INGV Sezione di Milano

We apply a nonparametric spectral inversion scheme to calculate source spectra, S wave attenuation, and site transfer functions from strong motion records in the epicentral region of the 1997–1998 Umbria‐Marche seismic sequence (central Italy). We use records from moderate size earthquakes (4.6 ≤ M l ≤ 5.9) to parameterize the spectral amplitude decay in the distance range from 5 to 40 km. We find that the average quality factor Q can be approximated by Q ( f ) = 49 f 0.9 , between 0.5 and 8 Hz, and the geometrical spreading by r −0.9 . At high frequencies ( f > 8 Hz) the dependence of Q on frequency weakens, and it takes an approximate constant value of 318. We fit the source spectra to the ω‐square model and calculate an average stress drop of (2 ± 1) MPa. The average value is consistent with the previous estimates from the weak events (1.4 < M l < 4.5) of the Umbria‐Marche seismic sequence. The most remarkable site effects are found in correspondence of large sedimentary basins, filled by alternation of sandy‐clayey deposits. The estimated spectral parameters are used to simulate acceleration spectra recorded during several earthquakes of the Umbria‐Marche sequence. Both point source and finite fault effects are considered. Furthermore, attenuation relationships for peak ground velocity and ground acceleration are estimated using synthetic data, and compared to existing relationships.

A hybrid deterministic-stochastic method (dsm) is developed to calculate synthetic time series of ground accelerations radiated from an extended source. The main goal of the proposed methodology is to include in the classical point-source stochastic method (pssm) the effects of the rupture propagation on a finite fault. This purpose is achieved through two important modifications of the pssm technique. First, the envelope does not have a predetermined functional form; rather, it is calculated deterministically following the isochron formulation with a kinematic rupture model. Second, we have generalized the various parameters of the point-source ground motion spectrum to account for the extended fault: corner frequency, distance from the fault, and radiation pattern are evaluated through the kinematic modeling. The guiding principal in all these modifications has been to develop a robust methodology capable of capturing the complexity of near-source ground motion even when input information about earthquake source, propagation medium, and site characteristics are of a very schematic nature. We show that the synthetic envelope contains the required information on the rupture process on extended fault, such as directivity effects and azimuthal variations depending on the source-to-receiver geometry. The method’s capability is demonstrated by modeling strong ground motions of the 1992 M w 7.3 Landers, California, earthquake and comparing them with the recorded accelerograms, which are clearly affected by directivity effects. The proposed technique reproduces the main characteristics of strong-motion recordings, and can be implemented using only a limited number of parameters to describe the source (dimension and geometry), the propagation medium (wave velocities and layers), and the site effects (transfer function). These characteristics are important for a methodology aimed to simulate ground-shaking scenarios for which a more complete description of the faulting process is not available.

Sand boils, which are also known as sand blows or sand volcanoes, are among the most common superficial effects induced by high-magnitude earthquakes. These generally occur in or close to alluvial plains when a strong earthquake (M >5) strikes on a lens of saturated and unconsolidated sand deposits that are constrained between silt-clay layers [Ambraseys 1988, Carter and Seed 1988, Galli 2000, Tuttle 2001, Obermeier et al. 2005], where the sediments are converted into a fluid suspension. The liquefaction phenomena requires the presence of saturated and uncompacted sand, and a groundwater table near the ground surface. This geological–geomorphological setting is common and widespread for the Po Plain (Italy) [Castiglioni et al. 1997]. The Po Plain (ca. 46,000 km2) represents 15% of the Italian territory. It hosts a population of about 20 million people (mean density of 450 people/km2) and many infrastructures. Thus, the Po Plain is an area of high vulnerability when considering the liquefaction potential in the case of a strong earthquake. Despite the potential, such phenomena are rarely observed in northern Italy [Cavallin et al. 1977, Galli 2000], because strong earthquakes are not frequent in this region; e.g., historical data report soil liquefaction near Ferrara in 1570 (M 5.3) and in Argenta 1624 (M 5.5) [Prestininzi and Romeo 2000, Galli 2000]. In the Emilia quakes of May 20 and 29, 2012, the most widespread coseismic effects were soil liquefaction and ground cracks, which occurred over wide areas in the Provinces of Modena, Ferrara, Bologna, Reggio Emilia and Mantova (Figure 1). […]

In the pre-1900 time-window of earthquake catalogs, it is not unusual to come face-to-face with “fake ” earthquakes errone-ously listed among true ones. Such mistakes have been disclosed for many events, and their nature revealed and discussed in quite a number of papers in the last thirty years. Some discover-ies of fake earthquakes originated from the revision of national catalogs (e.g., for France, Vogt 1979; for Italy, Guidoboni and Ferrari 1986 and Bellettati et al. 1993; for Germany, see a sum-mary in Grünthal 2004), and others come from projects deal-ing with European-wide catalogs (e.g., Stucchi and Camassi 1997). As a consequence of these investigations, in some well-studied European regions recent catalogs have been purged of most of these mistakes. A list of fake earthquakes is now avail-able in some regional databases (France: BRGM-EDF-IRSN/

