Himalaya: Dynamics of a Giant, Geodynamic Setting of the Himalayan Range

Rodolphe Cattin is a professor at the University of Montpellier, France. His activities performed in the Himalaya are on crustal structure imaging from ground and satellite observations, river dynamics and stress transfer associated with seismic events and surface processes. Jean-Luc Epard obtained his PhD from the University of Lausanne, Switzerland (structural and Alpine geology) in 1990. He has been involved in 14 field expeditions in the Himalaya as participant or leader. His main area of expertise is the Mandi-Manali-Leh transect (India).

Tributes xi
Eduardo GARZANTI, Vincent GODARD, Rodolphe CATTIN, György HETÉNYI, Jean-Luc EPARD and Martin ROBYR

Foreword xvii
Rodolphe CATTIN and Jean-Luc EPARD

Preface From Research to Education: The Example of the Seismology at School in Nepal Program xix
György HETÉNYI and Shiba SUBEDI

Part 1 Tectonic Framework of the Himalaya and Tibet 1

Chapter 1 Plate Reconstructions and Mantle Dynamics Leading to the India-Asia Collision 3
Gweltaz MAHÉO and Guillaume DUPONT-NIVET

1.1 Introduction 3

1.2 The India-Asia convergence and the age of the collision 6

1.2.1 The India-Asia convergence 6

1.2.2 The age of the India-Asia collision 7

1.3 Plate collision configurations 14

1.3.1 Reconstructing lost continental margins 14

1.3.2 Alternative collision configurations 16

1.4 Reconstruction of the Neotethys Ocean closure dynamic 17

1.4.1 Number of subduction accommodating the Neotethys closure 17

1.4.2 Location of the Intraoceanic subduction zone and associated arc 19

1.4.3 Driving forces of the India-Asia convergence during Neotethys closure 20

1.5 Conclusion 23

1.6 References 23

Chapter 2 Building the Tibetan Plateau During the Collision Between the India and Asia Plates 33
Anne REPLUMAZ, Cécile LASSERRE, Stéphane GUILLOT, Marie-Luce CHEVALIER, Fabio A CAPITANIO, Francesca FUNICIELLO, Fanny GOUSSIN and Shiguang WANG

2.1 Introduction 33

2.2 Present-day Tibetan crustal deformation 36

2.2.1 GPS velocity field and focal mechanisms in Tibet 36

2.2.2 Surface motions and deformation due to Indian indentation 38

2.3 Tibetan lithospheric mantle subduction during collision 39

2.3.1 Imaging ongoing subduction beneath Tibet 39

2.3.2 Imaging subduction of lithospheric Tibetan mantle during the collision 41

2.3.3 Volcanism in Tibet showing the subduction of lithospheric Asian mantle during the early collision 43

2.4 Modeling the Tibetan plateau formation during the indentation of the Indian continent into Asia 45

2.4.1 Analogue modeling of the Tibetan lithosphere subduction during the indentation of India 46

2.4.2 Numerical modeling of Asian thickening and extrusion during the subduction of a continental-oceanic plate 49

2.5 Conclusion 51

2.6 References 52

Chapter 3 The Major Thrust Faults and Shear Zones 57
Djordje GRUJIC and Isabelle COUTAND

3.1 Introduction 57

3.2 Some basic concepts 58

3.3 Main faults and shear zones 59

3.3.1 South Tibetan detachment system (STDS) 60

3.3.2 Main Central thrust (MCT) 67

3.3.3 Main Boundary thrust (MBT) 74

3.3.4 Main Frontal thrust (MFT) 77

3.3.5 Main Himalayan thrust (MHT), continental megathrust 81

3.4 Tectonic models 81

3.4.1 Fold-and-thrust belt versus channel flow 81

3.4.2 Coeval slip along the STDS and the MCT 84

3.5 Conclusion 87

3.6 References 87

Part 2 Along Strike Variations 101

Chapter 4 Seismological Imaging and Current Seismicity of the Himalayan Arc 103
György HETÉNYI, Jérôme VERGNE, Laurent BOLLINGER, Shiba SUBEDI, Konstantinos MICHAILOS and Dowchu DRUKPA

4.1 Introduction 103

4.2 Imaging by elastic waves 104

4.2.1 Active seismics 105

4.2.2 Passive seismics 105

4.2.3 Tomographic imaging for bulk properties 106

4.2.4 Wave reflections and conversions for interfaces 107

4.3 Exploring the Central Himalaya along cross-sections 108

4.3.1 Field experiments 108

4.3.2 Main interfaces 109

4.3.3 Where do subducted plates go? 115

4.4 Lateral variations 116

4.4.1 Lateral ramps on the MHT, along-arc Moho variations 116

4.4.2 Segmentation of the India plate lithosphere 117

4.4.3 The western and eastern syntaxes 119

4.5 Current seismicity of the Himalaya 120

4.5.1 Earthquake detection, location and activity 120

4.5.2 Seismicity of the Himalaya: an incomplete patchwork 121

4.5.3 Seismicity of the Himalaya: main features 123

4.6 Conclusion 125

4.7 References 126

Chapter 5 Gravity Observations and Models Along the Himalayan Arc 129
Rodolphe CATTIN, György HETÉNYI, Théo BERTHET and Jamyang CHOPHEL

