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Review of earthquakes and tsunami records and characterization of capable faults on the northwestern coast of ecuador

Abstract:

There are only few documented moderate to strong earthquakes associated with active tectonics of capable crustal faults in Ecuador’s northwestern coastal region. The short seismic record begins with the great earthquake and tsunami on January 31, 1906 (Mw 8.8), followed by other destructive earthquakes and tsunamis in the subduction zone, which are recorded on January 19, 1958 (Mw 7.6) and December 12, 1979 (Mw 7.7). Furthermore, modest earthquakes from capable faults have been registered on April 9, 1976 (Mw 6.7), January 2, 1981 (Mw 5.9), June 25, 1989 (Mw 6.3), April 20, 2016 (Mw 6.0) and January 31, 2017 (Mw 5.5, MLv 5.7). Earthquakes of minor magnitude have not been considered in this study, as they lack to cause coseismic ground effects. In this study, a catalog of geological fault has been delineated with 41 segments of capable and active faults on the sea floor and inland segments of Esmeraldas and Manabí provinces, as the instrumental seismic record does not provide sufficient information to evaluate the seismic risk due to faults capable of generating earthquakes larger than Mw≥6. This methodological approach allowed to estimate the seismicity levels in the order of 6.0≤Mw≤7.3 and rock peak ground accelerations in the order of 0.42g 0.26g. These values have been obtained from empirical regression equations applied to the length of capable geological faults.