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Minimum 1D velocity models and station corrections have been computed for the central Mediterranean area using two main data sets. The first one consists of accurate first arrival-time readings from 103 seismic events with magnitude (ML)≥3.5 recorded by the Italian National Seismic Network (RSN) and the AlpArray Seismic Network (AASN) in the period 2014–2021. Earthquakes were selected on the basis of their spatial distribution, epicentral distance to the nearest seismic station, and maximum distance traveled by Pn and Sn phases. This fine selection of high-quality data combined with the spatial density of the AlpArray seismic stations was decisive in obtaining high resolution for upper mantle velocity, especially in the Alpine belt. To obtain a denser coverage of crustal rays, we extended the first data set with P and S arrivals of local earthquakes from Istituto Nazionale di Geofisica e Vulcanologia (INGV) bulletin data (2016–2018). A total of 75,807 seismic phases (47,183 P phases and 28,264 S phases) have been inverted to calculate best-fit 1D velocity models, at regional and local scales. We then test the performance of the optimized velocity models by relocating the last four years of seismicity recorded by INGV (period 2017–2020). The computed velocity models are very effective for routine earthquake location, seismic monitoring, source parameter modeling, and future 3D seismic tomography.

We used the data from the dense, broadband AlpArray Seismic Network to derive a set of Receiver Function (RF) measurements on the Moho and Lithosphere-Asthenosphere Boundary (LAB) for a broad region encompassing the Western Alps and including the Ivrea Geophysical Body (IGB), a fragment of mantle emplaced in the lower continental crust. Our analysis fills an information gap since, in spite of numerous active and passive seismological investigations on the Alpine orogen, many of the observations focus on the Moho or the deeper part of the mantle, while reliable information on the LAB below the Alps is scarce. Moreover, our findings provide an additional contribution to resolving the debated topic of the existence of continuous or interrupted continental subduction below the Western Alps.We derive seismic velocity profiles of the crust-uppermost mantle below each of the 50 analyzed stations down to about 250 km depth, through the joint inversion of P and S RFs. We constrain the lateral variations of the Moho and LAB topographies across the colliding plates, and quantify the errors related to our measurements. Our observations allow us to considerably expand the published data of the Moho depth and to add a unique set of new measurements of the LAB (Monna et al., 2022). Our results yield a comparable thickness (on average 90–100 km) of the Eurasia and Adria lithospheres, which are colliding below the IGB; Eurasia is not presently subducting below Adria with vertical continuity. These findings suggest that there is a gap between the superficial (continental) European lithosphere and the deep (oceanic) lithosphere, confirming the discontinuous structure imaged by some seismic tomography models.the AlpArray Working Group: list on http://www.alparray.ethz.ch/home/Monna, S., Montuori, C., Frugoni, F., Piromallo, C., Vinnik, L., & AlpArray Working Group (2022). Moho and LAB across the Western Alps (Europe) from P and S receiver function analysis. Journal of Geophysical Research: Solid Earth, 127, e2022JB025141. https://doi.org/10.1029/2022JB02514

One important aspect of the seismicity is the spatiotemporal clustering; hence, the distinction between independent and triggered events is a critical part of the analysis of seismic catalogs. Stochastic declustering of seismicity allows a probabilistic distinction between these two kinds of events. Such an approach, usually performed with the epidemic-type aftershock sequence (ETAS) model, avoids the bias in the estimation of the frequency–magnitude distribution parameters if we consider a subset of the catalog, that is, only the independent or the triggered events. In this article, we present a framework to properly include the probabilities of any event to be independent (or triggered) both in the temporal variation of the seismic rates and in the estimation of the b-value of the Gutenberg–Richter law. This framework is then applied to a high-definition seismic catalog in the central part of Italy covering the period from April 2010 to December 2015. The results of our analysis show that the seismic activity from the beginning of the catalog to March 2013 is characterized by a low degree of clustering and a relatively high b-value, whereas the following period exhibits a higher degree of clustering and a smaller b-value.

