Michigan Technological University Digital Commons @ Michigan Tech Dissertations, Master's Theses and Master's Dissertations, Master's Theses and Master's Reports - Open Reports 2014 STATIC AND DYNAMIC STRESS CHANGE AT 27 VOLCANOES OF THE CENTRAL AMERICAN VOLCANIC ARC AFTER THE MW. 7.6 COSTA RICA EARTHQUAKE OF 5 SEPTEMBER 2012 Lorenzo Gratton Michigan Technological University Follow this and additional works at: https://digitalcommons.mtu.edu/etds Part of the Geology Commons, and the Geophysics and Seismology Commons Copyright 2014 Lorenzo Gratton Recommended Citation Gratton, Lorenzo, "STATIC AND DYNAMIC STRESS CHANGE AT 27 VOLCANOES OF THE CENTRAL AMERICAN VOLCANIC ARC AFTER THE MW. 7.6 COSTA RICA EARTHQUAKE OF 5 SEPTEMBER 2012", Master's Thesis, Michigan Technological University, 2014. https://digitalcommons.mtu.edu/etds/787 Follow this and additional works at: https://digitalcommons.mtu.edu/etds Part of the Geology Commons, and the Geophysics and Seismology Commons STATIC AND DYNAMIC STRESS CHANGE AT 27 VOLCANOES OF THE CENTRAL AMERICAN VOLCANIC ARC AFTER THE MW. 7.6 COSTA RICA EARTHQUAKE OF 5 SEPTEMBER 2012. By Lorenzo Gratton A THESIS Submitted in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE In Geology MICHIGAN TECHNOLOGICAL UNIVERSITY 2014 © 2014 Lorenzo Gratton This thesis has been approved in partial fulfillment of the requirements for the Degree of MASTER OF SCIENCE in Geology. Department of Geological and Mining Engineering and Sciences Thesis Advisor: Dr. Gregory P. Waite Committee Member: Dr. Simon Carn Committee Member: Dr. Alessandro Tibaldi Department Chair: John S. Gierke Table of Contents List of Figures ................................................................................................................5 List of Tables .................................................................................................................6 Abstract ........................................................................................................................7 1. Introduction ..........................................................................................................8 2. 5 September 2012 - Mw 7.6 Costa Rica Earthquake ..........................................12 2.1 Tectonic setting ............................................................................................12 2.2 Earthquake characteristics ..........................................................................13 2.2.1 Earthquake description ........................................................................13 2.2.2 Finite fault model and directivity data .................................................15 3 Central American Volcanic Arc ...........................................................................18 3.1 Geological setting ........................................................................................18 4. Volcanic activity following the earthquake ........................................................20 5. Static stress change ............................................................................................24 5.1 Introduction to Static Stress Change ...........................................................24 5.2 Methodology – Coulomb 3.3 .......................................................................26 5.3 Results of the Static Stress Change Analysis ................................................29 6. Dynamic stress change .......................................................................................35 6.1. Introduction .................................................................................................35 6.2. Use of dynamic stress change in the context of the work ..........................36 6.3. Synthetic seismograms ................................................................................38 6.3.1. Finite fault effects (directivity) .............................................................39 6.3.2. Synthetic seismogram testing ..............................................................42 6.3.3. Synthetic seismograms for the 27 volcanoes .......................................44 6.3.4. Synthetic seismograms from finite fault model ...................................46 3 6.4. Results ..........................................................................................................51 6.4.1. Single point source model ....................................................................51 6.4.2. Finite-fault model results .....................................................................54 7. Statistical Analysis ..............................................................................................57 7.1 Introduction .................................................................................................57 7.2 Methodology ................................................................................................57 7.3 Results ..........................................................................................................59 8. Discussion ...........................................................................................................60 9 Conclusion ..........................................................................................................62 10 References ..........................................................................................................63 11 Acknowledgements ............................................................................................67 Appendix A..................................................................................................................69 Appendix B ..................................................................................................................74 Appendix C ..................................................................................................................77 Appendix D .................................................................................................................85 Appendix E ..................................................................................................................86 Appendix F ..................................................................................................................89 Appendix G .................................................................................................................90 Appendix H .................................................................................................................92 4 List of Figures 2.1 Map of earthquake epicenter and volcanoes......................................................12 2.2 Earthquake focal mechanism..............................................................................14 2.3 Earthquake source time function........................................................................14 2.4 Earthquake slip distribution................................................................................15 4.1 Number of micro-earthquakes at Arenal............................................................21 4.2 Number of micro-earthquakes at Rincon de la Vieja...........................................22 4.3 Number of micro-earthquakes at Tenorio...........................................................23 5.1 Normal static stress change.................................................................................30 5.2 Normal static stress change for optimal faults....................................................32 5.3 Static stress change, strike orientation map.......................................................33 5.4 Static stress change, strike values.......................................................................34 6.1 Directivity effect on seismograms.......................................................................41 6.2 Seismic stations map...........................................................................................42 6.3 Synthetic seismograms testing............................................................................44 6.4 Example of synthetic seismograms.....................................................................45 6.5 Example of Finite Fault Model Synthetic seismograms.......................................48 6.6 Example of stack spectras...................................................................................49 6.7 Duration of seismic wave cycles..........................................................................50 6.8 Single point source PDS results...........................................................................53 6.9 Finite Fault Model PDS results.............................................................................55 5 List of Tables 2.1 Mw 7.6 Costa Rica earthquake characteristics.....................................................17 6.1 Single point source PDS results............................................................................51 6.2 Finite Fault Model PDS results.............................................................................54 6.3 Duration of seismic wave cycles results...............................................................56 7.1 Statistical analysis results....................................................................................59 A.1 Characteristics of the 27 volcanoes.....................................................................69 B.1 Signs of activity at the volcanoes following the earthquake...............................74 C.1 Obtained values of