Measurements of Active Tectonic Deformation Along the Pacific Coast of Mexico

California State University-Long Beach Foundation, Long Beach CA

Investigators

Abstract

This project is to obtaining field data, radiocarbon data and exposure ages on coastal landforms and the geologic record (stratigraphy) along the Guerrero Coast, on the Pacific coast of Mexico, to derive long-term rates of tectonic deformation in this area of high seismic. combining geomorphic, stratigraphic-sedimentological, radiocarbon and cosmogenic approaches are being used to assess the long-term records of tectonic deformation retained on the landscape and in coastal sediment sequences. Comprehensive assessment of the geomorphology and geology give insights into the Quaternary long-term rates of deformation of this active convergent margin. Measurements include precise surveying and dating of markers in the coastal landscape and in the stratigraphy indicative of tectonic deformation. The specific objective is to derive rates of tectonic deformation from geomorphic and stratigraphic studies of the Guerrero coastal area to generate a long-term deformation rate model of coastal tectonics and compare with the short-term rates derived from geodetic and seismic data. The specific work being carried out is: 1) Studies of geomorphic markers indicative of tectonic displacement (e.g. marine terraces, emerged tidal notches, marine platforms, beach ridges) on the Guerrero coast. These include remote sensing and GIS analysis, field surveying of geomorphic markers elevations, mapping, radiocarbon and cosmogenic dating of collected samples to determine the ages of emerged landforms; 2) Stratigraphic-sedimentological and radiocarbon studies of the coastal areas to assess the records of long-term crustal movements; 3) Comprehensive data analysis and development of a long-term rate deformation model of coastal tectonics. This work adds to the understanding, modeling and quantifying long-term (Quaternary) rates of tectonic deformation in an area of high seismic potential where historic earthquakes such as the Michoacan 1985 event caused 3000 deaths and hundreds of millions of dollars in economic and property losses. The Guerrero gap represents an area of high seismic potential, probably accumulating strain that could be released in a large magnitude earthquake.