5.1 Introduction 129

5.2 Methods 130

5.2.1 Measurements 130

5.2.2 Corrections 131

5.2.3 Anomalies 133

5.3 Isostasy 134

5.3.1 Local compensation 134

5.3.2 Regional compensation 136

5.3.3 Effective elastic thickness 137

5.4 Flexure of the Indian plate 138

5.4.1 Gravity anomaly across the Himalayan belt 138

5.4.2 Along-strike variation between Nepal and Bhutan 141

5.5 Satellite data contribution 143

5.5.1 Gravity measurements from space 143

5.5.2 Towards a three-dimensional image 145

5.6 Conclusion 147

5.7 References 148

Chapter 6 Topographic and Thermochronologic Constraints on the Himalayan Décollement Geometry 151
Peter A VAN DER BEEK, Rasmus C THIEDE, Vineet K GAHALAUT and Taylor F SCHILDGEN

6.1 Introduction 151

6.2 Methods 156

6.2.1 Quantitative geomorphic analysis 156

6.2.2 Measures of erosion at different timescales: cosmogenic nuclides and thermochronology 158

6.2.3 From exhumation to kinematics: thermo-kinematic models 162

6.3 Regional case studies 163

6.3.1 Central Himalaya-Nepal 163

6.4 Discussion 176

6.4.1 Constraints on MHT geometry and kinematics at different timescales 177

6.4.2 Nature and evolution of ramps on the MHT 178

6.4.3 Evidence for out-of-sequence thrusting? 179

6.4.4 Lateral segmentation of theMHT 181

6.5 Conclusion 182

6.6 References 183

Part 3 Focus 195

Chapter 7 Application of Near-surface Geophysical Methods for Imaging Active Faults in the Himalaya 197
Dowchu DRUKPA, Stéphanie GAUTIER and Rodolphe CATTIN

7.1 Introduction 197

7.2 Near-surface geophysics 198

7.2.1 Geophysical methods for fault mapping 200

7.2.2 Case study data and inversion technique 205

7.3 Geophysical results of case study from south Bhutan 208

7.3.1 Electrical resistivity tomography 208

7.3.2 Seismic tomography 211

7.3.3 Micro-gravity 213

7.4 Implications of near-surface geophysical findings 215

7.4.1 Subsurface imaging 215

7.4.2 Overthrusting slip rate assessment 216

7.4.3 Deformation at the topographic front 218

7.5 Conclusion 218

7.6 References 219

Chapter 8 Overview of Hydrothermal Systems in the Nepal Himalaya 225
Frédéric GIRAULT, Christian FRANCE-LANORD, Lok Bijaya ADHIKARI, Bishal Nath UPRETI, Kabi Raj PAUDYAL, Ananta Prasad GAJUREL, Pierre AGRINIER, Rémi LOSNO, Sandeep THAPA, Shashi TAMANG, Sudhan Singh MAHAT, Mukunda BHATTARAI, Bharat Prasad KOIRALA, Ratna Mani GUPTA, Kapil MAHARJAN, Nabin Ghising TAMANG, Hélène BOUQUEREL, Jérôme GAILLARDET, Mathieu DELLINGER, François PREVOT, Carine CHADUTEAU, Thomas RIGAUDIER, Nelly ASSAYAG and Frédéric PERRIER

8.1 Introduction 225

8.2 Measurement methods 228

8.2.1 Exploration approach 228

8.2.2 Thermal spring water measurements 229

8.2.3 CO2 flux and radon flux measurements 230

8.2.4 Carbon content and isotopic composition measurements 231

8.3 Summary of results at the hydrothermal sites in the Nepal Himalaya 232

8.3.1 Overview of hydrothermal sites in Far-Western Nepal 234

8.3.2 Overview of hydrothermal sites in Mid-Western Nepal 235

8.3.3 Overview of hydrothermal sites in Western Nepal 238

8.3.4 Overview of hydrothermal sites in Central Nepal 240

8.3.5 Overview of hydrothermal sites in Eastern Nepal 246

8.3.6 Overview of hydrothermal sites in the MFT zone 246

8.4 Conclusion 247

8.5 References 248

Conclusion 255
Rodolphe CATTIN and Jean-Luc EPARD

List of Authors 257

Index 263

Summaries of other volumes 267