Abstract Post‐orogenic back‐arc magmatism is accompanied by hydrothermal ore deposits and mineralizations derived from mantle and crustal sources. We investigate Zannone Island (ZI), back‐arc Tyrrhenian basin, Italy, to define the source(s) of mineralizing hydrothermal fluids and their relationships with the regional petrological‐tectonic setting. On ZI, early Miocene thrusting was overprinted by late Miocene post‐orogenic extension and related hydrothermal alteration. Since active submarine hydrothermal outflow is reported close to the island, Zannone provides an ideal site to determine the P ‐ T ‐ X evolution of the long‐lived hydrothermal system. We combined field work with microstructural analyses on syn‐tectonic quartz veins and carbonate mineralizations, X‐ray diffraction analysis, microthermometry and element mapping of fluid inclusions (FIs), C, O, and clumped isotopes, and analyses of noble gases (He‐Ne‐Ar) and CO 2 content in FIs. Our results document the evolution of a fluid system of magmatic origin with increasing mixing of meteoric fluids. Magmatic fluids were responsible for quartz veins precipitation at ∼125 to 150 MPa and ∼300°C–350°C. With the onset of extensional faulting, magmatic fluids progressively interacted with carbonate rocks and mixed with meteoric fluids, leading to (a) host rock alteration with associated carbonate and minor ore mineral precipitation, (b) progressive fluid neutralization, (c) cooling of the hydrothermal system (from ∼320°C to ∼86°C), and (d) embrittlement and fracturing of the host rocks. Both quartz and carbonate mineralizations show noble gases values lower than those from the adjacent active volcanic areas and submarine hydrothermal systems, indicating that the fossil‐to‐active hydrothermal history is associated with the emplacement of multiple magmatic intrusions.

ABSTRACT In the last decades, geophysicists and seismologists have focused their attention on the inversion of empirical surface‐waves’ dispersion curves from microtremor measurements for estimating the S‐wave velocity structure at a site. This procedure allows a fast and convenient investigation without strong active sources, which are difficult to deploy especially in urban areas. In this study we report on a 2D seismic noise array experiment carried out at Bevagna (central Italy) near the station BVG of the Italian Accelerometric Network (RAN). The site was investigated within the DPC‐INGV S4 Project (2007‐2009). The Rayleigh‐ and Love‐waves dispersion characteristics were estimated using different methods. The inversion of the dispersion curves was then performed independently, obtaining two estimations for the S‐wave velocity profiles. The results of cross‐hole logging near the seismic station are used for a comparison. The shear‐wave velocity profiles estimated by microtremor analyses range up to 150 m depth. The two independent procedures provide consistent shear‐wave velocity profiles for the shallow part of the model (20–30 m in depth) in agreement with the results of the cross‐hole logging. Some problems arise between 30–40 m in depth in the profile estimated by surface waves. In this range cross‐hole logging evidences an inversion of the S‐wave velocity. Although the cross‐hole logging stops at 40 m of depth, we are confident about the results provided by the Rayleigh‐wave analysis below 40–50 m. This case study suggests that greater efforts should be devoted to exploit the potential of a coupled analysis of Rayleigh and Love waves from microtremor array measurements.

This paper examines the housing market response to the earthquake that hit northern Italy in May 2012. The available literature shows that the average price of houses decreases after a disaster because of the potential underestimation of disaster risk by households, or because of a higher risk perception in reaction to the unforeseen emergency. The physical assessment of the earthquake damage scenario provided in this paper (the so-called macro-seismic approach), combined with a difference-in-difference model with a multi-valued treatment, is able to extrapolate indirect information on the subjective perception of risk. We provide evidence that differences in costs and risk perceptions of the earthquake arise at high levels of damage. Furthermore, we also provide evidence that building characteristics, as well as the state of maintenance of houses, play a relevant role for subjective risk assessment, even though this assessment may be not related to the effective capacity of the buildings to resist earthquakes.

The New Caledonia Ophiolite is cross-cut by coarse- to medium-grained pyroxenite and hornblende gabbro/diorite dykes intruded between 55.5 and 50 Ma (U–Pb zircon and 40 Ar/ 39 Ar hornblende), whereas the finer grained dolerites of tholeiitic affinity are younger (50–47 Ma). The production of hornblende gabbros/diorites was modelled by moderate degrees (20–40%) of partial melting of the high-temperature amphibolites of the metamorphic sole. The end-member compositions (hornblendites and anorthosites) resulted from solid-state phase segregation of crystal mushes within tectonically active magmatic conduits. Cascade reactions of the slab melts with mantle wedge peridotites successively formed clinoenstatite-bearing boninite magmas, which fed gabbronorite cumulate lenses at the mantle–crust transition; in turn, the clinoenstatite-bearing boninite melts reacted with peridotites to form websterites. The youngest magmas (of tholeiitic affinity) appeared c. 6 Myr after the inception of subduction when the cooler subducting slab plunged more steeply. Incipient slab retreat allowed corner flow, triggering low-pressure hydrous melting of the uplifted asthenosphere. The early stages of forearc magmatism were closely associated with transcurrent shear zones, which recorded oblique subduction inception. The early Eocene tectonic and magmatic features of the New Caledonia Ophiolite provide evidence for a north- or NE-dipping hot (forced) subduction zone in the SW Pacific, notably distinct from the slightly younger west-dipping Izu-Bonin–Marianna cold (spontaneous) subduction system. Supplementary material: Field pictures, additional diagrams, GPS location of dated samples, whole-rock geochemical and isotope data, Ar/Ar data, U–Pb zircon data, and distribution coefficients ( K d ) of trace elements used for modelling are available at https://doi.org/10.6084/m9.figshare.c.6949265 Thematic collection: This article is part of the Ophiolites, melanges and blueschists collection available at: https://www.lyellcollection.org/topic/collections/ophiolites-melanges-and-blueschists

