Folder
ROOT
_ScienceBase Catalog
__USGS Data Release Products
___Seismic Hazard, Risk, and Design for South America
____1) Source models for South America
The crustal fault model accounts for earthquakes that occur on faults that have not ruptured recently, but have have been active in historic and prehistoric periods. Although hundreds of Quaternary faults have been mapped, only a few of these faults have been studied sufficiently to reach a consensus regarding rate of deformation that can be applied in this hazard assessment. Information regarding the seismogenic source geometry and seismogenic source behavior that is necessary to model each fault is included for each fault. Files that can be used as input to computer hazard code are included.
The subduction model accounts for large earthquakes (M 7–9.5) that occur on the subduction interface. The subduction zones along the northern and western coast of South America, the Panama deformation zones, and the Lesser Antilles subduction zone of the Caribbean are considered in the subduction model of this hazard assessment. The subduction interface of the Nazca plate beneath the western coast of South America has been separated into five zones, down to a depth of 50 km. The five zones are based on the locations of impinging subduction ridges, dimensions of large earthquakes, and fault complications. An alternative model for Chile (Medina et al., 2017) is applied to the Nazca subduction zones 3–5. This...
The smoothed seismicity model is based on a uniform seismicity catalog that is used to assess the location and rate of future earthquakes. This catalog is declustered by removing foreshocks and aftershocks so that only independent events are considered, as required in the probabilistic probabilistic methodolgy used to assess seismic hazard. Future seismicity rates are estimated by counting historical earthquakes in a grid with a cell dimension of 0.1 degrees in latitude and longitude. These gridded earthquake rates are smoothed using a 50 kilometer fixed length smoothing kernel. Separate rate models were developed for the craton and active tectonic regions for earthquake depths between 0 and 50 km. Gridded...
In develpoing the hazard model for South America, the USGS considered the ground motion models (GMM) used for the conterminous United States because most of the equations consider global earthquakes and because the U.S. and South America are seismically quite similar, with the potential for active subduction, deep intraslab, crustal, and craton earthquakes. Included here is a table that summarizes the GMMs selected for each of the earthquake types and the weight applied within the model.
A uniform seismicity catalog is necessary to assess the location and rate of future earthquakes. This catalog is declustered by removing foreshocks and aftershocks so that only independent events are considered, as required in the probabilistic probabilistic methodolgy used to assess seismic hazard. The uniform and declustered catalogs are included here.
