1,721,023 research outputs found
A new method for the estimation of the completeness magnitude
No full textThe estimation of the magnitude of completeness mc have strong consequences in any statistical analysis of seismic catalogue and in the evaluation of the seismic hazard. Here a new method for its estimation is presented. The goodness of the method has been tested using 104 simulated catalogues. Then the method has been applied to five experimental seismic catalogues: Greece, Italy, Japan, Northern California and Southern California
Source characterisation of low frequency events at Stromboli and Vulcano islands (Isole Eolie, Italy)
No full textThe signal to noise ratio and the completeness magnitude: The effect of COVID19
No full textWe analyse the earthquakes catalogues for Italy, South California, and Greece across the COVID-19 lockdown period for each country. The results for Italy and Greece show that, even if the reduction of the signal to noise ratio has improved the earthquake detection capability, the completeness magnitude remains substantially unchanged, making the improved detection capability ineffective from the statistical point of view. A slight reduction (0.2) of the completeness magnitude is observed for South California, likely related to the relatively higher number of seismic stations located close to urban areas. Our findings suggest that—given the present configuration of the seismic network considered here—only an important decrease in the station spacing can produce a significant decrease of the completeness magnitude
Evaluation of the b Maps on the Faults of the Major (M > 7) South California Earthquakes
No full textWe use the Godano et al. (2022, ) method for evaluating the b maps of the faults associated with the largest earthquakes M >= 7.0 that occurred in California. The method allows an independent evaluation of the b parameter, avoiding the overlap of the cells and the omission of some earthquakes, while keeping all the available information in the catalog. We analyzed four large earthquakes: Landers, Hector Mine, Baja California, and Searles Valley. The maps obtained confirm that the b value can be considered as a strain meter and allow us to elucidate the presence of barriers, such as obstacles to the propagation of the fracture, on the fault of the analyzed earthquakes. A further estimated parameter is the time window during which aftershocks occur in the cell, Delta t. This quantity is very useful for a better definition of the aftershock generation mechanism. It reveals where the stress is released in a short time interval and how the complexity of the faulting process controls the occurrence of aftershocks on the fault, and also the duration of the entire sequence
The birth of a volcano: A nonlinear convective model for rock melting at the asthenosphere—Lithosphere boundary
No full textThe investigation of the physical processes determining the melting of the lithospheric rocks is of crucial importance for understanding the volcanic dynamics and its related consequences. Rock melting begins when a sufficiently high temperature is experienced by the rock solidus. The heat transfer from the asthenosphere to the lithosphere can be assumed as the main mechanism accountable for the partial melting of rocks, and initiating magma generation. The heat transfer to the lithosphere is considered to be governed mainly by the convective motion inside the asthenosphere. In order to mathematically describe this process, a generalization of a nonlinear convective 1D model, possibly representing a useful though simplified model for the birth of a volcano, and already analyzed from an analytical viewpoint (Godano et al., 2022), is investigated; here, we solve numerically some physically meaningful initial and boundary value problems, and discuss the results
b map evaluation and on-fault stress state for the Antakya 2023 earthquakes
No full textThe analysis of on-fault seismicity can enlighten the current stress state on the fault itself. Its definition is relevant to individuate fault patches that have not released all the accumulated stress even after the occurrence of a high magnitude earthquake. We use the b value to characterize the stress state on the fault of the Antakya 2023 main events, being b inversely proportional to the stress. The small magnitude seismicity occurring on the maximum slip fault-patches does not allow the b value estimation. This represents a strong indication that the maximum slip zone released most of the stress previously accumulated. Conversely, the lowest b values are located at the bends of the faults and close to the nucleation zone suggesting that, there, still exists not released stress implying that it could be reactivated in the future
b value enlightens different rheological behaviour in Campi Flegrei caldera
No full textThe Campi Flegrei caldera is one of the most dangerous volcanoes in the world and since 2005 it is in unrest. Here we evaluate the 3D tomography of the b value at the Campi Flegrei volcanic area revealing a very good correlation with the structure of the hydrothermal system involved in the bradiseismic phenomenon. More precisely, we observe the smallest b-values where we expect the higher stress/strain concentration, namely in the caprock, and for the deepest seismicity. Conversely, the largest b values are observed where the porosity of the medium allows the passage of the volcanic gases toward the surface. Values of b close to typical tectonic ones are observed where the presence of faulting structures is well documented
THE CHAOTICITY DEGREE OF THE CAMPI-FLEGREI SEISMICITY, SOUTHERN ITALY
Full text linkIn the present paper we use the general technique of Grassberger & Procaccia (1983) which allows us to reconstruct the phase space of the seismicity at Campi Flegrei from its time series and quantify the degree of chaoticity of such seismicity. We find that the seismic energy released in the Campi Flegrei area as a function of time does not exhibit a chaotic behaviour. On the contrary we determine that this phenomenon is quasi-periodic with fundamental periods of about 1.3 and 0.3 weeks
- …