Abstract Carbon dioxide is a key gas to monitor at volcanoes because its concentration and isotopic signature can indicate changes to magma supply and degassing behavior prior to eruptions, yet carbon isotopic fluctuations at volcanic summits are not well constrained. Here we present δ 13 C results measured from plume samples collected at Stromboli volcano, Italy, by Uncrewed Aerial Systems (UAS). We found contrasting volcanic δ 13 C signatures in 2018 during quiescence (−0.36 ± 0.59‰) versus 10 days before the 3 July 2019 paroxysm (−5.01 ± 0.56‰). Prior to the eruption, an influx of CO 2 ‐rich magma began degassing at deep levels (∼100 MPa) in an open‐system fashion, causing strong isotopic fractionation and maintaining high CO 2 /S t ratios in the gas. This influx occurred between 10 days and several months prior to the event, meaning that isotopic changes in the gas could be detected weeks to months before unrest.

Author: Bindi, Dino et al.; Genre: Journal Article; Finally published : 2014; Open Access; Title: A Magnitude Attenuation Function Derived for the 2014 Pisagua (Chile) Sequence Using Strong-Motion Data

The underwater volcanic activity associated with deep-seated mantle processes represents a primary driver of the chemical and biogeochemical evolution of the global oceans. Hydrothermal activity is often a manifestation of submarine volcanism, where fluxes of heat and magmatic volatiles confer both potential hazard and opportunities of resource exploitation. Despite this, research on shallow submarine arc volcanoes is still in an early stage and only a few continuous seafloor observing infrastructures have been developed until now.  The Kolumbo underwater volcano, located in the Aegean Sea, hosts one of the most active and dynamic hydrothermal vent fields, marking it - along with the proximity to the world-known Santorini island - a severe geohazard for a combination of reasons. Within the framework of the SANTORY (SANTORini’s seafloor volcanic observatorY) project, funded by the Hellenic Foundation for Research and Innovation and with the financial support of the Municipality of Thira, between 2022 and 2023, three oceanographic cruises were performed on submarine Kolumbo volcano. The oceanographic surveys were mainly aimed at the deployment of integrated operating sensors of state-of-the-art technology, for in situ monitoring. A new-generation stand-alone multiparametric observatory has been developed at INGV Palermo and deployed at the bottom of the crater (500 meters depth) for the first time in December 2022. The battery powered module has been able to operate autonomously for a 10-month-long period, collecting a dense, heterogeneous dataset able to describe the activity of the hydrothermal reservoir, highlighting its intense dynamic along the time.In June 2023, the observatory was recovered and re-deployed after brief maintenance operations including battery charging and data downloading. Finally, in October 2023, the observatory was definitely recovered.Here we present for the first time a mid-term-long chemical-physical data series acquired (pH, temperature, hydrostatic pressure, turbidity, conductivity, dissolved methane) along with passive acoustic and the preliminary findings of the system evolution within the observing window. A variety of local VT events likely sourced in the deeper portion of the plumbing system, together with several other minor seismic events related to fluid dynamics inside “fluid-filled” cracks and conduits has been revealed by passive acoustic data. Moreover the acoustic sensor recorded all the signals generated by the bubbles along the water column. The obtained results gave back an up to date picture of the ongoing Kolumbo degassing dynamics, hydrothermal and seismic activity. 

Carbon dioxide is a key gas to monitor at volcanoes because its fluctuation relative to other gases can be detected prior to eruptions, yet carbon isotopic fluctuations at volcanic summits are not well constrained. Here, we present carbon isotopes measured from plume samples collected at Stromboli volcano, Italy, by Unoccupied Aerial System (UAS). We found contrasting volcanic source δ13C in 2018 during quiescence (-0.36 ± 0.59 ‰) versus 10 days before the July 3rd 2019 paroxysm (-5.01 ± 0.56 ‰). During the buildup to the eruption, an influx of CO2-rich magma began degassing at deep levels (~100 MPa) in an open system fashion, causing strong isotopic fractionation and maintaining high CO2/St ratios in the gas. This influx occurred between 10 days prior to the event and up to several months beforehand, meaning that isotopic changes in the gas could be detected weeks to months before unrest.