1,721,029 research outputs found
Fault-based earthquake rupture forecast in Central Italy: remarks after the L’Aquila Mw 6.3 event.
No full textFiSH: MATLAB Tools to Turn Fault Data into Seismic-Hazard Models
No full textFaults have been increasingly integrated into seismic-hazard assessments. We have developed a package of MATLAB (http://www.mathworks.com/products/matlab, last accessed January 2016) tools (called FiSH), designed to help seismic-hazard modelers analyze fault data. These tools enable the derivation of expected earthquake rates, given common fault data, and allow researchers to test the consistency between the magnitude-frequency distributions (MFDs) assigned to a fault and some available observations. The basic assumption of FiSH is that the geometric and kinematic features of a fault are the expression of its seismogenic potential. Three tools have been designed to integrate the variable levels of information available: (1) the first tool allows users to convert fault geometry and slip rates into a global budget of the seismic moment released in a given time frame, taking uncertainties into account; (2) the second tool computes the recurrence parameters and associated uncertainties from historical and/or paleoseismological data; and (3) the third tool outputs time-independent or time-dependent earthquake rates for different MFD models. We present a test case to illustrate the capabilities of FiSH, on the Paganica normal fault in central Italy that ruptured during the 2009 L'Aquila earthquake sequence (mainshock Mw 6.3). The source codes are open, and we encourage users to handle the scripts, communicate with us regarding bugs, and/or suggest further improvements. Our intent is to distribute these tools in order to help researchers to pinpoint potential inconsistencies and obtain reliable fault-based seismic-hazard evaluations
Analisi probabilistica fault-based della pericolosità sismica volta alla definizione di input sismici: osservazioni dopo la sequenza sismica del 2016 in Italia Centrale
Full text linkThe Role of Viscoelastic Stress Transfer in Long-Term Earthquake Cascades: Insights After the Central Italy 2016–2017 Seismic Sequence
No full textCentral Italy is characterized by a network of active faults that interact in a complex manner. Coseismic Coulomb stress changes have been invoked by several authors to explain the concentration of moderate-to-strong earthquakes in this region, but none has considered the time-dependent viscoelastic relaxation of the lower crust and upper mantle as a possible additional source of stress changes at a regional scale. Here starting from the 1915 Mw 6.9 ± 0.2 Fucino earthquake, we calculated the coseismic plus postseismic Coulomb failure stress changes (ΔCFS) due to eight moderate-to-strong earthquakes that have struck Central Italy in the last century and culminated with the 2016–2017 sequence. Results from this modeling coupled with some synthetic tests simulating normal fault earthquakes with different magnitudes allowed us to highlight the importance of postseismic processes. In particular, the viscoelastic stress transfer due to events of Mw ≥ 6.5 can modify the spatial distribution of ΔCFS on a centennial timescale and therefore trigger events at larger distances. In addition, using these results, we identified other earthquake clusters in the historical catalogue (last 618 years), which, like the 1915–2017 series, were potentially modulated by both coseismic and postseismic processes. Finally, considering our calculations combined with historical and paleoseismological data, we suggest that several faults in Central Italy may be at present close to failure
Integration of geological and macroseismic data to define probable seismic scenarios in terms of macroseismic intensity and related seismogenic source models. The Maiella 1706 earthquake (Abruzzo, Italy).
No full textThe instrumental seismicity of the Abruzzo Region in Central Italy (1981-2003): Seismotectonic implications
No full textWe analyse the instrumental seismicity of the Abruzzo region in the period 1981-2003 in order to obtain a catalogue as homogeneous as possible in terms of location procedure and quality of the results. We analyse four temporal dataseis: 1981-1991; 1992-1996; 19971999 and 2000-2003. The 1981-1991 dataset is taken from the CSTI catalogue, opportunely selected by using quality criteria. The datasets from 1992 to 2003 are relocated by integrating the recordings of the national seismic network with the recordings of the local Abruzzo seismic network (operating from 1992 to 1999). Particular attention is paid to the velocity models, in order to account for the different stratigraphic/tectonic domains which characterize the Abruzzo region. In particular, we used 8 velocity models, applied to stations or groups of stations lying within relatively homogeneous areas. We obtained a database, selected for RMS s0.5s and hypocentral errors ≤5 km, of 985 events with 0.5≤M≤4.4 plus two events of moderate magnitude (Mw=5.9, Mw=5.5) corresponding to the largest shocks of the May 1984 Sangro Valley seismic sequence. We also computed 17 new focal mechanisms. The seismotectonic implications mainly concern the thickness of the seismogenic layer. A robust statistical estimate of the base of the seismogenic layer is given by the depth above which the 90% of seismicity occurs (D 90). The maximum thickness (15-17 km) is found in the eastern Abruzzo Apennines (surface heat flow ≤40 mW/m2). A thickness of 12-14 km is found in the western Abruzzo Apennines (40< surface heat flow s60 mW/m2). The observed depths are consistent with independent rheological data (B-D transition). The connection between the background seismicity and the geometry at depth of the active faults is Feasible only rarely (e.g. M. Gorzano normal fault in northern Abruzzo). More often the seismicity is spread within the seismogenic volume. Locally, it concentrates close to structural complexities or defines small seismic sequences activating inherited structures. The active faults south of L'Aquila are almost free from microseismic activity. The new focal mechanisms computed from the 1992-1999 database confirm and reinforce the existence of a dominating extensional regime across the Abruzzo Apennines
Cosmogenic He exposure dating as a tool to calculate slip rates: example from the Pernicana fault system (Mt. Etna)
No full textConstraining the slip rate of Mt. Etna active faults using cosmogenic 3He exposure dating of basalts
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