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The spatiotemporal relationship between geophysical, environmental, and geochemical responses during volcanic unrest is essentially unknown, making their joint use and interpretation for eruption forecasting challenging. Here, Empirical Orthogonal Functions analysis applied to GPS data allows the separation of the dominant deep‐sourced inflation from environmentally controlled signals associated with extension at Campi Flegrei caldera. This separation bridges the gap between deformation, seismic and geochemical responses, clarifying the processes underlying the ongoing volcanic unrest. Persistent meteoric forcing during the 2017–2018 hydrological year changed the decadal trend of seismic energy and secondary deformation components, pairing their spatial patterns. The result was a block in the carbon dioxide released in 2018 at Solfatara, the primary stress‐release valve at the caldera. The subsequent overpressure weakened the fractured eastern caldera, opening pathways for deep, hot materials to reach the surface. Our results give insight into how environmental forcing can favor volcanic unrest in pressurized calderas. Plain Language Summary Geophysics and geochemistry are two of the most essential disciplines to understand volcanic unrest and eruptions. Finding the link between deformation signals and their seismic and geochemical counterparts is crucial in understanding how a volcano works; however, a time‐resolved 3D analysis of signals sensitive to different processes, from magma migration to environmental forcing, is our best chance to understand how the volcano changes and when an eruption might occur. We borrowed standard oceanic and climatic data analysis techniques and applied them to GPS signals recorded during unrest at Campi Flegrei caldera. The results uncovered small deformation components linked to seismic migrations and variations in carbon dioxide fluxes measured at the Solfatara crater. These components clarify how a drought can weaken the shallowest crust, strengthening ongoing processes generated at depth. A wet hydrological year in the middle of the ongoing drought coincided with decreased emissions of carbon‐bearing fluids from Solfatara, the primary stress‐release valve of the caldera. This stress was eventually released when deep materials rose in the eastern caldera, producing seismicity. Highlighting small components in deformation signals linked to environmental changes appears essential to mark variations in volcanic behavior, in analogy to what is done by ambient noise interferometry. Key Points Advanced deformation analysis detects environmental components linked to seismic migrations and variations in carbon dioxide fluxes A wet hydrological year during a drought closed Solfatara, increasing pressure and breaking the shallow caldera in early 2018 The deep unrest sources cracked the weakened eastern caldera in 2018–2019, causing seismic unrest

We present exact expressions for the volume change of a pressurized ellipsoidal cavity in an infinite homogeneous elastic medium. The expressions can be used as approximate solutions also for a homogeneous half‐space. We show that previously published widely used expressions are correct for spheres but underestimate the ratio of the volume change to the product of pressure and volume in any other case. We discuss the capability to infer the shape of a single ellipsoidal cavity from far‐field deformation measurements. Our results indicate that source axis ratios may often be hard to estimate, whereas it may be easier to infer the volume change of the source. We also consider the case of a source region consisting of interconnected pressurized ellipsoidal cavities, neglecting mutually induced stress. If all the cavities share the same shape and orientation, the source is seen in the far field as a single ellipsoidal cavity and it is possible to compute the total volume change from surface displacements. The shape of the apparent single ellipsoid is the same as the shape of the constituting cavities and not of the source region. In any other case a single ellipsoidal cavity might even be unable to give the same surface displacements as the ensemble of cavities. Since sudden volume change of a cavity can generate seismic waves, we discuss the decomposition of the related moment tensor into isotropic, double‐couple, and compensated linear‐vector dipole force systems in case of magma exchange between two ellipsoidal cavities, giving relations for the moment tensor components.

Two laser strainmeters that operate at 1400‐m depth, about 20 km NE of the epicenter of the 6 April 2009 magnitude‐6.3 L'Aquila, Italy, earthquake, have produced a clear record of postseismic strain. Here we show the results from the analysis of the data related to the first few days after the event. Strain after about 1.5 days is fully consistent with afterslip on a stationary region of the earthquake causative fault. The preceding few‐hour‐long transient (whose seismic moment history is quasi‐exponential) is fully consistent with unilateral diffusive slip propagation toward the shallower part of the same fault. The propagation path ends where later afterslip probably occurred. Slip propagation similar to heat diffusion has been suggested to explain the observed scaling law between amplitude and duration of slow earthquakes; here we give the first observational evidence of the role and details of slow rupture propagation.

Two laser strainmeters that operate at 1400‐m depth, about 20 km NE of the epicenter of the 2009/04/06 magnitude‐6.3 L'Aquila, Italy, earthquake, have produced records of strain since 1995. During the two years before the event, no anomalous signal larger than a few tens of nanostrains is visible, limiting the volume of the possible earthquake preparation zone to less than 100 km3; moreover, earth tidal response is stable within 0.5% in amplitude and 0.5° in phase. Thus, reality of large‐scale precursory phenomena seems unlikely. During the last few days, there is some evidence of dilatancy of satured rock over the earthquake causative fault, maybe related to the foreshocks. Seconds before the event, strain is stable at the 10−12 level and prerupture nucleation slip in the hypocentral region is constrained to have a moment less than 2 × 1012 Nm, i. e. 0.00005% of the main shock seismic moment.

