is developed by the United States Department of Defense since early 1970s. GPS was opened to civilian use in the 1980s. It is formed by a constellation of 24 satellites in six orbital planes with four satellites in each plane which are km above the earth. The principal technique of GPS is to measure the time difference between the satellite clock and the user s receiver clock on the Earth and scale it by speed of light in order to obtain the distance between the receiver and the satellite observed. The approximate positions of the satellites are broadcasted along with the GPS signal to the user via navigation messages (almanac and ephemerides). Therefore, the position of the receiver can be determined by the known positions of the satellites and the computed distances between the receiver and the satellites (Xu, 2007). On the other hand, a Global Navigation Satellite System (GNSS) is the name covering all satellite positioning systems from different countries, namely, GPS (USA), GLONASS (Russia), Galileo (European Union), Compass (China), QZSS (Japan), IRNSS (India) and SBAS (Satellite Based Augmentation Systems) systems (Kahveci & Yıldız, 2009). The free global availability and accuracy of GPS signals for positioning and timing, combined with the low cost of receiver chipsets, has made GPS the preferred solution for a very wide and growing range of civilian applications (Locata, nd.) Some civilian applications of GPS can be written as: surveying, geodesy, geophysics, aviation, road transport, shipping & rail transport, meteorology, precision agriculture, recreational activities, etc. 3.1 The Segments of GPS GPS system consists of 3 segments which are Space, Control and user segments (Figure 3.1). 8

29 Figure 3.1 GPS segments (Infohost, nd) The Space Segment The space segment consists of 24 satellites (currently 31 in November 2014), nearly circular orbits about 20,200 km above the earth. The satellites are arranged in 6 orbital planes (Figure 3.2). Each plane is tilted at 55 degrees relative to the equator, to provide polar coverage. Each satellite orbits the earth twice a day. Therefore, at least four satellites are in view at any time, from any place on the earth s surface. This is significant because a GPS receiver requires signals from at least four satellites in order to determine its location in three dimensions (3D). Each satellite contains several atomic clocks to keep accurate time. Each satellite continuously broadcasts low-power radio signals that identify it and provide information about its location in space, as well as system timing and other data. Each GPS satellite transmits data on three frequencies: L1 ( MHz), L2 ( MHz) and L5 ( MHz). Pseudorandom noise (PRN) codes, along with satellite ephemerides, ionospheric model, and satellite clock corrections are superimposed onto the carrier (Kahveci & Yıldız, 2009). 9

30 The L1 and L2 carrier signals are modulated for receiving the information such as satellite clock corrections, orbital parameters to the receiver by some codes and navigation messages. In this modulation processing, unique meaningful PRN (Pseudo Random Noise) code number are given to each satellite. The satellite signal can be separated from each other by this unique PRN code (Montenbruck & Gill, 2000). Figure 3.2 The space segment of GPS (Colorado University, nd) At L1 frequency, there are two PRN codes and navigation message data. These two codes are called as C/A (Course/Acquisition, Clear/Access) code and P (Precise/Protected Code) codes. At L2 frequency, there are P code and navigation message data. In the other words, the C/A code which is available for civil users is transmitted with L1 frequency. P code which is available only for military is transmitted both L1 and L2 frequency (Kahveci & Yıldız, 2009) The Control Segment The Control Segment consists of tracking stations system located around the world (Figure 3.3). The Master Control station, located in Colorado, is responsible 10

31 for overall management of the remote monitoring and transmission sites. It measures signals from the satellites and it calculates any position or clock errors for each individual satellite based on information received from the monitor stations. The corrected data are uploaded by the Master Control station. Finally, the satellites send the new data over radio signals to the GPS receiver back to earth. The 4 Monitor Stations located around the world (Hawaii and Kwajalein in the Pacific Ocean; Diego Garcia in the Indian Ocean; Ascension Island in the Atlantic Ocean) track up to 11 satellites twice a day (Environmental, nd). Figure 3.3 The control segment of GPS (Environmental, nd) The User Segment The user segment consists of all civil and military GPS users. This segment requires having an antenna and a receiver for decoding and storing the information sent from the space segment. 3.2 Reference Coordinate Systems of GPS In formulating the mathematics of satellite navigation information, it is necessary to choose a reference coordinate system in which satellite and receiver can be 11

32 represented. In this formulation, it is typical to describe satellite and receiver states in terms of position and velocity vectors measured in a Cartesian coordinate system (Kaplan & Hegarty, 2006) Earth-Centered Inertial (Space-fixed) (ECI) Coordinate System For the purposes of measuring and determining the orbits of the GPS satellites, it is convenient to use an Earth-centered inertial (ECI) coordinate system, in which the origin is at the center of the mass of the Earth and whose axes are positing in fixed directions with the respect to the stars. In ECI coordinate system, the xy-plane is taken to coincide with the Earth's equatorial plane, the x-axis is permanently fixed in a particular direction relative to the celestial sphere, the z-axis is taken normal to the xy-plane in the direction of North Pole, and the y-axis is chosen to form right-handed coordinate system (Kaplan & Hegarty, 2006) Earth-Centered Earth-Fixed (ECEF) Coordinate System For the purpose of computing the position of a GPS receiver, it is more convenient to use a coordinate-system that rotates with the Earth, known as an Earthcentered Earth-fixed (ECEF) system. In such a coordinate system, it is easier to compute the latitude, longitude and height parameters that the receiver displays. As in ECI coordinate system, the ECEF coordinate systems' xy-plane is coincide with the Earth's equatorial plane. In the ECEF system, the x-axis points in the direction of 0 longitude, the y-axis points in the direction of 90 E longitude and the z-axis is chosen to be normal to the equatorial plane in the direction of the geographical North Pole. Therefore, the x, y, and z-axes rotate with the Earth. The Cartesian coordinates (x, y, and z) of the user's receiver are computed in ECEF system (Kaplan & Hegarty, 2006). 12

