The Earthquake Lights (EQL) of the 6 April 2009 Aquila Earthquake, in Central Italy
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Nat. Hazards Earth Syst. Sci., 10, 967–978, 2010 www.nat-hazards-earth-syst-sci.net/10/967/2010/ Natural Hazards doi:10.5194/nhess-10-967-2010 and Earth © Author(s) 2010. CC Attribution 3.0 License. System Sciences The earthquake lights (EQL) of the 6 April 2009 Aquila earthquake, in Central Italy C. Fidani Dipartimento di Fisica, Universita´ di Perugia, Via A. Pascoli, Perugia, Italy Received: 30 December 2009 – Revised: 22 March 2010 – Accepted: 12 April 2010 – Published: 7 May 2010 Abstract. A seven-month collection of testimonials about nitude (Mw) ≥5, the two strongest ones occurred on 7 April the 6 April 2009 earthquake in Aquila, Abruzzo region, (M=5.6), at 19:47 LT, and on 9 April (M=5.4), at 02:52 LT, Italy, was compiled into a catalogue of non-seismic phe- (Bindi, 2009). A summary of the Aquila seismic sequence is nomena. Luminous phenomena were often reported starting reported; earthquake times are compared with times of EQL about nine months before the strong shock and continued un- (Table 1). til about five months after the shock. A summary and list of A complete account of previous testimonials already com- the characteristics of these sightings was made according to piled (Fidani, 2005), dating back as far as 2000 BC and con- 20th century classifications and a comparison was made with tinuing to the present day, regard only vague statements con- the Galli outcomes. These sightings were distributed over a cerning the general features of luminosity. A critical re- large area around the city of Aquila, with a major extension view of luminous testimonies has stressed the importance to the north, up to 50 km. Various earthquake lights were cor- of selecting a scientific scope (Stothers, 2004). Middle-Age related with several landscape characteristics and the source legends have also been reinterpreted in a multidisciplinary and dynamic of the earthquake. Some preliminary considera- manner taking into account luminous phenomena (Piccardi, tions on the location of the sightings suggest a correlation be- 2005). The first collection of EQL data was compiled in tween electrical discharges and asperities, while flames were Italy in the early 20th century by the religious naturalist Ig- mostly seen along the Aterno Valley. nazio Galli; it contained a first ordering of historical phenom- ena based on the shapes and time evolutions (Galli, 1910). Seismological studies have also taken into account historical luminous phenomena, recognizing them as just the darkest 1 Introduction chapter in seismology (Sieberg, 1911). The same phenom- This study presents the preliminary results of a collection ena have been recorded in Japan (Terada, 1931), along with of testimonies about luminous phenomena related to seis- tsunamis (Terada, 1934). Frederic Montandon proposed a mic activity in and near Aquila before and after the main revised classification which reduced Galli’s number of EQL seismic event (M=6.3), at 03:32 LT on 6 April 2009. The types from nine to five (Montandon, 1948). The first EQLs main shock caused strong shaking in and near Aquila causing were photographically documented in 1966 along with a re- heavy damage and 307 casualties. The earthquake of 6 April port containing numerous testimonials during an earthquake 2009 was the strongest event in a sequence of seismic events swarm near Matsushiro (Yasui, 1973). A review of observa- that started a few months earlier; local seismic activity began tions has highlighted the well established existence of lumi- to increase in December 2008 (Pondrelli, 2010). The most nous phenomena plus proposed theories (Derr, 1973). After significant prior events occurred on 30 March (M=4.4), at Galli’s collection, EQLs were reported in Italy on two rare 15:38 LT, 5 April (M=4.2), at 22:48 LT and 6 April (M=3.9), occasions: the Irpinia earthquake in 1930 (Oddone, 1930; at 00:39 LT (Chiarabba, 2009). The main shock was followed Alfano, 1931) and the Friuli earthquake in 1976 (Matteu- by seven aftershocks within the first week; the moment mag- cig, 1985). Further reports have been published on cities in Canada (St-Laurent, 2000), Mexico (Araiza-Quijano, 1996), Japan (Enomoto, 1998), Greece (Soter, 1999) and more re- Correspondence to: C. Fidani cently in Peru (Lira, 2008). (cristiano.fidani@fisica.unipg.it) Published by Copernicus Publications on behalf of the European Geosciences Union. 