Introduction: Coronary microvascular dysfunction (CMD) is a potential cause of myocardial ischemia and may affect myocardial function. CMD can be identified, in patients with non-obstructive coronary artery disease (CAD), by a reduced transthoracic Doppler-derived coronary flow reserve (CFR), which is an index of coronary arterial reactivity. Hypothesis: The aim of this study was to investigate the dipyridamole-induced changes of global longitudinal strain (GLS) in patients with CMD. Methods: fiftythree patients (35M, 18F; mean age 67±8 years) without obstructive CAD, assessed by invasive coronary angiogram, underwent dipyridamole stress echocardiography. CFR were determined as the ratio of hyperaemic to baseline diastolic coronary flow velocity. CMD was defined as CFR < 2. GLS was visualized as a bull’s-eye map in a quick and feasible manner. In each patient, we used a frame rate of 70 frames/sec for adequate 2D strain analysis. We analyzed GLS at each step of stress test and compared peak-dose values with baseline. Results: Sixteen patients (30%) among the overall population showed CMD. There were no significant differences in baseline characteristics between patients with or without CMD. GLS, at baseline, was significantly lower in patients with CMD (-16.7±3.77 vs. -17.9±3.75 - p Conclusions: GLS analysis, performed by comparing dipyridamole peak-dose with baseline values, shows that in patients with CMD there is a different response of left ventricular myocardiim to stress test. It could be assumed that the inverse correlation between CFR and delta GLS reflects a progressive subclinical worsening of left ventricular myocardial function in these patients. Larger studies could confirm our data.

Background Coronary microvascular dysfunction (CMD) is a potential cause of myocardial ischemia and may affect myocardial function at rest and during stress. CMD can be identified, in patients with non-obstructive coronary artery disease (CAD), by a reduced transthoracic Doppler-derived coronary flow reserve (CFR), which is an index of coronary arterial reactivity, and can be impaired in both obstructive CAD and CMD. The aim of this study was to investigate the dipyridamole-induced changes of global longitudinal strain (GLS) in patients with CMD. Methods 43 patients (29M, 14F; mean age 68±7 years) without obstructive CAD, assessed by invasive coronary angiogram, underwent dipyridamole stress echocardiography. Coronary flow was assessed in the left anterior descending coronary artery (LAD) and was identified as the colour signal directed from the base to the apex of the left ventricle, containing the characteristic biphasic pulsed-Doppler flow signals. CFR were determined as the ratio of hyperaemic to baseline diastolic coronary flow velocity. CMD was defined as CFR GLS was measured using automated function imaging, through the positioning of three endocardial markers (two markers at the mitral annulus and one at the apex) in each apical view. Subsequently, the obtained segmental values of GLS were visualized as a bull's-eye map in a quick and feasible manner. We had optimal left ventricular endocardial tracking in the overall population. In each patient, we used a frame rate of 70 frames/sec for adequate 2D strain analysis. We analyzed GLS at each step of stress test and compared peak-dose values with baseline. Results Thirteen patients (30%) among the overall population showed CMD. There were no significant differences in baseline characteristics between patients with or without CMD. GLS, at baseline, was significantly lower in patients with CMD (−16.9±3.78 vs. −17.8±3.77 – p Conclusions GLS analysis, particularly performed by comparing dipyridamole peak-dose with baseline values, shows that in patients with CMD there is a different response of left ventricular myocardiim to stress test. It could be assumed that the inverse correlation between CFR and delta GLS reflects a progressive subclinical worsening of left ventricular myocardial function in these patients. Larger studies could confirm our data. Funding Acknowledgement Type of funding source: None

We present a detailed analysis of the seismic activity in the central Apennines based on a high quality seismogram data set collected from two temporary and three permanent networks. This integrated network recorded, between January 2009 and December 2013, a total of 7011 local earthquakes (6270 selected for this study), with local magnitudes M L ranging from 0.4 to 4.7. Hypocentres were located by using a reference 1D crustal velocity model determined with a genetic algorithm. The majority of the hypocenters are located beneath the axis of the Apenninic belt, while the rest are found along the peri-Tyrrhenian margin. Hypocentral depth distribution extends to a depth of 31 km with a pronounced peak between 8 and 12 km. Both low-to-moderate magnitude seismic sequences and diffuse swarm-like seismicity was observed. There were two major seismic swarms and a seismic sequence, which included the Marsica-Sora M L 4.7 main shock. A total of 468 fault plane solutions were derived from P -wave polarities. This new data set more than quadruples the number of focal mechanisms that was previously available for regional stress field analysis in the study region. The majority of the fault plane solutions in the central Apennines show predominantly normal fault movements, with T-axis trends oriented NE-SW. Focal mechanisms calculated in this study confirm that this area is in extension. For the seismic swarms-sequence in the Marsica-Sora area we also derived the azimuth and plunge of the principal stress axes by inverting fault plane solutions. We find a few right-lateral strike-slip focal mechanisms that possibly identify the prolongation of the strike-slip kinematics in the Gargano-Apulia foreland to the west, and mark the passage to the NW-SE striking normal faults of the inner Apenninic belt. The seismicity and stress distribution we observe might be consistent with a fragmented tectonic scenario in which faults with small dimensions release seismic energy in a diffused way.

