Palaeoseismological evidence for the 1570 Ferrara earthquake, Italy

Abstract

In May 2012, two earthquakes (Mw 6.1 and 5.9) affected the Po Plain, Italy. The strongest shock produced extensive secondary effects associated with liquefaction phenomena. Few weeks after the earthquakes, an exploratory trench was excavated across a levee of the palaeo‐Reno reach, where a system of aligned ground ruptures was observed. The investigated site well preserves the geomorphic expression of a fluvial body that mainly formed in the fifteenth to sixteenth centuries as historical sources and radiometric data testify. In the trench several features pinpointed the occurrence of past liquefaction events: (i) dikes filled with overpressured injected sand and associated with vertical displacements have no correspondence with the fractures mapped at the surface; (ii) thick dikes are buried by the plowed level or even by fluvial deposits; (iii) although some of the 2012 ground fractures characterized by vertical displacement and opening occurred in correspondence of thick dikes observed in the trench, sand and water ejection did not occur; (iv) some seismites (load casts) were observed in the trench well above the 2012 water level. The results strongly suggest that shaking has locally occurred in the past producing a sufficient ground motion capable of triggering liquefaction phenomena prior to, and likely stronger than, the May 2012 earthquake. Historical seismicity documents three seismic events that might have been able to generate liquefaction in the broader investigated area. Based on the analysis of their macroseismic fields, the 17 November 1570 Ferrara earthquake is the most likely causative event of the observed palaeoliquefactions.

Seismically Induced Soft‐Sediment Deformation Phenomena During the Volcano‐Tectonic Activity of Campi Flegrei Caldera (Southern Italy) in the Last 15 kyr

“…Liquefaction is often interpreted as seismically induced, during which saturated sands become fluid like as a consequence of the abrupt increase of the pore water pressure, thereby reducing the rigidity of loose sediments to zero (e.g., Allen, ; Caputo et al, ; Galli, ; Loope et al, ; Montenat et al, ; Owen, ; Tuttle et al, ; Wang, ; Youd, ). The loss of the ground strength can trigger landslides and, in inhabited areas, can cause buildings tilt and damage and destroy roadways and pipelines.…”

“…Other seismically induced soft‐sediment deformations (SSDs) are load structures and slumps frequently hosting minor thrust and normal faults, mainly recorded in coastal, deltaic, and turbidite settings and also in flat‐lying layers such as lacustrine sediments (Alsop & Marco, ; García‐Tortosa et al, ; Jiang et al, ; Moretti & Ronchi, ; Moretti & Sabato, ; Rodríguez‐Pascua et al, ; Uner, ). Although seismically induced sand dikes and slumps are commonly observed within the geological record, examples of paleosand volcanoes are very limited (e.g., Caputo et al, ; Loope et al, ). These features are useful for improving the paleoseismological record, especially in areas of low to moderate seismic activity.…”

GPR and high resolution seismic integrated methods to understand the liquefaction phenomena in the Mirabello Village (earthquake ML 5.9, 2012)

“…A trench in the survey area (Fig. 5) exposed the liquefaction features (Papathanassiou et al, 2012;Caputo et al, 2016) and we quantified their sizes that were compatible with GPR sections (Baradello et al, 2014).…”

Multiple X‐ray approaches to discriminate the origin of liquefied sand erupted during the 2012 Emilia Romagna earthquake

“…The A‐area was the most affected by this phenomenon and therefore the most studied . The stratigraphic section of this area can be deduced by combining the geological description of Borgatti et al and Facciorusso et al (Fig.…”

“…). Many studies investigated the causes of this phenomenon and suggest that it was because of the liquefaction of water‐saturated sand deposits induced by the earthquake . Few researcher put forward the idea that this phenomenon could have been enhanced by the presence of a gaseous phase .…”