Subduction age and stress state control on seismicity in the NW Pacific subducting plate

Intermediate depth (70-300 km) and deep (> 300 km) earthquakes have always been puzzling Earth scientists: their occurrence is a paradox, since the ductile behavior of rocks and the high confining pressure with increasing depths would theoretically preclude brittle failure and frictional sliding. The mechanisms proposed to explain deep earthquakes, mainly depending on the subducting plate age and stress state, are generally expressed by single parameters, unsuitable to comprehensively account for differences among distinct subduction zones or within the same slab. We analyze the Kurile and Izu-Bonin intraslab seismicity and detail the Gutenberg-Richter b-value along the subducted planes, interpreting its variation in terms of stress state, analogously to what usually done for shallow earthquakes. We demonstrate that, despite the slabs different properties (e.g., lithospheric age, stress state, dehydration rate), in both cases deep earthquakes are restricted to depths characterized by equal age from subduction initiation and are driven by stress regimes affected by the persistence of the metastable olivine wedge

Potential for rupture before eruption at Campi Flegrei caldera, Southern Italy

Volcanoes reawakening after long repose must rupture the crust before magma can erupt. Rupture is preceded by repeatable variations in the rate of seismicity with ground movement, which trace the amount of applied stress that is released by local earthquakes. A rupturing sequence has been developing across four episodes of ground uplift at Italy’s Campi Flegrei caldera: in 1950-1952, 1969-1972, 1982-1984 and since 2004. We predicted in 2016 that the approach to rupture would continue after an additional uplift of 30-40 cm at the location of largest movement. We have updated our analysis with new data on changes in the numbers of local earthquakes with amounts of ground movement. Here we show that subsequent events have confirmed our prediction and that the unrest has been changing the structure of Campi Flegrei’s crust. The results provide new constraints for evaluating the volcano’s potential to erupt or to subside without eruption

A common source for the destructive earthquakes in the volcanic island of Ischia (Southern Italy): insights from historical and recent seismicity

AbstractThe island of Ischia, located in the Gulf of Naples, represents an unusual case of resurgent caldera where small-to-moderate magnitude volcano-tectonic earthquakes generate large damage and catastrophic effects, as in the case of 4 March 1881 (Imax-VIII-IXMCS) and 28 July 1883 (Imax X-XI MCS) historical earthquakes, and of the recent 21 August 2017 MW = 3.9, event. All these earthquakes struck the northern area of the island. With about 65,000 inhabitants, Ischia is a popular touristic destination for thermals baths, hosting more than 3,000,000 visitors per year, thus representing a high seismic risk area. Assessing its seismic potential appears a fundamental goal and, to this end, the estimate of the magnitude of significant historical events and the characterization of their source are crucial. We report here a reassessment of historical data of damage of 1881 and 1883 earthquakes to evaluate the main source parameters of these events (obtained with the BOXER and EXISM software) and quantitatively compare, for the first time, the results with the source characteristics, obtained from instrumental data, of the recent 2017 earthquake. The results allowed us to assess the location, as well as the possible dimension and the related maximum magnitude, of the seismogenic structure responsible for such damaging earthquakes. Our results also provide an additional framework to define the mechanisms leading to earthquakes associated with the dynamics of calderas

Fluid-Triggered Aftershocks in an Anisotropic Hydraulic Conductivity Geological Complex: The Case of the 2016 Amatrice Sequence, Italy

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Coincident locations of rupture nucleation during the 2019 Le Teil earthquake, France and maximum stress change from local cement quarrying

AbstractEarthquake occurrence is ultimately controlled by tectonic stress load. Nevertheless, the 2019, Mw = 4.9, Le Teil earthquake in southern France occurred in an area where strain rates are relatively low. Human operations can produce increases in stress load and degradation of strength on nearby active faults, which raises the potential for failure. Here we present estimates of the rupture geometry and source directivity of the Le Teil earthquake based on differential synthetic aperture radar interferometry and seismic data. We find that almost two centuries of mass removal at a nearby cement quarry likely provided the required stress change to hasten the occurrence of the Le Teil earthquake by more than 18,000 years. We suggest that further mass removal in the area might lead to even stronger earthquakes, by activating deeper sectors of the same fault plane

