Search results for "seismic"

Seismic velocity structures of Southern Italy from tomographic imaging of the Ionian slab and petrological inferences.

2012

International audience; In this study we have determined detailed Vp and Vs seismic velocity models of the Ionian lithosphere subducting beneath the Tyrrhenian basin and of the surrounding mantle, by applying a post-processing technique to a large sample of local earthquake tomography studies. Our seismic velocity models permit us to infer the presence of low velocity anomalies within the slab, which we interpret as regions that are partially hydrated by fluids released during the subduction process. A petrological interpretation of the velocity anomalies gives new details on the magmatism of the volcanic Aeolian arc. Furthermore our velocity models provide a more detailed description of th…

Interaction between seismicity and deformation on different time scales in volcanic areas: Campi Flegrei and Stromboli

2019

We study oscillations recorded at Stromboli and Campi Flegrei by different sensors: seismometers, strainmeters and tiltmeters. We examine both the high-frequency (>0.5 Hz) portion of the spectrum and very long period signals up to tidal scales. In this context, seismicity and deformation are investigated on different time scales (from minutes to days/years) in order to identify the basic elements of their interaction, whose understanding should provide new insights on the predictive models. In this work, the strict relation of tides and volcanic processes is shown. At Stromboli, indeed the transition from the stationary phase to the non-stationary phase seems to have a tidal precu…

Integration of onshore and offshore seismic arrays to study the seismicity of the Calabrian Region: a two steps automatic procedure for the identific…

2014

Abstract. We plan to deploy in the Taranto Gulf some Ocean Bottom broadband Seismometer with Hydrophones. Our aim is to investigate the offshore seismicity of the Sibari Gulf. The seismographic network optimization consists in the identification of the optimal sites for the installation of the offshore stations, which is a crucial factor for the success of the monitoring campaign. In this paper, we propose a two steps automatic procedure for the identification of the best stations geometry. In the first step, based on the application of a set of a priori criteria, the suitable sites to host the ocean bottom seismic stations are identified. In the second step, the network improvement is eval…

Long term seismic noise acquisition and analysis in the Homestake Mine with tunable monolithic sensors

2009

In this paper we describe the scientific data recorded along one month of data taking of two mechanical monolithic horizontal sensor prototypes located in a blind-ended (side) tunnel 2000 ft deep in the Homestake (South Dakota, USA) mine chosen to host the Deep Underground Science and Engineering Laboratory (DUSEL). The two mechanical monolithic sensors, developed at the University of Salerno, are placed, in thermally insulating enclosures, onto concrete slabs connected to the bedrock, and behind a sound-proofing wall. The main goal of this experiment is to characterize the Homestake site in the frequency band 10-4 ÷ 30 H z and to estimate the level of Newtonian noise, providing also the ne…

Time-Frequency Filtering for Seismic Waves Clustering

2014

This paper introduces a new technique for clustering seismic events based on processing, in time-frequency domain, the waveforms recorded by seismographs. The detection of clusters of waveforms is performed by a k-means like algorithm which analyzes, at each iteration, the time-frequency content of the signals in order to optimally remove the non discriminant components which should compromise the grouping of waveforms. This step is followed by the allocation and by the computation of the cluster centroids on the basis of the filtered signals. The effectiveness of the method is shown on a real dataset of seismic waveforms.

The INGV's new OBS/H: Analysis of the signals recorded at the Marsili submarine volcano

2009

Abstract The ocean bottom seismometer with hydrophone deployed on the flat top of the Marsili submarine volcano (790 m deep) by the Gibilmanna OBS Lab (CNT–INGV) from 12th to 21st July, 2006, recorded more than 1000 transient seismic signals. Nineteen of these signals were associated with tectonic earthquakes: 1 teleseismic, 8 regional (located by INGV) and 10 small local seismic events (non located earthquakes). The regional events were used to determine sensor orientation. By comparing the signals recorded with typical volcanic seismic activity, we were able to group all the other signals into three categories: 817 volcano–tectonic type B (VT-B) events, 159 occurrences of high frequency t…

Monochromatic Long-Period Seismicity Prior to the 2012 Earthquake Swarm at Little Sitkin Volcano, Alaska

2021

Detection of the earliest stages of unrest is one of the most challenging and yet critically needed aspects of volcano monitoring. We investigate a sequence of five unusual long-period (LP) earthquakes that occurred in the days prior to the onset of a months-long volcano-tectonic (VT) earthquake swarm beneath Little Sitkin volcano in the Aleutian Islands during late 2012. The long-period earthquakes had two distinctive characteristics: their signals were dominated by a monochromatic spectral peak at approximately 0.57 Hz and they had impulsive P and S-wave arrivals on a seismometer located on Amchitka Island 80 km to the southeast of the volcano. In each case, the monochromatic earthquakes …

The Hydrothermal System of Solfatara Crater (Campi Flegrei, Italy) Inferred From Machine Learning Algorithms

2019

Two machine learning algorithms were applied to three multivariate datasets acquired at Solfatara volcano. Our aim was to find an unbiased and coherent synthesis among the large amount of data acquired within the crater and along two orthogonal vertical NNE- and WNW-trending cross-sections. The first algorithm includes a new approach for a soft K-means clustering based on the use of the silhouette index to control the color palette of the clusters. The second algorithm which uses the self-organizing maps incorporates an alternative method for choosing the number of nodes of the neural network which aims to avoid the need for downstream clustering of the results of the classification. Both m…

Semi-parametric estimation of the intensity function in space-time point processes

2009

Structural architecture and active deformation pattern in the northern sector of the Aeolian-Tindari-Letojanni fault system (SE Tyrrhenian Sea-NE Sic…

2017

Framed in the current geodynamics of the central Mediterranean, the Aeolian-Tindari-Letojanni fault system is part of a wider NW-SE oriented right-lateral wrench zone which accommodates diverging motion between regional-scale blocks located at the southern edge of the Calabrian Arc. In order to investigate the structural architecture and the active deformation pattern of the northern sector of this tectonic feature, structural observations on-land, high and very-high resolution seismic reflection data, swath bathymetry data and seismological and geodetic data were merged from the Lipari-Vulcano volcanic complex (central sector of the Aeolian Islands) to the Peloritani Mountains across the G…