Distribution of Seismicity Before the Larger Earthquakes in Italy in the Time Interval 1994–2004

Gentili, Stefania

doi:10.1007/s00024-010-0089-x

Cited by 14 publications

(2 citation statements)

References 18 publications

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“…A study applying the EMR method (Woessner & Wiemer, 2005) on seismic sequences during the period 1977-2004 in the NEI area (Gentili and Bressan, 2008) reports a M c ranging from 1.2 to 2.1, dependent on the seismic sequence analyzed. Other recent analyses of the variation of M c over time , Gentili, 2010 show an increase of M c from 0.5-1.5 in the period 1977-1987 to 1.5-2.5 in 1988-2007. All these studies refer to the conventional duration magnitude as given in the catalog.…”

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confidence: 99%

Probabilistic completeness assessment of the past 30 years of seismic monitoring in northeastern Italy

Gentili

Sugan

Peruzza

et al. 2011

Physics of the Earth and Planetary Interiors

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Completeness of the dataset is varying in space and time due to the evolution of network geometry, instrumental characteristics, and monitoring and processing strategies over time: this is a common feature for all the regional and national instrumental catalogues that should be properly accounted for in seismicity rates evaluations. For the first time, we quantify with the new PMC method detection probabilities of a regional network operating since the late 70's, also including paper records.PMC is based on empirical data and requires the earthquake catalog containing phase picks, the station locations and on-/off-times, and the attenuation relation used to compute local magnitudes.In the 30-year period, we identified four time windows, roughly corresponding to the main changes in the acquisition system. We reconstructed on-/off-times by merging the available information on instruments with the analysis of inter-pick times at each station.We revised the relationship between duration and local magnitudes as the calibration of duration magnitude demonstrated to be not homogeneous among the different acquisition systems.Moreover, we introduced some constraints on the application of the PMC method to improve its performance for networks with sparse data and show the role of missing events and of temporary networks on regional completeness maps.The results demonstrate that the OGS network is detecting earthquakes completely down to magnitude 1.5 for a large part of the Friuli-Venezia-Giulia region since the earliest stages of its functionality; the OGS instrumental catalogue is therefore the most precise and complete dataset available for this area. Our analysis shows that the change from analog to digital systems does not 3 necessarily correspond to an improvement in detection capabilities. The computed time series of completeness maps are available and should be considered for any seismicity study involving data from the OGS network.

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confidence: 99%

Probabilistic completeness assessment of the past 30 years of seismic monitoring in northeastern Italy

Gentili

Sugan

Peruzza

et al. 2011

Physics of the Earth and Planetary Interiors

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“…Although the two transients relate to two different faults, some characteristics of the 2004 Bovec-Krn M w = 5.1 earthquake sequence support the interpretation that, at least in that case, the Ravne fault acted as a valve. Gentili (2010) recognized seismic quiescence preceding the 2004 M w = 5.1 Bovec-Krn earthquake, which is compatible with an overpressure condition. On the other hand, the depth distribution of the aftershocks that followed the main shock is compatible with upward spreading, as it would be in the case of a fluid discharge (Bressan et al, 2018a).…”

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confidence: 85%

Recurrence of Fault Valve Behavior in a Continental Collision Area: Evidence From Tilt/Strain Measurements in Northern Adria

et al. 2021

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We analyzed the data recorded by the NE-Italy subsurface tilt and strainmeter network evidencing a coherent transient signal in the recordings of four tiltmeter sites in the 1984–1990 period that produced a tilt along the main fractures. Borrowing from classical seismology techniques, we used the uprise times to locate the transient signal source. The propagation velocity is compatible with a fluid diffusion process that starts from a source located close to the hypocenter of the February 10, 1983 Uccea earthquake, MD = 4.2 at the Italy-Slovenia border, at an estimated depth of 10.8 km. Our results add to the previous interpretation of a transient signal recorded by several global navigation satellite system (GNSS) stations in the 2006–2009 period in terms of fluid diffusion below the Bovec basin (Slovenia). That source was located upon continuation to the northwest of the Ravne fault, few kilometers to the northeast from the present one, and about 6 km from the July 12, 2004 Bovec–Krn earthquake, Mw = 5.1, depth ~6.1 km. These observations suggest that the area is subject to fault valve behavior episodes that released fluids trapped at depth to the surrounding region as pore-pressure bulges. The convergence between Alpine and External Dinarides structures in this area puts highly permeable dolomitic limestones in contact with low-permeable fine-grained limestones and flysch formations. Therefore, the conditions for overpressure generation can be created, whereas fault movements, from time to time, in close relation with seismic events, can enable fluid diffusion in the surroundings. We also estimated the possible fluid influx needed to maintain overpressure and possible discharge across both the faults. The study provides insights on pore–fluid pressure variations related to slow slip events from a context different from subduction or transform margins, i.e., in a continental collision area.

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Conditional Probabilities for Large Events Estimated by Small Earthquake Rate

Chen

2015

Pure Appl. Geophys.

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Distribution of Seismicity Before the Larger Earthquakes in Italy in the Time Interval 1994–2004

Cited by 14 publications

References 18 publications

Probabilistic completeness assessment of the past 30 years of seismic monitoring in northeastern Italy

Probabilistic completeness assessment of the past 30 years of seismic monitoring in northeastern Italy

Recurrence of Fault Valve Behavior in a Continental Collision Area: Evidence From Tilt/Strain Measurements in Northern Adria

Conditional Probabilities for Large Events Estimated by Small Earthquake Rate

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