T-waves are acoustic waves generated by earthquakes at the land–water interface. They can propagate efficiently for thousands of kilometers within the ocean’s low-velocity waveguide—the SOund Fixing And Ranging (SOFAR) channel. In the present work, we studied T-waves that propagate in the Ionian basin and are generated by regional earthquakes (epicentral distance

The SEISMOFAULTS project (www.seismofaults.it) was set up in 2016 with the general plan of exploring the seismicity of marine areas using deep seafloor observatories. The activity of the first two years (Seismofaults 2017 and 2018) consisted of the installation of a geophysical-geochemical temporary monitoring network over the Ionian Sea floor. Eleven ocean-bottom seismometers with hydrophones (OBS/H) and two seafloor geochemical-geophysical multiparametric observatories were deployed to: (1) identify seismically active faults; (2) identify potential geochemical precursors of earthquakes; and (3) understand possible cause–effect relationships between earthquakes and submarine slides. Furthermore, five gravity cores were collected from the Ionian Sea bottom and ~4082 km of geophysical acquisition, including multibeam and single channel seismic reflection data, were acquired for a total of 4970 km 2 high-resolution multibeam bathymetry. Using Niskin bottles, four water column samples were collected: two corresponding at the location of the two multiparametric observatories (i.e., along presumably-active fault zones), one corresponding at a recently discovered mud volcano, and one located above a presumably-active fault zone away from the other three sites. Preliminary results show: (1) a significant improvement in the quality and quantity of seismological records; (2) endogenous venting from presumably active faults; (3) active geofluid venting from a recently-discovered mud volcano; and (4) the correct use of most submarine devices. Preliminary results from the SEISMOFAULTS project show and confirm the potential of multidisciplinary marine studies, particularly in geologically active areas like southern Italy and the Mediterranean Sea.

We present the first high-quality catalog of early aftershocks of the three mainshocks of the 2016 central Italy Amatrice-Visso-Norcia normal faulting sequence. We located 10,574 manually picked aftershocks with a robust probabilistic, non-linear method achieving a significant improvement in the solution accuracy and magnitude completeness with respect to previous studies. Aftershock distribution and relocated mainshocks give insight into the complex architecture of major causative and subsidiary faults, thus providing crucial constraints on multi-segment rupture models. We document reactivation and kinematic inversion of a WNW-dipping listric structure, referable to the inherited Mts Sibillini Thrust (MST) that controlled segmentation of the causative normal faults. Spatial partitioning of aftershocks evidences that the MST lateral ramp had a dual control on rupture propagation, behaving as a barrier for the Amatrice and Visso mainshocks, and later as an asperity for the Norcia mainshock. We hypothesize that the Visso mainshock re-activated also the deep part of an optimally oriented preexisting thrust. Aftershock patterns reveal that the Amatrice Mw5.4 aftershock and the Norcia mainshock ruptured two distinct antithetic faults 3–4 km apart. Therefore, our results suggest to consider both the MST cross structure and the subsidiary antithetic fault in the finite-fault source modelling of the Norcia earthquake.

Geophysical studies point to a complex tectonic and geodynamic evolution of the Alboran Basin and Gulf of Cadiz. Tomographic images show strong seismic waves velocity contrasts in the upper mantle. The high velocity anomaly beneath the Alboran Sea recovered by a number of studies is now a well established feature. Several geodynamic reconstructions have been proposed also on the base of these images. We present and elaborate on results coming from a recent tomography study which concentrates on both the Alboran and the adjacent Atlantic region. These new results, while they confirm the existence of the fast anomaly below the Alboran region, also show interesting features of the lithosphere-asthenosphere system below the Atlantic. A high velocity body is imaged roughly below the Horseshoe Abyssal plain down to sub-lithospheric depths. This feature suggests either a possible initiation or relic subduction. Pronounced low velocity anomalies pervade the upper mantle below the Atlantic region and separate the lithospheres of the two regions. We also notice a strong change of the upper mantle velocity structure going from south to north across the Gorringe Bank. This variation in structure could be related to the different evolution in the opening of the central and northern Atlantic oceans.

