scholarly journals 3D-Kernel Based Imaging of an Improved Estimation of (Qc) in the Northern Apulia (Southern Italy)

2021 ◽  
Vol 11 (16) ◽  
pp. 7512
Author(s):  
Marilena Filippucci ◽  
Salvatore Lucente ◽  
Edoardo Del Pezzo ◽  
Salvatore de Lorenzo ◽  
Giacomo Prosser ◽  
...  
Keyword(s):  
Southern Italy ◽  
Active Tectonics ◽  
Quality Parameter ◽  
Seismic Attenuation ◽  
Theoretical Assumption ◽  
Low Frequencies ◽  
Mapping Procedure ◽  
Marche Region ◽  
Gargano Promontory ◽  
Seismic Networks

We investigate crustal seismic attenuation by the coda quality parameter (Qc) in the Gargano area (Southern Italy), using a recently released dataset composed of 191 small earthquakes (1.0 ≤ ML ≤ 2.8) recorded by the local OTRIONS and the Italian INGV seismic networks, over three years of seismic monitoring. Following the single back-scattering theoretical assumption, Qc was computed using different frequencies (in the range of 2–16 Hz) and different lapse times (from 10 to 40 s). The trend of Qc vs. frequency is the same as that observed in the adjacent Umbria-Marche region. Qc at 1 Hz varies between 11 and 63, indicating that the area is characterized by active tectonics, despite the absence of high-magnitude earthquakes in recent decades. The 3D mapping procedure, based on sensitivity kernels, revealed that the Gargano Promontory is characterized by very low and homogeneous Qc at low frequencies, and by high and heterogeneous Qc at high frequencies. The lateral variations of Qc at 12 Hz follow the trend of the Moho in this region and are in good agreement with other geophysical observations.

scholarly journals Seismic Envelopes of Coda Decay for Q-coda Attenuation Studies of the Gargano Promontory (Southern Italy) and Surrounding Regions

Data ◽  
2021 ◽  
Vol 6 (9) ◽  
pp. 98
Author(s):  
Marilena Filippucci ◽  
Salvatore Lucente ◽  
Salvatore de Lorenzo ◽  
Edoardo Del Pezzo ◽  
Giacomo Prosser ◽  
...  
Keyword(s):  
Quality Factor ◽  
Visual Inspection ◽  
Southern Italy ◽  
Seismic Attenuation ◽  
Single Source ◽  
S Wave ◽  
Central Frequency ◽  
Earthquake Catalogues ◽  
Gargano Promontory ◽  
Coda Attenuation

Here, we describe the dataset of seismic envelopes used to study the S-wave Q-coda attenuation quality factor Qc of the Gargano Promontory (Southern Italy). With this dataset, we investigated the crustal seismic attenuation by the Qc parameter. We collected this dataset starting from two different earthquake catalogues: the first regarding the period from April 2013 to July 2014; the second regarding the period from July 2015 to August 2018. Visual inspection of the envelopes was carried out on recordings filtered with a Butterworth two-poles filter with central frequency fc = 6 Hz. The obtained seismic envelopes of coda decay can be linearly fitted in a bilogarithmic diagram in order to obtain a series of single source-receiver measures of Qc for each seismogram component at different frequency fc. The analysis of the trend Qc(fc) gives important insights into the heterogeneity and the anelasticity of the sampled Earth medium.

TIMING AND CAUSES OF THE DROWNING AND BACK STEP OF THE APULIA CARBONATE PLATFORM (MONTE SACRO SEQUENCE, GARGANO PROMONTORY, SOUTHERN ITALY)

2019 ◽  
Author(s):  
Katherine Jones ◽  
◽  
Daniel J. Lehrmann ◽  
Michele Morsilli ◽  
Khalid Al-Ramadan ◽  
...  
Keyword(s):  
Southern Italy ◽  
Carbonate Platform ◽  
Gargano Promontory

Spatio-temporal variation of Anaelastic and Scattering Seismic Attenuation during the 2016-2017 Central Italy Seismic Sequence

2021 ◽  
Author(s):  
Simona Gabrielli ◽  
Aybige Akinci ◽  
Ferdinando Napolitano ◽  
Luca De Siena ◽  
Edoardo Del Pezzo ◽  
...  
Keyword(s):  
Wave Attenuation ◽  
Central Italy ◽  
Temporal Variations ◽  
Seismic Attenuation ◽  
Coda Wave ◽  
Seismic Sequence ◽  
Rock Fracturing ◽  
Low Frequencies ◽  
Main Shocks ◽  
Stress Changes