Magmatic unrest can be successfully monitored and studied from modeling of the induced surface deformation; one limiting factor however is the small number of available magmatic source models. Here we have obtained expressions (quadrupole approximation) for displacements and stresses from the inflation of any pressurized triaxial ellipsoid in an infinite elastic medium. The expressions can be evaluated by combining the effects of seven suitable point sources and are approximately valid also for a heterogeneous half‐space. Till now, the only available (approximate or exact) expressions for finite expansion sources referred to spheres, prolate spheroids, and horizontal circular cracks embedded in a homogeneous half‐space. Our approach allows to model also oblate spheroids and non‐axisymmetric sources, whose effects were previously estimable only in the far field through a moment tensor representation. We also show that when the deformation source is a vertically flattened ellipsoid, the inversion of superficial displacements using a general moment tensor may lead to wrong physical models of the deformation source itself. This may be the case for the Campi Flegrei caldera, as well as for other calderas.

Reliable use of strain data in geophysical studies requires their preliminary correction for ocean loading and various local distortions. These effects, in turn, can be estimated from the tidal records which are contributed by solid and oceanic loading. In this work, we estimate the oceanic tidal loading at two European strain stations (Baksan, Russia, and Gran Sasso, Italy) by analyzing the results obtained with the different Earth and ocean models. The influence of local distortions on the strain measurements at the two stations is estimated.

Several clustered slow earthquakes have been recorded by a geodetic interferometer in central Italy. The strain rise times of the events range from tens to thousands of seconds, and the seismic moment scales with the square root of the rise time. This scaling law contrasts with the conservative assumption of constant rupture velocity in fault modeling but is consistent with the occurrence of a slow rupture propagation analogous to heat diffusion in a slab.

ObjectivesTo evaluate aortic diameter and predictors of aortic dilatation using FDG-PET/CT in a longitudinally followed cohort of patients with large vessel vasculitis (LVV) compared with controls.MethodsAll consecutive patients with LVV who underwent at least 2 PET/CT scans between January 2008 and May 2015 were included. The first and last PET/CT study of each patient was independently evaluated by a radiologist and a nuclear medicine physician. The diameter of the aorta was measured at 3 different levels: ascending, descending thoracic and infrarenal aorta. Aortic dilation was defined as a diameter of >4 cm in the ascending,≥4 cm in the descending thoracic and ≥3 cm in the infrarenal aorta. Aortic FDG uptake was graded at the same levels using a 0–3 semiquantitative scale and was reported as negative (score 0 or 1) or positive (score 2 and 3). Patients younger than 50 years at symptoms’ onset were classified as Takayasu arteritis (TAK), while those older than 50 years as giant cell arteritis (GCA). 29 age- and sex-matched patients with lymphoma who underwent at least 2 PET/CT in the same time interval without evidence of aortic FDG uptake were selected as controls.Results93 patients with LVV were included in the study. 53% of patients were newly-diagnosed; the remaining 47% had a median disease duration of 34 months. At first PET/CT, the mean (SD) diameter of descending thoracic aorta was significantly higher in LVV patients compared with controls [28.07 (4.40) vs 25.60 (3.59) mm, p=0.012]. At last PET/CT, after a median time of 31 months, patients with LVV compared with controls had higher diameter of ascending [35.41 (5.54) vs 32.97 (4.11) mm, p=0.029] and descending thoracic aorta [28.42 (4.82) vs 25.72 (3.55) mm, p=0.007] and more frequently had aortic dilatation [19% vs 3%, p=0.023]. Significant predictors of aortic dilatation were male sex [OR 7.27, p=0.001], and the diameter of ascending [OR 2.03, p<0.001], descending thoracic [OR 1.57, p<0.001] and infrarenal [OR 1.25, p=0.005] aorta at first PET/CT study. Positive aortic FDG uptake, disease activity and elevated inflammatory markers at first PET/CT were not associated with an increased risk of aortic dilatation. The results remained unchanged when the analysis were restricted to the 48 newly-diagnosed LVV patients.According to age at symptoms onset, 56% of patients were classified as GCA and 44% as TAK. Compared with TAK, GCA patients had higher aortic diameter at all 3 levels evaluated in both first and last PET/CT study. However there were no differences in the proportion of patients with aortic dilatation (at last PET/CT 23% in GCA vs 15% in TAK, p=0.306). The results remained unchanged when the analysis were restricted to the newly-diagnosed patients.ConclusionsPatients with large vessel vasculitis are at increased risk of aortic dilatation compared with age- and sex-matched controls. Significant predictors of aortic dilatation are male sex and aortic diameter at first imaging study. Positive aortic FDG uptake at first PET/CT is not associated with increased risk of aortic dilatation.Disclosure of InterestNone declared