We present a review of our work on data acquired by GEOSTAR-class (GEophysical and Oceanographic STation for Abyssal Research) observatories deployed at three EMSO (European Multidisciplinary Seafloor and water-column Observatory; http://www.emso-eu.org) sites in southern European waters where strong geo-hazards are present: the Western Iberian Margin, the Western Ionian Sea, the Marmara Sea, and the Marsili basin in the Tyrrhenian Sea. A procedure for multiparameter data quality control is described. Then we explain why the seafloor is an interesting observation point for geophysical parameters and how it differs from land sites. We consider four interesting geophysical phenomena found at the EMSO sites that are related to geo-hazard. In the first case, we show how unknown seismicity and landslides in the Western Ionian Sea were identified and roughly localised through a single-sensor analysis based on the seismometer. In the second case, we concentrate on the problem of near-coast tsunami generation and describe a Tsunami Early Warning Detection (TEWD) system, tested in the Western Iberian Margin and currently operating in real time at the Western Ionian site. In the third case, we consider two large volcanoes in the central Mediterranean area, Mt. Etna and the Marsili seamount Signals from the seismometer and gravimeter recorded at the seafloor at 2100 m b.s.l. show various phases of Mt. Etna's 2002-2003 eruption. For the less-known Marsili we illustrate how several indicators coming from different sensors point to hydrothermal activity. A vector magnetometer at the two volcanic sites helps identify the magnetic lithospheric depth. In the fourth and final case, we present a multiparameter analysis which was focused on finding possible correlations between methane seepage and seismic energy release in the Gulf of Izmit (Marmara Sea). (C) 2013 Elsevier B.V. All rights reserved.

[1] In this study, we present a three-dimensional P wave upper-mantle tomography model of the southwest Iberian margin and Alboran Sea based on teleseismic arrival times recorded by Iberian and Moroccan land stations and by a seafloor network deployed for 1 year in the Gulf of Cadiz area during the European Commission Integrated observations from NEAR shore sourcES of Tsunamis: towards an early warning system (EC NEAREST) project. The three-dimensional model was computed down to 600 km depth. The tomographic images exhibit significant velocity contrasts, as large as 3%, confirming the complex evolution of this plate boundary region. Prominent high-velocity anomalies are found beneath Betics-Alboran Sea, off-shore southwest Portugal, and north Portugal, at sublithospheric depths. The transition zones between high- and low-velocity anomalies in southwest and south Iberia are associated to the contact of oceanic and continental lithosphere. The fast structure below the Alboran Sea-Granada area depicts an L-shaped body steeply dipping from the uppermost mantle to the transition zone where it becomes less curved. This anomaly is consistent with the results of previous tomographic investigations and recent geophysical data such as stress distribution, GPS measurements of plate motion, and anisotropy patterns. In the Atlantic domain, under the Horseshoe Abyssal Plain, the main feature is a high-velocity zone found at uppermost mantle depths. This feature appears laterally separated from the positive anomaly recovered in the Alboran domain by the interposition of low-velocity zones which characterize the lithosphere beneath the southwest Iberian peninsula margin, suggesting that there is no continuity between the high-velocity anomalies of the two domains west and east of the Gibraltar Strait.

The three volcanoes that are the object of this paper show different types of activity that are representative of the large variety of volcanism present in the Central Mediterranean area. Etna and Stromboli are sub-aerial volcanoes, with significant part of their structure under the sea, while the Marsili Seamount is submerged, and its activity is still open to debate. The study of these volcanoes can benefit from multi-parametric observations from the seafloor. Each volcano was studied with a different kind of observation system. Stromboli seismic recordings are acquired by means of a single Ocean Bottom Seismometer (OBS). From these data, it was possible to identify two different magma chambers at different depths. At Marsili Seamount, gravimetric and seismic signals are recorded by a battery-powered multi-disciplinary observatory (GEOSTAR). Gravimetric variations and seismic Short Duration Events (SDE) confirm the presence of hydrothermal activity. At the Etna observation site, seismic signals, water pressure, magnetic field and acoustic echo intensity are acquired in real-time thanks to a cabled multi-disciplinary observatory (NEMO-SN1 ). This observatory is one of the operative nodes of the European Multidisciplinary Seafloor and water-column Observatory (EMSO; www.emso-eu.org) research infrastructure. Through a multidisciplinary approach, we speculate about deep Etna sources and follow some significant events, such as volcanic ash diffusion in the seawater.