33 3.2.3 World Geodetic System-1984 (WGS-84) The standard physical model of the Earth used for GPS applications is World Geodetic System 1984 (WGS 84). This is the reference system used by U.S. Department of Defense where has the responsibility of using the GPS system. WGS 84 provides an ellipsoidal model of the Earth's shape. In this model, cross-section of Earth parallel to the equatorial plane are circular. The equatorial cross-section of the Earth has radius 6, km, which is the mean equatorial radius of the Earth (Kaplan & Hegarty, 2006). 3.3 Source of Errors GPS system is the highest accurate global positioning and navigation system although it has some weaknesses as in all other systems. In other words, some random and systematic deviations are involved in the results of GPS measurements (Kahveci & Yıldız, 2009). The main sources of errors which affect the distance measurements between satellites and receivers are explained briefly Ephemeris (Orbital Position) Errors Ephemeris errors are supposed to be a major factor limiting the usefulness of GPS in high precision geodesy and applications. Even though the satellites positions are constantly monitored, slight position or "ephemeris" errors can occur. So, if the satellite location information in GPS navigation message has low accuracy, this effect is called as ephemeris error. For removing the ephemeris errors, the satellite orbits should be measured more sensitively by measuring or modeling the forces acting on satellite with high accuracy (Kahveci & Yıldız, 2009) Satellite and Receiver Clock Errors Even though the GPS satellites are very sophisticated they contain some small errors in the system. The atomic clocks used in GPS satellites are very precise but 13

34 they're not perfect. Small discrepancies can occur, and these cause measurement errors in travel time. Since determining position is based on time measurements, the greatest source of error is caused by satellite clock drift. These errors are monitored and corrected by the Master Control Station. This effect can be removed by using sensitive atomic clocks or using differential observations (Kahveci & Yıldız, 2009). The role of the receiver and satellite clocks is very important in precise GPS surveying. The receiver and satellite clock errors are multiplied by the speed of light. Hence, because of the factor speed of light, a small clock error can cause a very large code and phase error on the earth. For example a clock error of 1 µs translates to 300 m in range error. GPS receivers use cheap quartz crystal oscillators, to keep the cost within a reasonable level. These oscillators have also the advantage of being small devices and consume less power. In absolute positioning, the receiver clock offset has to be estimated as an unknown parameter in the navigation solution which estimates the receiver position and receiver clock at the same time. The receiver clock offset can be estimated within 1 µs or better (Leick, 1995). In relative positioning, between satellites differencing eliminates the receiver clock error term. In Network RTK, where double difference is adopted as the main observable, receiver and satellite clocks are completely eliminated through differencing Atmospheric Effects The ionosphere and troposphere both refract the GPS signals. The ionosphere is the ionized part of the earth s atmosphere lying between about 50 km and several earth radii (Davies, 1990). The amount of free electrons is more enough to change the propagation of electromagnetic waves. The effects of ionosphere are different on code and phase measurements. While the ionosphere effects as group delay on code measurements, it effects as phase advance on phase measurements. Since the ionospheric effect is frequency dependent, this effect can be removed by using dualfrequency GPS receiver. Troposphere is the lowest layer and the non-ionized part of the atmosphere. The electromagnetic signals are affected by the neutral (non-ionized) atmosphere and this 14

35 effect is called tropospheric delay. Neutral atmosphere changes the speed and directions of the electromagnetic waves. The tropospheric delay is frequency independent and this effect can not be removed by using dual-frequency GPS receiver. This effect can be decreased by using suitable modeling (Kahveci & Yıldız, 2009) Selective Availability Selective Availability (SA) is the intentional degradation (limits accuracy of satellite signals) of the GPS system by the U.S. Department of Defense for security reasons. On May 1, 2000 the White House announced a decision to discontinue the intentional degradation of the GPS signals to the public beginning at midnight. (Kahveci & Yıldız, 2009) Multipath Multipath is the signal refection effect which is occurred when the satellite signals reach the receiver antenna by two or more paths. The possible sources of reflection around the receiver antenna are buildings, vehicles, water surfaces (sea, lake, etc.) and other reflective surfaces (Figure 3.4). If the antenna is kept stable at the same point a few days, the main effect of antenna signal reflection can be measured. Therefore, multipath error can be corrected by removing this effect (Kahveci & Yıldız, 2009). 15