Growth of a sinkhole in a seismic zone of the northern Apennines (Italy)

• Published in: Natural hazards and earth system sciences Vol. 18; no. 9; pp. 2355 - 2366
• Main Authors: La Rosa, Alessandro, Pagli, Carolina, Molli, Giancarlo, Casu, Francesco, De Luca, Claudio, Pieroni, Amerino, D'Amato Avanzi, Giacomo
• Format: Journal Article
• Language: English
• Published: Katlenburg-Lindau Copernicus GmbH 12-09-2018; Copernicus Publications
• Subjects: Collapse; Deformation mechanisms; Earthquakes; Economic impact; Evolution; Fault zones; Lakes; Seismic activity; Seismic zones; Seismicity; Sinkholes; Solifluction; Subsidence; Synthetic aperture radar interferometry; Italy
• ISSN: 1684-9981; 1561-8633; 1684-9981
• DOI: 10.5194/nhess-18-2355-2018

Sinkhole collapse is a major hazard causing substantial social and
economic losses. However, the surface deformations and sinkhole evolution are
rarely recorded, as these sites are known mainly after a collapse, making the
assessment of sinkhole-related hazard challenging. Furthermore, more than
40 % of the sinkholes of Italy are in seismically hazardous zones; it
remains unclear whether seismicity may trigger sinkhole collapse. Here we use
a multidisciplinary data set of InSAR, surface mapping and historical records
of sinkhole activity to show that the Prà di Lama lake is a long-lived
sinkhole that was formed in an active fault zone and grew
through several events of unrest characterized by episodic subsidence and
lake-level changes. Moreover, InSAR shows that continuous aseismic subsidence
at rates of up to 7.1 mm yr−1 occurred during 2003–2008, between events
of unrest. Earthquakes on the major faults near the sinkhole do not
trigger sinkhole activity but low-magnitude earthquakes at 4–12 km depth
occurred during sinkhole unrest in 1996 and 2016. We interpret our
observations as evidence of seismic creep at depth causing fracturing and
ultimately leading to the formation and growth of the Prà di Lama
sinkhole.