SUMMARY We map the b-value in the subduction zone of the Wellington region, New Zealand, using a high quality earthquake catalogue relocated with a 3-D seismic velocity model, consisting of 50 314 events that occurred between 1990 and 2005. In order to investigate heterogeneity in the crust of the overlying plate and in the upper plane of the Wadati–Benioff Zone (WBZ), we analyse a series of cross-sections perpendicular to the strike of the subduction zone. We calculate the b-values selecting events with magnitude of completeness ≥2.4 and depth ≤65 km and projecting the seismicity within 20 km on each side of the cross-sectional planes. We observe areas of high b-value (∼1.7) near the plate interface and regions of low b-value anomalies are detected both in the WBZ in the northwest region below 40 km depth and in the overlying plate in the northern South Island at 10 km depth. The anomalies are statistically significant based on Utsu's p-test and the bootstrap method and are not data processing method or parameter dependent. We compare the b-value distribution with previously determined 3-D distributions of Vp, Vp/Vs and Qp from seismic tomography. This comparison suggests that material inhomogeneity, caused by fluid filled cracks resulting from dehydration of the subducted slab and subducted sediments, is the predominant cause of b-value variation in the shallow part of this subduction zone. Our observations are consistent with a previously proposed conceptual model that fluid distribution in the shallow part of this subduction zone is controlled by the permeability of geological terranes in the overlying plate.

The deep seismicity and lateral distribution of seismic velocity in the Central Western Mediterranean, point to the existence under the Alboran and Tyrrhenian Seas of two lithospheric slabs reaching the mantle transition zone. Gibraltar and Calabrian narrow arcs correspond to the slabs. Similarities in the tectonic and mantle structure of the two areas have been explained by a common subduction and roll-back mechanism, in which the two arcs are symmetrical end members. We present a new 3-D tomographic model at mantle scale for the Calabrian Arc and compare it with a recently published model for the Gibraltar Arc by Monna et al. ( 2013a ). The two models, calculated with inversion of teleseismic phase arrivals, have a scale and parametrization that allow for a direct comparison. The inclusion in both inversions of ocean bottom seismometer broadband data improves the resolution of the areas underlying the seafloor networks. This additional information is used to resolve the deep structure and constrain the reconstruction of the Central Western Mediterranean geodynamic evolution. The Gibraltar tomography model suggests that the slab is separated from the Atlantic oceanic domain by a portion of African continental margin, whereas the Calabrian model displays a continuous oceanic slab that is connected, via a narrow passage (~ 350 km), to the Ionian basin oceanic domain. Starting from the comparison of the two models we propose the following interpretation: within the Mediterranean geodynamic regime (dominated by slab rollback) the geometry of the African continental margin, located on the lower plate, represents a critical control on the evolution of subduction. As buoyant continental lithosphere entered the subduction zones, slab pull caused tears in the subducted lithosphere. This tectonic response, which occurred in the final stages of arc evolution and was strongly controlled by the paleogeography of the subducted plates, explains the observed differences between the Gibraltar and Calabrian Arcs.

The Marsili Seamount is the largest European underwater volcano. It is Plio-Pleistocenic in age, rising up to more than 3000m from the seafloor in the SE Tyrrhenian basin (Central Mediterranean), a back arc basin which began progressively opening 10 Ma ago (Kastens et al., 1988). The seamount lies in a key area for understanding the evolution of the Tyrrhenian region, characterized by high values of heat flow (Della Vedova et al., 2001) and low values of Moho isobaths (Locardi and Nicolich, 1988). In spite of the large dimensions of the Marsili seamount, we still have limited knowledge of its present activity. Ocean explorationis dependent on available technology and infrastructure, which started to develop strongly only after the 1980s.

