Day 5: The Enigma of the San Isidro Landslides

Near San Isidro in Manabi there is a place known as ‘El Relleno’. Before the earthquake, this was a tranquil elevated green plateau overlooking miles of forest and fields in all directions. But on April 16 the ground deformed violently creating large depressions, “graben”-style, 12-20m deep, 30-50m across and hundreds or maybe thousands of meters long. With the ground under their feet moving up and down as if they were in an elevator and with sheds and stables crumbling around them, inhabitants narrowly escaped tragedy. Still, they lost their homes and 80 heads of cattle, chickens and crops, engulfed in the ocean of dirt and rock that was swirling around them.

With several parallel longitudinal depressions in the area, it seems as if the soil layers had bent sending the plateau 10m skywards. Not withstanding the curvature, the rocks seem to have fractured sending large volumes of soil and vegetation downwards again along parallel scarps. It must have been a violent deformation to create such a dramatic change in the landscape.

As we visited the site today, what we saw posed an interesting challenge. What happened here? What mechanism caused this? Was it indeed a compression-driven soil-bending event? Was it triggered by the weakening of deep layers of soil? Was what we saw the depression of a faulting system? Hard to say on site. We flew our drone and took long footage of the area in the hope that further analysis might bring a bit more clarity to this fascinating feature of this earthquake.

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