<p>Between August and October 2016, the Central Apennines in Italy have been struck by a long-lasting seismic sequence, known as the Amatrice (Mw 6.0) - Visso (Mw 5.9) - Norcia (Mw 6.5) sequence. The cascading ruptures occurred in this sequence have been considered connected to the fluid migration in the fault network, as suggested by previous studies. The behaviour of fluids in the crust is crucial to understand earthquakes occurrence and stress changes since fluids reduce fault stability. It has long been understood that the seismic attenuation is strongly controlled by the structural irregularity and heterogeneities; micro-cracks and cavities, either fluid-filled or dry, temperature and pressure variations cause a decrease in seismic wave amplitude and pulse broadening. Hence seismic attenuation imagining is a powerful tool to be a relevant provenance of information about the influence and abundance of fluids in a seismic sequence.</p><p>The aim of this work is to separate scattering and absorption contributions to the total attenuation of coda waves and to provide their spatial and temporal variations at different frequency bands of these quantities using two datasets: the first one comprising 592 earthquakes occurred before the sequence (March 2013-August 2016) and the second one comprising 763 events (ML > 2.8) from the Amatrice-Visso-Norcia sequence. Scattering and absorption have been measured through peak-delay and coda-wave attenuation parameters (the latter inverted using frequency-dependent sensitivity kernels).</p><p>The preliminary results show a clear difference between the pre-sequence and sequence images, mainly at low frequencies (1.5 Hz), where we can define a spatial increase of scattering with time attributed to rock fracturing and fluid circulation. The coda attenuation tomography also demonstrates a clear variation between the pre-sequence and the sequence over series of time windows being before and after the largest main shocks of the seismic sequence, with an increase of the attenuation in space with decreasing time. The peak delay indicates a high scattering area corresponding to the Gran Sasso massif and L’Aquila zone, where an important seismic sequence (Mw 6.3) occurred in 2009.</p>

scholarly journals Landslides, floods and sinkholes in a karst environment: the 1–6 September 2014 Gargano event, southern Italy

2017 ◽  
Vol 17 (3) ◽  
pp. 467-480 ◽  
Author(s):  
Maria Elena Martinotti ◽  
Luca Pisano ◽  
Ivan Marchesini ◽  
Mauro Rossi ◽  
Silvia Peruccacci ◽  
...  
Keyword(s):  
Southern Italy ◽  
Flash Floods ◽  
Temporal Information ◽  
Karst Area ◽  
Exceedance Probability ◽  
Karst Environment ◽  
Gargano Promontory ◽  
Landslide Forecasting ◽  
Landslide Early Warning ◽  
Torrential Rainfall

Abstract. In karst environments, heavy rainfall is known to cause multiple geohydrological hazards, including inundations, flash floods, landslides and sinkholes. We studied a period of intense rainfall from 1 to 6 September 2014 in the Gargano Promontory, a karst area in Puglia, southern Italy. In the period, a sequence of torrential rainfall events caused severe damage and claimed two fatalities. The amount and accuracy of the geographical and temporal information varied for the different hazards. The temporal information was most accurate for the inundation caused by a major river, less accurate for flash floods caused by minor torrents and even less accurate for landslides. For sinkholes, only generic information on the period of occurrence of the failures was available. Our analysis revealed that in the promontory, rainfall-driven hazards occurred in response to extreme meteorological conditions and that the karst landscape responded to the torrential rainfall with a threshold behaviour. We exploited the rainfall and the landslide information to design the new ensemble–non-exceedance probability (E-NEP) algorithm for the quantitative evaluation of the possible occurrence of rainfall-induced landslides and of related geohydrological hazards. The ensemble of the metrics produced by the E-NEP algorithm provided better diagnostics than the single metrics often used for landslide forecasting, including rainfall duration, cumulated rainfall and rainfall intensity. We expect that the E-NEP algorithm will be useful for landslide early warning in karst areas and in other similar environments. We acknowledge that further tests are needed to evaluate the algorithm in different meteorological, geological and physiographical settings.

scholarly journals Mineralogical and Geochemical Features of Cretaceous Bauxite from San Giovanni Rotondo (Apulia, Southern Italy): A Provenance Tool