The Geophysical and Oceanographic Station for Abyssal Research (GEOSTAR), an autonomous seafloor observatory that collects measurements benefiting a number of disciplines during missions up to 1 year long, will begin the second phase of its first mission in 2000. The 6–8 month investigation will take place at a depth of 3400 m in the southern Tyrrhenian basin of the central Mediterranean. GEOSTAR was funded by the European Community (EC) for $2.4 million (U.S. dollars) in 1995 as part of the Marine Science and Technology programme (MAST). The innovative deployment and recovery procedure GEOSTAR uses was derived from the “two-module” concept successfully applied by NASA in the Apollo and space shuttle missions, where one module performs tasks for the other, including deployment, switching on and off, performing checks, and recovery. The observatory communication system, which takes advantage of satellite telemetry, and the simultaneous acquisition of a set of various measurements with a unique time reference make GEOSTAR the first fundamental element of a multiparameter ocean network.

We mapped b-values in three dimensions in a cube of the crust with approximately 20 km dimensions under Mt. Etna. The earthquake catalog used contains 450 events with M≥2.5 for 1990-1997.9. Comparison of b-values derived from samples of N=50 events, extracted from volumes with radii ranging from 2.5 to 6 km, showed statistically highly significant differences between b=1.5±0.3 in most of the crust and b=3.0±0.5 in two volumes with r≤5 km, one located 2 km E of the summit of Etna and at 10±3 km depth and the other one WSW of Etna at a depth of about 3±2 km below sea level. We interpret these high b-value anomalies as an expression of two active magma chambers at those locations.

[1] In this study we map the distribution of the b-value of the Gutenberg-Richter law—as well as complementary seismicity parameters—along the fault responsible for the 2009 MW6.1 L'Aquila earthquake. We perform the calculations for two independent aftershock sub-catalogs, before and after a stable magnitude of completeness is reached. We find a substantial spatial variability of the b-values, which range from 0.6 to 1.3 over the fault plane. The comparison between the spatial distribution of the b-values and the main-shock slip pattern shows that the largest slip occurs in normal-to-high b-values portion of the fault plane, while low b-value is observed close to the main-shock nucleation. No substantial differences are found in the b-value computed before and after the main-shock struck in the small region of the fault plane populated by foreshocks.

Introduction. Takotsubo syndrome is a reversibile cardiomyopathy that often occurs during an emotional stress and is more frequent in post-menopausal women. Case presentation. We describe a clinic case of a 42 years old woman, admitted to our emergency unit because of a thoracic pain. The ECG showed ST-T elevation in V1- V4, the echocardiography revealed akinesia of apical segment of left ventricle. Coronary arteries were free from significant stenosis and ventriculography showed akinesia of apical segment of left ventricle. In the following days, ECG evolved toward a normalization of ST-T segment with appearance of negative T wave in V2-V6, and also the echocardiography showed a normalized LV wall motion. The patient was discharged and ECG and echocardiography were normal at two months follow up. Conclusion. In this case report, a young woman during puerperium presented with a Takotsubo syndrome. We speculate that the high Prolactin level and her emotional state contributed to the clinical manifestation of the syndrome.

NEMO-SN1, located in the central Mediterranean Sea, Western Ionian Sea, off Eastern Sicily Island (Southern Italy) at 2100 m water depth, 25 km from the harbour of the city of Catania, is a prototype of a cabled deep-sea multiparameter observatory and the first operating with real-time data transmission in Europe since 2005. NEMO-SN1 is also the first-established node of EMSO (European Multidisciplinary Seafloor Observatory, http://emso-eu.org), one of the incoming European large-scale research infrastructure included since 2006 in the Roadmap of the ESFRI (European Strategy Forum on Research Infrastructures, http://cordis.europa.eu/esfri/roadmap.htm), which will specifically address long-term monitoring of environmental processes related to Marine Ecosystems, Climate Change and Geo-hazards. NEMO-SN1 has been deployed and developed over the last decade thanks to Italian resources and to the EC project ESONET-NoE (European Seas Observatory NETwork — Network of Excellence, 2007–2011) that funded the LIDO-DM (Listening to the Deep Ocean — Demonstration Mission) and a technological interoperability test (http://www.esonet-emso.org/esonet-noe/). NEMO-SN1 is performing geophysical and environmental long-term monitoring by acquiring seismological, geomagnetic, gravimetric, accelerometric, physico-oceanographic, hydro-acoustic, bio-acoustic measurements specifically related to earthquakes and tsunamis generation and ambient noise characterisation in term of marine mammal sounds, environmental and anthropogenic sources. A further main feature of NEMO-SN1 is to be an important test-site for the construction of KM3NeT (Kilometre-Cube Underwater Neutrino Telescope, http://www.km3net.org/), another large-scale research infrastructure included in the ESFRI Roadmap constituted by a large volume neutrino telescope. The description of the observatory and the most recent data acquired will be presented and framed in the general objectives of EMSO.

