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Earthquake ground effects and intensity of the 16 april 2016 Mw 7.8 pedernales, ecuador, earthquake: Implications for the source characterization of large subduction earthquakes

Abstract:

Starting on the day after the mainshock, we mapped in the field and compiled all the available observations on earthquake environmental effects (EEEs) caused by the M<inf>w</inf> 7.8 subduction earthquake that hit the coastal region of Ecuador on 16 April 2016 (the Pedernales earthquake). These effects include: (a) permanent ground deformation, (b) open cracks, (c) liquefaction, (d) landslides, and (e) tsunami waves. We use these observations to evaluate the macroseismic field of the Environmental Seismic Intensity (ESI-07) scale and compare our results with published macroseismic data collected using traditional damage-based intensity scales. We found systematic difference in the assessed earthquake intensity and in the intensity attenuation with distance. A comparison of our dataset with the macroseismic data of six instrumental large-subduction earthquakes that occurred between Ecuador and Chile suggests that, for the Pedernales earthquake, the ESI-07 works better in the near field, whereas damage-based scales are more reliable in the far field. Therefore, we generate a single integrated intensity dataset for the Pedernales earthquake, including data measured with the European Macroseismic Scale 1998 (EMS-98), the modified Mercalli (MM) scale, and the ESI-07 scale. This new integrated macroseismic field provides reliable and comparable information on the seismogenic source, suggesting that a similar approach could be successfully applied to refine the source model of past subduction earthquakes in Ecuador and elsewhere.