968 C. Fidani: Aquila EQLs Table 1. The earthquake sequence list, time in LT and depth in km. ing through old classifications and newer classifications for space-time order, which allow for some interesting interpre- tations that are discussed in Sect. 5. Date Time Mw Latitude Longitude Depth 2 The collection of testimonials and their scopes 30 Mar 2009 15:38 4.4 42.321 13.376 9.8 30 Mar 2009 23:57 3.6 42.316 13.375 9.5 2 Apr 2009 13:11 2.9 42.310 13.374 10.1 The collection of testimonials began a few days after the 3 Apr 2009 06:44 3.3 42.314 13.376 9.2 main shock on 11 April 2009 in the Amatrice area (Lazio 5 Apr 2009 22:48 4.2 42.325 13.382 9.5 region) of Italy, about 50 km north of Aquila. A system- 6 Apr 2009 00:39 3.8 42.329 13.385 10.0 atic regional survey of the population was carried out us- 6 Apr 2009 03:32 6.3 42.343 13.380 8.9 ing questionnaires (Soter, 1999). The testimonies were col- 6 Apr 2009 04:37 5.1 42.360 13.328 8.7 lected by visiting the 179 camps prepared by the Italian Civil 6 Apr 2009 05:56 4.5 42.335 13.386 9.3 Protection (PotezioneCivile, 2009). Testimonials were also 6 Apr 2009 18:38 4.4 42.363 13.339 10.0 7 Apr 2009 01:15 5.1 42.363 13.385 9.7 collected in meeting places such as schools, malls, hospi- 7 Apr 2009 19:47 5.6 42.303 13.486 13.3 tals, coffee shops and social clubs. Furthermore, to collect 9 Apr 2009 02:52 5.4 42.484 13.343 15.4 data and supporting documents, personnel at public and pri- 9 Apr 2009 21:38 5.2 42.501 13.356 17.2 vate institutions such as the police, firemen, as well as forest 12 Apr 2009 20:05 3.6 42.384 13.388 9.8 rangers were interviewed. The order of the interviews moved 13 Apr 2009 23:14 5.0 42.498 13.377 9.0 from the least hit areas in the Rieti province to the most hit 26 Apr 2009 19:56 3.5 42.456 13.378 10.6 areas in Aquila. 5 May 2009 20:03 3.3 42.270 13.509 10.1 The aims of this data collection were to: 1) instruct the ge- 10 May 2009 18:00 3.8 42.301 13.479 10.0 7 Jun 2009 21:22 3.9 42.350 13.483 10.4 neral public on the existence of these earthquake-associated 11 Jun 2009 19:21 3.7 42.335 13.438 10.6 phenomena; 2) propose new hypotheses on earthquake pro- 15 Jun 2009 17:21 3.4 42.439 13.445 10.1 cesses; and 3) suggest new devices for systematic recording 29 Jun 2009 07:54 3.4 42.463 13.366 13.5 of these phenomena. At the time of the interviews less than 03 Jul 2009 13:03 4.3 42.409 13.387 8.8 1% of the people interviewed knew something about such 31 Aug 2009 16:09 3.3 42.250 13.517 10.0 phenomena; even though in the past Italy was one of the 24 Sep 2009 18:14 4.4 42.453 13.330 9.7 principal EQL research study centers (Fidani, 2005), with 30 Sep 2009 14:02 2.6 42.297 13.527 18.8 many 18th century reports that frequently described all the phenomena (Galli, 1910). On the other hand, atmospheric, electromagnetic and physiologic phenomena, which were observed mainly before and after the shaking, needs to be The processes to explain luminous phenomena were included in a larger process to be explained. Thus, new thought to be due to charge recombination. Thus, a sepa- instrument-based hypotheses are expected to give a notable ration of charge was necessary and was explained by some contribution, and can now be tested by low cost digital tech- physical effect such as: streaming potential (Terada, 1931), nology. piezoelectric (Finkelstein, 1973), water pore vaporization The main part of the data collection regards luminous and droplet disruption (Lockner, 1983) and localized charge phenomena which were abundantly observed on this oc- remains (Lockner, 1985). Sonoluminescence was also pro- casion. Secondary phenomena concern fluid emissions, posed as a possible process associated with seismic waves chasms, thermal release, unusual meteorological phenomena (Johnston, 1991). A recently study on positive charge gen- and sounds, radio and telecommunication disturbances and eration in igneous rocks opened the way to explaining lu- either human physiological alterations or changes in animal minous and other phenomena in a single coherent physical behavior. A questionnaire was compiled to collect valuable model (Freund, 2002). Charge accumulations at asperities information on the public perception (Bird, 2009) of these in the crust can produce corona discharges accompanied by phenomena, for which no instruments were active at the time the emission of light (St-Laurent, 2006). Laboratory ex- and site of the Aquila earthquake. The questions were in- periments on electrification obtained from mechanical dam- spired from previous works (Galli, 1910; Terada, 1931; Mat- age were also performed (Schloessin, 1985).