scholarly journals Linearization of the Sobolev and Babeyko's formulae for transformation of P-wave velocity to density in the Carpathian-Pannonian Basin region

2012 ◽  
Vol 42 (1) ◽  
pp. 15-23 ◽  
Author(s):  
Kristián Csicsay ◽  
Miroslav Bielik ◽  
Andrej Mojzeš ◽  
Eva Speváková ◽  
Bibiána Kytková ◽  
...  
Keyword(s):  
Wave Velocity ◽  
Pannonian Basin ◽  
Gravity Data ◽  
Initial Density ◽  
Real Data ◽  
P Wave ◽  
Seismic Velocities ◽  
P Wave Velocity ◽  
Density Relationship ◽  
Basin Region

Linearization of the Sobolev and Babeyko's formulae for transformation of P-wave velocity to density in the Carpathian-Pannonian Basin regionThe initial density model has to be based on a reasonable geological hypothesis and while the modelling process is non-unique, one of the interpretation aims is to define the robust parameters of the model. It is important at this stage to integrate the seismic and gravity data. One of the possibilities how to integrate these data is transformation of the seismic velocities to densities. The Sobolev and Babeyko's formulae belong to the most available relationships for this transformation. They are very complex and rigorous taking into account the PT conditions. On the other hand its application is relatively complicated. Therefore the main goal of the paper is to try to determine more easily the formula for transformation of the seismic velocities to densities. Based on the analysis of the results obtained using the Sobolev and Babeyko's formula on real data, we found out that in the Carpathian-Pannonian Basin region this formula can be transformed to simpler linear velocity-density relationship with required accuracy.

scholarly journals P-wave velocity and density structure beneath Mt. Vesuvius: a magma body in the upper edifice?

2013 ◽  
Vol 56 (4) ◽  
Author(s):  
Paolo Capuano ◽  
Guido Russo ◽  
Roberto Scarpa
Keyword(s):  
High Resolution ◽  
Wave Velocity ◽  
Gravity Data ◽  
High Energy ◽  
P Wave ◽  
Gravity Inversion ◽  
Density Structure ◽  
Resolution Image ◽  
High Resolution Image ◽  
P Wave Velocity

<p>A high-resolution image of the compressional wave velocity and density structure in the shallow edifice of Mount Vesuvius has been derived from simultaneous inversion of travel times and hypocentral parameters of local earthquakes and from gravity inversion. The robustness of the tomography solution has been improved by adding to the earthquake data a set of land based shots, used for constraining the travel time residuals. The results give a high resolution image of the P-wave velocity structure with details down to 300-500 m. The relocated local seismicity appears to extend down to 5 km depth below the central crater, distributed into two clusters, and separated by an anomalously high Vp region positioned at around 1 km depth. A zone with high Vp/Vs ratio in the upper layers is interpreted as produced by the presence of intense fluid circulation alternatively to the interpretation in terms of a small magma chamber inferred by petrologic studies. In this shallower zone the seismicity has the minimum energy, whilst most of the high-energy quakes (up to Magnitude 3.6) occur in the cluster located at greater depth. The seismicity appears to be located along almost vertical cracks, delimited by a high velocity body located along past intrusive body, corresponding to remnants of Mt. Somma. In this framework a gravity data inversion has been performed to study the shallower part of the volcano. Gravity data have been inverted using a method suitable for the application to scattered data in presence of relevant topography based on a discretization of the investigated medium performed by establishing an approximation of the topography by a triangular mesh. The tomography results, the retrieved density distribution, and the pattern of relocated seismicity exclude the presence of significant shallow magma reservoirs close to the central conduit. These should be located at depth higher than that of the base of the hypocenter volume, as evidenced by previous studies.</p>

scholarly journals Determination of rock densities in the Carpathian-Pannonian Basin lithosphere: based on the CELEBRATION 2000 experiment

2016 ◽  
Vol 46 (4) ◽  
pp. 269-287 ◽  
Author(s):  
Barbora Šimonová ◽  
Miroslav Bielik
Keyword(s):  
Lower Crust ◽  
Pannonian Basin ◽  
Average Density ◽  
East European Craton ◽  
P Wave ◽  
Seismic Velocities ◽  
Upper Crust ◽  
East European ◽  
P Wave Velocity

