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.

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.

Seismic attenuation tomography using body-wave energy normalised by the heterogeneous coda

2020 ◽  
Author(s):  
Panayiota Sketsiou ◽  
Luca De Siena ◽  
Simona Gabrielli ◽  
Ferdinando Napolitano
Keyword(s):  
Quality Factor ◽  
Wave Energy ◽  
Body Wave ◽  
Seismic Attenuation ◽  
Coda Wave ◽  
Total Quality ◽  
Lapse Time ◽  
Density Spectrum ◽  
Coda Normalization ◽  
Coda Attenuation

<p>Seismic waves lose energy during propagation in heterogeneous Earth media. Their decrease of amplitude, defined as seismic attenuation, is central in the description of seismic wave propagation. The attenuation of coherent waves can be described by the total quality factor, <em>Q</em>, and it is defined as the fractional energy lost per cycle, controlling the decay of the energy density spectrum with lapse time. The coda normalization (CN) method is a method to measure the attenuation of P- or S-waves by taking the ratio of the direct wave energy and late coda wave energy in order to remove the source and site effects from P- and S-wave spectra. One of the main assumptions of the CN method is that coda attenuation, i.e. the decay of coda energy with lapse time measured by the coda quality factor <em>Q<sub>c</sub></em> is constant. However, several studies showed that Q<sub>c</sub> is not uniform in the crust for the lapse times considered in most attenuation studies. In this work, we propose a method to overcome this assumption, measuring coda attenuation for each source-station path and evaluating the effect of different scattering regimes on the corresponding imaging. The data consists of passive waveforms from the fault network in the Pollino Area (Southern Italy) and Mount St. Helens volcano (USA).</p>

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

scholarly journals Simulation of seismic waves at the earth's crust (brittle–ductile transition) based on the Burgers model

Solid Earth ◽  
2014 ◽  
Vol 5 (2) ◽  
pp. 1001-1010 ◽  
Author(s):  
J. M. Carcione ◽  
F. Poletto ◽  
B. Farina ◽  
A. Craglietto
Keyword(s):  
Seismic Waves ◽  
In Situ Stress ◽  
Seismic Attenuation ◽  
Earth’S Crust ◽  
S Wave ◽  
Fourier Pseudospectral Method ◽  
Stress Criterion ◽  
Brittle Ductile Transition ◽  
Earth's Crust

Abstract. The earth's crust presents two dissimilar rheological behaviors depending on the in situ stress-temperature conditions. The upper, cooler part is brittle, while deeper zones are ductile. Seismic waves may reveal the presence of the transition but a proper characterization is required. We first obtain a stress–strain relation, including the effects of shear seismic attenuation and ductility due to shear deformations and plastic flow. The anelastic behavior is based on the Burgers mechanical model to describe the effects of seismic attenuation and steady-state creep flow. The shear Lamé constant of the brittle and ductile media depends on the in situ stress and temperature through the shear viscosity, which is obtained by the Arrhenius equation and the octahedral stress criterion. The P and S wave velocities decrease as depth and temperature increase due to the geothermal gradient, an effect which is more pronounced for shear waves. We then obtain the P−S and SH equations of motion recast in the velocity-stress formulation, including memory variables to avoid the computation of time convolutions. The equations correspond to isotropic anelastic and inhomogeneous media and are solved by a direct grid method based on the Runge–Kutta time stepping technique and the Fourier pseudospectral method. The algorithm is tested with success against known analytical solutions for different shear viscosities. A realistic example illustrates the computation of surface and reverse-VSP synthetic seismograms in the presence of an abrupt brittle–ductile transition.

scholarly journals P- and S-wave seismic attenuation for deep natural gas exploration and development

2005 ◽  
Author(s):  
Joel Walls ◽  
Richard Uden ◽  
Scott Singleton ◽  
Rone Shu ◽  
Gary Mavko
Keyword(s):  
Natural Gas ◽  
Seismic Attenuation ◽  
S Wave ◽  
Exploration And Development

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.

EFFECTS OF POROSITY ON SEISMIC ATTENUATION

1994 ◽  
Vol 02 (01) ◽  
pp. 53-69 ◽  
Author(s):  
YUE-FENG SUN ◽  
JOHN T. KUO ◽  
YU-CHIUNG TENG
Keyword(s):  
Quality Factor ◽  
Crack Density ◽  
Seismic Attenuation ◽  
Center Frequency ◽  
Fluid Content ◽  
Intrinsic Attenuation ◽  
Resolution Mapping ◽  
Waveform Change ◽  
Optimization Schemes ◽  
Quality Factor Q

Effects of porosity on the attenuation of wave propagation are studied. The effects of pore fluids and porous structures are significant on changing the shapes of propagating wavelets. The waveform change of a propagating wavelet is much more sensitive to porosity than intrinsic attenuation. The attenuation occurred in natural rocks may largely due to these porous effects in addition to the internal friction of the solid represented by the intrinsic quality factor Q. The waveform of a propagating wavelet is quantitatively associated with attenuation, porosity, and fluid content, and is characterized by three parameters: the porosity ϕ, the quality factor Q, and the center frequency f0. Estimations of attenuation, porosity, and fluid content can be made by optimal wavelet analysis. High-resolution mapping of subsurface structures can be achieved by solving the integral equation with the nonlinear optimization of the time-variant wavelets. The inversion and the optimization schemes have been applied to study the porous sea floor and the crustal axial magma chamber (AMC) on the East Pacific Rise. These results provide porosity, attenuation information, and the highly resolved wave events, for further evaluation of compressional and shear wave velocities and other physical properties such as crack density and aspect ratio.

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