University of Texas at El Paso DigitalCommons@UTEP Open Access Theses & Dissertations 2012-01-01 Seismic Reflection Study Of The aE st Potrillo Fault, Southwestern Dona Ana County, New Mexico Shane Alan Carley University of Texas at El Paso, [email protected] Follow this and additional works at: https://digitalcommons.utep.edu/open_etd Part of the Geology Commons, and the Geophysics and Seismology Commons Recommended Citation Carley, Shane Alan, "Seismic Reflection Study Of The East Potrillo Fault, Southwestern Dona Ana County, New Mexico" (2012). Open Access Theses & Dissertations. 2050. https://digitalcommons.utep.edu/open_etd/2050 This is brought to you for free and open access by DigitalCommons@UTEP. It has been accepted for inclusion in Open Access Theses & Dissertations by an authorized administrator of DigitalCommons@UTEP. For more information, please contact [email protected]. SEISMIC REFLECTION STUDY OF THE EAST POTRILLO FAULT, SOUTHWESTERN DONA ANA COUNTY, NEW MEXICO SHANE ALAN CARLEY Department of Geological Sciences APPROVED: Jose M. Hurtado, Jr., Ph.D. Laura Serpa, Ph.D., Chair Tom Gill, Ph.D. Benjamin C. Flores, Ph.D. Dean of the Graduate School Copyright © by Shane Alan Carley 2010 DEDICATION I dedicate this master’s thesis to my sister, Natalie, for constant encouragement and support. SEISMIC REFLECTION STUDY OF THE EAST POTRILLO FAULT, SOUTHWESTERN DONA ANA COUNTY, NEW MEXICO By SHANE ALAN CARLEY, B.S. GEOLOGY THESIS Presented to the Faculty of the Graduate School of The University of Texas at El Paso in Partial Fulfillment of the Requirements for the Degree of MASTER OF SCIENCE Department of Geological Sciences THE UNIVERSITY OF TEXAS AT EL PASO December 2012 ACKNOWLEDGEMENTS I would like to acknowledge my committee members: Dr. Kate C. Miller, Dr. Jose M. Hurtado, and Dr. Laura Serpa for their support during my thesis study. I would like to express extra thanks to Dr. Jose M. Hurtado for taking the role of a lead committee member in my unique situation. I would also like to thank Dr. Aaron A. Velasco for keeping an open door and his always helpful good advice. Another big thank you goes to Carlos J. Montana for his constant help and availability to handle the many technical issues I’ve had. I wish to thank Catherine Snelson at New Mexico Tech for providing access to the mini- vibrator source used in data acquisition. The instruments used in the field program were provided by the PASSCAL facility of the Incorporated Research Institutions for Seismology (IRIS) through the PASSCAL Instrument Center at UTEP. Data collected during this experiment are available through the IRIS Data Management Center. The facilities of the IRIS Consortium are supported by the NSF under Cooperative Agreement EAR-0552316 and by the Department of Energy National Nuclear Security Administration. Processing of the seismic data presented in this thesis was done with the software ProMAX, made available to UTEP through a Landmark University grant. And finally, I would like to thank my sister Natalie for her constant support throughout my continuing career as a scientist. v ABSTRACT The East Potrillo Mountains are located just north of the U.S.-Mexico border in southwestern Dona Ana County, New Mexico. Laramide and Rio Grande rift deformation has formed low- angle and high-angle Tertiary normal faults that are exposed in the area. Along the east flank of the range is the East Potrillo Fault identified on the surface as a north-striking scarp. Fault scarps associated with the East Potrillo Fault have been dated using slope degradation models and they range between 56 ka and 377 ka in age. Offset of geomorphic surfaces interpreted to be tectonic terraces records at least four earthquakes over that period of time, leading to an estimated recurrence interval of 33.5 kyr. Because of this paleoseismic history, the East Potrillo Fault potentially poses a significant seismic hazard to the over 2 million residents living in the border region. Our study presents two 2D seismic reflection profiles to give the first subsurface image of the East Potrillo Fault and potentially other subsidiary faults that have not broken the surface. Three faults are identified in the subsurface, two of which were previously unknown. The range bounding fault is identified 300 m west of observed fault scarps. The fault scarp is found to be formed from one of two secondary faults. It dips 75°s east and has a fault offset of 150 m. The other secondary fault is an antithetic fault dipping 75°s west and forms a graben within the EPF system. The vibroseis source data acquisition is found to be beneficial for characterizing unknown subsurface features. vi TABLE OF CONTENTS Page ACKNOWLEDGEMENTS .............................................................................................................v ABSTRACT ................................................................................................................................... vi TABLE OF CONTENTS .............................................................................................................. vii LIST OF FIGURES ..................................................................................................................... viii INTRODUCTION ...........................................................................................................................1 BACKGROUND .............................................................................................................................4 METHODS ....................................................................................................................................14 DATA PROCESSING ...................................................................................................................18 RESULTS ......................................................................................................................................35 DISCUSSION ................................................................................................................................41 CONCLUSIONS............................................................................................................................45 REFERENCES ..............................................................................................................................46 CURRICULUM VITA ..................................................................................................................48 vii LIST OF FIGURES Figure 1: Map of the study area. ................................................................................................................. 2 Figure 2: Location map of seismic lines. .................................................................................................... 3 Figure 3: Regional map of the Rio Grande Rift. ......................................................................................... 5 Figure 4: Geologic cross sections of the East Potrillo Mountains .............................................................. 8 Figure 5: Columnar stratigraphic section of study area. ........................................................................... 10 Figure 6: Gravity model of the Mesilla basin. .......................................................................................... 12 Figure 7: Gravity profile. .......................................................................................................................... 13 Figure 8: Picture of vibrosies source. ....................................................................................................... 15 Figure 9: Schematic of survey design. ...................................................................................................... 17 Figure 10: Processing flow chart. ............................................................................................................. 19 Figure 11: Schematic of vibroseis source. ................................................................................................ 20 Figure 12: Vibroseis correlation diagram. ................................................................................................ 21 Figure 13: Raw data example ................................................................................................................... 22 Figure 14: Data example after vibroseis correlation ................................................................................. 24 Figure 15: Static correction schematic. ..................................................................................................... 25 Figure 16: Example of typical common midpoint gather. ........................................................................ 27 Figure 17: Example of predictive deconvolution on data. ........................................................................ 28 Figure 18: Normal moveout schematic. .................................................................................................... 31 Figure 19: Example of Dip moveout correction. ...................................................................................... 32 Figure 20: Example of quality control. ..................................................................................................... 32 Figure 21: Stacked record section profile EP-1. ....................................................................................... 35 Figure 22: Stacked record section profile EP-1.5. ...................................................................................