Felt index, source parameters and ground motion evaluation for earthquakes at Mt. Vesuvius

Results of non-instrumental surveys carried out on the recent and past seismicity at Vesuvius fave been retaken in order to propose new analyses regarding source mechanisms and causative faults. We present the results of the October 9, 1999 earthquake, the most intense event since the 1944 eruption

Analysis of historical and recent earthquakes at Campi Flegrei caldera for seismic hazard evaluation

Introduction At Campi Flegrei about 500,000 people live on caldera and the risk associated to an eruption is very high, but its complete evaluation includes also the potential damage due to earthquakes accompanying eruptions. Moreover low-moderate energy earthquakes are also observed in volcanic active areas during quiescent periods. Generally such events are shallow and produce high intensities in the epicentral area. Today at Campi Flegrei the high housing density and economic value exposed make the area of considerable importance for mitigating seismic risk. To evaluate the effects of the earthquakes at Campi Flegrei, data are required on the location, source mechanism and damage levels of earthquakes, in addition to understanding how dynamic processes occur. A damage map of the maximum earthquake expected is proposed

Felt index, source parameters and ground motion evaluation for earthquakes at Mt. Vesuvius

Results of non-instrumental surveys carried out on the recent and past seismicity at Vesuvius fave been retaken in order to propose new analyses regarding source mechanisms and causative faults. We present the results of the October 9, 1999 earthquake, the most intense event since the 1944 eruption

Analysis of historical and present earthquakes at Vesuvius for seismic hazard evaluation

Introduction At Vesuvius about 600,000 people live on the volcano and the risk associated to a large eruption is very high, but its complete evaluation includes also the potential damage due to earthquakes accompanying eruptions. Moreover low-moderate energy earthquakes are also observed in volcanic active areas during quiescent periods. Generally such events are shallow and produce high intensities in the epicentral area. Today at Vesuvius the high housing density and economic value exposed make the area of considerable importance for mitigating seismic risk. To evaluate the effects of the earthquakes at Vesuvius, data are required on the location, source mechanism and damage levels of historical earthquakes, in addition to understanding how Vesuvius works. A damage map of the maximum earthquake recorded is proposed

On the mechanics of caldera resurgence of Ischia Island (southern Italy)

A model of caldera resurgence was applied to the Island of Ischia to explain uplift, volcanic activity and tectonics on Mount Epomeo, as well as historical seismicity and slow ground movements recorded for the past 2000 years. A two-dimensional mechanical model was utilized for the crust, which was considered to be an elastic plate overlying a laccolith. Geometric dimensions and mechanical parameters were constrained using geological, geophysical and geochemical data. We propose that a laccolith, with a diameter L of c. 10 km, and a depth of up to 1 km in the centre of the island, triggered the caldera resurgence after the Mount Epomeo Green Tuff eruption forming the caldera (55 000 a BP). A bending phase and a punched laccolith phase are thought to have caused the observed deformations in the caldera. These processes control the tectonics at the boundary of the Mount Epomeo resurgent structure, volcanic activity and dynamics of the island

Historical eartquakes at Ischia island and seismic hazard assessment

Hystorical data of seismicity at Ischia island (Southern Italy) cover a period of almost 800 years. Since 1228 numerous events exceeded VII MCS degree. The epicentral areas of the earthquakes are located in the northern sector of the island; only one earthquake (1302, VIII MCS degree) was correlated with the latter eruption occurred during 1301-02 AD along the eastern sector of the island. In few cases the earthquakes (1228, 1863, 1881, 1883 AD) were followed by landslides which have produces serious damage while, in average, ground effects (i.e. fractures, capacity and temperature variation of hot springs) were often observed before and after each event. The historical seismicity of Ischia shows the peculiar characteristics of volcanic earthquakes as shallow ipocentral depth ( 1 km), high intensity, strong directional attenuation of effects and local amplification of damages. At Ischia, the 1883 AD earthquake of “Casamicciola” represents the unique example of modern age earthquake in Mediterranean volcanic area which produced more than 2300 fatalities. The catastrophic effects of this earthquake (Imax=XI MCS degree) covered an area of about 3 km2 in the northern sector of the island, while strong attenuation effects were observed, especially along the south and east directions. From 1883 AD until today a seismic silence in the island has been observed. Some events have been felt from the beginning of the 20th century while, in the last 10 years just few events (M < 2), have been recorded by the INGV-OV surveillance seismic network, localized prevalently in the northern sector of the island. The lack of significant seismicity allow the study of macroseimic data of 1883 earthquake as the fundament issue for hazard assessment, also if considering the increasing of housing density and the high exposed value in the island. Data of earthquake damages and ground effects, obtained by archives sources and literature, have been utilized (also using GIS cross-correlation with geological data) in order to evaluate the tendency of the attenuation for different zones of the island, to detach the contribution of the source from the medium, and define the zones of maximum expected damage

