DOI: http://dx.doi.org/10.5027/andgeoV46n1-2991

Characterization of seismogenetic crustal faults in the Gulf of Guayaquil, Ecuador

Kervin Chunga, Fernando Mato, Maurizio Mulas, Felipe Ochoa-Cornejo

Abstract


Only few moderate to strong earthquakes associated with active tectonics of capable crustal faults have been documented for the Ecuador’s southern coastal region. The relatively short seismic record initiates with the Guayaquil earthquake in 1787 (Mw 6.5), which is followed by another destructive one in 1943 (Mw 6.2) and later the most recent one in 1980 (Mw 6.1). Unfortunately, these historical earthquake records do not provide sufficient information to evaluate the seismic risk for faulting capable to generate earthquakes with magnitude M≥6. Earthquakes of minor magnitudes are not considered in this study as they most unlikely cause ground coseismic effects. A catalog of geological faults has been delineated in this study with 40 segments of capable and active faults on the sea floor of the Gulf of Guayaquil and inland segments of Guayas, Santa Elena and El Oro provinces. This methodological approach allowed to estimate a variety of levels of seismicity in the order of 6.2 to 7.2 degrees of magnitude and rock peak ground accelerations in the order of 0.41g 0.24g. These values have been obtained from empirical regression equations applied to the length of capable geological faults. The F-40 seismogenic structure located in the accretionary prism, being close to the subduction zone, is capable to generate earthquakes in the order of 8.2 in magnitude, causing potential ground coseismic damage to the close-by city of Guayaquil. Furthermore, local tsunami hazards, may affect severely densely populated areas and developing industries sectors on the coast around the Gulf of Guayaquil. All this structural geological analysis provides new data, which need to be reconsidered in the seismic hazard evaluation. This may include for the generation of control spectra for vertical and horizontal components from capable fault. Subsequently, Ecuador´s most populated city may be affected by the reactivation of such geological faults.

Keywords


Capable fault, crustal earthquake, estimated magnitudes, Guayaquil Gulf.

How to cite this article Chunga, K., Mato, F., Mulas, M., and Ochoa-Cornejo, F., 2018, Characterization of seismogenetic crustal faults in the Gulf of Guayaquil, Ecuador: Andean Geology, v. 46, no. 1, , doi:http://dx.doi.org/10.5027/andgeoV46n1-2991