Minerals ◽  
2018 ◽  
Vol 8 (12) ◽  
pp. 567 ◽  
Author(s):  
Rosa Sinisi
Keyword(s):  
Rare Earth ◽  
Southern Italy ◽  
Dilution Effect ◽  
Source Material ◽  
Detrital Zircons ◽  
Chemical Compositions ◽  
Geochemical Proxies ◽  
Mineral Phases ◽  
Gargano Promontory ◽  
Parental Material

In this study, the mineralogical and chemical compositions of bauxite from San Giovanni Rotondo (SGR) on the Gargano Promontory (northern Apulia, Italy) are presented and discussed with the aim of assessing the nature of its source material. Bauxite from the SGR, which is known as the “Montecatini mine”, was exploited intensively until the 1970s to recover alumina. As with most of the autochthonous peri-Mediterranean bauxites, the studied deposit is a karst bauxite with a massive, matrix-supported texture and an oolitic structure. Boehmite and hematite are the main mineral phases, and anatase, rutile, and kaolinite are present in lesser amounts along with detrital zircons and monazite grains. Calcite is abundant only in the deposit’s lower portion, triggering a significant dilution effect on trace element concentrations. However, with respect to the average crust and chondrite compositions, strong enrichments of trace metals (up to 10X Upper Continental Crust’s (UCC)) and rare earth elements (REEs, up to 800X chondrite) exist throughout the studied deposit. The distribution of REEs, the (La/Yb)N and Eu/Eu* ratios, and an Eu/Eu* versus Sm/Nd diagram have been used for determining the bauxite’s provenance. These geochemical proxies point to a parental material consisting of a mixture of distant magmatic and siliciclastic components.

scholarly journals Knickpoints as geomorphic markers of active tectonics: A case study from northeastern Sicily (southern Italy)

Lithosphere ◽  
2016 ◽  
Vol 8 (6) ◽  
pp. 633-648 ◽  
Author(s):  
Francesco Pavano ◽  
Frank J. Pazzaglia ◽  
Stefano Catalano
Keyword(s):  
Southern Italy ◽  
Active Tectonics ◽  
Northeastern Sicily

Modulation of seismic noise near the San Jacinto fault in Southern California: Origin and observations of the cyclical time dependence and associated crustal properties

2020 ◽  
Author(s):  
Vladislav G Martynov ◽  
Luciana Astiz ◽  
Debi Kilb ◽  
Frank L Vernon
Keyword(s):  
Seismic Noise ◽  
Southern California ◽  
Low Frequency ◽  
Ocean Waves ◽  
Seismic Attenuation ◽  
Phase Lag ◽  
Low Frequencies ◽  
San Jacinto Fault ◽  
San Jacinto Fault Zone ◽  
Seismic Quality Factor

Summary We examine the cyclic amplitude variation of seismic noise recorded by continuous three-component broadband seismic data with durations spanning 91 to 713 days (2008–2011) from three different networks: Anza seismic network, IDA network and the Transportable seismic array. These stations surround the San Jacinto Fault Zone (SJFZ) in southern California. We find the seismic noise amplitudes exhibit a cyclical variation between 0.3 and 7.2 Hz. The high frequency (≥ 0.9 Hz) noise variations can be linked to human activity and are not a concern. Our primary interest is signals in the low frequencies (0.3–0.9 Hz), where the seismic noise is modulated by semi-diurnal tidal mode M2. These long-period (low frequency) variations of seismic noise can be attributed to a temporal change of the ocean waves breaking at the shoreline, driven by ocean tidal loading. We focus on the M2 variation of seismic noise at f = 0.6 Hz, travelling distances of ∼92 km through the crust from offshore California to the inland Anza, California, region. Relative to the shoreline station, data from the inland stations show a phase lag of ∼ –12°, which we attribute to the cyclic change in M2 that can alter crustal seismic attenuation. We also find that for mode M2 at 0.6 Hz, the amplitude variations of the seismic quality factor (Q) depend on azimuth and varies from 0.22 per cent (southeast to northwest) to 1.28 per cent (northeast to southwest) with Q = 25 for Rayleigh waves. We propose the direction dependence of the Q variation at 0.6 Hz reflects the preferred orientation of sub-faults parallel to the main faulting defined by the primarily N45° W strike of the SJFZ.

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