VULCANOLOGIA E SISMOLOGIA: IL GIAPPONE E NAPOLI

Il Giappone dista da Napoli 10.000 km ma l’arcipelago giapponese ha in comune con il Golfo di Napoli e la Campania Felix dei Romani la genesi geologica, in quanto sono stati formati da processi geodinamici del tutto simili, come la natura vulcanica dei suoli, il morbido paesaggio dei coni e dei crateri vulcanici, le manifestazioni fumaroliche delle «solfatare» ed il termalismo quali spie della presenza di masse di magma intrappolate nella crosta a piccola profondità, la sismicità, chiara manifestazione della non sopita dinamica di questi territori. Due terre con tali caratteristiche non potevano non incontrarsi per i comuni interessi nella crescita della conoscenza dei fenomeni vulcanici e sismici e per la mitigazione dei loro effetti sulle popolazioni esposte. Non a caso Italia e Giappone saranno nella seconda metà dell’Ottocento i paesi più avanzati nello studio dei terremoti e dei vulcani

Resurgence and flank failure of Mt. Epomeo, Ischia Island (Southern Italy)

Risorgenza e collasso laterale del Monte Epomeo, Isola d’Ischia Il Monte Epomeo (787 m a.s.l.), ubicato nel settore centrale dell’isola d’Ischia, mostra lo smantellamento del settore meridionale, depositi di debris e franamenti diffusi che testimoniano la natura instabile del monte. A seguito dell’eruzione ignimbritica del Tufo Verde dell’Epomeo (55.000 anni), che genera una struttura calderica (10x7 km2), inizia la risorgenza della caldera fino alla formazione del Monte Epomeo. Il sollevamento, generato dall’intrusione di un laccolite fino a circa 1 km di profondità, avrebbe determinato una forte instabilità gravitativa del blocco risorgente e prodotto uno o più collassi laterali. Questi hanno lasciato una struttura a ferro di cavallo, tipica di processi da “avalancing”, aperta verso sud, e depositi con topografia “hummocky” estesi a sud dell’Epomeo e rilevati recentemente da esplorazioni sul fondo marino. Il processo che ha generato il collasso e la formazione di un avalanche caldera è stato esaminato attraverso l’analisi della dinamica e dei caratteri geologici, geomorfologici e strutturali dell’area. Attualmente l’isola è caratterizzata da una fase di stasi della risorgenza testimoniata da una condizione di moderata stabilità dei versanti dell’Epomeo. Quanto osservato indicherebbe una bassa dinamica endogena nell’isola

Sea level changes, ground deformations, human settlements in the bay of Naples

Ground deformations in active volcanoes are considered precursors of eruptions according to the most tested models; therefore monitoring networks of ground deformations are installed on inhabited dangerous volcanoes. Direct measurements of such deformations are carried out since 1861 when Luigi Palmieri monitored the eruption at Mt. Vesuvius with levelings along the shoreline near the town of Torre del Greco. Relative sea level changes were measured at Serapeo in Pozzuoli in the middle of 19th century to record soil uplifts which are locally known as bradyseism. To enlarge the time series of data on these phenomena it is necessary to utilize historical and prehistorical informations on the location of shore-line of human settlements. As regards the regions of active volcanoes as the Neapolitan one three processes contribute to sea level changes as eustatism, regional tectonics and local intrusive and effusive phenomena. Therefore at the same time the relative sea level should be different at far-away places only few kilometres according to the volcanic activity. In fact eustatic and tectonic processes contribute to sea level changes with very lesser rates than volcanic activity. The Neapolitan region for its geological history is an excellent laboratory for testing the validation of new paradigms for some natural phenomena

Sorveglianza sismica a Stromboli: Settembre 1986

In the tex