Editorial Expression of Concern: Coincident locations of rupture nucleation during the 2019 Le Teil earthquake, France and maximum stress change from local cement quarrying

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Author Correction: Coincident locations of rupture nucleation during the 2019 Le Teil earthquake, France and maximum stress change from local cement quarrying

A Correction to this paper has been published: https://doi.org/10.1038/s43247-021-00109-

Data on Seismic Risk Perception in Italy

Risks perception involves complex cognitive processes of collecting, selecting and interpreting signals about events, activities or technologies that may have consequences on us, even if they are unpredictable, and their impact is uncertain. In the natural sciences ‘risk’ means the probability distribution of adverse effects, but the everyday use of ‘risk’ has different connotations (Renn, 2008), and the two terms, hazards and risk, are often used interchangeably by the public. Within the social sciences however the terminology of ‘risk perception’ has become the conventional standard (Slovic, 1987). A theory that offers an integrative, as well as empirically valid, approach in understanding and explaining risk perception is still missing. To understand the perception of risk is necessary to consider several areas: social, psychological, cultural frames, and their interactions. Among the various researches in the international context on the perception of natural hazards and risks, the approach using the method of semantic differential seems to be promising (Osgood, C.E., Suci, G., & Tannenbaum, P. 1957, The measurement of meaning. Urbana, IL: University of Illinois Press). We set up a test on seismic risk perception in Italy, based on the semantic differential. Opposite adjectives or terms are confronted on a Likert’s scale of seven points. The test consists in an informative part and six sections respectively dedicated to: hazard; vulnerability (home and workplace); exposed value (with reference to population and territory); seismic risk in general; risk information and their sources; comparison between seismic risk and other natural hazards. The test allows to obtain the perception scores for seismic hazard, exposed values, and vulnerability; then, these scores can be put in relation with the scientific knowledge, to check awareness and resiliency of the society. The first survey took place in Italy from January to June 2013, in the frame of the activities funded by the DPC-INGV S2 project (https://sites.google.com/site/ingvdpc2012progettos2/). Collected data will be discussed at regional scale. The improvement of our understanding on the perception of seismic risk would allow us in planning more effective information initiatives and in developing specific educational projects for risk mitigation

SCIENZAPERTA: EARTH SCIENCE FOR EVERYONE... FINALLY IN MILAN!

ScienzAperta is an outreach science venue that the Istituto Nazionale di Geofisica e Vulcanologia started in 2011 as the spring of science: the doors of the headquarters of science were finally opened to public. A number of events, conferences, seminars, guided tours through the Institute and its laboratories are every year offered to general public. The venue is held in most of the cities where the Institute is located, priority to high seismic and/or volcanic risk regions. On May 2014 we held ScienzAperta for the first time in Milano and open up the doors to schools specifically dealing mostly with seismic hazard in a region where general public not necessarily think it might We offered students conferences, seminars and educational activities to highlight the fun of science and jet raise awareness on proper behaviours in case of earthquake shaking. We asked students and teachers, from elementary to high schools, to fill in a questionnaire that we use to evaluate the appreciation the venue had. One hundred years after Giuseppe Mercalli’s death we could not forget to celebrate his science the city where he was born.UnpublishedMilano3T. Pericolosità sismica e contributo alla definizione del rischiorestricte

Comment on “The 21 August 2017 M d 4.0 Casamicciola Earthquake: First Evidence of Coseismic Normal Surface Faulting at the Ischia Volcanic Island” by

We are writing this comment because many aspects of the analysis presented by Nappi et al. (2018) are debatable. In particular, a major issue is relevant to the conclusion suggested by Nappi et al. (2018) about a seismogenic normal fault with northward dip. This finding is not well‐founded because the authors do not really present a causative source model. In addition, their statement is clearly not consistent with the Differential Interferometric Synthetic Aperture Radar (DInSAR), Global Positioning System (GPS) and seismological measurements presented in the article previously published by De Novellis et al. (2018). Moreover, we also report an evident error in the geologic map proposed by Nappi et al. (2018, their fig. 3).Published313-3156V. Pericolosità vulcanica e contributi alla stima del rischioJCR Journa