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

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-w 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.