Stromboli island, located in the southern Tyrrhenian sea, is the emerged part (about 900 meters above sea level) of an approximately 3 kilometer-high stratovolcano. Its persistent Strombolian activity, documented for more than 2000 years, is sometimes interrupted by lava effusions or major explosions. Despite the number of recently published geophysical studies aimed at clarifying the volcano's eruption dynamics, the spatial extent and geometrical characteristics of its plumbing system remain poorly understood. In fact, knowledge of the inner structure and the zones of magma storage is limited to the upper few hundred meters of the volcanic edifice (Chouet et al., 2003; Mattia et al., 2004) and P and S wave velocity models are available only in restricted areas (Petrosino et al., 2002). Over the past few years, Stromboli has experienced an increase in its activity, which started with the eruptive crisis of December 2002 to July 2003. The observed variations in Stromboli's eruptive behavior and the occurrence in December 2002 of a tsunami and in April 2003 of a paroxysmal vulcanian-type event with strong explosions and lava flows (Bonaccorso et al., 2003), have focused attention on the need to determine more suitable internal structure and velocity models of the volcano. To meet this need, a seismic tomography experiment through active seismics using air gun sources was done. A preliminary two-dimensional (2-D) tomographic study is presented here.

[1] The spatial pattern of the b value of the frequency-magnitude relation has been analyzed using gridding techniques beneath Mount Etna, Italy. A regional data set of 2900 events with Md (duration magnitude) ≥1.5 up to 15 km depth occurring between August 1999 and December 2005 has been used. Two regions with an abnormally high b value have been found, one centered beneath the southern part of the Valle del Bove, above the 6 km below sea level (bsl) deep basement, and the other beneath the summit region 2 km bsl east of the Central Craters. We can infer that these high b value anomalies are regions of increased crack density, and/or high pore pressure, related to the presence of nearby magma storage. This interpretation is supported by all the available geophysical evidence, such as tomographic studies and geodetic deformation measurements. The data set has also been subdivided into five periods, corresponding to different phases of volcanic activity: 2001 preeruption, 2001 eruptive, 2002–2003 preeruption, 2002–2003 eruptive, and 2002–2003 posteruption. The minimum magnitude of completeness, Mc, and the b value were computed for each period. A volume of anomalously high b values can be observed in each of these periods (except for the 2002–2003 preeruption interval). This approach has allowed the detection of the transient presence of magmatic intrusions during the various periods evaluated.

[1] Teleseismic traveltime data, recorded by temporary ocean bottom seismographs deployed in Tyrrhenian Sea around the Aeolian Islands (Tyrrhenian Deep-sea Experiment (TYDE)), have been used for the first time in Italy to refine the 3-D model for the deep P wave velocity structure of the southern Tyrrhenian subduction zone. The arrival times of 35 teleseisms have been combined with those recorded by the Italian National Network. In order to obtain a more complete azimuthal coverage of teleseismic rays, 80 events recorded by land stations from 1990 to 2002 have been included in the data set. In total, 2904 P and 314 PKPdf phases, 1300 recorded by ocean bottom instruments, have been collected. The upper mantle structure is reconstructed down to 500 km by a nonlinear inversion of the relative residuals computed with respect to the reference 1-D velocity model ak135. The obtained tomographic model has a higher resolution than those previously published thanks to the recordings of TYDE seafloor stations. Tomographic results confirm the presence of the Tyrrhenian slab imaged as a high-velocity body extending from the uppermost mantle down to the bottom velocity model with dip 70–75° NW. The model better defines the geometry of the seismogenic part of the slab. Its lateral extension is about 200 km in the depth interval 150–300 km, where most of the deep seismicity is concentrated. At uppermost mantle depths the fast structure has smaller lateral dimensions (about 100 km). The inversion also points out a wide well-resolved low-velocity zone completely surrounding the steeply dipping fast structure from the lower crust down to about 300 km. This feature suggests the presence of a three-dimensional circulation of asthenospheric flow around the Ionian slab caused by retreat and roll-back of the slab. Our results are in agreement with recent laboratory experiments, mantle anisotropy studies, geochemical and isotopic analyses, and modeling based on residual topography.