Abstract The international seismic project CELEBRATION 2000 brought very good information about the P-wave velocity distribution in the Carpathian-Pannonian Basin litosphere. In this paper seismic data were used for transformations of in situ P-wave velocities to in situ densities along all profiles running across the Western Carpathians and the Pannonian Basin: CEL01, CEL04, CEL05, CEL06, CEL09, CEL11 and CEL12. The calculation of rock densities in the crust and lower lithosphere was done by the transformation of seismic velocities to densities using the formulae of Sobolev-Babeyko, Christensen-Mooney and in the lower lithosphere also by Lachenbruch-Morgan’s formula. The density of the upper crust changes significantly in the vertical and horizontal directions, while the interval ranges of the calculated lower crust densities narrow down prominently. The lower lithosphere is the most homogeneous - the intervals of the calculated densities for this layer are already very narrow. The average density of the upper crust (ρ̅ = 2.60 g · cm−3) is the lowest in the Carpathian Foredeep region. On the contrary, the highest density of this layer (ρ̅ = 2.77 g · cm−3) is located in the Bohemian Massif. The average densities ρ̅ of the lower crust vary between 2.90 and 2.98 g · cm−3. The Palaeozoic Platform and the East European Craton have the highest density (ρ̅ = 2.98 g · cm−3 and ρ̅ = 2.97 g · cm−3, respectively). The lower crust density is the lowest (ρ̅ = 2.90 g · cm−3) in the Pannonian Basin. The range of calculated average densities ρ̅ for the lower lithosphere is changed in the interval from 3.35 to 3.40 g · cm−3. The heaviest lower lithosphere can be observed in the East European Craton (ρ̅ = 3.40 g · cm−3). The lower lithosphere of the Transdanubian Range and the Palaeozoic Platform is characterized by the lowest density ρ̅ = 3.35 g · cm−3.

scholarly journals 3D P-wave velocity image beneath the Pannonian Basin using traveltime tomography

2019 ◽  
Vol 54 (3) ◽  
pp. 373-386 ◽  
Author(s):  
Máté Timkó ◽  
István Kovács ◽  
Zoltán Wéber
Keyword(s):  
Wave Velocity ◽  
Pannonian Basin ◽  
P Wave ◽  
Traveltime Tomography ◽  
P Wave Velocity ◽  
Velocity Image

P-wave velocity anisotropy in an active methane venting pockmark: The Scanner Pockmark, northern North Sea

2020 ◽  
Author(s):  
Gaye Bayrakci ◽  
Timothy A. Minshull ◽  
Jonathan M. Bull ◽  
Timothy J. Henstock ◽  
Giuseppe Provenzano ◽  
...  
Keyword(s):  
Wave Velocity ◽  
North Sea ◽  
Image Resolution ◽  
P Wave ◽  
Bright Spot ◽  
Seismic Velocities ◽  
Clay Layer ◽  
Travel Times ◽  
P Wave Velocity ◽  
Northern North Sea

&lt;p&gt;Scanner pockmark is an active and continuous methane venting seafloor depression of ~ 900 x 450 m wide and 22 m deep. It is located in the northern North Sea, within the Witch Ground basin where the seafloor and shallow sediments are heavily affected by pockmarks and paleo-pockmarks of various sizes. A seismic chimney structure is present below the Scanner pockmark. It is expressed as a near-vertical column of acoustic blanking below a bright zone of gas-bearing sediments. Seismic chimneys are thought to host connected vertical fractures which may be concentric within the chimney and align parallel to maximum compression outside it. The crack geometry modifies the seismic velocities, and hence, the anisotropy measured inside and outside of the chimney is expected to be different.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;We carried out anisotropic P-wave tomography with a GI-gun wide-angle dataset recorded by the 25 Ocean Bottom Seismometers (OBSs) of the CHIMNEY experiment (2017). Travel times of more than 60,000 refracted phases propagating within a volume of 4 x 4 x 2 km were inverted for P-wave velocity and the direction and degree of P-wave anisotropy. The grid is centred on the Scanner Pockmark and has a y-axis parallel to -34&lt;sup&gt;o&lt;/sup&gt; N. The horizontal node interval is denser in the zone covered by the OBSs and the vertical node interval is denser near the seabed. A 3 iteration inversion leads to a chi&lt;sup&gt;2&lt;/sup&gt; misfit value of 1 and a root-mean-square misfit of &lt;10 ms. The results show a maximum P-wave anisotropy of 5%, and higher degrees of anisotropy correlates well with higher velocities. The fast P-wave velocity orientation, a proxy for fracture orientations, is 46&lt;sup&gt;o&lt;/sup&gt; N. The top of the chimney possibly links a bright spot mapped at 270 ms in two way travel time using RMS amplitudes of MCS data, to the surface gas emission. The bright spot corresponds to low tomographic P-wave velocity and anisotropy, suggesting that gas is located in a zone with unaligned fractures or porosity. This observation is in good agreement with early multi-channel seismic data interpretations which suggested that the gas is trapped within a sandy clay layer, the Ling Bank Formation, capped by an upper clay layer, the Coal Pit Formation. In the next step, we will invert the travel-times of reflected phases in order to increase the image resolution.&amp;#160;&amp;#160;&lt;/p&gt;

scholarly journals A P-wave velocity model of the upper crust of the Sannio region (Southern Apennines, Italy)

1998 ◽  
Vol 41 (4) ◽  
Author(s):  
G. Iannaccone ◽  
L. Improta ◽  
P. Capuano ◽  
A. Zollo ◽  
G. Biella ◽  
...  
Keyword(s):  
Wave Velocity ◽  
Seismic Velocity ◽  
Carbonate Platform ◽  
Velocity Model ◽  
P Wave ◽  
Seismic Velocities ◽  
Upper Crust ◽  
Near Surface ◽  
P Wave Velocity ◽  
Apulia Platform

