Surface Wave Derived Shear Velocity Structure of the Gamburtsev
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Washington University in St. Louis Washington University Open Scholarship All Theses and Dissertations (ETDs) 1-1-2011 Surface Wave Derived Shear Velocity Structure of the Gamburtsev Subglacial Mountains, Transantarctic Mountains, and West Antarctica and Shallow Seismicity of the Mariana and Tonga Subduction Zones David Heeszel Washington University in St. Louis Follow this and additional works at: https://openscholarship.wustl.edu/etd Recommended Citation Heeszel, David, "Surface Wave Derived Shear Velocity Structure of the Gamburtsev Subglacial Mountains, Transantarctic Mountains, and West Antarctica and Shallow Seismicity of the Mariana and Tonga Subduction Zones" (2011). All Theses and Dissertations (ETDs). 586. https://openscholarship.wustl.edu/etd/586 This Dissertation is brought to you for free and open access by Washington University Open Scholarship. It has been accepted for inclusion in All Theses and Dissertations (ETDs) by an authorized administrator of Washington University Open Scholarship. For more information, please contact [email protected]. WASHINGTON UNIVERSITY IN ST. LOUIS Department of Earth and Planetary Sciences Dissertation Examination Committee Douglas Wiens, Chair Jeffrey Catalano James Conder Martin Israel Philip Skemer Michael Wysession SURFACE WAVE DERIVED SHEAR VELOCITY STRUCTURE OF THE GAMBURTSEV SUBGLACIAL MOUNTAINS, TRANSANTARCTIC MOUNTAINS, AND WEST ANTARCTICA AND SHALLOW SEISMICITY OF THE MARIANA AND TONGA SUBDUCTION ZONES By David Scott Heeszel A dissertation presented to the Graduate School of Arts and Sciences of Washington University in partial fulfillment of the requirements for the degree of Doctor of Philosophy August 2011 St. Louis, Missouri Acknowledgements: When I think about the number of people who have helped me undertake the writing of this dissertation and the requisite research, it is difficult to know where to begin and perhaps more importantly end. First, I need to thank my advisor and mentor Doug Wiens for his support, guidance, and patience during my time here at Washington University. My wife, Lindsey, and daughter, Anika, have constantly provided love, support, distraction, and the oft required kick in the rear that have lead to the completion of this volume. I would also like to thank the other great people who work in the seismology group here particularly, Patrick Shore for the friendship and guidance he has offered me, Ghassan Aleqabi for forcing me to return to first principles, Garrett Euler, Moira Pyle, and Erica Emry for suffering with me through life as a graduate student. Many thanks to all of the graduate students, past and present, for their friendship and the front office staff for keeping me aware that there are indeed deadlines and rules. I also need to thank all of the people involved in the collection of the data I present here. Thanks to the TAMSEIS, GAMSEIS, POLENET, MARIANA, and TONGA06 field teams who are too numerous to list, this dissertation could not exist without your hard work. I owe a deep debt of gratitude to the National Science Foundation, which provided the financial resources to undertake these projects and the PASSCAL division of the Incorporated Research Insitutions for Seismology (IRIS) for providing instrumentation and seismic data. Finally, I want to thank my parents for always encouraging me to reach for more, do what I love, and pursue my own path through life. ii Table of Contents Table of Contents ...............................................................................................................iii List of Figures ....................................................................................................................vi List of Tables ....................................................................................................................vii Chapter 1 Introduction ........................................................................................................1 Chapter 2 Earthquake evidence for along-arc extension in the Mariana Islands.................3 Abstract .........................................................................................................................3 2.1 Introduction .............................................................................................................5 2.2 Data .........................................................................................................................7 2.3 Analysis ...................................................................................................................8 2.3.1 Earthquake Locations .....................................................................................8 2.3.2 Focal Mechanisms .......................................................................................10 2.4 Results ...................................................................................................................11 2.4.1 14°40’N, Northwest Rota ............................................................................11 2.4.2 Diamante Seamount Chain ..........................................................................12 2.4.3 16°40’N, Mariana Trough ............................................................................13 2.4.4 West Sarigan Seamount ...............................................................................14 2.4.5 Fore Arc Rise ...............................................................................................14 2.5 Discussion .............................................................................................................15 2.5.1 Extensional Swarms Associated with Volcanic Cross Chains ....................15 2.5.2 Seismicity and Deformation in the Mariana Microplate ..............................17 2.6 Conclusions .................................................................................................................18 2.7 Acknowledgements .....................................................................................................20 2.8 References ...................................................................................................................21 Chapter 3 Aftershock locations following the May 3, 2006 Mw8.0 Tonga earthquake: Evidence for slab tearing ..................................................................................................36 Abstract ........................................................................................................................36 3.1 Introduction ............................................................................................................38 3.2 Methods and Data ..................................................................................................39 3.3 Results ....................................................................................................................41 3.4 Discussion ..............................................................................................................42 3.4.1 Aftershock Locations ...................................................................................42 3.4.2 Downdip Seismicity .....................................................................................43 3.4.3 Updip Seismicity ..........................................................................................44 3.4.4 Seismic evidence for a complex rupture ......................................................45 3.5 Conclusions .............................................................................................................46 3.6 Acknowledgements .................................................................................................47 3.7 References ...............................................................................................................48 Chapter 4 Shear velocity structure of the Gamburtsev Subglacial Mountains, East Antarctica from inversion of teleseismic Rayleigh waves ................................................61 Abstract ........................................................................................................................61 4.1 Introduction ............................................................................................................63 4.2 Data Acquisition ....................................................................................................65 iii 4.3 Methods .................................................................................................................66 4.3.1 Data Processing ..............................................................................................66 4.3.2 Phase Velocity Inversion ...............................................................................67 4.3.3 Shear Velocity Inversion ................................................................................70 4.3.3.1 Linear Inversion .................................................................................70 4.3.3.2 Monte Carlo Modeling .......................................................................71 4.4 Results ....................................................................................................................73 4.4.1 Phase Velocities ............................................................................................73 4.4.1.1 Uniform Phase Velocities .................................................................73 4.4.1.2 Laterally Varying Phase Velocities ..................................................74 4.4.1.3 Azimuthal Anisotropy