GEER findings – ground failure

We did not found evidence for surface fault rupture. Scott Kieffer, Teddy Button, and students looked in the area of the Pettino and Paganica faults. Both faults are very well expressed at the surface, but we did not find evidence of displacement from this earthquake. However, recent reports from others indicate some ground failure in vicinity of Paganica fault, and some geologists are going into the field to look more carefully at this. Therefore, it is too early to conclude that there was no surface rupture.

Ground failure occurred at Lake Sinizzo, where slumping occurred around the rim of this natural lake (no obvious dam). We have performed detailed mapping of the ground fissures and measured crack widths so that displacement vectors can be developed. Surface soils are gravelly clay, but we don’t know what materials are at depth. Hence, we don’t know if this is a liquefaction issue or slope failure in clay. No sediment boils.  Displacement range from few cm to about 15 m. No structures were affected. A photograph along the margin of the lake is attached below.

Lake Sinizzo

Ground failure involving fissures but no sediment boils was also observed by George Mylonakis near Onna. There is a creek nearby, and this may have involved displacements towards the creek. The ground fissures passed around the foundation of a building in the area.

There are a number of other cases of slope displacements and rockfalls, some of which impacted structures. These were in the vicinity of Onna and Paganica. Additional reports continue to come in, so this information will change with time.