This paper describes the results of a seismic refraction profile conducted in October 1992 in the Sannio region, Southern Italy, to obtain a detailed P-wave velocity model of the upper crust. The profile, 75 km long, extended parallel to the Apenninic chain in a region frequently damaged in historical time by strong earthquakes. Six shots were fired at five sites and recorded by a number of seismic stations ranging from 41 to 71 with a spacing of 1-2 km along the recording line. We used a two-dimensional raytracing technique to model travel times and amplitudes of first and second arrivals. The obtained P-wave velocity model has a shallow structure with strong lateral variations in the southern portion of the profile. Near surface sediments of the Tertiary age are characterized by seismic velocities in the 3.0-4.1 km/s range. In the northern part of the profile these deposits overlie a layer with a velocity of 4.8 km/s that has been interpreted as a Mesozoic sedimentary succession. A high velocity body, corresponding to the limestones of the Western Carbonate Platform with a velocity of 6 km/s, characterizes the southernmost part of the profile at shallow depths. At a depth of about 4 km the model becomes laterally homogeneous showing a continuous layer with a thickness in the 3-4 km range and a velocity of 6 km/s corresponding to the Meso-Cenozoic limestone succession of the Apulia Carbonate Platform. This platform appears to be layered, as indicated by an increase in seismic velocity from 6 to 6.7 km/s at depths in the 6-8 km range, that has been interpreted as a lithological transition from limestones to Triassic dolomites and anhydrites of the Burano formation. A lower P-wave velocity of about 5.0-5.5 km/s is hypothesized at the bottom of the Apulia Platform at depths ranging from 10 km down to 12.5 km; these low velocities could be related to Permo-Triassic siliciclastic deposits of the Verrucano sequence drilled at the bottom of the Apulia Platform in the Apulia Foreland.

scholarly journals Prediction of seismic P-wave velocity using machine learning

Solid Earth ◽  
2019 ◽  
Vol 10 (6) ◽  
pp. 1989-2000 ◽  
Author(s):  
Ines Dumke ◽  
Christian Berndt
Keyword(s):  
Machine Learning ◽  
Wave Velocity ◽  
Seismic Velocity ◽  
P Wave ◽  
Training Dataset ◽  
Seismic Velocities ◽  
P Wave Velocity ◽  
Machine Learning Approach ◽  
Global Datasets ◽  
Spatial Predictors

Abstract. Measurements of seismic velocity as a function of depth are generally restricted to borehole locations and are therefore sparse in the world's oceans. Consequently, in the absence of measurements or suitable seismic data, studies requiring knowledge of seismic velocities often obtain these from simple empirical relationships. However, empirically derived velocities may be inaccurate, as they are typically limited to certain geological settings, and other parameters potentially influencing seismic velocities, such as depth to basement, crustal age, or heat flow, are not taken into account. Here, we present a machine learning approach to predict the overall trend of seismic P-wave velocity (vp) as a function of depth (z) for any marine location. Based on a training dataset consisting of vp(z) data from 333 boreholes and 38 geological and spatial predictors obtained from publicly available global datasets, a prediction model was created using the random forests method. In 60 % of the tested locations, the predicted seismic velocities were superior to those calculated empirically. The results indicate a promising potential for global prediction of vp(z) data, which will allow the improvement of geophysical models in areas lacking first-hand velocity data.

Seismological studies in a rock body at Chalk River, Ontario and their relation to fractures

1982 ◽  
Vol 19 (8) ◽  
pp. 1535-1547 ◽  
Author(s):  
C. Wright
Keyword(s):  
Wave Velocity ◽  
Test Site ◽  
P Wave ◽  
Seismic Velocities ◽  
S Wave ◽  
P Waves ◽  
Rock Body ◽  
Near Surface ◽  
Wave Velocities ◽  
P Wave Velocity

Seismological experiments have been undertaken at a test site near Chalk River, Ontario that consists of crystalline rocks covered by glacial sediments. Near-surface P and S wave velocity and amplitude variations have been measured along profiles less than 2 km in length. The P and S wave velocities were generally in the range 4.5–5.6 and 2.9–3.2 km/s, respectively. These results are consistent with propagation through fractured gneiss and monzonite, which form the bulk of the rock body. The P wave velocity falls below 5.0 km/s in a region where there is a major fault and in an area of high electrical conductivity; such velocity minima are therefore associated with fracture systems. For some paths, the P and 5 wave velocities were in the ranges 6.2–6.6 and 3.7–4.1 km/s, respectively, showing the presence of thin sheets of gabbro. Temporal changes in P travel times of up to 1.4% over a 12 h period were observed where the sediment cover was thickest. The cause may be changes in the water table. The absence of polarized SH arrivals from specially designed shear wave sources indicates the inhomogeneity of the test site. A Q value of 243 ± 53 for P waves was derived over one relatively homogeneous profile of about 600 m length. P wave velocity minima measured between depths of 25 and 250 m in a borehole correlate well with the distribution of fractures inferred from optical examination of borehole cores, laboratory measurements of seismic velocities, and tube wave studies.

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