Hydrological anomalies connected to earthquakes in southern Apennines (Italy)

Abstract

Abstract. The study of hydrological variations in the watersheds of seismic areas can be useful in order to acquire a new knowledge of the mechanisms by which earthquakes can produce hydrological anomalies. Italy has the availability of many long historical series both of hydrological parameters and of seismological data, and is an ideal laboratory to verify the validity of theoretical models proposed by various authors.In this work we analyse the hydrological anomalies associated with some of the big earthquakes that occurred in the last century in the southern Apennines: 1930Apennines: , 1980Apennines: and 1984 For these earthquakes we analysed hydrometric and pluviometric data looking for significant anomalies in springs, water wells and mountain streams. The influence of rainfalls on the normal flows of rivers, springs and wells has been ascertained. Also, the earthquake of 1805, for which a lot of hydrological perturbations have been reported, is considered in order to point out effects imputable to this earthquake that can be similar to the effects of the other big earthquakes.The considered seismic events exhibit different modes of energy release, different focal mechanisms and different propagation of effects on the invested areas. Furthermore, even if their epicentres were not localised in contiguous seismogenetic areas, it seems that the hydrological effects imputable to them took place in the same areas. Such phenomena have been compared with macroseismic fields and transformed in parameters, in order to derive empirical relationships between the dimensions of the event and the characteristics of the hydrological variations.The results of this work point to a close dependence among hydrological anomalies, regional structures and fault mechanisms, and indicate that many clear anomalies have been forerunners of earthquakes. In 1993, the Naples Bureau of the Hydrographic National Service started the continuous monitoring of hydrologic parameters by a network of automatic stations and transmission in real time; presently 7 acquifers are under control in which also pH, T , salinity, elecCorrespondence to: R. Pece (pece@unina.it) trical conductivity, dissolved oxygen are measured. We envisage to increase the number of monitoring sites and controlled parameters.

Water-table and discharge changes associated with the 2016–2017 seismic sequence in central Italy: hydrogeological data and a conceptual model for fractured carbonate aquifers

“…A similar mechanism was observed after the 1980 Irpinia earthquake at Caposele spring (Esposito et al 2001) and, more recently, in the Abruzzi region after the L'Aquila 2009 earthquake (Adinolfi Falcone et al 2012). This last case has been explained by a double effect: (1) pore pressure propagation due to dynamic stresses caused by the seismic waves, which determined the sudden peak, and (2) an increase of bulk hydraulic conductivity of the fractured aquifer due to fracture cleaning triggered by the pore pressure propagation, which induces mobilization by shaking fine particles that block fracture throats (Amoruso et al 2011).…”

“…The effects of past earthquakes on groundwater in central Italy have been described by previous papers. Esposito et al (2001) describe the effects of four earthquakes in southern Apennines including the 1980 Irpinia earthquake, which generated important hydrogeological changes as far as 200 km from the epicenter, including a significant increase of Caposele spring flow. Amoruso et al (2011) describe the hydrogeological changes in a fractured aquifer after the L'Aquila 2009 earthquake, inferring that those changes were probably connected with the increase of bulk hydraulic conductivity at the aquifer scale, mainly due to fracture cleaning, raising hydraulic heads in the discharge zones, and correspondingly lowering them in the recharge areas (Adinolfi Falcone et al 2012;Galassi et al 2014).…”

Hydrological and Geochemical Changes Related to Earthquakes - Examples: Three Great Earthquakes of the XX Century in the Southern Apennines (Italy)

“…About 200 landslide phenomena were observed in an area more than 20.000 Km 2 wide around the epicentre. The study of the hydrological effects has been carried out on measurements of water levels, spring flows measured each day, streamflow levels measured each day, continuous registration of water level in rivers (Esposito et al, 2001) We considered also many other similar, but less continuous, measurements carried out during 1975-1985 (periodicity varied from weekly to monthly) on springs and rivers which exhibited a clear anomaly. Most of them are in the high Sele river and on Matese mountains (figures 5a-f).…”

Ground effects and hydrological changes in the Southern Apennines (Italy) in response to the 23 July 1930 earthquake (<i>M<sub>S</sub></i>=6.7)

“…For earthquakes in Southern Italy, the pre-and co-seismic stresses and the tectonic deformations have been correlated with the hydrologic changes in order to find a possible model of interaction between stress state and hydrological variations (Onorati et al, 1994;Esposito et al, 2001). (Table 1).…”

“…1), a complex carbonate formation, we collected well-founded information and records of hydrological phenomena that cannot be ascribed to environmental or anthropic causes (Onorati and Tranfaglia, 1994;Onorati et al, 1994;Esposito et al, 1998Esposito et al, , 1999Esposito et al, , 2000Esposito et al, , 2001Pece et al, 1999;Porfido et al, 2002Porfido et al, , 2007.…”