2002-2003 Framework Program of the Italian National Group for the Defense against Earthquakes (GNDT)

[1] The pattern of b value of the frequency-magnitude relation, or mean magnitude, has been analyzed as function of space beneath Mt. Etna during the intense lateral eruption of July–August 2001. The data used (August 1999–August 2001), subdivided in the pre-eruptive and eruption period, show significant space variations in the b value. For each of the two periods, a volume of anomalously high b value can be observed in the southeastern flank of the volcano. The anomalies located at 3 ± 1 km (b = 1.84 ± 0.20), and at about 1 ± 1 km (b = 2.11 ± 0.29) depth are interpreted as two different steps of a magma migration process ended with the July–August 2001 eruption. All the available geophysical evidences such as geodetic deformation measurements, focal mechanism and tomographic studies support this interpretation.

The paper presents an overview of recent seafloor long-term single-frame multiparameter platform developed in the framework of the European Commission and Italian projects starting from the GEOSTAR prototype. The main features of the different systems are described as well as the sea missions that led to their validation. The ORION seafloor observatory network recently developed, based on the GEOSTAR-type platforms and engaged in a deep-sea mission at 3300 m w.d. in the Mediterranean Sea, is also described

We analyzed the seismicity of Northern Honshu-Hokkaido region using the declustered earthquake catalog compiled by the Japan Meteorological Agency (JMA), for the period between January 1970 and December 1994. Making use of the ZMAP software tool, we sought to determine whether the quiescence hypothesis is applicable to 16 main shocks (M ³ 7.0) of the JMA catalog. We found a highly significant seismic quiescence prior to the May 26, 1983 Nihonkai-Chubu, MJ 7.7, earthquake. The quiescence that preceded the event lasted more than 3.5 years, and was located in the Japan Sea, off Akita and Aomori Prefectures. It was characterized by a standard deviate Z = 7.4 (Tw = 3 years), within a volume of approximately 200 by 300 by 40 km around the hypocenter. This volume contained 16 earthquakes (M ? 3.8) during the background period which lasted more than 8 years preceding the quiescence, and none during this one. A high concentration of seismic activity exceeding 15 events per year followed the main shock before the rate returned back to the previous value. No quiescence was observed before another strong event of magnitude 7.8 which occurred on July 12, 1993, 200 km north of the former, while three quiescences with the same Z-value were observed in the same region and in the same time period, not followed by any main shocks (false alarms). The probability that the Nihonkai-Chubu earthquake correlated at random with the quiescence period is estimated as approximately 1%, based on the fraction of space-time covered by alarms. The seismicity rate variations observed before and after the 1983 Nihonkai-Chubu earthquake are similar to those observed in the rupture area of the 1980 Irpinia (Italy), M 6.9 earthquake.

We assess the first mission of the GEOSTAR (GEophysical and Oceanographic STation for Abyssal Research) deep-sea multidisciplinary observatory for its technical capacity, performance and quality of recorded data. The functioning of the system was verified by analyzing oceanographic, seismological and geomagnetic measurements. Despite the mission’s short duration (21 days), its data demonstrated the observatory’s technological reliability and scientific value. After analyzing the oceanographic data, we found two different regimes of seawater circulation and a sharp and deepening pycnocline, linked to a down-welling phenomenon. The reliability of the magnetic and seismological measurements was evaluated by comparison with those made using on-land sensors. Such comparison of magnetic signals recorded by permanent land geomagnetic stations and GEOSTAR during a “quiet” day and one with a magnetic storm confirmed the correct functioning of the sensor and allowed us to estimate the seafloor observatory’s orientation. The magnitudes of regional seismic events recorded by our GEOSTAR seismometer agreed with those computed from land stations. GEOSTAR has thus proven itself reliable for integrating other deep-sea observation systems, such as modular observatories, arrays, and instrumented submarine cables.