Geomorphology as a tool for analysis of seismogenic sources in Latin America and the Caribbean

Abstract

Latin America and the Caribbean region have experienced numerous destructive earthquakes. Earthquakes represent one of the main causes of massive casualties and economic loss due mainly to the proximity of populated areas to plate boundaries and other dynamic parts of the Earth’s crust. Seismic ruptures related to shallow earthquakes (< 30 km deep) larger than magnitude M 6.0 may reach the surface, leaving imprints in the landscape. These structures correspond to crustal weaknesses where rock failure has been concentrated and stresses have been released episodically through time. Seismic recurrence along these structures is underlined by historical seismicity as confirmed by geologic information. Earth–surface deformation during an earthquake is concentrated at the epicentral region where the most important damage usually takes place. This coseismic deformation is related to the faults and folds linked at depth with the primary seismic sources. Part of these fault lines lie offshore, related to subduction zones and other major plate interaction features. However, many earthquake-related structures are located in continental areas. The surface deformation related to historic and prehistoric earthquakes allows their recognition and analysis in terms of the significance and characteristics of past earthquakes and the probability for future ones. These faults and folds can be regarded as potential seismogenic sources, highlighted sometimes by active seismicity and/or historic records of destructive earthquakes. However, many potentially active structures show no evidence of historic or instrumental seismicity. For those cases, gathering data with a time frame larger than the one provided by seismic catalogues is crucial for a proper seismic hazard assessment. Therefore terrain analysis and geomorphologic techniques are considered to be a primary tool for providing basic information in the seismic hazard evaluation of a specific structure or region. This chapter examines, through some examples, the contribution of the geomorphologic analysis to the evaluation of geological structures considered to be hazardous seismogenic sources in Latin America and the Caribbean.