BUILDING A GEOREFERENCED DATABASE FOR THE 1976 GUATEMALAN EARTHQUAKE RUPTURE OF THE MOTAGUA FAULT SYSTEM ALONG THE NORTH AMERICAN-CARIBBEAN PLATE BOUNDARY

The 1976 magnitude 7.5 Guatemala earthquake ruptured the Motagua fault along the North American-Caribbean plate boundary in one of the most devastating earthquakes in the 20^th Century that resulted in over 23,000 fatalities. For a major plate boundary, very little is known about the long-term rupture history of the Motagua fault, the probability of future earthquakes, or the hazards it poses to the large and growing population in Guatemala. In this study, we sought to relocate sites along the 1976 Motagua fault rupture by analyzing archival material from George Plafker of the U.S. Geological Survey who was part of the team that collected data on the effects of the earthquake within days of the event. The data included 1250 original 35 mm slides, numerous annotated 1:50:000 scale topographic maps, several hundred aerial photographs, a 1978 field trip guidebook, and various other original documents that are only available in paper format. Of particular help was USGS Open-File Report 77-165 which is a photo archive and description of 54 35 mm slides including images of primary and secondary strike-slip faulting, landslides, liquefaction, and some sites of structural damage. Maps, photographs, and reports from the 1976 Guatemalan earthquake were digitally scanned. The process of georeferencing the data proved difficult, as names and locations of many towns, roads, and geographic features have changed or no longer exist. The data were georeferenced using Google Earth and ArcMap, and when possible, correlated to field notes and map annotations. After the files were georeferenced, a geodatabase was built in ArcMap thus providing easily accessible geospatial data for photographs. The 1976 Guatemala earthquake georeferenced database can then be loaded into a mobile GIS software such as Touch GIS for use in the field. Prior to this project, locating any of these past field sites and points of interest along the 1976 Guatemalan earthquake rupture was hindered by the lack of GPS coordinates. The new database will benefit future paleoseismic and seismic hazard analyses research.