APPLICATION OF GEOGRAPHIC INFORMATION SYSTEMS IN THE DOCUMENTATION OF QUATERNARY FAULTS IN MÉXICO

This paper presents the initial results of a compilation of Quaternary faults in México through the application of Geographic Information Systems (GIS) software. Fault traces were georeferenced, digitally-processed, and vectorized using the programs ArcMap, Grass GIS and Quantum GIS due to their ease in handling and their versatility in importing and exporting files. Grass GIS and Quantum GIS additionally correspond to open-source software. The documentation consists of a compilation of mapped geologic structures exhibiting surface faulting within the last 2.6 million years, with greater emphasis placed on faults with known displacement in the Holocene (last 11,700 years). Faults were classified following an assessment of their recent motion based on a review of documented seismologic and geologic information including evidence from seismic recordings, historical earthquakes, GPS measurements, and paleoseismic, geomorphologic, and structural studies. Faults were placed into one of three principal categories: 1) Type A faults with strong indicators of fault displacement in the Holocene, 2) Type B structures that may have moved during the Holocene, and 3) Type C faults that show evidence of displacement in the Pleistocene. GIS tools developed in this study incorporate available pertinent fault information including the name of the fault, the type of faulting, the fault length, the average strike, the average dip, the sense of motion, the evidence for fault displacement, the date, magnitude and the maximum known displacement of the last seismic event, the estimated slip rate, the recurrence interval and the corresponding references. Individual faults and distributed fault systems were identified, principally along the Trans Mexican Volcanic Belt and along the Baja California peninsula, resulting in the compilation of a total of 234 individual fault traces (39 Type A, 9 Type B, and 186 Type C). The main objective of the work was to create a database of Quaternary faults for México that can be readily updated in the future. The documentation and updating of this geologic information is important to identify active and potentially-active faults that can affect the seismic hazard, particularly in intraplate regions of the country.